The Life of Frank Coles Phillips (1902-1982) and the Structural Geology of the Moine Petrofabric Controversy

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The Life of Frank Coles Phillips (1902-1982) and the Structural Geology of the Moine Petrofabric Controversy

Geological Society Memoirs Society Book Editors A. J. FLEET (CHIEF EDITOR) P. DOYLE F. J. GREGORY J. S. GRIFFITHS A. J. HARTLEY R. E. HOLDSWORTH

A. C. MORTON N. S. ROBINS M. S. STOKER J. P. TURNER

Reviewing procedures The Society makes every effort to ensure that the scientific and production quality of its books matches that of its journals. Since 1997, all book proposals have been refereed by specialist reviewers as well as by the Society's Books Editorial Committee. If the referees identify weaknesses in the proposal, these must be addressed before the proposal is accepted. Once the book is accepted, the Society has a team of Book Editors (listed above) who ensure that the volume editors follow strict guidelines on refereeing and quality control. We insist that individual papers can only be accepted after satisfactory review by two independent referees. The questions on the review forms are similar to those for Journal of the Geological Society. The referees' forms and comments must be available to the Society's Book Editors on request. Although many of the books result from meetings, the editors are expected to commission papers that were not presented at the meeting to ensure that the book provides a balanced coverage of the subject. Being accepted for presentation at the meeting does not guarantee inclusion in the book. More information about submitting a proposal and producing a Memoir can be found on the Society's web site: www.geolsoc.org.uk. It is recommended that reference to all or part of this book should be made in one of the following ways: HOWARTH, R. J. & LEAKE, B. E. 2002. The Life of Frank Coles Phillips (1902-1982) and the Structural Geology of the Moine Petrofabric Controversy. Geological Society, London, Memoirs, 23.

GEOLOGICAL SOCIETY MEMOIR NO. 23

The Life of Frank Coles Phillips (1902-1982) and the Structural Geology of the Moine Petrofabric Controversy BY

RICHARD J. HOWARTH Department of Geological Sciences, University College London, UK

and

BERNARD E. LEAKE Department of Earth Sciences, Cardiff University, Wales, UK

2002 Published by The Geological Society London

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iv

Contents Preface

vi

1. Family background and personality

1

2. School years (1910-1920)

3

3. Cambridge (1920-1935) First degree Research studentship Post-doctoral work The Green Bed study The universal stage Stereographic projection New skills Departmental reorganization

5 5 5 10 10 11 12 12 13

4. Petrofabric research Basic principles Sander's petrofabric method Kinematic interpretation Structural petrology at Cambridge

15 15 15 18 21

5. Understanding of Moine geology in the 1930s

23

6. Cambridge (1936-1946) Microfabric of the Moine schists. I The Tarskavaig Moines' Other pre-war activity War years Petrofabrics of the Ben Vuirich granite Dissonant voices Microfabric of the Moine schists. II A return to crystallography Time for a change

26 26 31 31 32 32 34 35 38 38

7. Liverpool (1947) The appointment A new environment Catastrophe Aftermath

39 39 39 40 40

8. Bristol (1948-1952) The petrofabric controversy begins Phillips prepares a rebuttal A counter-example from Norway Structural petrology short courses

41 41 43 45 47

9. An Australian lecture-tour Western Australia South Australia New South Wales Queensland Return to New South Wales Outcome

48 49 49 50 51 51 51

10. Background to controversy Developments in understanding of Moine geology during the 1950s and 1960s

53

11. Bristol (1953-1967)

Stereograms for macroscopic data New petrofabric difficulties Cornish sea-floor studies Further controversy The Moine fabric debate almost fizzles out Gemstones

53 55

55 56 58 58 59 59

12. Retirement

62

13. Benefits of hindsight The true significance of Sander's b-axis The explanation of 'crossed-girdles' The nature of the Moine Thrust Unravelling the Tarskavaig Moines' The cause of Kvale's confusion Modern understanding of the cause of the lineation and fabrics measured by Phillips in the Moine rocks

63 63 64 64 64 65

14. Conclusion

72

Notes

73

References

82

Index

92

67

V

Preface The English petrographer, mineralogist and structural petrologist Frank Coles Phillips is best known to mineralogists and geologists today for his now-classic textbooks An Introduction to Crystallography (1946) and The Use of Stereographic Projection in Structural Geology (1954); and to gemmologists for his major revision of Herbert Smith's Gemstones (1958). The adoption in Britain of the stereogram as a fundamental interpretational tool in structural geology owes much to the second of Phillips' books, and the development of structural geology in Australia was influenced by a lecture-tour which he undertook in 1953. A superb teacher, Phillips' main legacy lies in the students he trained and in the influence of his textbooks. As a result of his fluency in German, by 1932 Phillips, by then a young lecturer in the Department of Mineralogy at Cambridge University, had taken up the new techniques, first advocated by the Austrian geologist Bruno Sander (1884-1979) in 1930, for the analysis of Gefugekunde (petrofabrics) of geological bodies; i.e. the interpretation of the three-dimensional fabric of rocks, based on the determination of the statistical distribution of the orientation of particular crystallographic axes of minerals such as quartz, muscovite and biotite, accomplished by means of the 'universal' microscope stage (the petrofabric method). In 1937, at a time when the interpretation of structural geology in Britain was largely a field-based, qualitative practice, Phillips published a pioneering study in which he applied Sander's quantitative methods in an attempt to unravel the complex structural history of the Moine rocks of NW Scotland. Much of Phillips' subsequent research focused on the application of the petrofabric method to the Moine, and later to the metamorphic rocks of SW England, doggedly following the rules for kinematic interpretation as laid down by Sander in the 1930s and later embodied in his cryptic and partly incomprehensible magnum opus Einfiihrung in die Gefugekunde der geologischen Korper (An Introduction to the Study of Fabrics of Geological Bodies; 1948-50), eventually made available to a wider audience in a heroic English translation by Phillips, published in 1970. Unfortunately, as time went on, suspicion began to grow amongst structural geologists that Sander's rules were both ambiguous and meaningless as regards the deformation of real rocks. Their application to the Moine, in which the 'girdles' defined by the orientation of the optic c-axes of the quartz crystals in the rock fabric, were found to lie in NNE-SSW planes, perpendicular to the common lineation, led Phillips to the conclusion that 'the origin of the linear structures is connected with folding due to movements along south-west to north-east lines, earlier than the post-Cambrian displacements . . . . it is the lineation parallel to the b-axis of the fabric which has provided the direction of yield during the later thrust-movements,' a deduction rejected by his contemporaries as inconsistent with the NNE-SSW strike of the Moine rocks. This resulted in Moine petrofabrics becoming embroiled in a long-running controversy. Another principal conclusion of Phillips' work, which subsequently became rather overlooked in the disagreements which arose over movement direction in relation to petrofabric girdles, was his apparent demonstration that the Moine metasediments have a regional metamorphic fabric that pre-dated the Moine Thrust movements and was broken down in the Moine Thrust Zone - a view erroneously taken by H. H. Read as confirming his 1934 hypothesis that the Moines were Lewisian in age. The present depth of understanding of multiple folding (a phenomenon which was unrecognized in 1937) and the complex relationships which can develop between folding, pre-existing lineations, and petrofabrics simply did not exist at the time that Phillips was undertaking his pioneering studies. The on-going controversy regarding the interpretation of Phillips' petrofabric

results was initially resolved by D. Flinn's demonstration in 1962 that neither fold axes nor axial planes necessarily indicate movement directions or the directions of flow in rocks, but the situation has only been completely resolved since the mid-1980s, as a result of four crucial findings. (1) Pre-thrusting structures (?Precambrian) have been discovered throughout the Moine rocks of the northern Highlands; these include an early bedding-parallel foliation and a weakly preserved north-south to NNE-SSW trending mineral lineation. (2) The examinations of deformed conglomerates and related fabric studies have convinced many geologists that both the regional WNW-ESE 'stretching' (extension) lineation and its associated quartz c-axis girdles, found by Phillips, result from the WNW-directed Caledonian movements which formed the Moine Thrust. (3) The widespread recognition of sheath folds in the Moine rocks has revealed that fold axes originally formed oblique to the WNW-ESE lineation have often been rotated into parallelism with this lineation during ductile deformation; the geometry and facing directions of the sheath folds and related flow perturbation folds are consistent with top-to-the-WNWdirected thrusting. (4) A continuity of structures has been recognized between (i) the cover rocks and the Lewisian basement, and (ii) the Moine Thrust Zone and the overlying Moine Nappe, which Phillips first recognized but did not interpret correctly. In effect, therefore, Phillips was not entirely wrong but, as Flinn put it, 'right (to some extent) for the wrong reasons', largely because of Sander's confusion between the movement directions of externally applied forces and those of internal movements in response to the applied forces. One of us (R. J. H.) was taught by Phillips (1960-1963), while the other was a colleague of his on the staff at the University of Bristol for ten years (1957-1967). Our critical review of Phillips' research is set in the context of contemporaneous developments in structural and Moine geology. It was promoted by the lack of any obituary notice, or account of his scientific work, by either the Mineralogical Society or The Geological Society of London. It is unfortunate that he died at a time when obituary notices no longer appeared in the Proceedings of The Geological Society and before their present system of including them in the Annual Report began. Mr W. F. C. Phillips is sincerely thanked for giving us much personal information about his late father, for the loan of his father's Australian diary and photograph album, and for permission to reproduce various photographs; Mrs S. J. C. Toogood is also thanked for permission to reproduce Figure 1.1 and for providing us with useful comments on aspects of her father's life. We are also particularly grateful to Professor Derek Flinn, University of Liverpool, for his most useful comments on aspects of the structural interpretations made by Sander, Phillips, Anderson, and others, and for providing the photograph of the Funzie conglomerate; to Dr Robert E. Holdsworth, University of Durham, for his useful criticism in his role as Geological Society editor and for providing the photograph of the 'eye structure'; to Professor Richard Law, Virginia Polytechnic Institute and State University, USA, for copious information regarding work by himself and his colleagues on the Moine Thrust and for providing the photographs of the Stack of Glencoul and the Moine Thrust; and to Professor Lionel Weiss for providing us with photographs of various Moine structures and the Bygdin conglomerate. Dr G. A. Chinner, Dr G. Evans and Professor I. N. McCave all kindly provided us with additional photographic material. Dr Chinner is also thanked for his personal reminiscences, and for providing us with Dr Henry's notes (1935) of Phillips' lectures on oremicroscopy. Professor Mervyn Paterson, Australian National University, vi

PREFACE

also kindly sent us a copy of his excellent lecture notes made at the time of Phillips' (1952) Australian tour. Dr A. C. Bishop, Dr C. Bowler, Dr R. Bradshaw, Dr G. A. Chinner, Professor W. A. Deer, Professor E. den Tex, Professor D. L. Dineley, Professor D. T. Donovan, Professor G. Evans, Dr R. C. Evans, Professor D. Flinn, Dr D. Goldring, the late Dr P. L. Hancock, Mr W. B. Harland, Dr B. E. Hobbs, Dr M. R. W. Johnson, Dr P. J. Leggo, Professor B. Marshall, Professor J. L. M. Morrison and Mrs O. Morrison, Professor M. S. Paterson, Dr P. A. Sabine, the late Professor R. J. G. Savage, the late Professor R. M. Shackleton, Professor D. J. Shearman, Dr D. Shelley, Professor R. L. Stanton, Professor L. E. Weiss, Professor A. J. R. White and Professor E. H. T. Whitten are all thanked for their personal reminiscences. We would also like to thank A. Allan, Archivist, University of Liverpool; Ms R. Banger, Librarian, Department of Earth Sciences, University of Cambridge; Ms M. Farrar, Cambridge University Archives; D. Freeman, Curator, Royal Geological Society of Cornwall; R. Gillanders, Land Survey Records Officer, British Geological Survey National Geological Records Centre; R. Horrocks, Archivist, Liverpool Record Office; F. J. Jeffery, Archivist, Plymouth College; Dr E. Loeffler, Department of Earth Sciences, University of Bristol; D. P. F. McCallum, Board of Graduate Studies, University of Cambridge; Ms P. M. Mellor, Department of Earth Sciences, University of Sheffield; K. Murphy, Executive Secretary, The Mineralogical Society; Professor J. G. Ramsay; Ms N. Steven, Development and Alumni Relations Office, University of Bristol; the late Dr J. C. Thackray, Archivist, The Geological Society of London; Sir Tony Wrigley, Master, Corpus Christi College, Cambridge; Ms W. Cawthorne and other library staff of The Geological Society of London; and G. Waller, Superintendent of the Manuscripts Reading Room, Cambridge University Library; and in Australia: Associate Professor D. F. Branagan, School of Geosciences, University of Sydney; L. T. Dillon, University Archivist, The University of New South Wales, Sydney; Ms O. Doubrovskaya, Senior Records Officer, University of Technology, Sydney;

vii

R. Gurney, University of Sydney Archives; Dr B. Hobbs, Chief, CSIRO Division of Exploration and Mining, Wembley; Professor D. R. Oldroyd, School of Science and Technology Studies, University of New South Wales; and Ms K. Percival, University Archivist, University of Adelaide, for providing us with much useful information. Professors Oldroyd and Branagan, and Dr Peter L. Lowenstein (Zimbabwe) assisted us with determining the location of some of the places visited by Phillips in 1939 and 1953. Stuart Baldwin, Bill George, Wendy Cawthorne, Ms G. Douglas, Librarian and Archivist, Linnean Society, London, and Bob Ellis, Norfolk and Norwich Naturalists' Society, all assisted us to trace the bibliographic reference to Phillips' 1934 Scolt Island study. Graham Chinner, John Cope, John Cosgrove, Derek Flinn, Robert Holdsworth, Michael Johnson, David Oldroyd, John Platt, David Shelley and Jack Soper all provided us with helpful, encouraging (and, in some cases, challenging) comments on various versions of our manuscript. We also thank the following persons and organizations for their permission to use quotations from various letters and sources, and/or permission to reproduce photographs and other illustrative material: The American Geophysical Union, American Journal of Science, Bergen Museum, British Association for the Advancement of Science, Cambridge University Press, Dr G. A. Chinner, Dr J. W. Cosgrove, Professor G. Evans, Dr R. C. Evans, Dr N. Fairbairn, Professor D. Flinn, Gemmological Association, Geological Society of America, Geological Society of London, Professor A. L. Harris, Dr B. Hobbs, Dr M. R. W. Johnson, Professor R. D. Law, Professor G. S. Lister, Professor I. N. McCave, Mineralogical Society, Norsk Geologiske Tidsskrift, Professor M. S. Paterson, Pearson Education Ltd, Mr W. F. C. Phillips, the late Professor N. Rast, Royal Society of Edinburgh, Societe Geologique de Belgique, Dr N. J. Soper, Springer-Verlag Ltd, Mrs S. J. C. Toogood, University of Liverpool, Professor L. E. Weiss, John Wiley & Sons Inc., and Mrs J. H. Winchell. We have tried to contact copyright holders (or their literary executors) for permission in all cases and apologize for any omissions where tracing them has not been successful.

1. Family background and personality

The petrographer,1 mineralogist and structural petrologist,2 Frank Coles Phillips (Fig. 1.1) was born on 19 March 1902, at 19 Lipson Avenue, Plymouth, Devon, the youngest of the three children of Nicholas Phillips, an Inland Revenue officer, and his wife Kate Phillips (nee Salmon). He had an older brother, Richard Salmon (b. 1898) and sister Dorothy Kate (b. 1899). He never liked his first name and subsequently preferred to be called either Coles, a family name (his father's mother was a Coles) or Phil, depending on how well one knew him. The printed labels which identified his many microscope slides of rock thin-sections3 bore the name 'F. Coles Phillips'. He was a thin, rather gaunt figure, who began to go prematurely bald at the age of 28. In consequence, he customarily wore a hat in the field, at first favouring a trilby and later a flat cap. In his early years he smoked a pipe, but this gradually gave way to cigarettes, or the occasional cigar, interspersed by non-smoking gaps which could last a year. One of nature's gentlemen, he inspired a great deal of warmth and affection in all students, and everyone always spoke very highly of him, as both a teacher and a person. However, a colleague from Phillips' time on the staff of the Department of Mineralogy at Cambridge in the 1930s, the

Fig. 1.1. Frank Coles Phillips (1802-1982). Reproduced with the permission of Mr W. F. C. Phillips and Mrs S. J. C. Toogood.

crystallographer Robert C. Evans (b. 1909), recalls (pers. comm. 1999) that while in those days Phillips was courteous to his colleagues, he was never warm, and could appear to be somewhat aloof.4 Phillips had an extensive knowledge of German and French, and 'dabbled' (Anon. 1982) in Russian, Chinese and Italian, all of which were effectively employed during the course of his lifelong research activities. During his career at the universities of Cambridge, Liverpool and Bristol, Phillips was recognized as a marvellously clear and precise lecturer, a very conscientious and diligent supervisor of student practicals, and an excellent systematic teacher. This impression is reinforced by notes taken during his lectures on ore mineralogy by Norman F. M. Henry at Cambridge in 1935 (G. A. Chinner, pers. comm. 1999) and on structural petrology by Mervyn Silas Paterson (b. 1925), during Phillips' lecture-tour in Australia in 1952 (M. S. Paterson, pers. comm. 1998), which attest to the scholarly and precise nature of Phillips' teaching. Although Phillips was perhaps more of a petrographer than a petrologist, he was a wonderful manipulator of the microscope and particularly a special instrument used in conjunction with it to measure certain optical properties of crystals, the Federov universal stage5 (the use of which is described in Chapter 3). He would never leave a practical until the last student had left the laboratory, and would go to immense trouble to help to identify even the most unimportant minor constituent. Disliking arguments, he would try to avoid being involved or taking one side. Just occasionally, however, he could show a moment of irritation, such as when discussing Doris Reynolds' (1899-1985) ideas on metasomatism in the origin of granites, which challenged the then-current view of their magmatic genesis (Reynolds 1946). Nevertheless, he was incredibly reluctant to impose his will on, or to bother, a student. Graham Evans recalls (pers. comm. 1997) that, when undertaking a final-year special project, Phillips felt that students could approach him if they needed help, but that it would be intrusive for him to bother them. With his PhD students, for instance, he maintained the traditional view, long held in Cambridge, that PhD work was a study carried out entirely independently by the candidate and the supervisor's role was limited to agreeing or suggesting the topic and responding to occasional direct requests for help, but not to interfering, or producing solutions; this was the candidate's job. Phillips' natural diffidence meant he was unwilling to decide between competing interpretations for a candidate. As the nature of PhD supervision changed with time, some students looked for more; others, such as David Shelley (pers. comm. 1997), were happy to choose their own areas and topics of research and to be left alone by Phillips to get on with it. From his school-days, when he used to subscribe to Junior Mechanics and, later, to Model Engineer, Phillips' principal hobbies were carpentry and mechanics. In later life he maintained his own workshop and, rather than rely on technicians, made many of the crystal models he used in his lecture demonstrations. (He exhibited a 'Model showing the morphological relationship in twin gliding in calcite' at a meeting of the Mineralogical Society on 9 March 1939.) He also constructed a universal stage for his microscope, a considerable feat of craftsmanship (R. Bradshaw, pers. comm. 1998). A keen horologist, Phillips' house contained a large number of striking and chiming clocks, which were carefully adjusted to strike in sequence in order to avoid an hourly

1

2

THE LIFE OF FRANK COLES PHILLIPS (1902-1982)

cacophony of sound. In an interview with the Adelaide News in 1953, he said he liked to make clocks and 'do curious things by constructing unusual types of clock movements'. These included making clocks showing tidal movements and work calendars. He added 'I make things for my wife like electric mixers - anything in fact that makes the workshop domestically useful'. Mervyn Paterson (pers. comm. 1997) recalls Phillips' arrangements on his bathtub for book reading. He was also an enthusiastic gardener, bookbinder, wine-maker, painter and decorator (the maintenance of his Bristol home has been likened to the painting of the Forth Bridge), a shrewd investor, and a collector of gemstones. During his later years in Bristol, he was appointed a governor of King's School, Bruton, Somerset, to advise on science teaching. A member of the Church of England, he was active in church affairs in Bristol. Following his subsequent move to Brockenhurst, Hampshire, Phillips continued to be closely involved with church activities in his retirement, acting as verger and (together with his wife) custodian of the old church for the many visitors who came on summer afternoons (Mrs S. J. C. Toogood, pers. comm. 1999). Although not one to take part in sports, Phillips was always a brisk walker and when at school used to undertake long walks on Dartmoor. Even when approaching retirement at 65, he could still energetically lead a field class of students from the front. His gentlemanly nature also manifested itself in the field. During an extended visit to Australia in 1953, he greatly impressed the participants on one particular field trip by his willingness to open the many wire gates which had to be passed (G. A. Chinner, pers. comm. 1997). Phillips tended to be a creature of habit: everything in his teaching was done to a set pattern; for example, every other year he went to Cornwall, alternating with North Wales for his secondyear undergraduate field trip. Stopping for afternoon tea was a regular part of the proceedings (even on his Australian field trips, his journal records that he enjoyed the occasional 'tea and scones'). In his lectures, he would use the words 'astonishingly' and 'frantically' (e.g. 'a frantically high refractive index') so often

that the students used to count them: 17 'astonishingly's' and 10 'frantically's' in one lecture was believed to be the record (J. C. Cope, pers. comm. 1999). His fieldwork concentrated on specimen collection and excursion studies, rather than geological mapping, and he preferred not to become involved in the geological interpretation of contentious areas or even to visit research students in the field. This is probably because he did not like making decisions with the inadequate data that characterize geological mapping in poorly exposed areas. Phillips' personal record of his rock collection 'Catalogue of hand-specimens. Recompiled in 1949', an undated foolscap notebook6 (referred to hereafter as Notebook), includes over 4000 entries collected over an unknown period prior to 1925 and subsequently up to February 1964.7 Phillips married (Ruby Barbara) Seonee Barker, daughter of Leon Barker, a civil engineer, and his wife Catherine, at Bournemouth on 19 June 1929. Seonee was born on 17 January 1904 in India; following a fashion for naming children after Indian places, which developed among the British in India during Victorian times, she was named after Seonee Chappara (now called Seoni) on a main railway line in Madhya Pradesh, where she and her sister were born while her father was working on construction of the Indian railways (Mrs S. J. C. Toogood, pers. comm. 1999). Described as a 'tall, imperious person, with a heart of gold', Seonee had a lively sense of humour, and used to undertake a lot of welfare work for the elderly when the family lived in Bristol (Mrs O. Morrison, pers. comm. 1997). She was also a great believer in ghost stories, and in 1957 recounted how, in an extremely old house in Cambridge which was known to be haunted, the family cat would 'suddenly curve its spine and hiss ferociously at a corner of the dining room, apparently seeing the ghost of a former resident' (E. den Tex, W. F. C. Phillips, pers. comms 1998, 1999). Referred to by some in the Bristol department as The Duchess', she was well able to hold her own against the snobbery of wives of some of the more senior academics. They had one son (William, b. 1931) and one daughter (Joanna, b. 1934).

2. School years (1910-1920)

Following a short time at Headland College, Plymouth, in May 1910, Phillips (then aged 8 years 2 months and living at 2 Woodford Villas, Plymouth) joined Plymouth College as a dayboy, a year after his older brother was admitted. It is thought very probable that during his ten years at the school Phillips was greatly influenced by one of the masters, Joseph Thompson (1859-1922).8 School records (F. J. Jeffery, pers. comm. 1997) show that Phillips' career at this time was marked by outstanding academic success. He was awarded the annual Form Prize each year from 1911 to 1916. This was followed by Form Prizes for German, mathematics, natural science and geography (1917); English (1918); French and natural science (1919); French (1920); the Brown Prize for mathematics (1918 and 1920); and the Murch Memorial Prize for natural science (1918-1920); and, in November 1918, he obtained credits in English, French, German, elementary and additional maths, physics and chemistry in the Oxford and Cambridge School Certificate. Despite this daunting record, his school years were not simply devoted to scholastic achievement. In the Natural History Society he was curator of botany in the school museum (1916) and, following the amalgamation of the Natural History Society and the Science Library to form the Natural Science Society in 1916, he became its librarian and treasurer (1917-1920). He also read papers to the Society on: 'Magnetism', The microscope' and 'Petrol motors' (1916); 'Electrical transmission of the voice' and 'Chemistry and the camera' (1917); The origin and manufacture of paper' (1919); and 'How the coin of our realm is made' (1920). An active participant in the Debating Society, in October 1917, Phillips seconded the motion That in the opinion of this House, the British Empire was in greater danger in 1815 than it was in 1914-15'; in November 1917, he proposed that 'Large forests

should be preserved as fuel'; and in January 1920 that The Dartmoor Hydro-electric Scheme should not be proceeded with'; but was unlucky in that none of these motions were carried. He was also secretary of the Photographic Society (1918-1920), editor of the school magazine, The Plymouthian (1918-1920), and librarian of the Junior Library (1919). He was appointed a school prefect in 1918; became joint Captain of North Town House (a position normally only reached by those who excelled at sport; F. J. Jeffery, pers. comm. 1997) in 1918; and Head of School the following year. Pupils at the college were not entirely sheltered from the impact of World War I. There was weekly drill for members of the Officer Training Corps; papers read to the Natural Science Society included such topics as 'Explosives' and 'Poison gases'; and in November 1917, the Debating Society carried a motion that 'Military training should be compulsory for all over 13 years of age'. Phillips attended a six-week Public School Agricultural Camp at Hartland, Devon, in the summer of 1918. Although its purpose was to assist local farmers with bringing in the harvest, for the first time it was run along military lines. The editorial of The Plymouthian for December 1918, written by Phillips and his co-editor, R. A. Emerson, began 'Although the Armistice has been signed, nothing extraordinary in our school life marked the event. However, it has been rumoured that the tuck shop will soon re-open with all its former enticements'. Nevertheless, in that same month, when members of the school entertained the wounded of the nearby Hyde Park Hospital and Wearde Camp with concerts and performances of a sketch, 'Ici on parle Francais' (in which Phillips took part), the Roll of Honour containing the names of former pupils killed in action exceeded 500. In 1919, Phillips gave an illustrated lecture to the Natural Science Society on Tin mining and dressing', '... using photographs of a

Fig. 2.1. Locality map of SW England (black dots indicate places mentioned in text).

3

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local mine to illustrate the different methods employed' (Donnelly 1919). This may have been the Birch Tor and Vitifer mine, which is located on the Dartmoor Granite, just north of Widecombe in the Moor (Fig. 2.1).9 It has been suggested (F. J. Jeffery, pers. comm. 1997) that Phillips' geological interests may have been influenced by Richard Hansford Worth (fl. 1868-1950). Worth, who also lived in Plymouth, was an active member of the Devon Association and published many papers on geological, petrological and archaeological research in Devon,10 including a paper on historical aspects of the tin-mining on Dartmoor (Worth 1914) while Phillips was at school. Phillips' record of his early rock collection includes a specimen11 described as '"Eddystone Gneiss," garnetiferous hornblende schist12 ... given to me by H. Syner, from R. H. Worth' and a comment in Phillips (I964a) shows that this was apparently one of a suite of dredge-haul samples which had been described by Worth (1908). Phillips also noted against a specimen, which he collected in 1955 from the Meldon aplite quarries, Cornwall,13 that it was the 'dark igneous [rock] of R. H. Worth'. Phillips' first printed scientific publication, 'Relativity', appeared

in The Plymouthian (Phillips 1920a, b). This described the results of two expeditions, organized by the Astronomer Royal, Frank Dyson (1868-1939), of Greenwich Observatory and his chief assistant, (Sir) Arthur Stanley Eddington (1882-1944; FRS, 1914) (Learner 1982), to observe the solar eclipse of 29 May 1919 at Sobral, Brazil, and on Principe Island in the Gulf of Guinea. They found that the path of light from distant stars at the solar limb was bent by c. 2 arc seconds as it passed the sun, as a result of the solar gravitational field. Since such a deflection could not be explained by classical theory, this observation was thought to provide experimental support for Einstein's theory of relativity (Learner 1982; Steeds 1990). In December 1919, Phillips was awarded the Oxford and Cambridge Higher Certificate in natural science, physics, chemistry, mathematics, French and German. This was followed, in April 1920, by the award of an Open Exhibition to read science and mathematics at Cambridge. Phillips was also awarded a Joan Bennett Scholarship of the City of Plymouth. He left the school in July 1920 and also successfully passed the Intermediate BSc (London) examination that July, before proceeding to Cambridge.

3. Cambridge (1920-1935)

First degree Phillips entered Corpus Christi College (CCC), Cambridge,14 as an Exhibitioner in September 1920. The following year, he obtained a first class in the Mathematical Tripos, Part I, and was awarded the Manners Scholarship. In 1922 he was awarded a Foundation Scholarship (at CCC) and the Bishop Green Cup, and was appointed to the position of Temporary Demonstrator in Petrology at the Sedgwick Museum, under the supervision of Alfred Marker (1859-1939; FRS, 1902), Reader in Petrology. Phillips was also elected to membership of the Geologists' Association in May 1922. The following year he gained his BA, obtaining a first class in Part I of the Natural Sciences Tripos (geology, mineralogy, chemistry and physics). He was again awarded the Bishop Green Cup and, in addition, the Wiltshire Prize for Geology with Mineralogy.15 He subsequently graduated with a first class in Part II (geology) of the Natural Sciences Tripos in 1924, and was awarded the Cowell Scholarship (CCC). Research studentship The following year Phillips began the research for his PhD dissertation, The Geology of the Shetland Islands, with Special Reference to the Petrology of the Igneous Rocks (Phillips 1927a), under the supervision of Harker with 'assistance' from Cecil Edgar Tilley (1894-1973; FRS, 1938), who was at that time University Demonstrator in Petrology. Phillips was also appointed Student Demonstrator in Mineralogy (1925-1928), under the supervision of the Professor of Mineralogy, Arthur Hutchinson (1866-1937; FRS, 1922)16 with Robert Heron Rastall (1871-1950) and Thomas Crawford Phemister (1902-1982) as his fellow demonstrators. Phillips' financial support was provided by the award of the Amy Mary Preston Read [University] Scholarship and the Caldwell [Research] Studentship (CCC). His fieldwork expenses were partially covered by the award of the Daniel Pidgeon Fund of The Geological Society of London (referred to as the Geological Society hereafter), for 1925, and the costs of his thinsectioning and chemical analysis were to be defrayed by a grant from the Royal Society. During the course of these studies, Phillips was elected to membership of the Mineralogical Society in June 1926 (K. Murphy, pers. comm. 1996) and received his MA on 18 February 1927 (Ms M. Farrar, pers. comm. 1999). Systematic mapping of the Shetland Islands (Fig. 3.1) by staff of the Geological Survey had begun in the late 1920s and continued during the 1930s, with Herbert Harold Read (1889-1970; FRS, 1939)17 working on Unst, and the petrographer James Phemister (1893-1986)18 on Fetlar. However, progress was very slow because staff kept being transferred to other duties. Although a number of individual studies had been published, in 1925 no 1: 63 360 maps had yet been published for Shetland. The igneous rocks of the sills and dykes19 penetrating the Old Red Sandstone20 were known to be interesting (e.g. Peach & Home 1887; Geikie 1897, I, pp. 292-293, 345; Flett 1900), but would not be fully described by the Geological Survey for a long time. Harker later wrote that when the Shetland Islands were chosen as a place which 'would repay investigation by a petrologist', the geology of the whole area was felt to be too large a subject for a PhD dissertation, and that after a general preliminary survey, Phillips should concentrate his work mainly on 'the crystalline

Fig. 3.1. Locality map of the Shetland Islands.

schists, or the plutonic rocks associated with them, or again the much younger igneous rocks of Old Red Sandstone age' (Harker 1927, p. 1). Phillips consequently began his field programme with a general survey of Mainland, the largest of the islands (Fig. 3.1), and detailed collecting and mapping of the Old Red Sandstone and the igneous rocks which lie mainly in the northwestern part of Mainland. However, the course of these studies was disrupted when Phillips discovered that Dr T. M. Finlay (ft. 1925-1935) had been working in the Old Red Sandstone for 'a number of years,' (although by 1925 he had as yet published nothing; Finlay 1926, 1931). Phillips consequently abandoned his own work on the igneous rocks associated with the Old Red Sandstone, apart from publishing his discovery of riebeckite-bearing21 granophyre22 dykes associated with the alkaline 'granite' of Ronas Hill (Fig. 3.1). In this paper, Phillips (1926) gave the first chemical analysis of these riebeckite-bearing dykes and compared it with an analysis of the 'granite' which the dyke cut (both chemical analyses being by himself). He showed that they were so similar that, taken in conjunction with the same granophyric texture in the dyke and in the apophyses23 of the 'granite', the dykes and the 'granite' were derived from the same magmatic activity, with the dykes being the last phase.24 Most importantly, he concluded from petrography that some of the riebeckite, together with associated epidote,25 albite26 and iron ore, constituted pseudomorphs27 after calcic amphibole phenocrysts28 had been reacted upon by alkaline solutions of magmatic origin. Riebeckite also occurred as latestage magmatic crystals in the groundmass with albite and quartz. This evidence of increasing alkalinity of the magma supported the hypothesis that the calcic amphibole had been reacted on by

5

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late-stage hydrothermal solutions29 to produce the observed mineral assemblage. Phillips (1926, pp. 76-77) believed that this evidence supported an Old Red Sandstone (Devonian) age for the alkaline igneous activity. 30 This was of interest because (i) it might have a bearing on the age of similar dykes in the Orkneys, which had hitherto been believed to be Tertiary in age;31 and (ii) a similar suite of rocks, also thought to be Devonian in age, had been reported from southern Finland. The second year of Phillips' PhD now became focused on the petrology of the serpentinites,32 gabbros33 and associated rocks of Unst, Fetlar (Fig. 3.2) and Mainland. His dissertation contains beautifully drawn petrographic sketches as well as photomicrographs.34 This work included a detailed mineralogical study of the chromite35 deposits of Unst, in which he found (in a concentrate from the milled chromite ore) traces of platinum, palladium, iridium and/or 'osmiridium'. He also described the alteration products of the gabbros and peridotites36 (i.e. serpentine, asbestos,37 anthophyllite,38 chlorite,39 magnesite,40 talc,41 dolomite,42 ankerite,43 breunnerite,44 aragonite45 and brucite46) and explained their secondary origin. He postulated that the Unst serpentinite mass was produced by differentiation 47 in situ, with the chromite ore-bodies resulting from the earliest crystallization, immediately followed by olivine.48 This was itself 'closelyfollowed' by the intrusion of gabbro, later 'pegmatoid-gabbro' veins and, finally, hydrothermal alteration. In view of the fact that much of Phillips' later work was devoted to the microscopical study of rock fabrics in the Western Highlands of Scotland, it seems particularly ironic that in his PhD dissertation, he dismisses what is believed (D. Flinn, pers. comm. 1996) to be the first attempt, by the antiquary and geologist Samuel Hibbert (1782-1848), to describe lineation49 (Hibbert 1822, pp. 27-28, 80, pl. I) attributable to the elongation of the mineral grains making up a rock (Fig. 3.3) and to map the changes in its orientation throughout Shetland (Hibbert 1822, pl. VIII), as being 'of historical interest only' (Phillips 1927a, p. 4, 1927c, p. 623).50 We would agree with Flinn (pers. comm. 1999) that the handcoloured regional geological map of the Shetland Islands at a scale of 1 inch to 5 miles (1 in:5 mi or 1:316 800) in Phillips' dissertation appears largely to follow the earlier work of Heddle (1878a, b, c, 1879) or Peach & Home (1879, 1887). Certainly, Phillips' map of Unst and Fetlar (Fig. 3.2) closely resembles Heddle's maps of Unst (Heddle 1878a, pl. I, ff. p. 12) and Fetlar (Heddle 1878b, pl. III, ff. p. 114). Flinn (pers. comm. 1999, 2001) suggests that Heddle, Peach and Home all produced their maps by transposing Hibbert's (1822, pl. VIII) geological map onto a more modern base, which resulted in the addition of a few errors. Furthermore, although Phillips was the first to identify the protoliths51 of the serpentinite mass, his attempt to show their spatial distribution (Fig. 3.4) appears to be extremely generalized.52 However, we would argue that the lack of what would be considered, by modern standards (or even those of the Geological Survey in the 1930s and 1940s), detailed geological mapping (cf. Fig. 3.5) in Phillips' dissertation resulted from the lack of emphasis placed by the Department of Mineralogy on such issues, both during his undergraduate years and subsequently. This view appears to be supported by Harker's (1927) comments as internal examiner of Phillips' PhD dissertation. He felt that Phillips' work showed all the signs of sound inference on the basis of keen observation and that Phillips was always careful to distinguish 'what is proved from what is conjectured'. Moreover, his geological map was in itself considered by Harker to be a useful contribution representing 'a considerable advance upon those already published' (sic), while Phillips' more detailed maps were evidence of 'careful study of the field relations of the various igneous rocks dealt with'. While it is possible that it is Phillips' field maps which were being referred to in Harker's second comment, the only maps of Unst and Fetlar in his thesis are the same as those in his later publication (Phillips 1927c), reproduced here as Figures 3.2 and 3.4.

Fig. 3.2. Geological map of Unst and Fetlar, Shetland Islands. Reproduced with the permission of Mr W. F. C. Phillips and The Geological Society, London, from figure 1 of F. C. Phillips, 1927, 'The serpentines and associated rocks and minerals of the Shetland Isles', Quarterly Journal of the Geological Society, London, 83, 622-651.

What is considerably less easy to explain, particularly in view of Harker's comments, is what led Phillips to apparently reverse in his map the areas occupied by peridotite and dunite53 in his description of the Unst serpentine body (compare Figs 3.4 and 3.5). This is not just an accidental transposition which occurred when writing the legend for his map (Fig. 3.4), as it is corroborated in his text. We return to this point below. Harker also commended the quality of Phillips' photomicrographs, commenting that 'photographic reproduction is, as a rule,

CAMBRIDGE (1920-1935)

7

Fig. 3.3. Lineation in Moine schist, Glenshiel. Reproduced with permission of the author and the publisher from figure 55b of L. E. Weiss, 1972, The Minor Structures of Deformed Rocks, Springer, Berlin, copyright © 1972 Springer-Verlag,

ill adapted to rock slices, and many published illustrations of the kind are of little value, but here the subjects have been so well selected that almost every figure is clear and instructive' (Harker 1927, pp. 1-3). The external examiner, the senior Geological Survey petrographer Herbert Henry Thomas (1876-1935; FRS, 1927), wrote (Thomas 1927) that Phillips, whose views had, he felt, been expressed with 'pleasing moderation,' had made an excellent job of elucidating the geology of a somewhat remote and geologically complex area. Thomas also singled out for praise Phillips' petrographical study of the gneisses54 and ore-bodies. He had no hesitation in agreeing with Harker's conclusion that the dissertation was 'a thoroughly good piece of work' (Harker 1927, p. 3) and recommended Phillips for the degree of PhD. The correspondence (Harker 1927; Thomas 1927) suggests that Phillips successfully passed the oral examination on 20 June 1927. The award of his degree was formally approved by the Degree Committee on 19 October and Phillips received his PhD on 28 October 1927 (Ms M. Farrar, pers. comm. 1999). As has been noted, the principal results from the second year of Phillips' doctoral study were subsequently published (Phillips 1927b,c) and a further paper (Phillips 1928a) described an epidote-allanite55-xenotime56 granite and a chlorite-garnetandalusite57 schist from Shetland, and an occurrence of a serpentine mineral from Unst. In the year in which Phillips completed his dissertation, a German geologist, Gustav Steinmann (1856-1929), first drew

attention to the apparent genetic connection between the occurrence of serpentinites and associated ultramafic rocks, with deepwater sediments, such as spilites58 and chert59 (Steinmann 1927). However, it was not until the late 1960s that the meaning of this association began to be understood. This came about as a result of the discovery of mid-ocean ridges and the subsequent realization that sea-floor spreading took place. By 1970, the analogy between such 'ophiolite complexes' and the structure of the upper mantle beneath the Mid-Atlantic Ridge had become generally accepted (Nicolas 1989, p. 4). Subsequent research (Anon. 1972) showed that ophiolite complexes are not restricted to what were midocean ridges, but may also incorporate rocks from island-arc and marginal basin settings (Coleman & Irwin 1974). Reinterpretation of Alpine 'green rocks' by workers such as Ian Graham Gass (1926-1992; FRS, 1983) and Robert Coleman (Gass 1967; Coleman 1971) also suggested that ophiolite complexes can represent fragments of oceanic lithosphere thrust up over continental margins. In the Shetland Isles, work by Read and J. Phemister (in Wilson et al 1931; Read 1934a) and Flinn (1958) provided the first detailed maps of the structure of Unst and Fetlar. However, it was not until almost 50 years after Phillips' study that it was realized (Garson & Plant 1973) that the 'serpentine,' 'pyroxenite' and 'greenstone' (gabbro) association represents an ophiolite complex, now tilted on its side and emplaced on top of metasediments. Subsequent studies (Flinn et al. 1979; Flinn 1985; Pritchard 1985) have provided increasingly detailed knowledge regarding these

8


Fig. 3.4. Geological map of the 'Unst intrusion', Shetland Islands. Reproduced with the permission of Mr W. F. C. Phillips and The Geological Society, London, from figure 2 of F. C. Phillips, 1927, The serpentines and associated rocks and minerals of the Shetland Isles', Quarterly Journal of the Geological Society, London, 83, 622-651.

rocks. The lowest part of the sequence, the peridotite serpentine (Iherzolite-harzburgite), is interpreted as representing residual mantle; the chromite-bearing, banded (layered), dunite-wehrlitepyroxenite rocks were crystallized at the base of the magma chamber; and the gabbro formed after further fractionation in the chamber.60 The chromite-bearing dunite lenses are believed to have been produced by magma rising up through the harzburgite. Finally, lavas fed upwards, to form a sheeted dyke complex in the gabbro at the top of the succession, together with volcanic cap rocks (see Pritchard 1985, figs 1, 3, 13). Many of these rocks were subsequently altered by extensive serpentinization (through reaction with hydrothermal solutions, most probably seawater heated by proximity to the magma chamber) prior to being emplaced. The associated melanges,61 consisting of metasediments containing ophiolite debris, are similar to those found in conjunction with ophiolite complexes elsewhere, which have been interpreted (Coleman & Irwin 1974) as being structures which mark the boundary of the suture zone within which the ophiolite complex occurs. At the time Phillips was working on his PhD, there appear to have been a number of different views on the nomenclature of the ultrabasic rocks in question. For example, in the discussion

following the reading of Phillips' paper at the Geological Society, the igneous petrologist Alfred Kingsley Wells (1890-1980)62 suggested that all three members of the ultrabasic intrusion could properly be called peridotite, 'in the sense that they were all felspar-free, olivine-rich, ultrabasic plutonic rocks' (Wells in Phillips 1927c, p. 651); dunite could also be defined (Holmes 1928, p. 85) as a chromite-bearing peridotite consisting 'essentially' of olivine. Phillips (1927c, p. 652) explained that his nomenclature dunite, an olivine (forsterite) rock; peridotite, an olivine-augite (clinopyroxene) rock; and Iherzolite, an olivine-enstatite (orthopyroxene)-augite rock - was consistent with that recommended by the 'British Committee' (Committee on British Petrographic Nomenclature 1921). Phillips (1927c, p. 622) believed that the serpentine and gabbro complex, as a whole, represented an intrusion 'injected' into the schists which, as remarked above, had 'undergone differentiation in situ' (Phillips 1927c, p. 645). He considered that its western margin on Unst (where it was 'faulted' against the schists of the country rock) with its associated zone of highly altered serpentine and carbonate rocks63 represented the hydrothermally altered western boundary of the intrusion. Phillips' (1927c) text suggests that his interpretation, as shown in his map of the


9

Fig. 3.5. Geological map of Unst and Fetlar, Shetland Islands. Reproduced with permission of the author and The Geological Society, London, from D. Flinn 1958, 'On the nappe structure of north-east Shetland', Quarterly Journal of the Geological Society, London, 114, 107-136. This map has been used at the suggestion of Professor Flinn (pers. comm. 2001) in preference to his more recent work (Flinn 1985, 1999) as it was an edited 'close copy' of the geological maps of Unst and Fetlar made by Read and Phemister in the 1930s.

complex (Fig. 3.4), may have been misled by a combination of factors. (i) We have suggested that he would have almost certainly had little training in field mapping, and Pritchard's (1985, p. 1174) account makes it clear how complex the nature of the extremely altered serpentine is, with 'dykes' of dunite occurring within the harzburgite (the olivine-orthopyroxene rock, which is believed to represent residual mantle, and which actually lies below the dunite; Pritchard 1985, fig. 13) at all levels. (ii) Phillips was misled by Bowen's (1915, 1928) theoretical model for the progress of differentiation in such a body as a

result of progressive crystallization, in which the early crystallization of spinel would be followed by forsterite and 'the inevitable result would be a body consisting of calcic plagioclase, olivine and magnesian pyroxenes' (Bowen 1915, quoted in Phillips 1927c, p. 646). (iii) From study of thin-sections of the serpentine, Phillips correctly interpreted the presence of bastite pseudomorphs64 as indicative of the presence of pyroxene, but he believed (Phillips 1927c, p. 628) that this was the next phase to separate from the melt; 65 he also correctly recognized (cf. Pritchard 1985, p. 1180), that some of the orthopyroxenes overgrew earlier olivines and clinopyroxenes. (iv) At the time of Phillips' work, there was absolutely no reason


10

for him to suspect that the olivine-rich pyroxene-bearing rock, Iherzolite, whose presence he noted (Phillips 1927c, p. 628), represented anything other than part of the magma chamber within which the chromite had precipitated. (In fact, as has been noted, the Iherzolite-harzburgite, in modern times interpreted as probable mantle rock, must lie below this horizon.) Furthermore, following Bowen's model, Phillips (1927c, p. 645) believed that deposition of the chromite would be greatest where the cooling rate was 'most accentuated', and that this would be adjacent to the 'margin of the intrusion', characterized by the major deposit at Quayhouse, and that the 'sporadic' occurrence of the other deposits was attributable to the 'lack of carriage to completion' of the gravity-settling process.66 It is therefore suggested that Phillips' 'sketch map' of the intrusion (Fig. 3.4) is intended to reflect his conceptual model of the results of the 'differentiation in situ' rather than the reality on the ground.

Post-doctoral work Phillips was elected to a CCC Research Fellowship in October 1927. The following month, he was proposed for Fellowship of the Geological Society by Harker, Tilley, John Edward Marr (1857-1933; FRS, 1891), professor at St. Johns College, and Walter Campbell Smith (1887-1988), who was a Corpus Christi graduate (J. C. Thackray, pers. comm. 1996). Phillips was formally elected the following January. The first published results arising from work done as a research fellow appeared surprisingly quickly in December 1928 when Phillips (1928b) published the first of his investigations, which intermittently continued for 40 years, into the petrology of the metamorphic rocks67 of SW England. This was a study of the metamorphism of the Upper Devonian rocks of north Cornwall, east of Camelford and north of the Bodmin Moor granite (Fig. 2.1). It is probable that Tilley suggested the area to Phillips as Tilley (1923) had already published on the Start Point rocks and also on some chloritoid68 rocks (Tilley 1925a) including those of Tintagel, Cornwall. Phillips did not undertake any mapping, other than tracing with thin-sections the outer aureole69 of the granite, but studied the thermal metamorphism70 of the phyllites,71 especially the chloritoid and garnet-bearing varieties. He concluded that the porphyroblastic72 white mica, chlorite and chloritoid, previously ascribed to the thermal metamorphism, were crystallized during an earlier pre-granite dynamic metamorphism.73 In October 1928, Phillips was appointed University Demonstrator (in Mineralogy), while Tilley was promoted to Lecturer in Petrology. Robert Evans (pers. comm. 1999) recalled that although Phillips was elected to a Research Fellowship, this was not continued as an Official Fellowship when he got his University appointment, and I think this rankled. I think it is probably true that Tilley did not help much in this matter ... but at the time Colleges could not afford to elect fellows unless they could bring with them the promise of a substantial contribution to College undergraduate teaching. Scientists could rarely afford the time for this and in a subject such as mineralogy the numbers were far too small. Thus there were many who held a University post but no College fellowship. By 1929, the Department of Mineralogy had largely evolved into a school of crystallography and crystal physics, whereas the study of petrology had progressed quite separately under Harker at the Sedgwick Museum. The staff consisted of Hutchinson; the Irish X-ray crystallographer and physicist John Desmond Bernal (1901-1971; FRS, 1937), who had been appointed University Lecturer in Structural Crystallography in 1926; and William Alfred 'Peter' Wooster (1903-1984) and Phillips as University

Demonstrators. Wooster had graduated in physics in 1924 and was appointed Demonstrator in 1927 (Anon. 1984); he would spend his entire career in Cambridge, specializing in crystal physics. Under Hutchinson, mineralogy was strictly classical, based on descriptive mineralogy and morphological crystallography (R. C. Evans, pers. comm. 1999). Hutchinson taught the general elementary course. Bernal was principally concerned with maintaining the X-ray equipment and instructing students in its use and the interpretation of the results (Bernal 1926). Wooster and Phillips both assisted with the general course. In addition, Wooster lectured on the physical properties of crystals, while Phillips demonstrated the optical properties of minerals 'which are of especial importance to Petrologists' (Seward et al 1929) and assisted students with the chemical analysis of rocks and minerals. Lecturing conditions must have been somewhat daunting since the room in which they took place consisted of half an old wooden hut with a leaky roof which was often too cold for comfort in the winter and became unbearably hot in the summer (Seward et al. 1929). Although students were encouraged, if they so wished, to attend lectures on economic geology and petrology in the Sedgwick Museum, the majority attending the mineralogy course also took classes in physics, chemistry and mathematics rather than geology (Seward et al. 1929, appendix, table III).

The Green Bed study On 5 November 1929, Phillips read two papers at the Mineralogical Society, one of which was on 'Some mineralogical and chemical changes induced by progressive metamorphism in the Green Group of the Scottish Dalradian' (Phillips 1930a). This formation (subsequently known as the 'Green Bed') is a discontinuous series of volcanic tuffs within what is now called the Southern Highland Group of the Upper Dalradian, which can be traced along its SW-NE strike across the Central Highlands (Fig. 3.6). This sequence, consisting predominantly of deep-water sediments, also includes basic volcanic lavas and ashes. It is now thought to have been laid down during the late Cambrian (c. 520-500 million years (Ma) ago) and later subjected to regional (Dalradian) metamorphism (c. 520-490 Ma ago), although cooling continued until c. 390 Ma ago (Johnson 1991). The object of Phillips' study, 'encouraged and assisted by Harker and Hutchinson', with some handspecimens provided by Tilley, was to investigate the nature of changes induced, particularly in plagioclase74 compositions, as one progressed northwards from regions of lower-grade75 metamorphism in the SW into higher-grade regimes. Index minerals defining zones of increasing intensity of regional metamorphism had been recognized in the Scottish Highlands since the pioneering work of George Barrow (1853-1932) at the end of the nineteenth century (Barrow 1893). The Green Bed study was prompted by the introduction of the concept of metamorphic fades by the Finnish geologist Pentti Eskola (1883-1964) in 1919-1920. Eskola (1922) defined a metamorphic facies as 'a group of rocks characterised by a definite set of minerals which, under conditions obtaining during their formation, were in perfect equilibrium with each other'. Tilley (1922, 1923, 1924, 1925a, b) had begun to apply these new ideas in the United Kingdom. In fact, he had already discussed the mineralogy of the Green Bed (Tilley 1923) and used it as an example when he subsequently introduced the term isograd (Tilley 1924, p. 169) to describe a line on a map which joins points of similar pressure and temperature conditions in a suite of metamorphic rocks, as inferred from the entry of a particular mineral, such as chlorite or biotite,76 into their mineral compositions. Even so, he felt that there was still a need to determine the chemical compositions of both the bulk rock and individual minerals in order to obtain greater insight into the chemical changes which took place during the metamorphic process (Phillips 1930a, pp. 8-9). Only one previous major element chemical analysis77 of the


11

Fig. 3.6. Sketch-map to show the approximate location of the 'Green Beds' within the Upper Dalradian rocks of the Central Highlands of Scotland. Redrawn with the permission of The Mineralogical Society from figure 3 of F. C. Phillips, 1930, 'Some mineralogical and chemical changes induced by progressive metamorphism in the Green Group of the Scottish Dalradian', Mineralogical Magazine, 22, 239-256, with additional geological detail based, with the permission of Professor N. Rast, on an extract from figure 1 of N. Rast, 1963, 'Structure and metamorphism of the Dalradian rocks of Scotland', in Johnson, M. R. W. & Stewart, F. H. (eds), The British Caledonides, Oliver & Boyd, Edinburgh, 123-142.

Green Bed schists (from Ardlui, Loch Lomond) existed (Anon. 1904, pp. 57-58). Phillips had five more analyses made of rocks from Argyllshire, Perthshire and Forfarshire which spanned the range of increasing metamorphic grades. Phillips found that the Green Bed compositions ranged from 46% to 73% silica (SiO2), and it therefore became essential to examine the elemental variation independently from that of SiO2.78 Because of Phillips' familiarity with German, he became aware of developments published only in that language sooner than most British petrologists and geologists. He now made a perceptive and yet early use in Britain of the system of so-called Niggli values (Niggli & Beger 1923; Niggli 1924), devised by the Swiss geochemist and mineralogist Paul Niggli (1888-1953) for representing chemical analyses of rocks.79 Niggli's method has the advantage of considering element content not as weight percentage of oxide but in terms of molecular amounts of oxides. This much more fundamental representation enables equal combining-power to be established. Most importantly, however, the molecular amounts of the aluminium, calcium, sodium, potassium, iron, magnesium and manganese oxides are calculated independently of the SiO2 content of the rock. This means that element variations attributable solely to variation in SiO2, the largest common variable in rock compositions, are nullified. Using a ternary plot80 based on the relative proportions of the Niggli values a/, alk and c/fm (Fig. 3.7) and a bivariate plot of Niggli mg versus k, Phillips was able to show in each case that, despite large variations in si, the Green Bed schists could be considered essentially isochemical in nature.81 It then remained to investigate whether there were significant changes in the composition of the ubiquitous plagioclase feldspars with increasing metamorphic grade. Fortunately, plagioclase compositions (defined in terms of the relative proportions of their albite-anorthite end-members) can be estimated by means of measurement of the optical properties of the crystals. The universal stage An ordinary petrological microscope has only one stage,82 which rotates horizontally (or nearly so) about a single vertical axis only; so in order that the orientation of the optical axes of individual

Fig. 3.7. Ternary diagram to show that the chemical composition of the Green Beds, in terms of relative proportions of Niggli al, alk, c/fm and si (the value written by each point), is homogeneous and falls into the field for basic igneous rocks. Reproduced with permission of Mr W. F. C. Phillips and The Mineralogical Society, London, from figure 1 of F. C. Phillips, 1930, 'Some mineralogical and chemical changes induced by progressive metamorphism in the Green Group of the Scottish Dalradian', Mineralogical Magazine, 22, 239-256.

12


grains lying in any three-dimensional position can be measured, it is necessary to use a so-called universal stage (Fig. 3.8), developed by the Russian crystallographer Evgraf Stepanovich Federov (1853-1919) (Fedorov 1891, 1892, 1893). This accessory (Fig. 3.9) enables a thin-section to be tipped and rotated into almost any three-dimensional position as it allows a notional (notional because it assumes the microscope user sits facing the north) east-west tilting about a horizontal notional north-south axis; a notional north-south tilting about a horizontal notional east-west axis; and rotation about vertical axes both outside and inside the above two axes. The complex optical effects of reflection and refraction caused by tilting the thin-section are minimized by temporarily adhering two glass hemispheres to the thin-section, one above it and the other below (the upper hemisphere is visible in Fig. 3.9). The inside, or inner stage, is of necessity quite small in area, because of the restricted space and the need to avoid the use of larger than necessary glass hemispheres, so special, small-sized thin-sections have to be employed in this work. Phillips now had to learn how to make such measurements, using a microscope provided with a universal stage which had been purchased by the department during the 1927-1928 academic year (Hutchinson 1929).

Stereographic projection Interpretation of universal stage results necessitated familiarity with the manipulation of three-dimensional orientation data using Stereographic net methods. The Stereographic projection has a long history (Howarth 1996a), which can be traced back to the work of the astronomer Hipparchos (ft. 180-125 BC). He devised the method in order to project the positions of stars in the celestial sphere onto an equatorial plane, so as to construct maps of the heavens (for examples, see Snyder 1984). Figure 3.10, based on a crystallographical example in Phillips (1946), illustrates the principle of the projection. Consider a crystal to be placed at the centre of a sphere. Now imagine performing the following steps: (i) construct the normals (perpendiculars) to the crystal faces by extending straight lines from the centre of the sphere outwards, through the mid-point of each face forming the upper half of the crystal, until these lines touch the inner surface of the upper hemisphere; (ii) mark these points, the poles; (iii) now construct a new set of straight lines joining each of these poles to the nominal south pole. The upper hemisphere equatorial Stereographic projection corresponds to the locations of the points where these lines cut the equatorial plane. In practice, given the orientation data for the faces, the required points are generally plotted directly onto a sheet of semi-translucent paper laid over a Stereographic net. Fig. 3.11 shows an example of such a net, marked out with a 2° mesh of meridians of (nominal) longitude and parallels of (nominal) latitude.83 Mineralogists first adopted the Stereographic projection, to enable them to present a synoptic view of the orientations of crystal faces, in about 1820. Federov later adopted it, in the 1880s, to portray results obtained with the universal goniometer, an instrument which he had developed to enable the accurate measurement of the interfacial angles of crystals.84 His subsequent invention of the universal stage (Fedorov 1891), described above, was underpinned by his development of methods to interpret the measurements obtained with it, by means of the Stereographic projection.85 An additional advantage of the graphical approach based on manipulations using the Stereographic net is that the geometrical operations required to undertake three-dimensional rotations of points and planes in the sphere can be accomplished very easily.

New skills

Fig. 3.8. Microscope fitted with a Federov universal stage. Reproduced from figure 326 of A. Johannsen, 1918, Manual of Petrographic Methods, Hafner, New York.

Phillips learnt the necessary universal stage techniques (Fedorov 1892, 1893, 1897) from Campbell Smith86 and quickly made use of his new skill. His first publication involving the use of the universal stage was published in December 1929. This concerned the correlation between composition and optical properties in both pericline and acline-A twinning 87 in plagioclase (Phillips 1929). This was followed by his paper on the Green Bed, published in June 1930 (Phillips 1930a); and a third contribution, describing an enstatite-anthophyllite88 rock, appeared in November 1930 (Phillips 1930b). On the basis of his universal stage work, Phillips was able to show that as one progressed northeastwards along the strike of the Green Bed (Fig. 3.6), and the metamorphic grade correspondingly increased89 through the chlorite, biotite, garnet, and kyanite to sillimanite 90 zones, it was found that the average plagioclase (albite-anorthite) composition in the schists gradually changed from containing 90-95% of the albite end-member to 63%; similar variation was also shown in the epidiorite91 sills (100% albite, again decreasing to 63%). Furthermore, he was able to show that where the plagioclases in the schists were zoned,92 the cores of the crystals were less anorthitic than their outer shells (the reverse of the situation commonly found when feldspars had crystallized from a melt). Phillips inferred that the regional metamorphic zones, which were interpreted as being 'primarily temperature-controlled', were actually being influenced by the


13

Fig. 3.9. View of a universal stage (c. 1929) showing the four axes (A1, A2, A3, A4; nomenclature of Berek 1924) about which the thin-section can be rotated. Reproduced, with the permission of Mrs J. H. Winchell from figure 86 of A. N. Winchell 1937, Elements of Optical Mineralogy. Part /, Wiley, New York.

Fig. 3.10. View of the poles to the normals of the faces of a crystal and their upper hemisphere equatorial stereographic projection. Open points lie in the rear half of the upper hemisphere. Adapted with the permission of Mr W. F. C. Phillips and Pearson Education Limited from figure 30 of F. C. Phillips, 1946, An Introduction to Crystallography, Longmans, Green, London.

high-temperature, high-pressure conditions intrusion of the 'Older Granites'.

caused

by the

Departmental reorganization In 1929, the impending simultaneous retirement of both Harker and Hutchinson in 1931 prompted the university to review the

Fig. 3.11. Wulff equatorial stereographic net; 2° mesh with 10° lines shown bolder. Notional north is at the top of the figure. Reproduced with the permission of Mr W. F. C. Phillips from figure 86 of F. C. Phillips, 1960, The Use of Stereographic Projection in Structural Geology, Edward Arnold, London.

positions of the hitherto separate departments of mineralogy and petrology (Seward et al. 1929). It was eventually recommended that a new Department of Mineralogy and Petrology be established, and that crystallography (up to then within the Department of Mineralogy) should become a subdepartment of the Cavendish Laboratory. Tilley was appointed Professor of Mineralogy and Petrology in 1931, to head the new department (a position he was to retain until his retirement in 1961) and Phillips was appointed Assistant Director of Studies in Natural Sciences (CCC). The following year, Phillips was appointed University

14


Lecturer in Mineralogy and Petrology, and was also elected to the Council of the Mineralogical Society (1932-1934). Tilley was a brilliant petrologist, favoured with a photographic memory. Following a year's sabbatical at the Geophysical Laboratory of the Carnegie Institution of Washington in 1927, he had also acquired a keen interest in experimental petrology.93 When Tilley took up his position in 1931, he wanted to add crystal physics, crystal chemistry and X-ray crystallography to the Tripos. Robert Evans and Wooster were accordingly appointed to the teaching staff, in 1933 and 1935 respectively, on completion of their PhD degrees at the Cavendish Laboratory, to cover these subjects. Harker still appeared occasionally in the department and Rastall did a little teaching in the practical classes (R. C. Evans, pers. comm. 1999; Anon. 1984). Tilley disliked administration, and 'as a perfectionist his preoccupation in conducting his department, coupled with his natural shyness, led him to present ... a rather brusque and occasionally forbidding front. ... For many who knew him only in Cambridge, his fundamental warmth was revealed when on retirement he shed the anxiety of office' (Chinner 1974, p. 494). It has been said that a cleaner in the department once remarked Tilley may be the Professor but Coles Phillips is the gentleman'. However, Robert Evans recalls that although Phillips was courteous to his colleagues, he was never warm.94 He writes: some of the Corpus imagined 'superiority' rubbed off on to Phil in little ways, and in the lab he made it clear at the daily tea party of staff and research students ([which] Tilley never attended) that he was the senior person and should sit at the head of the table. On one occasion I introduced a guest whom Phil received in a polite but rather cool manner. On some later occasion, the guest's name was mentioned and I remarked that he too was a Corpus man. 'Oh', said Phil, 'If I had known he was from Corpus, I would have unbent a little.' (R. C. Evans, pers. comm. 1999).

There is evidence that Phillips acted as curator during the time of the transition from the Mineralogy Department to Mineralogy and Petrology, introducing in 1932 a new cataloguing system which followed that adopted by the Mineral Department of the British Museum. In the following year he examined the mineral collection of the crystallographer William Hallowes Miller (1801-1880; FRS, 1838),95 formerly Professor of Mineralogy at Cambridge, to see if it was of interest for possible addition to the Cambridge collections (G. A. Chinner, pers. comm. 1999). During these early years, Phillips' publications were conventional studies in petrography (Phillips 1928a, b, 1930a, b, 1934) or mineralogy (Phillips 1929, 1931a, 19320; Phillips & Wooster 1933). His final publication on Shetland (Phillips 1930b) described the intergrowth of enstatite and anthophyllite in which universal stage measurements of the optic axial angle of the pyroxene and its positive sign confirmed the pyroxene as enstatite. The pyroxene was interpreted as crystallizing around the anthophyllite and being later.96 Possibly as a result of his detailed examination of the Unst chromite with its opaque ferritchromite (see Fig. 3.4 for locations of these deposits), Phillips had become increasingly interested in determinative methods for opaque minerals, especially in the problems of determining the indices of refraction, absorption and reflectivity accurately (Phillips 1931b,19326,1933) and, probably in 1933, he began teaching a course in ore-mineralogy (G. A. Chinner, pers. comm. 1999). Phillips' publications on optical theory and practice show that by the early 1930s, he was not only a master of quite abstruse transmitted and reflected light theory, but also an expert in the practical manipulations needed to obtain the measurements necessary to identify minerals. He was also contributing fundamental data on the reflection properties of opaque minerals which, at that time, were much less well known than transmitted light properties. He later developed an ore-polishing machine (Phillips 19370), and he remained keenly interested in the construction of such equipment thereafter.

4. Petrofabric research

Basic principles Exactly what first attracted Phillips' attention to the new science (Sander 1930) which became known as petrofabrics 97 (Sander 1934) or structural petrology 98 in the English-language literature is not known, but Phillips' interest in this topic probably began during the course of his 'Green Bed' study. Petrofabrics is concerned with measuring the three-dimensional geographical orientation of mineral grains in rocks, primarily in order to deduce the directions of the tectonic forces responsible for making any preferred orientations detected. It had long been appreciated, from field and laboratory studies on rocks (and also from metallurgical studies), that rocks deform under tectonic forces by recrystallization of existing minerals, chemical reactions producing new minerals, and by rotation of the mineral grains. In combination, these three processes construct in the rock a new texture or fabric, which reflects the tectonism that produced it. In order to determine the spatial orientation of this fabric correctly, it is therefore necessary to collect rock samples which are carefully orientated geographically. This is achieved in each case by making suitable marks on the surface of the rocks, defining the geographical and spatial orientation of each specimen, before it is removed from the outcrop." This enables the orientation in the field to be precisely transferred right through to the final thin-section of the rock. The thin-section is cut from the field sample in a known orientation with regard to any visible foliationplane100 or lineation in the rock, and the thickness of the rock in the thin-section is reduced by cutting and grinding to 0.03 mm, thin enough to allow the transmission of light for microscopic study. Two minerals are particularly useful and easy to study by petrofabrics: mica and quartz. Both are very common, and often abundant, minerals in metamorphic rocks. Mica has one very good cleavage plane,101 which is readily recognized in thin-section, and the orientation of the normal to this basal {001}-cleavage (Fig. 4.1a) can be measured. The platy crystals are generally aligned with {001} parallel to any planes of schistosity or foliation in the rock. Quartz has only one optic axis, coincident with its crystallographic c-axis, i.e. {0001} axis (Fig. 4.1b), and the orientation of this axis can be quickly ascertained. Quartz grains in sediments may be elongate both parallel to the c-axis (Wayland 1939; Ingerson & Ramisch 1942) as well as to the rhombohedral {1011} zone faces (Ingerson & Ramisch, 1942; Bloss 1957), hence the crystallographic c-axis need not necessarily coincide with the longest shape-axis of a grain. In high-grade metamorphic rocks, such as schists and gneisses, formed under conditions of high pressure and temperature, the relationship becomes even more complex. The quartz crystals in such rocks have irregular boundaries and no longer exhibit crystal faces. The patterns of preferred orientation shown by their c-axes may be weak, or even random (often as a result of recrystallization), but are more commonly exhibited as sets of axes normal to one, two or three planes of symmetry, and often show a complex relationship to any visible lineation in the rock.102 By measuring the orientations of a few hundred quartz or mica grains by means of a universal stage, a composite picture is obtained for a particular rock specimen. Then, since the original orientation of the specimen in the field, and that of the thinsection made from it, are known, the equivalent orientations of the quartz or mica grains in the field can be determined. The necessary corrections to the raw universal stage measurements

Fig. 4.1. (a) Mica crystal showing the normal to the {001} basal cleavage, (b) Quartz crystal showing location of the crystallographic (optic) c-axis or {0001} -axis.

required to obtain these results are most conveniently handled by means of graphical techniques103 based on the principle of stereographic projection, discussed earlier.

Sander's petrofabric method Petrofabric methods were originally devised by the Austrian mineralogist, Walter Schmidt (1885-1945), but his techniques, and

15

16


methods for interpretation of the results in structural terms, were significantly extended by his fellow countryman, the geologist Bruno Hermann Max Sander (1884-1979) in the mid-1920s. Although their early work on the preferred crystallographical orientation of mineral grains in deformed rocks began with twodimensional analyses (Sander 1911), by 1925 both Schmidt and Sander had the use of a universal stage, thus enabling determination of the disposition in three dimensions of the optic c-axes of quartz, or the normals to the basal cleavage of mica. In the case of structural (as opposed to crystallographic) measurements, it generally became conventional to plot data with reference to the lower hemisphere.104 Figure 4.2a shows the lower hemisphere cut by a plane passing through the centre of the

reference (or projection) sphere and dipping to the lower right of the figure. The stereographic projection onto the equatorial plane of the intersection of the dipping plane with the lower hemisphere of the enclosing sphere can be seen in Figure 4.2b. The position of the normal to the plane at the centre of the projection sphere and its stereographic projection onto the equatorial plane is shown in Figure 4.3a. Finally, Figure 4.3b shows the completed equatorial stereographic projection, as would be obtained by plotting the data using a net like that of Figure 3.11. In the case of observations taken from nature, there is a natural statistical variation in the orientation directions being measured (because no planar feature will be absolutely flat) and there will an unavoidable, although relatively small, error inherent in both

Fig. 4.2. (a) Intersection of a dipping plane with the lower hemisphere, (b) View of lower hemisphere equatorial stereographic projection of the intersection of the plane with the projection sphere. Redrawn, with permission of Professor B. E. Hobbs, from figure Al of B. E. Hobbs, W. D. Means & P. F. Williams, 1976, An Outline of Structural Geology, Wiley, New York.

Fig. 4.3. (a) View of lower hemisphere equatorial stereographic projection of the plane and the normal (pole) to the plane, (b) Lower hemisphere equatorial stereographic projection of the plane and the normal to the plane. Redrawn, with permission of Professor B. E. Hobbs, from figure A6 of B. E. Hobbs, W. D. Means & P. F. Williams, 1976, An Outline of Structural Geology, Wiley, New York.

PETROFRABRIC RESEARCH

the measurement of the original field orientation and the universal stage manipulations. These factors combine to give a spread of values about a mean orientation direction for any given element of the fabric of the rock, which leads to a cloud of points about the location of the mean in the projection onto the lower hemisphere. Schmidt wanted to be able to contour the spatial density of the disposition of the cloud of several hundred points on the equatorial projection, which represents a set of measured grain orientations, in order to enhance the patterns present, and so aid interpretation of the results. However, the stereographic projection does not have the property of keeping the area of a given shape constant when it is projected from the lower hemisphere onto the equatorial plane. Schmidt (1925, fig. 1) therefore adopted an equatorial equal-area projection of the sphere, originally devised by Lambert (1772) for cartographical purposes. Figure 4.4 shows the resultant 2° equal-area net, which subsequently became known as the 'Schmidt' net, a term coined by Sander (Sander & Schmidegg 1926, fig. 30; Knopf 1933, p. 438). In both the stereographic and equal-area projections, the angle of dip of the projection of a plane increases through the meridians of notional longitude from 0° at the centre to 90° at the periphery. The effect of the equal-area property can be seen in Figure 4.4 by noting the relative lack of change in the size of, say, a 10° by 10° sub-area, as one moves horizontally from the centre of the net along the equator to the periphery when compared to the equivalent in the stereographic projection (Fig. 3.11). The length of the diagonal of this sub-area increases by only 12% in the case of the equal-area projection, as compared to 81% with the stereographic projection. (A small amount of distortion is inevitable, irrespective of which of many alternative methods is used, since one is projecting the surface of a hemisphere onto a plane.) Consequently, the equal-area projection proved ideal for the plotting and subsequent statistical analysis of the locations of measured optical axes, the normals to mica cleavages, or (particularly in later years) orientation data for larger-scale structural features such as lineations or fold axes.

Fig. 4.4. Equal-area equatorial 'Schmidt' (Lambert) net; 2° mesh with 10° lines shown bolder. Reproduced with the permission of Mr W. F. C. Phillips from figure 73 of F. C. Phillips, 1960, The Use of Stereographic Projection in Structural Geology, Edward Arnold, London.

17

The relationship between orientations in the original threedimensional space of the geological specimen and the equivalent disposition of points in the equal-area plots is illustrated in Figure 4.5. The near-vertical lines in the first example (Fig. 4.5a), show the normals to, say, the cleavage faces of a set of selected mica crystals which can be imagined as embedded in a nearhorizontal planar surface, such as a foliation-plane in a metamorphic rock. If the three-dimensional orientation of these normals were to be measured in an orientated specimen (by means of the universal stage), they would project onto the lower hemisphere, plotted as though each normal passes through the centre of the reference sphere (Fig. 4.5b). The resultant cloud of points is shown in the corresponding equal-area projection in Figure 4.5c; its maximum spatial-density occurs close to the origin (0° dip). Figure 4.5d-f shows a similar set of illustrations for the normals to mica flakes on a near-vertical surface which strikes east-west. Note that because the normals are projected solely onto the lower hemisphere, the bunches of normals corresponding to faces dipping in opposite directions become split as a result of the near-verticality of the plane. Hence, in the equal-area projection (Fig. 4.5f), the two halves of the corresponding cloud of points lie diametrically opposite each other about a north-south azimuth which is perpendicular to the strike-direction of the original surface. Finally, Figure 4.5g-i illustrates the normals to cleavage planes of mica lying on a surface which has been affected by a single phase of deformation in which axes of the symmetrical microfolds are horizontal and run north-south. Schmidt (1925) introduced a method to enhance the spatial pattern shown by the scatter of points in equal-area plots, such as Figure 4.5c, f and i. He counted the number of points falling within a transparent 'counting circle', which had a diameter such that it enclosed 1% of the total projection area.105 In this operation, the counting circle is moved systematically over the plot in steps centred on a regular grid which covers the whole of the projection area.106 The frequency count at each grid node is recorded (due allowance being made for continuity at diametrically opposite points around the perimeter of the projection). Finally, the counts are contoured to show the changing pattern of spatial density. Figure 4.6 shows a similar treatment applied to macrostructural data. Recalling that the angle of dip of the projection of a plane increases through the meridians of notional longitude from 0° at the centre to 90° at the periphery (Figure 4.3), it should be evident that this example shows the presence of two dominant sets of near-vertical joint planes which strike approximately NW-SE and NE-SW: their mean planes are vertical and intersect at an angle of about 110° to each other, symmetrical about the north-south direction. A third, less dominant, set of vertical joint planes bisects these and strikes north-south. In petrofabric work, a local area of high density in a contoured plot (shown by the darker tones in Fig. 4.7a) is referred to as a maximum, and where the orientation of a group of poles to the crystallographic optic c-axes of quartz or to the normals to the basal cleavage of mica (Fig. 4.1) form a more or less complete belt (cf. Fig. 4.5i), this is referred to as a girdle (Sander & Schmidegg 1926, pp. 389, 393, 402; Knopf 1933, p. 456). An arc drawn through such a set of points on the projection corresponds to a best-fit great-circle (Fig. 4.2b), and therefore gives the orientation of the statistical average plane fitted to the set of data. The normal to this plane is termed the girdle axis and its pole may be plotted on the diagram. If two girdles intersect (Fig. 4.7b), they are referred to as crossed-girdles (Sander 1950, 1970, p. 252). Sander's methods were potentially made available to a wider audience with the publication (in German) of his books A Study of the Fabrics of Rocks (Sander 1930) and An Introduction to the Study of Fabrics of Geological Bodies (Sander 1948, 1950; English translation published in 1970). Unfortunately, his passion for exactness and accuracy of expression (Muller-Salzburg 1980) led to a writing-style which was convoluted and difficult to follow.107 As

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Fig. 4.5. Examples of the normals to small areas on (a) a slightly uneven horizontal surface, (d) a vertical surface striking east-west; and (g) a surface folded about horizontal north-south axes, (b, e, h) Views of the collective data for the poles within the lower hemisphere of the projection sphere, (c, f, i) The resultant lower hemisphere equatorial stereographic projection. Redrawn, with permission of Professor B. E. Hobbs, from figure All of B. E. Hobbs, W. D. Means & P. F. Williams, 1976, An Outline of Structural Geology, Wiley, New York.

Phillips (1937b) noted, Sander's introduction of a new and complex terminology, for which many terms lacked convenient English equivalents, made the texts extremely difficult for readers who were not already fluent in German to understand. Despite this, as Flinn has remarked (pers. comm. 1996), Sander rapidly attained what would now be called 'guru' status and, as a result, over the next few years his Innsbruck laboratory was visited by many geologists from North America, Europe and Scandinavia108 eager to learn the new techniques.109 These visitors included the Americans Eleanora Frances Knopf (nee Bliss, 1883-1974) and Earl Ingerson (1906-1983), and the Canadian Harold Williams Fairbairn (1906-1994). Their subsequent expositions in English of the methods used by Schmidt and Sander (Knopf 1933; Sander 1934; Fairbairn 1935, 1937, 1949; Ingerson 1938a, b, 1944) did much to promote the use of petrofabric techniques, which became widely accepted as a new field of study. Phillips did not visit Sander himself (W. F. C. Phillips, pers. comm. 1997; Wieseneder 1980), probably because his excellent knowledge of German enabled him to read the original literature and, as he was already accomplished in universal stage techniques, he did not feel it to be necessary.

Kinematic interpretation Sander was an experienced field geologist before he became involved in structural petrology. He began mapping in the Tauern area of the Austrian Alps110 in 1908 while at the Technische Hochschule (Institute of Technology), Vienna. In 1912 he joined the staff of the Geologische Reichsanstaldt (Imperial Geological Institute), Vienna, prior to taking up his position as Professor of

Mineralogy and Petrography at the University of Innsbruck in 1922, where he spent the remainder of his career (Felkel 1974; Ruttner et al 1980). According to Knopf (1933, p. 441), Sander's thinking was much influenced by the work of the American geologist George Ferdinand Becker (1847-1919) whose paper 'Finite homogeneous strain, flow and rupture of rocks' (Becker 1893) presented, according to Pollard & Aydin (1988, p. 1182), 'a remarkably complete treatment of finite strain111 analysis, anticipating the popularity of the technique among structural geologists of the last few decades'. However, it was to prove unfortunate that Becker regarded the evidence provided by deformed fossils (e.g. Heim 1878, Atlas, plates XIV, XV), which had already been correctly interpreted by Harker (1885, 1886) as a flattening phenomenon which could be geometrically related to the finitestrain ellipsoid,112 as inconclusive. Instead, Becker maintained that slaty cleavage occurred along shear planes, and that this was attributable to high shearing strain resulting from pressure being applied in a direction inclined at an oblique angle to the plane in which the cleavage subsequently developed. This seems particularly surprising in view of the fact that the French geologist Gabriel-Auguste Daubree (1814-1896) had already shown experimentally, using mixtures of clay with sand, mica and feldspar crystals extruded under high pressure, that lineation developed parallel to the flow direction, and that subjected to similar conditions, the bullet-shaped fossils Belemnites niger (similar to those found deformed, apparently pulled apart, in the Mont-Blanc massif, in the 1840s) broke apart and the fragments again aligned themselves parallel to the flow direction of the material in which they were embedded (Daubree 1879, pp. 391-432, especially fig. 143, p. 413, fig. 144, p. 415 and figs 151-153, p. 420). It is


Fig. 4.6. (a) Equal-area lower hemisphere projection of the poles to three sets of near-vertical joint planes, Start Point, Devon, (b) The same, contoured to show spatial point-density using a counting-circle of 1 % area size; empty (minimum density) regions shown white; maximum density regions shown black; contour intervals not given, probably 1 (1) 6%. Redrawn with permission of Mr W. F. C. Phillips from figures 77 and 79 of F. C. Phillips, 1960, The Use of Stereographic Projection in Structural Geology, Edward Arnold, London.

quite clear that Daubree envisaged schistosity and related phenomena in rocks to be produced by the realignment of the material constituting the rock as a result of viscous, plastic flow under high pressure, and he suggested that cleavage, foliation and 'lamination' were all attributable to the same cause (Daubree 1879, p. 423). Sander (1930, p. 62) coined the term tectonite to mean a rock in which 'componental movements in the fabric can be integrated to a picture of the movement or deformation of the domain under consideration'. Undoubtedly, he felt certain that his new approach was entirely objective, and that the observable fabric of the rock provided a direct record of the forces involved in its deformation.

19

Fig. 4.7. (a) Contoured petrofabric diagram (lower hemisphere equalarea projection, 300 quartz grains counted, and a counting-circle of 1% area size; contours 1 (1) 7%) of psammitic Moine schist showing a nearly complete girdle; empty (minimum density) regions shown white; maximum density regions shown black. Thin-section normal to strike; 'baxis pitches 12° E 32° S.' (b) Example of petrofabric diagram for quartz-muscovite Moine schist showing crossed-girdles. 'Projection rotated until parallel to b-axis [pitches 30° S 5° E] after measurement in section perpendicular to strike.' Contours 1 (1) 5%. Redrawn with the permission of Mr W. F. C. Phillips and The Geological Society, London, from figures D6 and D18 of F. C. Phillips, 1937, 'A fabric study of some Moine schists and associated rocks', Quarterly Journal of the Geological Society, London, 93, 581-620.

He stated: 'it is not on the basis of theoretical considerations, but by means of fabric analysis, that we obtain a conclusive movement-picture of the domain. Without this, a clear tectonic movement-picture of large domains may be achieved only by the application of personal experience, which must be more or less subjective' (Sander 1948, 1970, p. 71).113 Sander (1930, p. 146, 1950, p. 26, 1970, p. 83) was also convinced that the fabrics of the

20


rocks could be interpreted in terms of various types of internal symmetry arrangement which could be identified statistically from the patterns made by the girdles in the contoured petrofabric diagrams. He distinguished between monodinic fabrics, having a single plane of symmetry, with one axis normal to it; orthorhombic fabrics, with the symmetry of a triaxial ellipsoid (i.e. with three mutually perpendicular planes of symmetry and three axes normal to them); and triclinic fabrics, which have no planes of symmetry; and stated that 'the plane of deformation is a plane of symmetry for the movement-process and all the tectonic fabrics engendered by it, down to the scale of the grain-fabric' (Sander 1948, 1970, p. 69).114 Since the work of Eduard Suess (1831-1914) at the end of the nineteenth century (Suess 1875, 1883-1909) the Alpine chain had been generally accepted as having been moved northwards. Sander's observations convinced him that lineation generally occurred parallel, or subparallel, to the axes of folds, and that (apart from slickensides115 on fault or thrust planes) the presence of lineation perpendicular to the axes of folds was rare. In order to describe the fabric of a rock, and to suggest possible conclusions about the nature of the deformation which gave rise to it, Sander (in Sander & Schmidegg 1926, p. 328; Sander 1930, p. 46) established a reference frame of three mutually perpendicular kinematic axes {a, b, c}. On the basis of fieldwork in the eastern Alps by Schmidt and himself, Sander defined the b-axis, which Schmidt (1932, p. 46) had referred to as the 'tectonic strike', as being coincident with any lineation visible at the scale of a handspecimen or outcrop. Sander assumed it to be parallel to an axis of shear,116 or parallel or subparallel to a fold-axis, which he termed the B-axis (Sander 1950,1970, p. 70), whose presence gave rise to the lineation (Fig. 4.8). He also stated that 'at right angles to the direction of tectonic flow or at right angles to the grinding movement there will occur lateral extension and packing. This has long been described as stretching and cross-folding in the Alps' (Sander 1950,1970, p. 494). The b-axis was thus regarded as lying,

Fig. 4.8. Sketch to show what Phillips called Sander's (in Sander & Schmidegg 1926) 'orthodox' interpretation of his reference axes {a, b, c} in relation to the plane containing the fold axis (B). Sander defined the b-axis as being.coincident with any lineation visible in hand-specimen or outcrop; his assumed direction of compression, orthogonal to B, is also shown.

in general, perpendicular to a rather vaguely defined 'direction of tectonic transport'. Curiously, a few years before Schmidt and Sander began their work in the Austrian Alps, the Swiss geologist Albert Heim (1849-1937), who was studying the Swiss Alps, also made use of an orthogonal kinematic reference-coordinate system. He concluded, from the field evidence which he had found, that the direction of 'stretching' was always perpendicular to the axes of folds and he seems to have made little mention of stretching parallel to the axes of folds. Consequently, Heim's inferred direction of movement, parallel to lineation, was the equivalent of Sander's a-axis direction (Heim 1921, pp. 82-85). Such differences in emphasis may, in part, reflect experience gained by the original investigators in field areas with differing characteristics, 117 since modern work is revealing that Alpine tectonics are far more complex than they were once thought to be.118 Nevertheless, Sander believed that 'the development of fabricelements with their greatest diameter parallel to [an external axis of rotation, such as a fold axis] B is a familiar feature on a scale from grain-dimensions to giant technically rolled rods,119 and is known in distorted fossils' (Sander 1948, 1970, p. 67). He was also of the opinion that it could be explained by a mechanism in which there was a translational movement parallel to a, accompanied by grain rotation around the axis of internal or external rotation, b: 'with rotation about B ... extensions perpendicular to B are nullified, whilst extensions parallel to B integrate, so that a rod or noodle parallel to B is produced, as is demonstrated by the act of rolling out noodles by hand' (Sander 1970, p. 66).120 Sander's aaxis was, by definition, perpendicular to the b-axis (Fig. 4.8), and he believed it to be coincident with the direction of slip or the direction of dip of the limbs of the fold. It was regarded by both Schmidt (1932, p. 46) and Sander (1948, 1970, p. 70) as representing the direction of overall transport of the material (Sander 1948, 1970, fig. 64, p. 168). The c-axis was, by definition, normal to the ab plane (Fig. 4.8). Sander believed that the natural choice for the plane in which any geologist would draw the cross-section of a major structure would be parallel to ac (Sander 1948, 1970, p. 72), the 'plane of deformation' (Sander 1948, 1970, p. 69) which, as remarked above, 'is a plane of symmetry for the movementprocess and all the tectonic fabrics engendered by it, down to the scale of the grain-fabric' (Sander 1970, p. 69). Figure 4.9 illustrates Sander's coordinate system as applied to features visible at a grain-size scale, more like that encountered in the thin-sections used for petrofabric analysis. With hindsight, it is ironical that Knopf (1933, p. 441) wrote that Sander's new petrofabric methods were 'less speculative and less prone to the fallacies of inference' than were earlier methods of investigation of rock structure, for it is now realized that embodied in Sander's work were a number of assumptions regarding the kinematic interpretation of the observed microfabrics which made his rules inherently ambiguous. At least part of the problem is attributable to lack of knowledge in the years between, say, 1911 and 1932, when the work which established the basics of structural petrology regarding the mechanisms involved in crystal deformation was being carried out.121 Sander followed Schmidt (1932, pp. 188-192) in assuming that in many cases, the deformation of crystals such as quartz took place by plastic deformation. This was believed to involve movement along either a single set of shear planes (simple shear)122 or on two sets, symmetrically orientated such that the direction of greatest applied compression acts in the plane of the bisector of the obtuse angle between them (pure shear).123 Under these conditions, it was believed that in an equal-area projection the poles to the quartz optic c-axes would tend to occupy a great circle normal to the kinematic b-axis of the fabric, and would exhibit density maxima which corresponded to the orientations of the two glide-planes which lie close to the maximum shear-stress directions about the direction of greatest applied compression. The petrofabric diagram for quartz in Figure 6.2a shows an excellent


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think the deformation was pure shear then they take the lineation.

Fig. 4.9. Schematic diagram to illustrate Sander's {a, b, c} coordinate system in relation to the main features of the fabric of a metamorphic rock composed of aggregates of quartz grains enclosed by a web of mica leaves. The quartz aggregates are visibly flattened and show some elongation. There is a conspicuous foliation (parallel to the top of the block) and lineation (parallel to the b-axis). Cross-fractures parallel to the ac plane are also visible. Redrawn with permission of the publisher from figure 5 of H. W. Fairbairn, 1949, Structural Petrology of Deformed Rocks, AddisonWesley, Cambridge, Massachusetts.

It was not until some 30 years after Schmidt and Sander first began their work that Flinn (1956b) demonstrated that rock deformation had usually to be treated as a true three-dimensional process124 and that by doing so, the apparent ambiguities of kinematic interpretation which resulted from the early work became resolved. Such problems were compounded because of confusion between the movement directions of externally applied forces and those of internal movements in response to the applied forces. Although Sander's work contained an occasional cautionary note, such as 'Fabric studies must not favour one of the three possible cases (transport perpendicular to B, transport parallel to B, or no tectonically evident transport) from the outset, but must analyse case by case which of these predominates' (Sander 1948, 1970, p. 171), his hypothesis that the direction of the b-axis was generally perpendicular to the 'direction of transport' was widely accepted as fact for many years.125 For example: Phillips (1937b, p. 591) commented 'the b-axis of the girdle is ... perpendicular to the plane of movement (Sander 1930, p. 57) ... a finding of fabric analysis which has not been seriously challenged'; the American geologist Marland Pratt Billings (b. 1902) wrote: 'in the Austrian Alps it was early demonstrated that a is parallel to the direction of movement, whereas b is perpendicular to it. Thus the fabric axes are rather directly and simply related to the movements in the rock. That lineation is perpendicular to the direction of movement is one of the fundamental tenets of structural geology' (Billings 1942, p. 347); and Fairbairn (1949, p. 6) stated 'b is limited by Sander to parallelism with fold axes, a direction almost always associated with lineation. It is commonly perpendicular to a since the direction of movement in the development of a major fold is normal to its axial line'. Phillips (like many others) simply followed Sander's rules as well as he could. Structural petrology at Cambridge

example of a fabric of this type, which would have appeared to be entirely consistent with Schmidt's model. In this figure, the greatest applied compression would have been assumed to be acting vertically, in the plane of the diagram; the two pairs of symmetrically placed maxima (shown by the darker contours) lie within Schmidt's 'permissible' zones, and the less dense regions at the top and bottom of the diagram correspond to his 'forbidden' zones, in which his model predicted that glide planes were unlikely to occur. Phillips (1937b, p. 591) followed Sander (1930, p. 57) in believing that the b-axis of the girdle is perpendicular to the plane containing the axes of greatest and least principal stress, and therefore to the plane of movement. However, it must be borne in mind that in the 1930s, there was no real knowledge of how the fabric of a mineral such as quartz actually developed when a rock was deformed, although Wenk & Christie (1991) and Pollard (2000) have pointed out that Sander apparently ignored the pioneering work of Taylor (1934, 1938) and Orowan (1934) on polycrystalline plasticity and dislocation, which have materially assisted the development of an improved understanding of the development of deformation textures. Flinn (pers. comm. 1998) suggests that underlying Schmidt and Sander's work was the unspecified implicit assumption that the rock has suffered twodimensional [as opposed to three-dimensional] deformation [and that] the 'deformation plane' - the plane containing all the vectors which have changed in length during the deformation is a symmetry plane in the rock. Within the deformation plane is the 'transport direction' labelled a. . . . If users are of the opinion that the rock has suffered simple shear then the shear direction is taken as a, but if they are more sophisticated and

Phillips' early familiarity with Schmidt's and Sander's work is shown by the fact that when he described the results of his Green Bed study (Phillips 1930a), he wrote that although 'no attempt has yet been made to investigate [the systematic orientation of the feldspar crystals] on the lines developed by Sander and Schmidt, work with the universal stage makes it quite apparent that there is some regularity of arrangement' (Phillips 1930a, p. 248). By 1932 Phillips was giving lectures on structural petrology to undergraduates at Cambridge (although Tilley would not provide him with funding to obtain a second universal stage). Phillips' pioneering adoption of the petrofabric method in Britain was not an accident, but the logical coming-together of his detailed optical and crystallographical knowledge, honed by some years of teaching excellent students; his familiarity with stereographic methods, as extensively used by him in crystallography; his already developed skill in using the universal stage to determine feldspar compositions, using the methods of Fedorov (1892, 1893, 1897) and other mineralogical studies; his significant experience in examining the metamorphic rocks of Shetland, Cornwall and the Scottish Dalradian; combined with a predilection towards laboratory, rather than extensive field studies. The laborious hours spent at the microscope determining and plotting thousands of mineral orientations was not to the liking of field geologists. This combination of experience and talents found in Phillips fitted him well for petrofabric research; if later-discovered knowledge of structural geology had also been available, it would have been ideal. In the University Reporter of 6 March 1934, the Woodwardian Professor, Owen Thomas Jones (1878-1967), announced on behalf of the examiners that the subject for the forthcoming 1937

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Sedgwick Prize (awarded triennially on the basis of either an essay or a body of published work) would be The application of modern technique to the elucidation of some specific geological problem' (G. Waller, pers. comm. 1998). Phillips decided that he

would enter for it. The same year, Stuart Olof Agrell (1913-1996) graduated from the new Department of Mineralogy and Petrology and began study for his PhD dissertation under Phillips' supervision (Chinner 1998).

5. Understanding of Moine geology in the 1930s

The Moine rocks, or 'Moines' as Johnstone & Mykura (1989) and many others colloquially call the formal Moine Supergroup (Gibbons & Harris 1994), are a thick succession of metamorphosed sedimentary rocks, mainly psammites126 and semipelites,127 which occupy the largest part of the Northern Highlands of Scotland (Fig. 5.1). The metamorphic grade is mostly amphibolite fades128 with widespread garnet- to sillimanite-zone rocks, some migmatites129 and some low-grade greenschist facies130 rocks, especially in the west where the metamorphic grade declines. Although not obvious, the Moine succession rests unconformably131 on the Lewisian rocks of the Precambrian basement.132 The Moine metasediments generally lack distinctive sedimentary lithologies or bands which can be traced for substantial distances. Consequently, unravelling the internal structure of the Moine has proved to be exceptionally difficult and it is still not complete because of its complexity, the generally uniform

lithology and the varied degree of exposure, which ranges from excellent to abysmal. The term Moine itself, which derives from 'a'Mhoine', meaning 'the peat bog' (in North Sutherland; Green 1935, p. Ixiv), is expressive of the last difficulty. The history of the understanding of the geology of the Moine Supergroup up to the publication of the great memoir on the geology of the NW Highlands by Charles Thomas Clough (1852-1916), William Gunn (1837-1902), Lionel Wordsworth Hinxman (1855-1936), John Home (1848-1928) and Benjamin Neeve Peach (1824-1926) (Peach et al. 1907) has been fully documented in gripping detail by Oldroyd (1990). The brilliant deduction by Charles Lapworth (1842-1920) that the Moine had been thrust WNW onto Lewisian Gneiss, Torridonian Sandstone133 and the Cambro-Ordovician Durness succession134 (Lapworth 1883) was confirmed, although the actual amount of movement, recognized as being substantial and determined as

Fig. 5.1. Modern geological map of the Northwest Highlands, Scotland, showing the major geological units and the positions of the Moine Thrust; Sgurr Beag Slide (S. B. T., a ductile thrust); and the Loch Quoich Line (Q), the eastern limit of severe tectonic reworking (?Caledonian) overprinting ?Precambrian structures (Roberts & Harris 1983). Redrawn with permission of the authors and The Geological Society, London, from figure 4.1 of A. L. Harris and M. R. W. Johnson, 1991, 'Moine', in Craig, G. Y. (ed.) Geology of Scotland, The Geological Society, London, 87-123.

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being at least tens of kilometres (Peach et al. 1907), was, and is, still uncertain. However, the recognition of the importance of thrusting in the history of the Moine Supergroup did not, in itself, illuminate their age of deposition and subsequent metamorphism. During the mid-1930s when Phillips initiated his studies of the petrofabrics of the Moine metasediments, little was known about their stratigraphy, and therefore their structure, because the first major stratigraphical study was not completed until the 1939 publication by James Ernest Richey (1886-1968) and William Quarrier Kennedy (1903-1974; FRS, 1949). However, this only encompassed the Loch Monar area (Fig. 5.2), and what is now thought to be the bottom of the Moine succession. Although lithological variations in the psammites and semipelites had been recognized (e.g. by Peach & Home 1930, p. 178), they had not been systematically traced over the whole Moine outcrop. Furthermore, the use of the sedimentary structures of crossbedding135 and graded-bedding136 to determine the original wayup137 in deformed sedimentary successions was not generally known in Britain until after the Norwegian geologist Thorolf Vogt (1888-1958) tutored (Sir) Edward Battersby Bailey (1881-1965; FRS, 1930) who, in his turn, rapidly instructed Archibald Allison

(1906-1992) in the application of these methods. Their work (Bailey 1930; Vogt 1930; Allison 1933) resulted in the first reliable determination of the stratigraphical succession in the Dalradian rocks. By the early 1930s, all that seemed certain was the lithology of the Moine metasediments, their general NNE strike, the existence of regional metamorphism and folding, and that they were bounded in the west by a series of ESE-dipping thrusts (the most important of which was the Moine Thrust), while to the east they passed under the unconformably overlying, unmetamorphosed, Old Red Sandstone (Fig. 5.1). Since there were no radiometric age determinations available on any of the rocks involved, the present understanding - that the Lewisian Gneiss has a history extending from at least 2800 to 1600 Ma ago, with the overlying Torridonian being deposited (or undergoing diagenesis138) c. 1000 Ma (Turnbull et al. 1996); that the Moine rocks themselves were c. 1000 to 850 Ma in sedimentation (Gibbons & Harris 1994), with a major thermal event at 870 Ma (Friend et al. 1997; Millar 1999) followed by regional metamorphism about 800 Ma ago (Rogers et al. 1998; Vance et al. 1998); that they underwent a final younger period of folding and metamorphism in the Ordovician,

Fig. 5.2. Locality map of the Northwest Highlands of Scotland (black dots indicate places mentioned in text).

UNDERSTANDING THE MOINE GEOLOGY IN THE 1930S

about 470 Ma ago (Kinny et al 1999; Soper el al 1999); and, lastly, that the Moine Thrust movements took place at 430-408 Ma (van Breeman et al. 1979; Freeman et al. 1998) - was all totally unknown. There was, however, a very vigorous debate taking place about the ages of deposition, metamorphism and folding of the Moine relative to those of the other rocks in NW Scotland. The posthumous, and long-awaited, publication in 1930 of Peach and Home's final considered views on the Moine triggered a revival of the arguments about the age of the Moine sedimentation and metamorphism. In part, this was because Peach and Home themselves could not agree upon the matter. Peach (in Peach & Home 1930) subscribed to the view that the Moine metasediments were the metamorphosed eastern stratigraphical equivalents of the Torridonian Sandstones, since both lay unconformably on the Lewisian Gneiss with basal conglomerates,139 and both were arenaceous sequences.140 Peach claimed that this explained the observed increase in metamorphic grade eastwards. On the other hand, Home maintained (in Peach & Home 1930, p. 147) that the Moine metasediments were pre-Torridonian and had been metamorphosed before the Torridonian deposition, thus explaining their different metamorphic states, their differing lithologies in detail, the lack of the north-south variation in the Moine which is found in the Torridonian, the rarity of basal conglomerate in the Moine and the lack of Torridonian rocks in the extreme north of Scotland, whereas the Moine metasediments are still present above the thrusts in this area. The eminent John Walter Gregory (1864-1932), Professor of Geology at the University of Glasgow, seized upon this difference of opinion when reviewing Peach & Home's (1930) book in Nature and devoted most of his review (Gregory 1931) to it. Gregory claimed that their book provided the first coherent statement by Peach of the evidence for his view. However, Gregory rejected Peach's hypothesis largely, it seemed, on the basis of some pebbles in the Torridonian Sandstone which Gregory considered to be Moine rocks. Thus, Gregory supported Home's interpretation. This development was rapidly followed by the publication in 1931 of the memoir on Central Sutherland by Read and then by Read's opinion, stated by him (Read 1934b) to be supported by Barrow (on the basis of the evidence in the discussion of Tilley's (I925b) paper on the metamorphic zones in the Highlands), that the Moine metasediments were in fact Lewisian in age. This view was based on the similarity of amphibolites141 in the Moine succession with those in the Lewisian and rejected the idea that

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the Survey-mapped Lewisian rocks within the Moine were inliers142 and not part of the normal stratigraphical sequence. Read explained the lower metamorphic grade in the western part of the Moine outcrop as being retrogressive metamorphism143 caused by the late thrusting of the Moine rocks and this was superimposed on an earlier regional metamorphism that affected both the Moine and the Lewisian rocks. All this public discussion, and much private argument, led to the British Association for the Advancement of Science devoting a whole session in its 1934 meeting in Aberdeen to these questions about the Moine. Following this, John Frederick Norman Green (1873-1949) made his 1935 Presidential address to the Geological Society on the subject of The Moines' in which he stated: The central problem ... is ... whether there have been one or two periods of regional metamorphism' (Green 1935, p. lxix). Phillips' subsequent work clearly showed that the answer to Green's question was 'two'. It was not therefore surprising that this scene of almost perennial disagreement (the proposal that the Moine metasediments were altered Torridonian Sandstones had originally been made by Macculloch (1819, II, p. 94)), which seemed to reach a climax in the 1930s, should prompt Phillips to consider using the new method of petrofabrics to contribute to the debate. The choice of the Moine for the first major use of the petrofabric tool in Britain was in some respects ideal: quartz and micas were major constituents of the rocks and were easy to measure; there was no other immediate prospect of establishing the overall direction of the tectonic forces that had acted on the rocks; and the most important point about whether the fabric of the Moine metasediments pre-dated the Moine Thrust movements or was produced by them, which Phillips specifically addressed, could be easily determined by traversing the Moine Thrust Zone and observing what happened to the fabrics under the influence of thrusting. On the other hand, it could be argued that it was a poor choice, because the petrofabric interpretation of movement directions could not be unequivocally checked by the normal method of mapping structure by tracing the convolutions of a distinctive stratigraphical succession and, with the depth of entrenched opinion, any conclusions were likely to be challenged. There is little doubt, however, that Phillips did not foresee how controversial his work would turn out to be, and that what was a quick, if laborious, few months' work would dog him for the rest of his career.

6. Cambridge (1936-1946)

Microfabric of the Moine schists. I In March 1936, Phillips began fieldwork for his next project, 'A fabric study of some Moine Schists and associated rocks' (Phillips 1937b). This was based on a collection of 'about 200 orientated specimens,144 with accompanying field data' from an area lying mainly north of Glen Moriston and NW of Glen Mor (Glenmorenan-Albin), the 97 km long depression which forms the 'Great Glen' of Scotland (Fig. 5.2). He completed the work amazingly quickly - in less than a year, he submitted the manuscript to the Quarterly Journal of the Geological Society. It was sent to Read (who was by then George Herdman Professor of Geology at the University of Liverpool, following his appointment in 1931) for review on 17 March 1937. It is almost certain that this manuscript also formed the basis for Phillips' Sedgwick Prize submission. It was announced in the University Reporter of 2 March 1937 (G. Waller, pers. comm. 1998), that the prize had been jointly awarded to Phillips and to the geophysicist (Sir) Edward Crisp Bullard (1907-1980).145 Sander had already made a plea that 'there ought not to be microtectonists and megatectonists working independently of each other, but rather one group of workers investigating the correlations between process in large and small units' (Sander 1934, p. 37). For his part, Phillips (1937b, p. 584) stated that 'any attempt to make fabric studies a substitute for fieldwork, rather than a valuable auxiliary in the course of the subsequent work in the laboratory, is thoroughly deplored'. He consequently set the findings from his petrofabric analysis within the context of a regional synthesis of data for lineation directions, which he had compiled from observations recorded on pre-existing 1 in:l mi (1:63 360) Geological Survey maps and his own field observations (Fig. 6.1), yielding data for a total of 82 localities. Phillips' paper describes the results of petrofabric analyses for quartz and mica in a total of 80 thin-sections, made from orientated specimens taken from 35 localities, of which 31 lay to the east of the outcrop of the Moine Thrust. Together, his petrofabric data comprised a total of some 20 000 separate measurements of the spatial orientation of the optic c-axes of the individual quartz grains or the normals to the basal cleavage of muscovite or biotite (Fig. 4.1). Phillips analysed the micas in each case in order to determine the orientation of the foliation plane. This information was then inserted into the diagram resulting from analysis of the quartz (Fig. 6.2a; Phillips 1937b, p. 586). The results were found to be consistent in each case. Phillips' petrofabric analyses (a selection of which are shown in their spatial context in Fig. 6.2b) indicated a consistent regional pattern, in which the 'b-axis' of the microfabric in the Moine schists had a broadly NW-SE orientation and plunged146 to the SE, although there was some variation about this direction. Furthermore, this orientation generally appeared to coincide with that of the macroscale structures observed in the field (Fig. 6.1), i.e. (i) the lineations discernible at hand-specimen scale on foliation planes, and (ii) the larger-scale 'rodding' (the development of long pencils of several centimetres diameter of quartzo-feldspathic material on the foliation planes parallel to minor fold axes) and related 'mullion' structures (Fig. 6.3), first described and mapped by Clough in Peach et al (1907). The selection of Phillips' petrofabric diagrams for the Moine schist reproduced in Figure 6.2b shows that the majority exhibit a disposition of points which lie close to a great circle (Figs 4.2b and

4.3), corresponding to low-angle scatter about a plane perpendicular to the b-axis. As mentioned earlier, Phillips followed Schmidt's (1932, p. 171 et seq.) explanation, adopted by Sander, for the possible mode of development of the girdle: each grain rotates as a result of intergranular movement until its orientation relative to the direction of shear stress is such that movement takes place along glide-planes within the crystals. Under these conditions, Schmidt (1932, p. 192) showed that the poles to the optic c-axes of the quartz crystals would then tend to occupy a great circle, normal to the kinematic b-axis. This plane would, by definition, contain the axes of greatest and least principal stress. The b-axis would therefore also be perpendicular to the plane of movement (Sander 1930, p. 57), 'a finding of fabric analysis which has not been seriously challenged' (Phillips 19307b, pp. 588-591). Furthermore: The belief in 'stretching' parallel to the elongation is not surprising in view of outward appearances, but fabric analysis suggests that of such linear features in schists, the vast majority lie parallel to the b-axis, and therefore perpendicular to the direction of movement, as distinct from the slickensides on a surface of movement in a shear-zone tectonite. Even a 'stretched belemnite' lies with its apparent direction of stretching parallel to the b-axis of a quartz girdle (Ladurner 1933, p. 487). . . . An alternative to mere stretching, . . . more nearly in accord with the findings of fabric analysis, is also considered. 'We may suppose, however, that rodding can be produced in any cube of rock by subjecting it to equal pressures from four sides in opposite pairs, leaving the contents to squeeze out, as it were, towards the other two sides, on which the pressure is less' (Clough in Peach et al. 1912, p. 49). Here it will be observed that the chief pressure was normal to the direction of extension. The true significance is also frequently hinted at in descriptions of linear foliation in the Lewisian and other rocks - 'parallel with the pitch147 of the folds in the district' (Teall in Peach et al. 1907, p. 97); 'thin stripes or rods which run parallel to the axial planes of the large folds affecting the rocks' (Clough, in Peach et al. 1912, p. 247) and many other references. (Phillips 1937ft, pp. 593-594, our italicization; quoted with permission of Mr W. F. C. Phillips and The Geological Society, London). Flinn (pers. comm. 1998) points out that the widespread usage (even today) of the descriptor 'a stretching lineation' is, strictly speaking, a misnomer, since true 'stretching' cannot generally take place in metamorphic rocks148 as the confining pressure is too great. Properly regarded as extension lineations, they always develop parallel to the longest axis (X) of the three-dimensional deformation ellipsoid149 (Flinn 1956ft). Phillips was therefore correct in viewing the phenomenon as an extension lineation, rather than having been literally 'stretched'. This is why he concluded that b-axes could be interpreted in the same way as fold axes and that 'it can safely be asserted that the deformation responsible for the production of the fabric has acted in a plane more or less perpendicular to them' (Phillips 1937b, p. 591). Figure 6.4a shows Phillips' synoptic plot of the spatial disposition of the kinematic b-axes on the lower hemisphere, which he compared to similar plots for the dip of the foliation planes in (i) orientated specimens collected during field traverses (Fig. 6.4b) and (ii) the samples for which the b-axes have been determined (Fig. 6.4c). Using a rotation of the frame of reference to a

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Fig. 6.1. Regional map of 'lineations believed to represent b-axes' (Phillips 1937b, p. 594); heavy line (our emphasis) shows location of the outcrop of the Moine Thrust. Note that in this figure, Phillips also shows that NW-SE oriented lineation has been found at a few localities in the Moine and Dalradian lying to the SE of the Great Glen Fault (whose trace is indicated by the diagonal SW-NE alignment of the lochs in Glen Mor at the centre of the map, cf. Figure 5.2). Redrawn with the permission of Mr W. F. C. Phillips and The Geological Society, London, from figure 5 of F. C. Phillips, 1937, 'A fabric study of some Moine schists and associated rocks', Quarterly Journal of the Geological Society, 93, 581-620.

common view in which the plane of foliation and direction of the lineation are vertical, he then obtained a composite diagram (Fig. 6.4d) in which density maxima from the individual quartz petrofabric diagrams for his Moine schist samples were shown in relation to the foliation plane and b-axis. Phillips (1937b, p. 599) commented that the marked bilateral symmetry about the foliation plane agreed very well with that predicted by Schmidt (1932) for a fabric reflecting the presence of a pair of glide planes which are symmetrically bisected by the visible foliation plane, and which corresponds to compression normal to the foliation plane. Not long before Phillips published these results on the Moine schists, Henno Martin (fl. 1935-1984), a former student of the leading German structural geologist Hans Cloos (1886-1951) at the University of Breslau (now Wroclaw, Poland), had been undertaking a study of mylonites150 in Sweden. In the course of this work, he investigated the relationship between the pronounced lineation, the direction of movement (as inferred from slickensides on the fault planes) and the quartz fabric, at four localities in the Strobel granite, Vetternsee, southern Sweden (Martin 1935). His petrofabric diagrams were orientated with the foliation plane horizontal and the B-axis (in this case, the macro-

scopic lineation) vertical out of the plane of the paper. In all cases, the girdle distributions for the quartz axes showed maxima which Martin interpreted as being related to two conjugate sets of microscopic-scale shear planes, symmetrically disposed about the plane of foliation. However, while in two cases the field evidence appeared to support movement parallel to the lineation, in the other two it seemed to be perpendicular to it. As a result, Martin claimed that Sander's interpretation of the b-girdle petrofabric diagrams was not reliable. In reply, Sander (1936) claimed that the quartz fabric might not necessarily reflect the major movement and suggested the possibility that a 'more intense' movement parallel to B might have occurred. However, neither Sander, nor Phillips (1937b, p. 599) in later discussion, were convinced by Martin's claimed counter-example, and neither appeared to be unduly concerned by his evidence. Furthermore, Phillips (1937b) noted that in a discussion of the origin of rodding observed near Oykell Bridge, Sutherland (Fig. 5.2), Read, following Clough (in Peach et al 1907), had suggested that the structure was explicable by two phases of folding: a first phase resulting from compression acting in a NE-SW direction; and a second acting at right angles, producing 'a stretching along north-west and south-east lines and with axial

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Fig. 6.2. Examples of contoured (lower hemisphere equal-area projection) petrofabric diagrams for preferred orientation of quartz optic c-axes in quartz-muscovite-biotite schist samples of the Moine schists of the Northwest Highlands of Scotland (Phillips 1937b). Contours in all plots 1 (1) 5+%, except muscovite which is 1 (1) 5,10 (5) 20%. (a) Phillips illustrated his method with two diagrams for muscovite and quartz in a thin-section cut perpendicular to lineation in an oriented specimen from his locality 6 (see map in b). Muscovite: poles to normals to basal cleavage in 250 muscovite grains; point-density is contoured using a circle of 1% area size; projection rotated so that b-axis is vertical. Quartz', poles to optic c-axes in 250 quartz grains in the same thin-section. Symbols: in both diagrams '[t]he dotted [line or] curve ... represents the foliation surface as determined statistically by the distribution of the mica' (Phillips 1937b, p. 586; our italics); in the diagram for quartz '[t]he direction of dip of this surface is indicated by an arrow joining the centre of the projection to a point on the dotted curve surrounded by a small square' (Phillips 1937ft, p. 586). In this example, the b-axis pitches 22° E 2° S (Phillips 1937ft, pp. 609, 616). (b) Lower hemisphere equal-area projections for quartz; 250-300 grains determined in each case; symbols as in (a). The original thinsection(s) were cut perpendicular to lineation (Dl, Dll, D15, D22, D23); to dip (D3, D6, D20, D19); to strike (D8, D18, D19); and parallel to lineation (Dll). The map (partially redrawn, Phillips 1937ft, fig. 2) shows the orientation of the inferred b-axes as determined by Phillips at all localities which are numbered; 'the pitch [plunge] in a south-easterly direction is inversely proportional to the length of the line' (Phillips 1937ft, p. 590). Orientations for the examples illustrated are as follows: Dl, 22° E 2° S; D3, 17° E 30° S; D6, 33° E 16° S; D8, 0° E 40° S; Dll, 23° SSE; D15, 18° S 11° E; D20, 30° S 22° E; D22, 20° E 43° S; D18, 30° S 5° E; D19, 65° SE; D23, 52° E 42° S (Phillips 1937ft, pp. 608-615). Localities marked 'U' lying to the west of the outcrop of the Moine Thrust (heavy line, our emphasis) are those where Phillips found an 'unordered' (i.e. essentially random) fabric, hence no b-axis orientation existed. R. D. Law (pers. comm. 2000) attributes this to the fact that deformation in this area generally occurs by brittle fracturing, hence there is little crystal plastic deformation and consequently crystal preferred orientation. No length scale was given in the original map. The elements of this composite illustration are reproduced with the permission of Mr W. F. C. Phillips and The Geological Society, London, from plates XXXIV and XXXV and figure 2 of F. C. Phillips, 1937, A fabric study of some Moine schists and associated rocks, Quarterly Journal of the Geological Society, 93, 581-620. planes [of the folds] dipping south-east... a stretching effect quite independent of foliation, roughly at right-angles to the trend of the Moine Thrust' (Read et al 1926). Phillips had also visited Oykell Bridge, in March 1936,151 and had examined some of the mullions (Fig. 6.3) in detail. He concluded that although there was

good evidence for the presence of a b-axis parallel to the length of the mullions, the form of the individual mullions was not always due to the presence of small folds, as was apparently also true of the quartz rods of Beinn Thutaig (Ben Hutig) (Phemister 1936, p. 23). This is why Phillips was convinced that the regional-scale


29

Fig. 6.3. Mullion structures in Moine schistose quartzite, Strath Oykell. Reproduced with permission of the author and the publishers from figure 65a of L. E. Weiss, 1972, The Minor Structures of Deformed Rocks, Springer, Berlin.

structural pattern which he had observed at both micro- and macroscales suggested that although 'the origin of the linear structures is connected with folding due to movements along south-west to north-east lines, earlier than the post-Cambrian displacements. ... it is the lineation parallel to the 6-axis of the fabric which has provided the direction of yield during the later thrust-movements' (Phillips 1937b, p. 597). Subsequent difficulties arose from the attempt to assign a date to this earlier event. It had already been suggested that the general metamorphism could be of early Caledonian age 'the dislocation phase being merely "the late breaking-down of structures produced at a rather earlier time during the movements"' (Peach quoted in Phillips 1937b, p. 604). Because NW-SE fold axes had already been extensively mapped by the Geological Survey in the 'Lewisian rocks of the foreland' (Precambrian basement), as well as widely elsewhere, it had been suggested by Read that 'the Moine series and its metamorphism . . . [were] of pre-Torridonian date' (quoted in Phillips 19376, p. 605) and Phillips felt that his investigation supported Read's hypothesis. Thus, a principal conclusion of Phillips' work, which subsequently became rather overlooked in the disagreements which arose over movement direction in relation to petrofabric girdles, was his apparent demonstration that the Moine metasediments have a regional metamorphic fabric which pre-dated the Moine Thrust movements and was broken down in the Moine Thrust Zone - thus in agreement with, although not proving, Read's (19346) hypothesis. Phillips had carefully examined transitional samples and concluded that the typical girdle 'seems almost completely lost' under the influence of the thrust movements. This confirmed that there had been regional metamorphism of the

Moine rocks before the Moine thrusting, and thus solved one major contentious issue, even if it opened another. Read, the referee of Phillips' paper, must have been delighted to see his own hypothesis apparently confirmed. Recognizing the huge amount of work on which Phillips' pioneering study had been based, he suggested only minor amendments and recommended (22 April 1937) that it be published without delay (J. C. Thackray, pers. comm. 1996). In the discussion following the reading of the paper (5 May 1937; Phillips 1937c) at the Geological Society, Read naturally welcomed its findings. However, rather surprisingly (in view of his referee's comments), he added that he was concerned about the interpretation of the orientation of the directions of applied pressure as SW-NE and wished to be reassured 'that this interpretation of B tectonites was unquestioned by students of petrofabrics' (Read 1937). This could be taken to imply that Phillips did not discuss Martin's work in the oral presentation of his paper, although he did so in the manuscript (Phillips 19376, p. 599). Read also pointed out that in the area of central Perthshire in which he had worked, small-scale SE-pitching 'flat folds' were minor structures in comparison to the 'constant' NW-SE trend of the (major) fold axes (Read 1937). John Green (1873-1949) recalled that 'Barrow, in 1884, in defiance of all authority, came to the conclusion that the crystallisation of the local Moine rocks was not related to the thrusting, but was older and had partly been broken down by it' (Green 1937). However, it was Tilley who put his finger on the problems that would remain for many years. He said that: From the wealth and consistency of the evidence presented . . . the reality of the girdle fabric could not be doubted. The

30


Fig. 6.4. (a) Phillips' composite diagram (lower hemisphere equal-area projection) to show the locations of the 6-axes, inferred (where they could be determined) from petrofabric analyses from his localities in the Moine schists (Phillips 1937b, fig. 1). (b) Dip of foliation planes of 100 orientated handspecimens collected during his field traverses (Phillips 1937b, fig. 4). (c) Dip of foliation planes in the hand-specimens used for petrofabric analyses from which the 6-axes were determined (Phillips 1937b, fig. 3). (d) Composite lower hemisphere equal-area projection showing the locations of 'prominent quartz maxima' (Phillips 19376, p. 598), i.e. locations of maximum pointdensity in the contoured petrofabric diagrams for quartz, in relation to the plane of foliation (dashed line) which has been rotated into the vertical plane, and inferred 6-axis which lies at the centre of the diagram (Phillips 19376, fig. 7). Note the approximate symmetry shown by the two pairs of point-clouds about the foliation plane. Phillips interpreted this as being entirely consistent with 'Schmidt's idealised diagram (Schmidt 1932, pp. 191-192, fig. 49) of a typical girdle for mehrscharige Gleitung', i.e. in which 'the two surfaces of greatest shearing stress both have at times been effective as glide planes' (Phillips 19376, p. 589), 'with its "forbidden sectors" around the axis of principal stress and prominent maxima on the boundaries of these areas' (Phillips 19376, p. 598). Reproduced with the permission of Mr W. F. C. Phillips and The Geological Society, London, from figures 1, 3, 4 and 7 of F. C. Phillips, 1937, 'A fabric study of some Moine schists and associated rocks', Quarterly Journal of the Geological Society, 93, 581-620. currently accepted interpretation required a deformation acting along south-west and north-easterly lines. How was the direction of movement indicated by the b-axes to be reconciled with the north-north-easterly strike of the Moine schists which the Geological Survey recorded for a greater part of the Moine belt? To the question of what was the minimum amount of differential movement necessary to produce an orientated grain fabric, no answer seemed at present forthcoming. Sander himself had admitted that often only the last chapter of a deformation could be inferred from the fabric of a rock. Quartz was a mineral very readily recrystallised under stress, and the speaker was tempted to enquire whether a re-orientation of quartz might not occur under a deformation which did not appreciably affect the coarse structures or megatectonics of the rocks.... In connection with the author's remarks on the influence of the post-Cambrian movement, he would add that the effects of the Moine Thrust at Glenelg ... recalled those described in the zone of dislocation-metamorphism152 farther north, in Sutherland . . . the net effect was the imposition of a new and strongly orientated quartz fabric which he considered owed its development essentially to the Moine Thrust movement (Tilley 1937; quoted with permission of The Geological Society, London). Tilley articulated the main reservation and doubt of most geologists at the time: namely, how could the principal pre-Moine Thrust movements be compressive NE-SW when the stratigraphy and strike of the Moine metasediments (as shortly afterwards confirmed by Richey & Kennedy (1939) in Morar) was generally

NNE-SSW? Any major NE-SW movements were expected to produce NW-SE strikes. It was this discrepancy which ignited the Moine petrofabric controversy involving the interpretation of the movement directions which produced girdles of the poles to quartz c-axes and indirectly the movements which produced lineations. Tilley's concerns also arose as a result of the general lack of appreciation at that time of the true structural complexity of the region. The certain recognition that several distinct phases of superposed folding existed would only become apparent in the 1950s (as a result of the introduction into Scottish geology of detailed quantitative techniques for determining structural geometry). It had previously been assumed by many that the southeasterly plunging structures mapped by Clough and Hinxman were directly attributable to northwesterly movement of the Moine Thrust, acting perpendicular to its generally SW-NE strike (Peach et al 1907). Phillips responded to the discussants that: he recognised the great difficulty of reconciling the north-east and south-westerly strike over large areas with the conclusions which he had reached. He had worded these conclusions cautiously because he knew that to many of those more closely acquainted than he with the Moine rocks in the field the results were not acceptable, and they were therefore inclined to doubt the interpretation which he had put upon the fabric. On the other hand, he believed that this interpretation was unambiguous and the only one possible unless the whole structure of fabric analysis were questioned. As Professor Read had pointed


out, there was also an extensive development of folding striking north-west and south-east, and the lack of relationship of the fabric to the visible folding elsewhere was apparently due to the later folding having no reconstructive effect. . . . Professor Tilley had referred to Glenelg, but he felt that ... this district was in some respects peculiar. Only [in this region] had he found a fabric approaching that of a true S-tectonite.153 The orientation still corresponded to movements along south-west and north-east lines, and this fabric .. . was definitely broken up by the actual dislocations. Nothing similar had yet been found approaching the thrust in districts farther north, and he therefore believed that this was an original feature of the fabric around Glenelg rather than an effect of the overthrust movements (Phillips 1938b; quoted with permission of the British Association for the Advancement of Science and Mr W. F. C. Phillips). The scepticism regarding Phillips' interpretation of the petrofabrics of the Moine rocks undoubtedly included much adverse verbal comment additional to that published in the formal discussion, which only included those statements subsequently submitted in writing by those who had participated. These disapproving views are alluded to by Phillips in the above quotation. They rankled with him greatly, and much of his research during the following years, even into the 1950s, was ultimately aimed at justifying his 1937 conclusions and systematically closing off various objections - except, curiously, that he was slow to critically examine in print the basis for accepting that the movement direction had to be perpendicular to the b-axis. One recalls Donald Bertram Mclntyre's (b. 1923) comment that 'Sander's work began with field determination of the geometry and kinematics, and that the petrofabric interpretations followed... . [His] procedure had not been followed in Scotland, and . .. this was one reason why the conclusions drawn by Dr Coles Phillips ... had not met with general approval' (Mclntyre 1953, pp. cxiv-cxv, our italics).

The 'Tarskavaig Moines' In April 1937, just before the reading on 5 May of his Moine petrofabric paper, Phillips collected samples154 from the Tarskavaig Moines', an area of Moine rocks lying north of the Point of Sleat at the southern tip of the Isle of Syke (Fig. 5.2). The Tarskavaig Moine schists' were considered by Clough (in Peach et al. 1907) to be Moine metasediments which were more weakly metamorphosed. Being quartzo-feldspathic metasedimentary schists in lithology, they were very similar to the Moine rocks but occur in the Tarskavaig Nappe.155 This lies structurally below, and to the west of, the Moine Thrust, in a small area between Tarskavaig and the Point of Sleat (Fig. 6.5). Phillips' purpose was principally to ascertain whether his discovery of the characteristic Moine fabric could be used as a tool to resolve the disputed status of the Tarskavaig Moines': were they true Moine, sheared Torridonian, or both, if the Moine metasediments correlated with the Torridonian? In selecting his sampling localities, Phillips relied on an existing 1:126720 (2 in:l mi) Geological Survey map by Clough. He found that, with 'only one exception' (locality 10, Fig. 6.5), the Tarskavaig Moine' rocks examined (e.g. localities 6, 7 and 8 in Fig. 6.5) yielded a quartz fabric which corresponded to a b-axis orientated SW-NE (i.e. broadly parallel to the Moine Thrust Zone). Similar results were also obtained when the Torridonian' rocks were sufficiently deformed to show an ordered fabric. However, samples from localities known to lie SE of the thrust plane 'mapped [by the Geological Survey] as true Moine schists' (Phillips 1939, p. 234) were generally found to be crushed and mylonitized, but sometimes lenses of ungranulated quartz were preserved within the material 'granulated156 by the dislocation-metamorphism'

31

(Phillips 1939, p. 234). These localities (11 and 13 in Fig. 6.5) exhibited the same, apparently ubiquitous, SE-pitching157 b-axes which he had found in his 1937 study. Phillips wisely concluded that arguments based on the petrographic character of the Torridonian, Tarskavaig Moines' and Moine schists would prove of little help in assessing their relative ages.158 Following Sander's kinematic rules, Phillips (1938b, 1939) therefore suggested that the quartz fabric of the Tarskavaig Moines' was related to the overthrusting from the SE, whereas, as he had inferred before, the fabric of the rocks lying to the SE of the thrust complex 'existed prior to the dislocations, and [was] broken down by the thrust movements' (Phillips 1939, p. 239). He concluded that the Tarskavaig Moines' were actually Torridonian. Phillips (1938b) first presented these results orally, at a meeting of the British Association held in Cambridge in the summer of 1938.

Other pre-war activity In addition to his work on the Tarskavaig Moines' in 1937, Phillips began his second term on the Council of the Mineralogical Society (1937-1940). He also found time during the year to examine the fabric formed by olivine crystals in the dunites159 and related igneous rocks of Rum and Skye, in which the parallel orientation of the crystals was sufficient to produce planes along which the rocks could easily be split. The American experimental petrologist Norman Levi Bowen (1887-1956) had suggested (Bowen 1928; Bowen & Schairer 1933) that such rocks originated through local accumulation of olivine crystals, emplaced as a largely crystalline mass from which the interstitial liquid had been essentially displaced, and that the olivine crystals remained as such and did not become part of the liquid by re-melting or re-solution. However, it had recently been argued by the Italian structural petrologist Ciro Andreatta (1906-1960) in Italy and the German mineralogist Theodor Ernst (fl. 1904-1977) that the fabric of these types of rock was the result of previous metamorphism (Andreatta 1934; Ernst 1935, 1936). Phillips' examination of the fabric of the Rum and Skye intrusions enabled him to firmly reject such a hypothesis, concluding that 'the stresses acting during the emplacement of an olivine-rich intrusive already largely crystalline can develop in the rock precisely those features of the fabric which have been considered to indicate a metamorphic origin' (Phillips 1938a, p. 134). In March 1938, Phillips was awarded a moiety of the Murchison Fund of the Geological Society. In his presidential address, O. T. Jones drew particular attention to Phillips' studies of opaque ore minerals, his petrographical work on the serpentine rocks of the Shetland Isles, the metamorphism of Cornish and Highland rocks and his petrofabric studies, concluding that his work was 'always characterised by meticulous care, wide mineralogical and petrographical knowledge, and admirable clarity of presentation' (Jones 1938). Two months later, a group photograph of the staff of the Department of Mineralogy and Petrology (Fig. 6.6) shows Phillips on the 'front bench' alongside Harker, Tilley, Rastall and Wooster, with whom Phillips had carried out a joint investigation of a proposed method for the determination of the refractive index of liquids (Phillips & Wooster 1933). Following the death of the petrologist and mining geologist Frederick Hatch (1864-1932), the third edition of Hatch & Rastall's Petrology of the Sedimentary Rocks, revised by Rastall's Cambridge colleague Maurice Black (1904-1973), contained Phillips' revision of the appendix by the mineralogist and economic geologist Thomas Crook (1876-1937) on the diagnostic properties of detrital minerals (Crook & Phillips 1938). Originally written for the first edition, this appendix had been omitted from the second (1919) edition on grounds of cost, but it was now felt worthwhile to include an updated version.160

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Fig. 6.5. Examples of contoured (equalarea projection) petrofabric diagrams for preferred orientation of 300 quartz optical c-axes in the Moine and Tarskavaig Nappes at the southern extremity of the Isle of Skye, Northwest Highlands of Scotland; contours 1 (1) 5% (reproduced with permission of Mr W. F. C. Phillips and Cambridge University Press from figs 6, 7, 8, 10, 11 and 13 of F. C. Phillips, 1939, The micro-fabric of some members of the Tarskavaig-Moine' Series', Geological Magazine, 75, p. 229-240) in the context of a modern geological map (redrawn with permission of Professor R. D. Law and Cambridge University Press from figs 2 and 11 of R. D. Law & G. J. Potts, 1987, The Tarskavaig Nappe of Skye, northwest of Scotland: a re-examination of the fabrics and their kinematic significance', Geological Magazine, 124, 231-248). Note the difference in girdle orientation as shown at localities 10, 11 and 13, where Phillips inferred the presence of a NW-SE oriented b-axis, as compared to localities 6, 7 and 8, at which he inferred the presence of a NE-SW directed b-axis (Phillips 1939, pp. 233-234). Copyright © 1939, 1987 Cambridge University Press.

War years In June 1939, Phillips undertook a major field trip to Southern Africa.161 He sailed on the liner Imperial Star to Cape Town, where he visited Table Mountain. He then travelled northwards to the Northern Cape District of South Africa, where he collected from granites north of Springbok (Springbokfontein), and eclogites162 at Klein Pellar (Little Pella), both of which are located close to the Orange River (Fig. 6.7). He then travelled to Southern Rhodesia (now Zimbabwe), where he first visited the Geological Survey at Salisbury (Harare).163 He subsequently collected specimens from the Great Dyke in the Umvukwe Range, NNW of Salisbury; and visited Wankie (Hwange), Bulawayo, Sinoia (Chinhoyi), the Alaska copper mine and a gold mine164 in the Lomagundi (Makonde) district, and the Victoria Falls (Fig. 6.7).165 Triplite from Wankie, later described by Leake & Phillips (1965), was probably also obtained on this trip, as it was a gift to Phillips from R. Mcl. Tyndale-Biscoe of the National Museum, Bulawayo. Returning from South Africa following the Declaration of War on 3 September 1939, Phillips found himself too old for army service. He initially worked in a munitions factory near Poole, Dorset, because he wanted to do something to help, but he was soon called back to Cambridge as he was in a reserved occupation

(W. F. C. Phillips, pers. comm. 2000). Nevertheless, he became a member of Cambridge Civil Defence Services and subsequently a sergeant in the Home Guard (May 1940-December 1944). During the long periods in which he was required to be awake to undertake firewatching duties in the event of an air raid, he spent the time laboriously making the universal stage measurements for 'hundreds' of petrofabric diagrams, in order to extend his earlier work on the Moine metasediments. Petrofabrics of the Ben Vuirich granite Phillips' research student, Agrell, had moved to take up a position at Manchester University in 1938. Following the outbreak of World War II, Agrell became involved in a new field, the study of the mineralogy of industrial slags. The aim of this was the improvement of furnace efficiency, a necessity if the domestic production of iron and steel was to be maximized. This work must have taken up much of his time and as Agrell suffered from dyslexia, which made writing difficult for him, he consequently published relatively few papers during his career (Chinner 1998, p. 667). It is therefore not too surprising that his PhD dissertation, begun under Phillip's supervision in 1934, was not submitted until May 1941.


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Fig. 6.6. Staff of the Department of Mineralogy and Petrology, Cambridge University, May 1938, with some visiting researchers. Seated, front row, left to right: F. C. Phillips, A. Harker, C. E. Tilley, R. H. Rastall, W. A. Wooster; seated, centre, left to right: A. T. J. Dollar, S. O. Agrell, R. C. Evans, N. F. M. Henry, R. S. Nockolds, C. O. Hutton; standing, left to right: T. Deans, F. Walker, A. J. Hall, I. Fankuchen, R. T. Prider. Reproduced with permission of Professor I. N. McCave, Department of Earth Sciences, University of Cambridge.

The final work (Agrell 1941) consists of two quite unrelated sections. Part I 'On the petrology of the adinoles of Dinas Head, Cornwall' (Fig. 2.1) contains no mention of petrofabrics and some of this work was published prior to submission of the dissertation (Agrell 1939). Part II 'On the results of petrofabric analysis of the [Precambrian]166 Ben Vuirich granite, Pitlochry, Perthshire and the surrounding Dalradian metasediments', is rather surprising in that, apparently ignoring the techniques for the systematic investigation of granite batholiths pioneered by Hans Cloos (1921, 1922, 1926; H. Cloos et al 1927) and his students (e.g. Balk 1925, 1931, 1936, 1937; E. Cloos 1931, 1932, 1934), other than a citation of Grout & Balk (1934), it has no discussion of their work, nor does it contain either a detailed geological or a structural map of the granite (see Fig. 5.2 for location). The dissertation simply presents an outline geological map, together with contoured equal-area stereograms (mainly for quartz and biotite) at 18 localities within the granite and 16 localities in the surrounding metasediments (Agrell 1941, fig. 17, following p. 35), although a tiny synoptic structural map appears in a later illustration summarizing his petrofabric results (Agrell 1941, p. fig. 37, following p. 54).167 One can only conclude that this apparent lack of emphasis on the field geology reflected the perspective of the former Department of Mineralogy and Petrology at Cambridge. Nevertheless, Agrell (1941, pp. 74-76, 83-87) concluded that the granite was intruded into 'normal' (i.e. not regionally metamorphosed) sediments, producing a hornfelsed 168 northwestern

margin; the formation of the NW-SE striking foliation and 'NW-SE b-axes' pitching at 65° to the SE in the granite was later than its intrusion; and that there was evidence from the surrounding schists that the whole was affected by a second, later, NE-SW striking foliation 'which appears as small puckers or strain-slips' associated with horizontal NE-SW b-axes. It is unfortunate that no results from the second part of Agrell's dissertation were ever published, for as well as complementing Phillips' work on the Moine schists, it dealt for the first time in Britain with the detailed microfabric of an intrusive body, its aureole and outside. Furthermore, Agrell's interpretation is in accord with that recently published by Tanner (1996), that the intrusion is earlier than the initial phase of regional deformation (Dl) and intruded into non-metamorphic rocks, although Tanner & Leslie (1994) had previously suggested that it was a post-Dl intrusion. In common with other early investigators, Agrell attributed the occasional appearance of possible crossed-girdles in schists SE of the granite to 'overprinting' 169 and believed that the Carn Chuinneag and Inchbae granites showed similar relationships. However, in his final conclusions, Agrell (1941, pp. 83-84) noted that although Phillips' (1937b) hypothesis (that there were two periods of deformation: (i) post-Lewisian and pre-Torridonian; (ii) post-Cambrian and pre-Moine Thrust), appeared to be confirmed by his later work on the Tarskavaig schists (Phillips 1939), the evidence was not absolutely conclusive. Wright (1908)

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Fig. 6.7. Locality map of places visited by Phillips in South Africa and Southern Rhodesia (now Zimbabwe) in 1939 (black dots indicate places mentioned in text; see text for modern place-name equivalents).

had shown that the Torridonian rocks of Colonsay exhibit two sets of foliation planes, with a distinct time-gap between each; and the Dalradian outcrops in the Pitlochry district showed no evidence of folding 'bearing the normal relation to the early b-axes.' Agrell believed that 'these facts, together with the occurrence of the two lineations so clearly at right angles to each other, suggest that both may be part of the same deformation period, and represent different reactions at different stages of the deformation.' He realized that since this hypothesis did not follow the currently accepted theories for girdle development, more supporting evidence would be required but 'the possibility must nevertheless be borne in mind'. Agrell also suggested that since no girdles consistent with a second period of deformation had been found in the Moine (Phillips 1937ft), although they did occur in the Dalradian Schists and Struan Flags (Robertson 1939) and there was evidence for two phases of deformation in the foliation of the Torridonian rocks of Islay and Colonsay (Wilkinson 1907; Wright 1908; Wright & Bailey 1911), the intensity of deformation appeared to increase southwards. However, he ended on a cautious note: 'Speculation here is of little use except to indicate a needed line of future research especially in the injection complexes' Agrell (1941, p. 84). In view of the problems which Phillips' adoption of Sander's 'orthodox' interpretation (i.e. a transport direction which is in general perpendicular to that shown by the lineation), as Anderson (1948, p. 122) and Phillips (1951b, p. 229) called it, was to cause him in later years, it is of interest that, although not clearly articulated in Agrell's dissertation, his student also appears to have had his doubts about it.

Dissonant voices With the passage of time, the 'orthodox' interpretation had also begun to be questioned by other workers, such as Martin (1935) and Anders Kvale (fl. 1936-1975), both of whom had a background of extensive field-mapping experience in Norway. They both supported what Phillips (1951ft, p. 229) later came to call the 'alternative' or 'revised' hypothesis, which envisaged the direction of mass-transport as dominantly parallel to lineation (Martin 1935; Kvale 1941). The influential German-American structural geologist Ernst Cloos (1898-1974; the younger brother of Hans Cloos), commented adversely (in Cloos & Hietanen 1941, p. 37): The determination of a B-axis with the universal stage takes a day or two or sometimes more; the measurement of a fold axis takes 5 min or less.... If the final result is the same it seems a waste of time to use the universal stage and statistical analysis', although he recognized that the statistical analysis of megascopic data could prove useful. Nevertheless, he admitted the need to supplement the field data with limited petrographical observation since 'field data alone say little about the rock fabric, rotation, mineral sequence, alterations, microscopic axes and so forth'. Ernst Cloos was in an excellent position to make this contrast since, on their emigration from Germany to the United States in the 1930s, both he and Robert Balk (1899-1955) had acted as emissaries for the approach to structural analysis pioneered by Ernst's brother (H. Cloos 1921, 1922; Cloos et al 1927). Hans Cloos's methods were founded on very detailed field mapping; the measurement of the orientations of structures such as lineations, fold axes and joint planes; and the synthesis of this information


35

in map form (H. Cloos 1921, 1922, 1926).170 Both Balk (1925, 1931) and Ernst Cloos (1931, 1932, 1934, 1936, 1937) subsequently applied these techniques with great success in the United States. Although their early work was focused on understanding the mechanisms by which major granitic intrusions were emplaced, by the late 1930s, Ernst Cloos was investigating the structural geology of areas of complex metamorphic rocks and had taught himself the techniques of petrofabric analysis (E. Cloos 1937; Cloos & Hietanen 1941).

Microfabric of the Moine schists. II Phillips began his third three-year term on the Council of the Mineralogical Society in 1943. That August, he undertook further fieldwork in the Western Highlands of Scotland.171 This painstaking continuation of his study of the Moine metasediments was designed to establish, beyond any doubt whatsoever, that the discoveries he had made in his 'preliminary survey' of 1937 were indeed correct. He consequently extended the number of specimens studied for their petrofabrics and their geographical distribution, in order to confirm the girdle's pattern, and its orientation, that it was the earliest metamorphic fabric in the Moine rocks, and that it was broken down by the dislocationmetamorphism associated with the thrusting. In order to clarify the relationship of the grain orientation to the foliation and lineation, Phillips (1945) now found it useful to represent the composite data for quartz and the micas in equalarea projections rotated so that the foliation plane plots as a vertical great circle that runs from left to right in the diagram (Fig. 6.8). He also employed a different approach to the production of the petrographic diagrams, by making composites of the results from many individual specimens at different localities. In order to clarify the fabric pattern, he first rotated the foliation plane in such a way that the direction corresponding to the lineation (which lies in the foliation plane) was vertical (Fig. 6.8a), thus emphasizing the girdle distribution of the quartz c-axes (Fig. 6.9b, e). Secondly, he also rotated the lineation by 90° to lie horizontally in the plane of the projection (Figs 6.8b, 6.9c, f), so as to view the girdle sideways on, a technique which has been found to be extremely useful in modern work.172 Whereas Phillips' previous petrofabric diagrams were based on individual universal stage measurements of c. 300 grains per thinsection, by means of rotation of the data for many thin-sections into their true geographical orientations, he was now able to produce composite plots of the poles to a total of 12 450 optic caxes of quartz from 50 randomly selected localities (Fig. 6.9a); 4250 normals to cleavage-planes of muscovite173 from 25 localities (Fig. 6.9d); and 4500 normals to cleavages of biotite, from 25 localities, etc. Because of the very large number of data-points, statistical variability was greatly reduced, and the orientation patterns were considerably clarified. Phillips (1945, p. 205) believed that because these composite diagrams were based on such a large body of data, they would eliminate any chance of bias caused by the presence of a weak orientation present in only a few specimens and that, if there was no true preferred orientation, then the plot would exhibit a uniform distribution of points. His results (Phillips 1945, fig. 4) showed that in specimens of 'Torridonian and Cambrian sediments visibly affected by the overthrusting movements of the Caledonian orogeny' (Phillips 1945, p. 206), the optic axes appeared to be consistent with a b-axis orientated NE-SW; whereas over large areas of the Moine outcrop, the pattern of the quartz girdles indicated a NW-SE orientated b-axis parallel to the SE-plunging lineation. He commented that the girdle arrangement of the quartz, muscovite, and biotite, and the lineation parallel to the b-axis of the girdle are features characteristic of the fabric of a B tectonite. Two other features

Fig. 6.8. Sketch to illustrate the derivation of the two rotated lower hemisphere equal-area projections used by Phillips (1945) in his analysis of composite data: (a) plane of foliation (f; broken line) and pole to lineation (1) vertical in the projection; (b) plane of foliation vertical in the projection; lineation in plane of paper. Also shown are the non-genetic {X, Y, Z) reference coordinates of Law et al (1992).

frequently observed in such tectonites, however, are absent from typical Moine schists. Unlike the micas, quartz does not usually show any very pronounced elongation and ac cracks174 are rarely seen when sections parallel to b are examined. The absence of these features is, I believe, to be accounted for as a result of overprinting by a later movement (Phillips 1945, p. 209; quoted with permission of Mr W. F. C. Phillips). In addition, near the Carn Chuinneag intrusion, Ross-shire175 (see Fig. 5.2 for location) the original unmetamorphosed sediments were preserved from the effects of regional metamorphism by conversion to a hornfels. Here, Phillips found that quartz showed no preferred orientation. However, a short distance away, 'the early-developing white-mica is arranged in a definite girdle, with its axis lying south-south-east, almost horizontal' while 'less than one mile from the outcrop of the granite [the Moine metasediments] gave the usual type of quartz girdle with a b-axis plunging 45° slightly east of south' (Phillips 1945, p. 210). He concluded from this, and other evidence described in Geological Survey memoirs, that the fabric was therefore 'the earliest deformation-fabric imprinted upon the sediments constituting the Moine schists' (Phillips 1945, p. 210) Furthermore, in some localities, Phillips found that the approximately NW-SE lineation was oblique to the axes of the 'isoclinal folds176 [which] usually run almost at right angles to this direction' (Phillips 1945, p. 211). In one case, he was able to follow the lineation 'as it turns over from the upper to the middle limb' of

36


Fig. 6.9. (a) Composite contoured (equal-area projection) petrofabric diagram for preferred orientation of the poles to 12 450 quartz optic c-axes based on '50 diagrams from widely scattered localities' of the Moine schist in the Northwest Highlands of Scotland, each having been 'rotated to their true geographical orientations and then combined' (Phillips 1945, p. 205 and fig. 1). (b) Composite petrofabric diagram for preferred orientation of poles to 6000 quartz optical c-axes 'from 25 specimens of Moine schist showing a well-marked lineation ... mainly determined in the Moine schists by the elongation of the micas'. Prior to making the composite, each diagram has been rotated as in Figure 6.8a; the dashed line is the plane of foliation. Note 'the clearly defined girdle and the pair of maxima set on either side of the foliations surface' (Phillips 1945, pp. 207-208, fig. 5a). (c) Diagram rotated as in Figure 6.8b so that the lineation lies in the plane of the paper (Phillips 1945, p. 208, fig. 5b). (d) Composite petrofabric diagram for preferred orientation of the poles to the normals to 4240 cleavage-planes of muscovite, based on 25 diagrams from the same localities in the geographical orientation, as used in (a) (Phillips 1945, p. 206 and fig. 2). (e) The muscovite data of (d) rotated as in Figure 6.8a (Phillips 1945, p. 208 and fig. 6a). (f) The muscovite data of (d) rotated as in Figure 6.8b. Note 'a marked maximum ... indicating the orientation of the majority of flakes parallel to the visible foliation and with a continuous girdle normal to the lineation' (Phillips 1945, p. 208, fig. 6b). Contours in (a)-(d) 0.5 (1) 2.5+%, in (e) and (f) 1 (1) 7, 9 (2) 15%. Reproduced with permission of Mr W. F. C. Phillips and Cambridge University Press from figures 1, 2, 5 and 6 of F. C. Phillips, 1945, The micro-fabric of the Moine Schists', Geological Magazine, 82, 205-220, copyright © 1945 Cambridge University Press. the fold. Moreover, using his skill with stereographic projections, he plotted this progressive change in orientation of the lineation, showing that its position corresponded with that which would be expected if it had been folded. Thus, it seemed difficult to avoid the conclusion that the lineation, and therefore the 5-tectonite177 fabric which it expresses, were in existence before the isoclinal folding was overprinted. The obliquity of the lineation to the axes of the isoclinal folding also suggests in itself a lack of genetic relationship between these two features (Phillips 1945, p. 211; quoted with permission of Mr W. F. C. Phillips). Although Phillips did not state it explicitly, in emphasizing that the petrofabric girdles were earlier and unrelated to the later folds with NE-SW trending axial planes, it was implicit that this explained why the NE-SW movement direction which he had deduced in 1937 was different from the NW-SE movement needed to produce NE-SW folding and strike directions in the Moine rocks and thus, in effect, rebutted the criticism of his 1937 paper. He also pointed out (quoting from Flett, in Peach et al. 1912) that the 'strike of the beds i.e. the largest area of

well-preserved hornfels [at Cam Chuinneag] lies at right angles to the strike of the regional movements'. On entering the shear zones where intense 'dislocation-metamorphism' occurred 'as one approaches the thrust', Phillips observed that the earlier fabric tended to be obliterated without a new one 'being built up'. In addition: there is frequently a slight discordance between the attitudes of the mica girdles on the one hand and of the quartz on the other .. . the effect being as if the [mica] had been rotated slightly about a NE-SW axis [e.g. Fig. 6.10a]. Such a displacement might reasonably be ascribed to the SE-NW overthrust movements, and to this same overprinting I believe should be referred also the lack of notable elongation of the quartz, and possibly also the absence of the ac cracks referred to above. The movements, which found the fabric already in existence, had little effect on the micas except in the belt of actual dislocationmetamorphism, but they have recrystallised the quartz with loss of elongation, healing of any previously existing cracks, slight displacement of the fabric, and little loss of preferred orientation (Phillips 1945, pp. 216-217; quoted with permission of Mr W. F. C. Phillips and The Geological Society, London).


37

Fig. 6.10. Composite contoured (equal-area projection) petrofabric diagram for preferred orientation of the poles to 250 quartz optic c-axes (solid contours) and to the normals to 250 cleavage planes of muscovite (dashed contours) from a single locality (Glencarron Lodge) in the Moine schist, combined in their true geographical orientations (Phillips 1945, fig. 20). Phillips inferred from the slight discordance between the position of the maximum of the mica diagram and the quartz girdle (which he also found elsewhere), that the latter 'had been rotated slightly about a NE-SW axis' (Phillips 1945, p. 216). (b-f) Sequence of illustrations of petrofabric diagrams for preferred orientation of quartz optic c-axes from various localities (details in Phillips 1945, pp. 217-218) in the Moine schist to show progressive development of 'crossed-girdles'. In all cases, the diagrams have been rotated as in Figure 6.8b so that the lineation lies in the plane of the paper; the dashed line is the plane of foliation. Contours 1(1)9%. Reproduced with permission of Mr W. F. C. Phillips and Cambridge University Press from figures 20, 22-27 of F. C. Phillips, 1945, The micro-fabric of the Moine Schists', Geological Magazine, 82, 205-220, copyright © 1945 Cambridge University Press.

The occasional appearance of 'crossed-girdles' in some of Phillips' quartz diagrams (Fig. 6.10b-f) was 'tentatively regarded as evidence for considering that the more complex diagrams here represent over-printing on previously-existing B-tectonite fabric during the Caledonian overthrusting' (Phillips 1945, p. 218). The uncertainty of his conclusion was a result of the fact that, at this time, the interpretation of such complex fabrics was in its infancy, and there was considerable debate (even among structural petrologists) as to whether such a pattern was the result of a single deformation or 'two successive non-parallel movements'.178 However, there was by this time a conviction amongst many geologists that the general NE-SW strike of the Moine metasediments must necessarily be perpendicular to a single 'dominant' northwesterly direction of transport of the Moine Thrust, and therefore Phillips' (1931b) results (and similar findings obtained by petrofabric workers elsewhere in the world) were greeted with increasing scepticism. This view was reinforced by further publications by Kvale (1945, 1946) and by Trygve Strand (1903-1976) in 1945, which reported evidence of extension parallel to the movement direction in the Norwegian Caledonides. Renewed criticism also came from North America where Ernst Cloos echoed Kvale's (1941, 1945, 1946) criticisms, commenting

that while structural petrologists often assumed that movement occurred within the direction of the plane of the girdle perpendicular to the lineation, with rotation (either by rolling or gliding) about an axis coincident with the lineation, since many of these lineations appeared to lie perpendicular to 'fold axes, regional trends, and all other such directions which seem to indicate the movement direction . . . fabric analyses show movements perpendicular to undisputed geological evidence, and authors as a rule see the necessity of adopting two phases of movement perpendicular to each other' (E. Cloos 1946, p. 4). In order to make a further point about Phillips' work in the Northwest Highlands, Cloos (who had never visited the area) took the recorded attitudes of bedding, cleavage and lineation from published Geological Survey map sheets covering the Assynt district179 and compiled his own regional structural synthesis (Cloos 1946, plate 9). He then wrote: Phillips' (1937) interpretation of diagrams, showing girdles normal to the rods in the Scottish Highlands, assumes a compression at an angle of approximately 90° to the free movement on the thrust planes. Lineation [in E. Cloos's synthesis] is most pronounced in the vicinity of the thrust planes and dips


38

southeast. The dip remains constant even where cleavage or bedding strikes parallel to the lineation.... probably the now visible portion of the [quartz] deformation is only a component of the entire movement and not representative.... If the small amount of post-crystalline deformation which is visible is used in analysing the regional deformation plan, the interpretation rests on inches of movement and does not take into consideration the miles which preceded the last phase. Principal movement has been to the northwest and resulted in the present disposition of the formations as seen on the maps. ... Subordinate movements may well have been perpendicular to the general direction of advance and resulted in the arrangement seen in girdles around the direction of rodding (E. Cloos 1946, p. 28; reproduced with permission of the editor, Geological Society of America). Ernst Cloos then reiterated the view he had previously expressed in 1941, namely, that although structural petrology might have its uses, it was unlikely to provide more information than could be arrived at from field observations (Cloos 1946, p. 32). However, it was to be some years before Phillips replied to these criticisms.

A return to crystallography Early in 1946, Phillips travelled to Germany, under the authority of the British Control Commission, to inspect laboratory facilities in connection with war reparations. In the course of this visit, he met Professor Paul Ramdohr (1890-1985), a mineralogist and 'one of the founding fathers' of ore microscopy, who had been making his own polished sections since 1925 (Schreyer 1986, p. 839). Doubtless he and Phillips had many common interests in this field. Ramdohr presented him with a specimen180 of the copper-ore malachite, from the Belgian Congo. This may have been a somewhat ironic symbol of the renewal of post-war relationships between like-minded scientists, since the specimen had become oxidized in the fire which followed the bombing of the Friedrich Wilhelm University, Berlin, in the spring offensive of the previous year. During this visit, Phillips may also have visited the mining town of St Andreasberg, located in the Hartz mountains, 16 km SE of Clausthal.181 Phillips' first textbook, An Introduction to Crystallography, based on the lectures which he gave to aspiring Cambridge mineralogists, petrologists, geologists and material scientists, was published in 1946. Part 1 dealt with the external symmetry of crystals, crystal morphology and the graphical and numerical procedures used. As early as page 20, it introduced the crystallographic uses of the stereographic projection, in which he was by now an expert, at a time when it was little used by British geologists. The development of classical crystallography and the use of the optical goniometer182 preceded a detailed account of the 32

crystal classes. This was the first textbook on the morphology of crystals to adopt the elegant Hermann-Mauguin notation (first introduced in Hermann 1935) for the 32 crystal classes and the discussion of space-groups.183 Then followed a chapter on parallel growth and twinning, one on mathematical relationships, including the geometry of spherical triangles (the gist of which later became of wider application in plate tectonics) and, finally, one on methods for accurately drawing crystals from both stereographic and gnomonic184 projections. Part 2 dealt with the symmetry of the internal arrangement, with the study of spacegroups developed to a point which enabled the direct use of the space-group atlas International Tables for Determination of Crystal Structures (Hermann 1935). Phillips also discussed the relationship of crystal habit to the symmetry of the structural pattern. The book was unusually well illustrated for its time with over 500 text figures. A small touch, indicative of the author's breadth of interests, was his inclusion of footnotes giving brief biographical details of 21 crystallographers. Intended as an undergraduate text, the book was well received, particularly for its clarity of exposition, both at home (F. A. B. 1947) and in the United States (Faust 1950). Its favourable reception ensured its future continuance as a standard text and it would pass through three more editions (Phillips 1956a, 1963a, 1971) reviewed by Faust (1957), Levinson (1964) and Nockolds (S. R. N. 1972). The only significant change in the later editions was the addition to the second and subsequent editions of a chapter on the diffraction of X-rays by crystals. The book was widely used and appeared at a time when there were very few geological textbooks, and none that dealt with crystallography so comprehensively. It immediately established Phillips as a pedagogical expert in crystallography.

Time for a change Following the end of the war, Phillips began to feel that Tilley had not given him a chance for promotion, that he had been in Cambridge long enough, and that perhaps it was time he sought a position elsewhere (W. F. C. Phillips, pers. comm. 1997). It has also been suggested (on the basis of comments he made later in life to colleagues at Bristol University) that he felt that Tilley was very unsupportive of his staff as regards fellowships in college (G. Evans, pers comm. 1997) and of his own work on petrofabrics (R. J. G. Savage, pers. comm. 1997). Nevertheless, it appears that he never criticized Tilley sharply at home (W. F. C. Phillips, pers. comm. 1997). In an attempt to encourage him to remain in Cambridge, Phillips was appointed to the pensionable position of Lector in Mineralogy by Trinity College in 1946, although he continued to hold the positions of Assistant Director of Studies in Natural Sciences (CCC) and University Lecturer in Mineralogy and Petrology.

7. Liverpool (1947)

The appointment The University of Liverpool advertised the position of the George Herdman Chair of Geology in 1946, seven years after Read had left in 1939 to become head of department at Imperial College, London. Twelve applications were received. Phillips' referees were the geologist Tressilian Charles Nicholas (1888-1989) and O. T. Jones. Nicholas is best known as an extraordinarily successful Senior Bursar (1929-1956) of Trinity College, Cambridge. Having retired from lecturing in 1936 (M. A. A. 1990) he was elected Chairman of the Faculty of Geography and Geology. He had taught Phillips as an undergraduate, had seen the commencement of his teaching and research, and appreciated his 'publicspirited, hard-working and excellent' administrative abilities, when Phillips worked under him as Secretary to the Faculty Board. Nicholas wrote very positively (letter of 27 August 1946, quoted in Anon. 1946), to say that he had every confidence that Phillips would make a very good head of department who could be expected to establish a school of research workers in new fields, such as that of petrofabrics. This view was independently, and equally strongly, supported by Jones (letter of 11 August 1946, quoted in Anon. 1946) who emphasized Phillips' acknowledged role as the leading British expert on petrofabric methods. Following consultation with the external advisers (Tilley and Read), a shortlist of four candidates was drawn up. Interviews (at which the external advisers were present) were held on 17 September 1946. These reduced the shortlist to Phillips and a palaeontologist, Dr Thomas Stanley Westoll (1912-1995; FRS, 1952), who was at that time a lecturer in the Department of Geology and Mineralogy, University of Aberdeen, with the odds in favour of Phillips because it was felt that he had somewhat broader experience than Westoll. The casting vote was put to T. C. Phemister, Professor and Head of Department of Geology and Mineralogy at the University of Aberdeen (1937-1939, 1945-1972). On completion of his PhD at Cambridge in 1926, Phemister had joined the staff of the University of British Columbia (1926-1933), where he worked on the genesis of the Sudbury nickel ores, before returning to Cambridge as University Demonstrator in Mineralogy and Petrology (1933-1937). He knew Phillips well from their overlapping time as fellow demonstrators at this period and, as a result of his interest in Phillips' work, Phemister had had a technician build a universal stage for him following his arrival at Aberdeen in 1937 (P. A. Sabine, pers. comm. 2000). Phemister now unequivocally recommended Phillips for the position (letter of 21 October 1946, quoted in Anon. 1946) on the grounds that, although the promise of future distinction for both candidates appeared to be similar, Phillips' work was likely to be more fundamental and 'more readily directed into strictly geological channels', and also that he was likely to be the better administrator. Consequently, Phillips' appointment to the George Herdman Chair was announced by the University on 6 November 1946, and appeared in the 30 November issue of Nature.185

A new environment Quite apart from the culture-shock of transition from 1 Shaftesbury Road, Cambridge, to living in Birkenhead and working in an industrial city which had suffered severely from wartime bombing,

the department into which Phillips arrived to take up his duties in January 1947 had its own problems. In the previous autumn term, with only a 'small' staff available, 63 students had registered for courses in geology and 16 students from the Faculty of Arts were also joining the first-year course in geology. 'Owing to time-table difficulties and shortage of microscopes and geological maps, the laboratory work of this group of students had to be taken in triplicate. Similarly, the usual field-classes had to be duplicated in order to reduce them to a convenient number. [Provision of] maps and microscopes ... cannot be increased for some time to come' (Anon. 1947a). Despite these difficulties, the year seemed to start well for Phillips, with the publication of a further note concerning the Moine problem. He now reported finding the same NW-SE striking lineation parallel to the b-axis of a girdle fabric, previously described by him from the Moine schists east of the Moine Thrust, in the ortho-gneisses186 and hornblende187 schists of the Lewisian rocks from the foreland region of the Northwest Highlands (Phillips 1941 a, p. 58), thus providing further evidence for the unusually widespread nature of this phenomenon. At the March meeting of the Liverpool Geological Society,188 Phillips was elected as an Ordinary Member (Anon. 1947b), and at about this time a favourable review of his Crystallography textbook appeared (F. A. B. 1947). Later in the year, he was appointed a member of the General Organising Committee for the forthcoming 18th Session of the International Geological Congress (Anon. 1947a; Butler 1950, pp. 15, 35) and wrote a review of the geology and geochemistry of oceanic evaporite deposits (Phillips 1947b). Although Phillips' appointment fortunately made up for the previous lack of a petrologist (caused by the retirement of a member of staff), during the Lent and summer terms 'the burden of teaching duties laid upon the .. . small staff . .. left little time for research' (Anon. 1947a). Moreover, the Jane Herdman Laboratories of Geology were only partly available, as their wartime occupants had not yet been fully removed, giving accommodation problems. Phillips soon began to find the administration of his department burdensome (R. M. Shackleton, pers. comm. 1996). Whenever time could be spared from such duties, he retreated into curating the Traill Mineral Collection, housed under the glass dome in the top of the Jane Herdman Building. This comprised some 3000 mineral specimens, collected in the early part of the nineteenth century and presented to the university by the Liverpool Royal Institution in 1942 (Neaverson 1950). In mid-September, Phillips attended the annual conference of the British Rheologists' Club, held at the University of Manchester, where he gave a talk on the preferred orientation of minerals and the mechanism of rock flow. He pointed out that the primary flow of igneous rocks, consolidating from a melt, may frequently be traced in a linear or platy parallelism of phenocrysts or included fragments in flow layers, while unconsolidated sediments showed primary flow structures as a result of their flow by reason of their high water content. Rocks are found folded to a degree which can vary from gentle flexures to the recumbent overfolds, or nappes, of mountain systems, such as the Alps, with amplitudes of many miles; these have responded to compressional stress by flowing, in the sense that they have acquired a permanent deformation without loss of cohesion. He then discussed in detail the actual means by which rock flow was thought to be achieved, and

39

40


gave evidence of dimensional and lattice orientation of individual fabric elements, showing how their fabric could be studied by Xray methods. The fact that in most deformed rocks some degree of preferred orientation is present, suggested that at some stage a new mechanism of translation-gliding operated which allowed further deformation without continued rotation. While there appeared to be good evidence for translation-gliding in minerals such as mica, and twin-gliding in calcite, there was still no certain evidence of the mechanism by which the plasticity of quartz was achieved (Mardles 1947). The Phillips family had initially found life in post-war Liverpool difficult to adjust to. They had not appreciated the substantial difference between living in a northern industrial area and the environs of Cambridge in which they had, until then, spent much of their lives. This, together with the privations of rationing and Phillips' heavy workload, was proving very stressful. Nevertheless, by that autumn, the family were beginning to feel more settled. Catastrophe At seven o'clock on the morning of 10 October, women cleaners arriving at the Department of Organic Chemistry found their entry to the corridor on the top floor barred by smoke and fumes issuing from a research laboratory door, a fire having broken out on the floor. The fire brigade was called, but the laboratory was almost completely burnt out. The corridor was left smokeblackened for a considerable distance from the door and a second laboratory, on the floor below, had to be temporarily evacuated on account of the large quantity of water used to extinguish the fire seeping through from the floor above. The report in the Liverpool Echo (10 October 1947; R. Horrocks, pers. comm. 1997) merely noted that several students lost valuable books and records of their research work but that the work of the department would not be seriously affected. Unfortunately, Phillips' room in the Department of Geology abutted the rear of the laboratory. As well as losing many of his research notes and papers, the hundreds of petrofabric diagrams which he had so laboriously compiled during the war years were either completely destroyed, or had the corners bearing the corresponding specimen numbers scorched off.189 Coming on top of the already existing stress, the loss of his research material precipitated a severe nervous breakdown. It was reported at the Faculty of Science Board Meeting of 13 October that Phillips had been granted leave of absence from the university on account of ill-health (A. Allan, pers. comm. 1996). Optimistically, on 18 October he was elected Vice-President for the 1947-1948 Session of the Liverpool Geological Society, which would commence the following month (Anon. 1948a), but the position was never taken up. Had Phillips remained in good health, there would have been no question of the family leaving the area. Unfortunately, as a result of his nervous breakdown, he was quite incapable of

continuing in the job at that time (Mrs S. J. C. Toogood, pers. comm. 1999). Phillips accordingly resigned the Chair at Liverpool, on grounds of ill-health, in December 1947 (Anon. 1948b). The family sold their house in Birkenhead and returned to Cambridge so that he could receive medical treatment. Phillips spent many months in nursing and convalescent homes, while the family lived with relatives in Bournemouth until he had fully recovered and could seek a new position elsewhere (W. F. C. Phillips, Mrs S. J. C. Toogood, pers. comms 1997, 1999). Regrettably, at that time there was still a stigma attached to the occurrence of mental illness. The events of the year were so traumatic, that although Phillips' brief tenure at Liverpool 'since 1947' appeared under his Who's Who entry for 1949, it was not mentioned in subsequent volumes. Aftermath It is ironical that the vacant Liverpool Chair was filled in October 1948 by Robert Millner Shackleton (1909-2001; FRS, 1971), a man of legendary prowess in the field and destined to become one of the most influential of British structural geologists, for he was unenthusiastic regarding structural petrology 'because of the absurd misinterpretations which experts (including Sander himself) drew from them' (R. M. Shackleton, pers. comm. 1996). He had taken his BSc (1931) and PhD (1934) at Liverpool, although he pursued the major part of his PhD studies of the volcanic and associated rocks of the Moel Hebog area, near Snowdon, Wales, at Imperial College (1932-1934). Following a year as an exploration geologist in Fiji, he joined the teaching staff at Imperial College (1936-1940). He then rejoined Imperial College, on his return from wartime service with the Mining and Geological Department, Kenya (1940-1945). By 1947 he was a lecturer, reluctantly teaching petrology as Read was apparently by then of the opinion that there was no future in structural geology (R. M. Shackleton, pers. comm. 1996). Curiously, it was not that long since Read had appointed Gilbert Wilson (1899-1986), originally a mining geologist who had taken his PhD at Imperial College in 1931, as Assistant Lecturer in 1940 (Williams 1963) in order to take advantage of the experience Wilson had gained while taking his MSc in structural geology at the University of Wisconsin in 1926 (W. S. Pitcher, pers. comm. 2000). Wilson became a very influential teacher, setting up the first systematic course in structural geology in a British university (J. G. R. & J. C. 1988). He was appointed Lecturer in Physical and Structural Geology in 1946 and Reader in 1952. Together with Read and Wallace Spencer Pitcher (b. 1919) (who joined the staff as a demonstrator in 1947 and was appointed Assistant Lecturer by Read in 1948), Wilson directed the group of young structural geologists which would carry out groundbreaking work in the Northwest Highlands of Scotland in the 1950s and who included John Sutton (1919-1992; FRS 1966), Janet Vida Watson (1923-1985; FRS 1979) and John Graham Ramsay (b. 1931; FRS 1973).

8. Bristol (1948-1952)

At the invitation of Professor Walter Frederick Whittard (1902-1966; FRS, 1957), palaeontologist, stratigrapher, and a formidable head of department, Phillips came to the Department of Geology at the University of Bristol in 1948, as Lecturer in Geology. D. T. Donovan (pers. comm. 2000) recalls being told by Whittard that he believed that Phillips' distinction merited a readership, but that as the university did not (then, at least) appoint directly to readerships, Phillips was offered the position of lecturer on the understanding that he would be promoted to Reader as soon as possible.190 The family, who were keen on caravanning, initially lived in the family caravan for a few months until permanent accommodation could be found. They then moved to Westaway, 89 Coombe Lane, Bristol, and this was to remain their home until Phillips retired from the department, his large Armstrong-Siddeley car being used less and less as traffic congestion increased. When Phillips arrived at Bristol he was known internationally for his textbook on crystallography and was an expert on optical mineralogy, but while there he never taught either subject, being responsible for the teaching of petrology. This very curious situation (quite inexplicable to those outside the department) arose because when Phillips arrived in Bristol, in his customary polite manner he asked Igor Serge Loupekine (1920-1993), who had been teaching mineralogy, crystallography and petrology in the department since his graduation in 1943 (Savage 1993), what he wished to retain. Loupekine chose the mineralogy and crystallography, and so Phillips taught the petrology.

The petrofabric controversy begins In England, difficulty in accepting Sander's 'orthodox' interpretation had already been touched on by Agrell in his dissertation. Now Kennedy, who had become Professor of Geology at the University of Leeds in 1945, was beginning to have his own doubts. Having spent a postdoctoral year (1927-1928) studying mineralogy and petrology under Niggli at the Technische Hochschule (Technical University) in Zurich, he was familiar with the structure of the Swiss Alps. On his return from Switzerland, Kennedy joined the Geological Survey, where he spent 17 years working in the Scottish Highlands, which included a study of the stratigraphy, structure and lineations in the Morar-Knoydart area of the Moine succession (Richey & Kennedy 1939). As a result, he was of the opinion that relating lineation to a particular tectonic movement was no easy task, and the issue was further complicated by uncertainty as to the actual amount of movement necessary to develop an orientated fabric in the rocks. For example, the south-south-easterly lineation in the Tarskavaig Nappe . . . might be due either to the major north-north-westerly travel of the thrust mass or to the late, very minor, north-to-south movement, amounting to only a few feet, which, on the evidence of a displaced dyke, was known to have taken place (Kennedy 1948). Ernest Masson Anderson (1877-1960) had left Edinburgh University in 1898, having gained a BSc with first-class honours in mathematics and natural philosophy and an MA. Following a short period as a teacher, he joined the Geological Survey in 1903. Influenced by Clough's work (c. 1884-1907) on the mapping and

interpretation of lineation and other structural features of the Dalradian schists in Argyll and elsewhere, Anderson became particularly interested in this topic. During his years with the Survey (1903-1928), he mapped terrain in the Lewisian, Moinian and Torridonian in Scotland (in Peach et al. 1912, 1913; Hinxman et al. 1915; Anderson 1923) similar to that worked in by Phillips, as well as younger rocks. Following his retirement in 1928, Anderson then applied his mathematical skills to the interpretation of crustal dynamics (A. G. M. 1961). He was now 'influenced' by Kennedy 'to take an interest in the relation of lineation to petrofabric' (Anderson 1948, p. 125). As a result, Anderson 'entered the petrofabrics arena', as Tilley (1948, p. 129) put it, with gusto, applying his mathematical skills to the topic, and launching a strong attack on the existing methods of petrofabric interpretation at a meeting of the Geological Society held on 11 February 1948. Anderson (1948, p. 101) agreed that the lineation of the micaceous rocks ran parallel to the elongation and to the pitch of minor folds, while at the same time it was perpendicular to the direction of concentration of the poles to the quartz c-axes and normals to the mica cleavage, and also perpendicular to the planes of the girdles in B-tectonites. However, he added that while minor folds exhibiting these characteristics 'appear to be a world-wide phenomenon ... it should not be assumed that they are parallel, in any district, to the main system of folding' (Anderson 1948, p. 101, our italics). Anderson did not really define what he meant by 'main system of folding' but, as pointed out by Weiss (1954, pp. 27-28), he evidently had in mind a direction subparallel to the strike of the Moine Thrust. Anderson went on to suggest that the true direction of tectonic transport corresponding to the NW-SE lineations observed by Phillips was not, as Phillips had interpreted it (following Schmidt and Sander), 'transverse to the lineation, and to the mullions, or crenulate folds, by which it is accompanied' (Anderson 1948, p. 104). On the contrary, Anderson (1948, pp. 102-103) argued that the evidence on which both Schmidt and Sander had based their conclusions seemed, on close examination, to be somewhat tenuous and he cited a number of counter-examples to support this claim. These included evidence obtained from deformed conglomerates in Norway (Fig. 8.1) by Strand (1945) and Kvale (1945). In Germany, Ludwig Ruger (1896-1955) described lineations (Ruger 1933) which were parallel to the inferred direction of 'stretching' of deformed clasts,191 and Martin (1935) had observed lineation in mylonites associated with granites in southern Sweden which was in some cases parallel to the direction of movement, but in another case was perpendicular to it; and Kvale (1941, 1946) had reported a similar phenomenon from SW Norway. Balk (1936, p. 716) had noted lineations in metamorphic rocks from New York State, USA, in which 'the trend of the linear structure coincides with the direction of movement in the various thrust faults'. Kvale (1946) and Balk (1936) also described the occurrence of folds with axes parallel to the direction of thrust movement. Strand maintained that his petrofabric diagrams showed girdles in a direction normal to the (inferred) principal direction of movement, and he agreed with both Martin and Kvale that 'girdles are generally ambiguous as to the determination of the direction of movement' (Strand 1945, p. 25). Strand then criticized Sander (1936) for maintaining that 'a girdle is always a testimony of a separate act of deformation with a direction parallel to the girdle', i.e. normal to the b-axis.

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Fig. 8.1. Deformed pebbles in the Bygdin conglomerate, southern Norway. Reproduced with permission of the author and publisher from figure 176b of L. E. Weiss, 1972, The Minor Structures of Deformed Rocks, Springer, Berlin.

Fig. 8.2. Gilbert Wilson's 'orthodox' Sanderian interpretation of minor structures in the Moine schist. Extract from figure 13.2 of G. Wilson & J. Cosgrove, 1982, Introduction to Smallscale Geological Structures, George Allen and Unwin, London (the original version of this figure, with Frenchlanguage annotation, appeared as fig. 46 of G. Wilson, 1961, The tectonic significance of small-scale structures and their importance to the geologist in the field', Annales de la Societe geologique de Belgique, 84, 423-548); our version is reproduced with permission of Dr J. Cosgrove and the Societe geologique de Belgique.

Indeed, such were the contrasts in interpretation of evidence in the field that Wilson later recalled that when Kvale subsequently visited the Scottish Highlands in 1951, on a field trip led by Donald Mclntyre,192 Kvale suggested that many of the minor structures which he was shown, such as the axes of rods, mullions, etc., which Wilson considered to be b-structures (Fig. 8.2), 'were really in a parallel to the movements which culminated in the

WNW drive of the Moine thrust' (Wilson 1961, p. 532). The reasons underlying Kvale's views are discussed in more detail below. Although Sander (1936) admitted the possibility that perhaps a 'more intense' movement could take place parallel to B, Anderson believed that the issue had not been seriously addressed in Sander (1948) and concluded that 'a rather fundamental mistake has

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hitherto usually been made [by implication by Schmidt, Sander, Fairbairn, Phillips, etc.] in the interpretation of petrofabric structures' (Anderson 1948, p. 125). In the discussion which followed the reading of Anderson's paper, this conclusion was welcomed by both Shackleton (1948) and Kennedy (1948), whereas Agrell (1948)193 said that 'while he agreed that lineation normal to [the] girdle and in the direction of movement occurred in the Highlands, there were also areas in which lineation was normal to the direction of movement' and he felt 'that the anomalies in interpretation of fabric might in part be due to differences of fabric lineation relations in schists of differing ages'. Tilley (1948) expressed a more cautious point of view, and wondered 'whether reorientation of quartz might not occur under the imposition of stresses which remained unrevealed in the coarse structures of rocks seen in the field'. He hoped that the programmes of experimental rock deformation, recently begun in the USA at Harvard and Berkeley,194 might 'provide the surest guiding lines to the solution of the perplexing problems before them' (Tilley 1948, p. 129). In the written record of the discussion, Wilson (1948) alone doubted Anderson's thesis. If Phillips was present at Anderson's talk (which is most unlikely as he had resigned only weeks before), he made no recorded comment. Inevitably, he must have found the united opposition of three of the leading structural geologists profoundly depressing, particularly so when, having lost his research material in the Liverpool fire, he no longer had access to his original evidence. The New Zealand-American metamorphic petrologist Francis John Turner (1904-1985; FRSNZ, 1938) first went to the United States to study structural petrology under Knopf at Yale in 1938. Returning to New Zealand on the outbreak of World War II, he continued lecturing at the University of Otago, Dunedin, and applying both structural petrology and Eskola's concept of metamorphic facies to the Otago schists (Turner 1938a, b, 1939, 1940). In 1946, having failed to become director of the New Zealand Geological Survey, he emigrated to the United States to join the faculty at the University of California in Berkeley. Within two years, he had begun joint work with David Tressel Griggs (1911-1974), who was at that time at the University of California at Los Angeles, on a long-term programme (1949-1975) of experimental rock deformation (Borg & Weiss 1997) intended to bring about a greater understanding of the fundamental mechanisms which underpin the interpretation of the results of structural petrology. Turner's (1948) memoir, Mineralogical and Structural Evolution of the Metamorphic Rocks, the first modern text on this topic, was largely based on his experience with the Otago schists, together with some of the early experimental results. In this text, although he also followed Sander's basic rules, Turner was careful to distinguish between the case in which the a-axis is the slip direction in a (monoclinic) fabric dominated by a single set of slip-planes and in which it may be shown by the presence of slickensides; and that in which 'flattened' fabrics occur as a result of slip on two (or more) symmetrically inclined equivalent sets of slip-planes, in which case the ab-plane is represented by the plane of flattening. In this situation, the a-axis is still perpendicular to b (= B), which is now represented by the line of intersection of the slip planes; however, it is now no longer a direction of actual slip movement, but 'is still the direction of tectonic transport, since it is the direction of maximum elongation of the deformed mass, even though deformation is achieved by simultaneous slip movements on surfaces symmetrically inclined to ab' (Turner 1948, p. 198). He added that the occurrence of an apparent discrepancy between the orientations of fabric axes established on the basis of megascopic and petrofabric data in 'flattened' rocks, recognized by Phillips (1937b, p. 587) was entirely explicable 'when it is recognized that in such rocks a is not a direction of slip movement, but the direction of maximum elongation' (Turner 1948, p. 198, f.n.). Phillips (1949) subsequently replied to the criticisms levelled at

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his work by both Ernst Cloos (1946) and Anderson (1948).195 In this paper, Phillips argued that Cloos had misinterpreted the evidence provided by the Geological Survey maps of the Assynt area, since some observers (notably Clough) were well aware of the importance of lineation, whereas 'others mapped only the strike and dip of the schistosity' (Phillips 1949, p. 280) and that little reliance could therefore be placed on the apparent spatial distribution of the map symbols.196 Phillips (1949, pp. 280-281) refuted Cloos's 'generalisation that lineation increases in intensity towards the outcrop of the thrust', pointing out that examination of such [Geological Survey] map-sheets as 107, 101, 92 and 91 will at once reveal that a lineation, sufficiently pronounced to attract attention in the field, is present in many Lewisian rocks. Indeed, nearly 50 symbols which lie within the Lewisian of the foreland structurally below unmoved Torridonian, and not within the area occupied by Moinian rocks are shown in Cloos [1946, plate 9]. ... Examination in the field197 has confirmed that over a wide area of the foreland and also in rocks mapped as displaced Lewisian masses and in some at least of the supposed inliers, a south-easterly plunging lineation is a characteristic feature of the fabric.... The direction of [NW-SE] lineation is normal to a girdle of the grain-fabric [for] quartz, muscovite, biotite, and hornblende (Phillips 1949, pp. 282-283; quoted with permission of Mr W. F. C. Phillips). He went on to suggest that an argument [such at that advanced by E. Cloos] which seeks a direct correlation between the distribution of lineation in Moinian rocks and the outcrops of the overthrusts is ... weakened by the widespread development of a closely similar lineation in Lewisian rocks, both of the foreland and in displaced masses.198 ... Even ... if the validity should eventually be established of the sweeping conclusion reached by Anderson (1948, p. 125) that 'a rather fundamental mistake has hitherto usually been made in the interpretation of petrofabric structures', and lineation of this type should be proved to be always parallel to the direction of shear ('direction of transport'), the problem presented by the close resemblance between the fabrics of the Moinian and of Lewisian rocks still calls for solution (Phillips 1949, pp. 285-286; quoted with permission of Mr W. F. C. Phillips).

Phillips prepares a rebuttal In March 1949, Phillips (accompanied by Whittard) visited the old Botallack tin-mining area, on the western margin of the Lands End Granite, near St Just, Cornwall (Fig. 2.1), to take samples of the Kenidjack hornfels,199 which he had previously sampled at some time prior to 1927.200 That July, Phillips began work in the Start Point area of Devon201 (Fig. 2.1) in order to gather further evidence in support for the 'orthodox' interpretation that the fabric b-axis was perpendicular to that of the applied stress. By January 1950 (the year in which he was promoted to Reader in Petrology), he appeared to have satisfied himself that, in general, the conventional Sander model was valid and that 'there was no support for the suggestion [i.e. the alternative model] recently put forward' by Anderson (Phillips 1950). The study of deformed and lineated quartzite pebbles and boulders in conglomerates promised to enable an estimate of the true deformation suffered by the clasts to be made, and thus to reveal any relationship between the quartz petrofabrics of the clasts and the deformation. Consequently, Phillips examined clasts from the highly sheared Funzie202 Conglomerate (Fig. 8.3) at The Snap in the SE of Fetlar, Shetland (Figs 3.1 and 3.5). He subsequently reached the surprising conclusion that

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Fig. 8.3. Deformed pebbles in the Funzie Conglomerate, The Snap, Fetlar, Shetland Islands. Photograph courtesy of Professor D. Flinn.

Here are to be found many deformed ('stretched') boulders of granulite, quartzite, and other rock-types The fabric of such boulders shows a well-defined girdle of mica, and often of quartz, with its axis parallel to the length of the boulder and therefore in the direction of shearing. Here, indeed, would seem at first sight to be excellent evidence in support of the revised interpretation of such a girdle and associated lineation. Detailed study of the boulders of various rock-types and of the matrix, however (which I hope to publish in full at a later date), seem to prove that these particular boulders possessed a highlyorientated fabric at the time of their incorporation in the conglomerate and that the shearing movements were overprinted on the original fabric at the time of the later movements (Phillips 1951b, pp. 231-232, our italics; quoted with permission of Mr W. F. C. Phillips). At first sight, Phillips appears to have begun his detailed work on the Funzie Conglomerate in 1951, with a visit following his attendance at the Edinburgh meeting of the British Association for the Advancement of Science.203 However, although the above quotation appears in Phillips' (19516) discussion of 'Apparent coincidences in the life-history of the Moine Schists', in the issue of the Geological Magazine dated 8 August 1951,204 a footnote on the first page of the article states: The substance of this paper was incorporated in a more general discussion presented before Section C at the Birmingham Meeting of the British Association, 5th September, 1950' i.e. prior to his visit to Fetlar in August 1951, which itself postdated the publication of the Geological Magazine article.

In 1953, on his 60th birthday, Phemister resigned from his recently attained position of Assistant Director of the Geological Survey in order to resume work in the Shetlands205 and it seems that Phemister, who was not a structural specialist, had invited Phillips to begin a study of the Funzie Conglomerate (P. A. Sabine, oral comm. 1998). However, it is a mystery exactly when (or how) the specimens were obtained upon which Phillips' comments in his 1951 paper were based. In view of his apparent lack of interest in lineations when he was working on his dissertation, it seems most unlikely that he would have collected orientated specimens in the 1920s. Furthermore, neither his Notebook entries for 1925-1926 referring to specimens which he collected from Fetlar, nor his dissertation, mention such a conglomerate.206 It is also improbable that Phillips visited Fetlar between 1926 and 1951, as his son has a clear recollection that during their visit to the island in the August of 1951,207 the residents recalled his father's previous visit in the late 1920s (W. F. C. Phillips, pers. comm. 1999). Nor is there any evidence in the Geological Survey archives that Phillips might have obtained specimens of the conglomerate from James Phemister (R. Gillanders, pers. comm. 2000). While it is possible that there was another (at present unidentified) source of material from the conglomerate, as Phemister mentions that his attention was first drawn to the conglomerate by an unidentified student (who we are sure was not Phillips)208 in 1926-1927, we think that the most likely solution is that the specimens were collected by Phemister in a private capacity and passed on, by him, to Phillips. In Phillips' (19516) discussion of his petrofabric results from the Moine metasediments, he was at least willing to contemplate the

BRISTOL (1948-1952)

implications of both the 'orthodox' (Sander 1930, 1948) and the 'alternative' or 'revised' (Anderson 1948) kinematic interpretation, in which the girdle was supposedly normal to the main movements, which were assumed to be parallel to the lineation. Hence, folds with axes parallel to the lineation acquired a different significance: they were no longer regarded as parallel to the main structural lines of the region, but as crenulate folds on the flanks of the fundamental structures and perpendicular thereto. Although Phillips (1951b, pp. 229-230, 232) believed that few structural petrologists would maintain that the 'revised' interpretation was universally applicable, he admitted that it could not be proved that it never applies. He also (Phillips 1951ft, pp. 232-233) pointed out the curious fact that the Cambrian quartzites, the sheared Torridonian, the 'Tarskavaig Moines', and the Moine schists themselves immediately adjacent to the outcrop of the Moine Thrust Zone, all have variably developed girdles which show the 'orthodox' relationship to the northwesterly movements of the Moine Thrust; whereas the Moine of the highest nappe and the Inchbae Gneiss (intruded into the Moine before the metamorphism), corresponded to the 'revised' interpretation. Also, if the fabric in the Lewisian was acquired prior to the Moine sedimentation, then it was an extraordinary coincidence that the girdles in the Lewisian rocks were similar, both in orientation and in style, to those in the Moine metasediments away from the Moine Thrust Zone. Phillips was obviously aware of the fact that radioactive dating methods (although then in their infancy) had begun, and commented that considerable help would be given to clarify 'the present confused situation' if absolute (or even relative) dates could be determined (Phillips 1951ft, pp. 234-235). Although he still appeared to favour the 'orthodox' interpretation, 209 he never published the more detailed work (referred to in Phillips 1951ft) on the Funzie Conglomerate, which suggests that he had at least some residual uncertainty (but see also below). Further support for Phillips' views, and his reiteration (Phillips 19510, 1953c) that an apparently similar lineation existed SE of the Great Glen, was subsequently voiced in studies undertaken by Wilson (1950, 1951, 1953a) and Mclntyre (1951a, ft, c, d). However, Anderson (1951a, ft), Shackleton (1951) and others remained extremely sceptical of Phillips' kinematic interpretation of the fabric.

A counter-example from Norway Two years after Kvale's participation on the 1951 field excursion led by Mclntyre to the Scottish Highlands, in a paper (read on his behalf by Wilson, on 1 July 1953, to a meeting of the Geological Society of London), Kvale questioned Mclntyre's (1951d) support for Phillips' views. The reasons for his scepticism go back to the years 1936-1942, when he undertook an extensive programme of field-mapping (accompanied by chemical and petrological studies) in the mountainous and sparsely inhabited terrain of the Bergsdalen quadrangle, an area of c. 940 km2 whose SW corner lies 20 km east of Bergen, in the southern Caledonides of western Norway (Fig. 8.4). The rocks in the NE of the quadrangle are composed of migmatites in the Precambrian basement of the Baltic Shield. These basement rocks have been overthrust by two, kilometre-thick, slices composed of Precambrian quartzites, quartz schists and conglomerates, volcanics and intrusives, known as the lower and upper Bergsdalen Nappes, which have been transported towards the ESE (Kvale 1946, p. 29) and probably represent detached fragments of the western Baltic Shield (Fossen 1992). They are separated by a 100-200 m thick group of strongly sheared phyllites and mica schists (Kvale 1946, 1948), which are now known to represent a major decollement zone210 (developed within the Late Precambrian to Lower Palaeozoic sediments on top of the Baltic Shield), which underlies the Caledonian nappes throughout southern Norway (Fossen 1992, 1993). The Bergsdalen

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Nappes were themselves overthrust by far-travelled Precambrian crust, which is now represented by the largely gneissose and plutonic rocks of the Jotun Nappe Complex (Fossen 1992, p. 1035), located just to the NE of the area of Figure 8.4. Following his first summer of fieldwork, Kvale decided that unravelling the complexities of the geology of the area could not be achieved by means of 'petrographic methods alone' (Kvale 1948, p. 1). However, through a fortunate meeting with Balk, who visited Norway in 1937, Kvale learnt of the innovative approach to structural geology which had been pioneered by the Cloos brothers. As a consequence, Kvale managed to obtain a scholarship which enabled him to spend the winter of 1938-1939 working with Ernst Cloos, who had been on the staff of Johns Hopkins University, Baltimore, USA, since 1931.211 As a result, Kvale returned to Norway trained in the methods used by the Cloos school of structural mapping and also in structural petrology,212 and was keen to compare these macro- and microtectonic approaches in his study of the Bergsdalen quadrangle (Kvale 1941, p. 191, 1946, p. 8). However, as Kvale gradually compiled his structural map of the area, the picture which began to emerge revealed complex folding and the frequent occurrence of two or more lineation directions in a single outcrop. Owing to the general lack of understanding of the results of multiple phases of deformation at that time, these proved difficult to interpret: 'if in this case we accept the linear structures as being normal to the directions of movement, we would have three or four different directions of movement in this truly Caledonian block' (Kvale 1948, p. 195). Moreover, the general trend of the lineations seemed to change over the area (Fig. 8.4). For example, in the northwestern part of the quadrangle, Kvale found that the trend of the most prominent lineation gradually changed from approximately SW-NE to W-E as one got closer to the upper boundary of the lower overthrust mass. He concluded that while the latter was parallel to the inferred direction of mass movement (i.e. to Sander's 0-axis), the former was 'parallel to the b-axis'. Moreover, 'the lineation in the greater part of the overthrust mass does not at all fit into this coordinate system . . . the 0-axis of the migmatite area has become parallel to the b-axis of the border zone of the lower overthrust mass' (Kvale 1948, p. 195). Nor did the results from structural petrology help to clarify the picture. Kvale (1946, p. 16) found that the petrofabric diagrams invariably showed more-or-less complete girdles intersecting in the tectonic c-axis. However, the b-axes of the mica girdles appeared to be parallel to the visible (B-axis) lineation 'regardless of the angle between this direction and the direction of principal movement'. In addition, where the deformation was most intense, Kvale interpreted the symmetry of the diagrams as corresponding to the tectonic 0-axis 'which in these cases is parallel to the direction of movement' and perpendicular to the lineation. He consequently concluded that: The direction of local tectonic transport as inferred from the [petrofabric] diagrams, is therefore not the direction of the movement of large crustal masses as determined in the field. The local patterns of movement may be at varying angles to the movement patterns of the larger masses and even, in many cases, perpendicular to it. The fabric 0-axis, as determined in a petrofabric diagram, is therefore no reliable indicator of the direction of tectonic transport, if by these words is meant the principal direction of mass movement. Even if several diagrams from an area give identical results, as along the Moine thrust in Scotland (Phillips 1937ft, c), they do not prove that the direction of movement of the mass as a whole was in the plane of symmetry (Kvale 1948, p. 205; quoted with permission of the information manager/editor, Bergen Museum). Although Kvale (1946, 1948) promised publication of a final part of his treatise on the Bergsdalen quadrangle, which would be

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Fig. 8.4. Lineation trends in the Bergsdalen Quadrangle, Norway. Reproduced with permission of the editorial board from figure 1 of A. Kvale, 1941, Tetrografisk-tektoniske unders0kelser i fjellkjeden mellom Bergensbuene og Voss\ Norsk Geologisk Tidsskrift, 21, 191-198. Legend (translated from the Norwegian by Professor R. SindingLarsen): I, migmatites [Western Gneiss Region of the Baltic Shield, Precambrian basement]; II, lower thrust sheet [Lower Bergsdalen Nappe]; IIIA, micaschist between the thrust sheets; IIIB, the Samnanger area [ophiolitic and island arc-related rocks of the Major Bergen Arc]; IIIC, the Norheimsund area [ophiolitic rocks of the Hardangerfjord Group]; IV, upper thrust sheet [Upper Bergsdalen Nappe]. 1, Lineation; 2, fold axes; 3, lines of intersection between schistosity and fissility; 4, slickensides; 5; parallel to thrust sheet; 6, parallel to the thrust direction; 7, parallel to the deviated thrust direction; 8, parallel to the direction of the mountain chain. Arrows point to the slip direction of the lineaments. Nos 1–4 show the icons for the four linear structures when they are parallel to the thrust front; nos 5-8 show the icons for the linear structures when they are parallel to the various directions. All the linear structures 1–4 can have the direction 5-8. The icons represent the combination of two sequences. Note that the unlabelled strip between the two thrusts forming the southeastern boundary of area I and the northwestern boundary of area II is also composed of the micaschists (IIIA). Text within square brackets is modern terminology from Fossen (1993).

devoted to the petrofabrics, it never appeared, possibly as a result of disillusionment with the utility of the 'Sanderian method'. It is therefore hardly surprising that in his paper to the Geological Society, Kvale concluded, with regard to the Northwest Highlands (Mclntyre 1951c,d): 'there are numerous indications of minor movements perpendicular to the lineation; that there is no obvious evidence of movement parallel to the lineation; and that the main direction of tectonic transport cannot be determined in the area' (Kvale 1953, p. 62). In the discussion of Kvale's paper, Wilson (1953b, p. 68) pointed out that the author 'was not trying to demonstrate, as others had attempted, that all lineations were in a; but he had shown that similar-looking structures could occur in a, in b, or at oblique angles to the general movement, and it behoved workers in this field to beware'. Nevertheless, in his later written reply to the comments made at the meeting, e.g. Phillips (1953a), Kvale reiterated that in his experience folded rocks, or rocks exhibiting a strong megascopic lineation, common[ly] give fabric diagrams having a

monoclinic symmetry with the ac-plane perpendicular to the linear structure. Nevertheless, the field evidence had completely convinced him that the minerals in some cases achieved their present orientation while the rocks were thrust parallel to the lineation on the fold-axis. [The author] therefore regards fabric diagrams as inconclusive evidence for the determination of the main direction of tectonic transport (Kvale 1953, pp. 70-71; quoted with permission of the Geological Society, London). Kvale (1953, p. 72) consequently recommended that 'the linear structures between the Moine Thrust and the Highland border should be studied as a unit, and attempts should be made to unveil the kinematic history of the entire area. In order to do this a regional survey of all types of linear structures throughout the Highlands would be needed'. This is essentially what happened over the next few years, based on a series of regional studies213 carried out by staff and research students from the universities of Bristol, Edinburgh, Glasgow, Imperial College (London), Leeds, Liverpool, etc., and staff from the Geological Survey.

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Structural petrology short courses When Phillips moved to Bristol, although Whittard did not initially encourage him to teach structural petrology in the undergraduate course (P. Hancock, pers. comm. 1996), he did allow him to run a series of what would now be called 'short courses' on the subject. The first of these was given in early January 1950, during the winter vacation (Wenk 1979), the year Phillips was appointed Reader in Petrology. The participants included Donald Bowes (an Adelaide graduate who was then studying at Imperial College), Douglas J. Shearman (who had been recently appointed as an Assistant Lecturer at Imperial College), Sutton, Watson and Lionel Edward Weiss (b. 1927) (Wenk 1979; D. J. Shearman, pers. comm. 1997). Bowes returned to Adelaide in February 1950, almost immediately after attending Phillips' course at Bristol, and he encouraged Alfred William Kleeman (1913-1982), a senior lecturer in the Adelaide department, to spend a period in Bristol during his forthcoming sabbatical leave (Phillips 1954b, p. vi), so that he too could learn from Phillips. In March 1951, Kleeman successfully applied to the University of Adelaide to work with Phillips, whom he regarded as the leading British authority on structural petrology, and during his leave (August 1951-March 1952) Kleeman spent about four months studying rock specimens from the Houghton Area in the Adelaide Hills and from the South Para River near the Barossa Diversion Weir (Fig. 9.1) under Phillips' guidance.214 Kleeman subsequently wrote that he felt encouraged by the results of this study to continue work in the Houghton area on his return to Australia, confident that it would improve understanding of the

47

structural geology of the Mt Lofty Ranges (unpublished correspondence, 22 April 1952, University of Adelaide Archives; K. Percival, pers. comm. 1998). Between 2 and 10 January, Kleeman assisted Phillips in a short course on structural petrology, attended by 25 students.215 The lectures and laboratory practical work (for which the students216 had to provide their own universal stages) for the course focused on the determination of grain orientation in deformed rocks217 and, as might be expected, Sander's views figured very strongly in the verbal presentations (E. H. T. Whitten, pers. comm. 1996).218 The course ended with a field trip to the Start schists at Start Point in Devon (Fig. 2.1).219 In 1951-1952, Phillips was president of the Geological Section of the Bristol Naturalists' Society and in 1952 he embarked on a fourth term on the Council of the Mineralogical Society. The following year, Phillips gave his first structural petrology course to final-year undergraduate students at Bristol and this continued into the 1960s (G. Evans, D. C. Goldring and D. Shelley, pers. comms 1997, 1997, 1999). A few of the students who studied under Phillips at Bristol subsequently went on to research and publish in the field (e.g. Shelley 1993). Phillips' Easter field excursions to Cornwall and North Wales, which took place in alternate years, were renowned for the exactitude of the time allowed at each stop, which remained the same, almost to the minute, year after year (R. Bradshaw, pers. comm. 1998). Phillips even had a book in which he recorded the times of the various stages of the train journeys he undertook and these were then compared with those of previous such excursions (D. Shelley, pers. comm. 1999).

9. An Australian lecture-tour

It may well have been Kleeman who suggested that Phillips should visit Australia to repeat his 'Vacation School in Structural Petrology' at the University of Adelaide (Fig. 9.1), and doubtless the British Council (which eventually sponsored the July-October 1953 visit) would have encouraged him to give lectures elsewhere. For instance, the University of Western Australia in Perth would have been an obvious place to visit, in view of Phillips' pre-war acquaintance with Rex Prider (ft. 1938-1985) at Cambridge

(Fig. 6.6), which may have been renewed during Prider's year of study-leave in Britain and Europe in 1952-1953. Leaving on 2 July 1953, Phillips travelled on the liner Strathnaver via Gibraltar, Port Said and the Gulf of Suez to the Red Sea, Aden, Bombay and Colombo,220 and arrived at Fremantle on 28 July.221 During his voyage, he read a book on Australia (Taylor 1943), and began 'serious work'. Although Phillips (1953b, p. 4) mentions 'reading Sander' (presumably, Sander 1948, 1950) on the

Fig. 9.1. Location map of Australia (black dots indicate places mentioned in text).

48

AN AUSTRALIAN LECTURE-TOUR

49

ship, he may also have been working on the manuscript for his forthcoming book The Use of Stereographic Projection in Structural Geology (Phillips 1954b).222

Western Australia During his week in Nedlands, near Perth, where the University of Western Australia is located, Phillips was hosted by his former Cambridge colleague Prider, who had been appointed to the Chair of Geology at the University in 1949. On 29 July, Phillips met various staff at the Government Laboratory in Perth 223 where he was shown work on the preparation of polished ore minerals, the equipment being of particular engineering interest to him. Phillips gave seminars on structural petrology to university students and to staff, as well as a talk on his ore-polishing machine. On 31 July he lectured to the West Australian division of the Geological Society of Australia. Much of the rest of his time was taken up by field trips with members of the department, to examine the granites and metamorphic rocks of the surrounding region.224 Between 6 and 9 August, Phillips visited the celebrated Kalgoorlie gold-mining area,225 hosted by J. D. Campbell of the Western Mining Corporation who gave him an 'excellent account of the structures of the field ... [Campbell's] en echelon folding gives reversed plunges, so that the minor folds (? and lineation) are unsafe guides to major structures, though the trend is constant' (Phillips 1953b, p. 8). They visited the Kurrang Conglomerate outcrop, where Phillips 'collected some pebbles, but they seem to be clearly original shapes and not stretched' (Phillips 1953b, p. 8) before going on to see the Black Flag metasediments and pillow lavas of the goldfields in the Mount Hunt area.

South Australia On 9 August, Phillips travelled by train to Adelaide, where the 'Vacation School in Structural Petrology' was to take place 'under the direction of Dr F. Coles Phillips .. . assisted by Mr A. W. Kleeman'. The few days before the course were spent mainly in preparation activities, but on 14 August, Phillips gave a lecture to a combined meeting of the South Australia branch of the Geological Society and the Royal Society of South Australia, 'which seemed to go off quite well'. The following day he joined his host, Kleeman, and the research students Graham A. Chinner (b. 1932), Bryan George Forbes, Margaret Sando (b. 1932) and Allan James Risley White (b. 1931), for a visit to Chinner's study area. The geology was 'excellent'226 but the weather was wet (Fig. 9.2) and Phillips' (19536, p. 10) laconic comment that on the return journey they 'tried to cross Tanunda Creek, but car nearly went in nose first' understates a narrow escape from drowning.227 The course began on 17 August.228 The participants included: E. V. Robinson (University of Queensland); Mervyn S. Paterson and Miss Langley (Australian National University, ANU); Wally B. Dallwitz and David A. White (Bureau of Mineral Resources, BMR); George F. U. Baker, an English mineralogist and petrologist who had emigrated to Australia in 1925, and J. Weymouth (Commonwealth Scientific and Industrial Organisation, CSIRO, Melbourne); Chinner, Forbes, White and Mrs Summers (University of Adelaide); Bryan Wells (University of Melbourne); Alan H. Spry (University of Tasmania); and the petrologist Alec W. G. Whittle (South Australia Department of Mines).229 Paterson had at this time only just started his subsequent outstanding work in experimental rock deformation in the Rock Physics Laboratory in the Geophysics Department at ANU, which he had recently set up at the invitation of the head of department, Professor J. C. Jaeger. Paterson's attendance on Phillips' course was particularly important, because it was there that, as a

Fig. 9.2. Phillips, with pipe (in left hand) and geological hammer, making the best of a rainy field excursion during his visit to the Tanunda Creek area, South Australia, Saturday 15 August 1953 (photograph autographed 'F. Coles Phillips, September, 1953' in lower right). Photograph courtesy of Dr G. A. Chinner.

physicist, he had his first exposure to the problems of the fabric of deformed rocks and, as a result, was significantly influenced into entering the field of rock and mineral deformation (M. S. Paterson, pers. comm. 1997). In general, there were two lectures in the mornings, and the afternoons were spent on practicals, with Kleeman assisting with the universal stage work. Field excursions were made to the Archaean230 gneisses and metasediments in the Houghton district, where Kleeman was working;231 to the Palmer area;232 and to exposures near the Millbrook reservoir.233 The course ended with a 'successful question session', followed by sherry, a closing speech by Baker, and the presentation of a book to Phillips before the last practical. On 1 September, Phillips went into the field with Kleeman, Whittle, White and Bruno Campana (Fig. 9.3) to look at pebble beds in the Archaean schists between Yankalilla Bay and Rapid Bay.234 Phillips, doubtless thinking of the Funzie Conglomerate, noted that while the pebble beds were clearly sheared,235 and the schists showed lineation down-dip, he was still not convinced . . . that the orientated pebbles are not an original sedimentation feature.236 Where abundant they seem to be accompanied by undistorted pebbles, particularly of feldspar. Where they lie in a sandy matrix they appeared to be usually parallel to the foreset beds237 of excellent false- [cross-]

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Fig. 9.3. Field excursion to Yankalilla Bay area, South Australia, Tuesday 1 September 1953. Left to right: Bruno Campana, Allan White, Alf Kleeman, Frank Coles Phillips, Alec Whittle. Reproduced with permission of Mr W. F. C. Phillips.

bedding revealed by black iron-ore bands (Phillips 1953b, p. 14; quoted with permission of Mr W. F. C. Phillips). The following day, Phillips gave a lecture on The Caledonian of Scotland' to second- and third-year students and spent the Thursday in the field with the economic geologist Eric Aroha Rudd (1910-1999), Arthur Richard Alderman (ft. 1901-1980), and Kleeman, visiting the Nairne pyrite mine.238 Then on 5 September, he travelled to Radium Hill239 with Whittle where, over the weekend, they visited the various mine sites.240 On the following three days Phillips toured the Zinc Corporation and New Broken Hill Consolidated mines (in New South Wales), where he collected specimens from Broken Hill241 which included rodded quartz from the major fault zones,242 returning to Adelaide on the Wednesday evening. Later in the week, Phillips went to see Whittle's ore-polishing apparatus at the Department of Mines, and apparently picked up some useful ideas from his technician (Phillips 1953b, p. 17), before visiting their new chemical and petrological laboratories. That weekend, Phillips drove to Melbourne. New South Wales During the following week Phillips gave a lecture to students at the University of Melbourne and visited the local CSIRO office. He also saw a good deal of the local geology, as well as visiting the Wattle Gully and Central Deborah gold mines, and Yallourn coal mine.243 On 14 and 18 September, Phillips had discussions with the Dutch structural geologist, Emile den Tex (ft. 1918). Den Tex had come to Australia as a Teaching Fellow at the University of

Sydney in 1950, following completion of his PhD (den Tex 1950) at the University of Leiden in 1949, during which he had learnt universal stage techniques from Professor Ernst Niggli. He was now in the third year of his lectureship at the University of Melbourne. Phillips, Turner and Ingerson had all advised Edwin Sherbon Hills (1906-1986; FRS, 1954), Professor of Geology and Mineralogy at the university since 1944, 'concerning petrofabric analysis' for the first edition of his Outlines of Structural Geology (Hills 1940) and the resultant brief appendix (Hills 1940, pp. 144-160) was retained unchanged into the second edition (Hills 1953). By 1952, Hills had convinced den Tex of the promise held by microfabric studies for deeper insights into the structure of igneous and metamorphic rocks. Den Tex (pers. comm. 1998) writes that, so far as his meso- and microfabric background was concerned, he was essentially a selftaught student through reading the works of Sander, Schmidt, the Cloos brothers, Ingerson, Turner and Fairbairn. He now attended Phillips' lectures and discussed his own work on the resolution of planar and linear structures in stereographic projections (den Tex 1953), as well as his study of the orientation of aegirine244 crystals in random thin-sections (den Tex 1954a) with Phillips. Den Tex records that his papers profited from Phillips' critical review and suggestions (E. den Tex, pers. comm. 1998). Phillips flew on to Sydney on 22 September. His hosts were two British geologists who had both emigrated to Australia: the geophysicist and coal geologist Professor Charles E. Marshall (fl. 1949-1973), and a senior lecturer in his department, the structural geologist and petrologist Harold Rutledge (1920-1954). Prior to his move to Australia in 1952, Rutledge had worked on the Loch Doon complex (Galloway) and the metamorphic rocks of the Fannish Forest area of the Scottish Highlands, and was now

AN AUSTRALIAN LECTURE-TOUR

engaged on similar studies at the Broken Hill mine and elsewhere in New South Wales (this work would unfortunately be terminated with his death in a plane crash the following year; A. H. 1954). Over the next fortnight, Phillips gave two general lectures on 'Introduction to petrofabric analysis', and a series of four paired discussions and demonstrations on Techniques and application of petrofabric studies' which included optical techniques, stresses and gliding, and graphical methods.245 All of these took place in the Department of Geology at Sydney University. On 29 September, Phillips lectured to the New South Wales Division of the Geological Society of Australia. Richard Limon Stanton, then a temporary lecturer at the University of Sydney, also attended Phillips' lectures. At that time Stanton had the idea 'then quite unacceptable and wrong' (R. L. Stanton, pers. comm. 1998) that some of the Lower Palaeozoic sulphide ores he was working on from the Bathurst district, NSW, might be the products of island arc volcanic activity and had been metamorphosed along with the volcanic and sedimentary rocks that enclosed them. As part of his investigations (Stanton 1956) he thought he should look at the petrofabrics of the sulphides in relation to those of the associated metamorphic rocks. He discussed his ideas with Phillips, who was very interested and encouraging (R. L. Stanton, pers. comm. 1998). Phillips' spare time was occupied by reading a PhD dissertation by G. F. R. Joklik, of the Bureau of Mineral Resources (BMR), Canberra, for which he had been appointed the external examiner. Phillips also visited coastal exposures of the Triassic and Permian sedimentary rocks, quarries exposing latite sills, granites in the Mt Victoria region, the Mt Gibraltar microsyenite, and cappings of laterite246 on the Hawkesbury sandstone.247 On Sunday 4 October, Phillips met Emeritus Professor Leo Arthur Cotton (1883-1963) and Phillips (1953b, p. 23) subsequently recorded that during their discussion he told Cotton that he was working on the manuscript of his book on the use of stereographic projection in structural geology. Cotton (who had retired from the staff of the university in 1948) would undoubtedly have been keenly interested in this, as he had himself promoted the use of stereographic techniques during courses in geological mapping which he gave at the University of Sydney in the 1930s. A student of Cotton's, M. D. Garretty, had completed an MSc thesis in 1937 on The geology and ore deposits of the Tavua goldfield and a DSc dissertation in 1947 on the Mineralisation of the ore bodies at Broken Hill, New South Wales. Cotton (in Cotton & Garretty 1945, (unnumbered) p. i) stated that Garretty had 'considerably extended the use of the [stereographic] projection to include the solution of new problems encountered in the course of his professional work. Having found these methods to be of great practical value, he suggested their publication'. A manuscript of their book was intended to have been sent abroad for publication in 1939, but this was delayed by the onset of World War II and the 'subsequent pre-occupation of the authors in special war time activities' (Cotton & Garretty 1945, (unnumbered) p. i). However, as a result of continuing demand from colleagues, their extremely thorough treatment of the subject eventually appeared in April 1945, as a co-authored 'technical summary' for North Broken Hill Limited, which was also privately circulated and never appeared in book form. According to Phillips (1954ft, p. vi), he first learnt of Cotton and Garretty's report from Kleeman during the latter's visit to Bristol in 1952, and Phillips appears to have received a copy of it from Cotton following their meeting. It was to significantly influence his own book (discussed below).

Queensland Phillips flew on to Brisbane on Tuesday 6 October, 1953. On the Thursday, he gave his first lecture in the Department of Geology,

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and a second on 12 October. The following day, he also lectured to the Geological Society, which was 'apparently quite a success'. He was gratified that the invertebrate palaeontologist and stratigrapher Dorothy Hill (1907-1997; FRS, 1965), who was at that time working on the compilation of the new geological and structural maps of Queensland, and who had driven him to the meeting, 'had very complimentary remarks to make about my suitability as a visiting lecturer'. Phillips spent much of the rest of the week in the field.248

Return to New South Wales On 15 October, Phillips left temperatures in the 90s Fahrenheit for cooler weather in Canberra. At a party that evening he met Professor Jaeger, Paterson and the petrologist Germaine Anne Joplin (fl. 1931-1986),249 all from ANU; and Norman Henry Fisher (fl. 1928-1981), director of the BMR. At the time of Phillips' visit, Joplin had just been appointed to Jager's Geophysics Department, where she was working on the metamorphic rocks of Mt Isa, NW Queensland, with a view to suggesting the programme of experimental work which Paterson should carry out in the Rock Physics Laboratory. The following day Phillips was in the field in the Cooma district with Joplin and D. C. Moye, head of the Engineering Geology Branch of the Snowy-Mountains Hydro-electric Authority, New South Wales.250 The next three days were spent with Moye and other geologists from the Hydro-electric Authority, examining the geology of the Jindabyne Valley, Tumut Pond and Adaminaby dam sites.251 Deep snow was still present on the higher ground. On 19 October, Phillips met up with Wally B. Dallwitz (who had attended his course in Adelaide) and the Estonian stratigrapher and palaeontologist Armin Aleksander Opick (1898-1983),252 both from the BMR, Canberra, for a session on the local geology.253 In the afternoon Phillips gave one lecture at the BMR, and a second to an audience of physical sciences staff and students. The following day,254 he visited a 40-year old dam with Dallwitz and Opick and noted cracking of the concrete due to expansion and astutely commented that it was possibly 'caused by cryptocrystalline silica' (Phillips 1953b, p. 28).255 Leaving on 22 October, Phillips returned briefly to Sydney, where he completed his external examiner's report on Joklik's (1954) PhD dissertation. The following day, he flew back to England on a BOAC Speedbird, returning via Darwin, Jakarta, Singapore, Karachi, Beirut and Zurich, and arrived back in Bristol on Tuesday 27 October, having travelled during the course of his lecture tour a total distance which he computed as 28 200 miles.

Outcome There is no doubt that his Australian visit was successful. Before Phillips left Australia, Kleeman wrote to him (19 October) in Canberra, to say 'You will, I am sure, know how very much we have appreciated your visit. You must also know what a great stimulus you have given to geology in the Australian Universities. We all hope you will be able to visit us again'. As has been mentioned above, Phillips' lecture course had been particularly important to Paterson. The visit also led to Alan White going to King's College London (where Phillips was an external examiner) to study for his PhD. Alf Kleeman, already a senior lecturer in the department at Adelaide, subsequently obtained his PhD with a dissertation on A Reconnaissance of the Structural Petrology of the Mount Lofty Ranges (Kleeman & White 1956) and retained an interest in structural petrology for the rest of his life (D. F. Branagan, pers. comm. 1998). As with all Phillips' courses in structural petrology, it increased the number of geologists who could use the universal stage and stereographic plots, at a time when few had these skills. Both had useful applications in areas such as

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structural geology and the determination of plagioclase compositions before the era of electron microprobe analysis. The controversy over the interpretation of the forces responsible for producing girdles in petrofabric diagrams and the significance of 'a and b axes' was then at its height in Australia. Den Tex (pers. comm. 1998) recalls that Allan F. Wilson, Senior Lecturer, and later Professor of Geology, in the University of Western Australia, was stimulated to undertake fabric studies in central Australia as a result of Phillips' visit. This led to a controversy with geologists of the Bureau of Mineral Resources over a and b lineations in the Musgrave Ranges and the Arunta Block. Unfortunately, as pointed out by den Tex (1954b), Wilson's interpretation left much to be desired. Shortly after this, den Tex (1955) published the results of his fabric study of the Kosciusko granite in the Snowy Mountains of New South Wales and was invited by the Broken Hill Mine Managers' Association to conduct a microfabric study of the mineral lode and its immediate wall rock, in an attempt to resolve a dispute over whether the ore minerals were syngenetic256 or epigenetic.257 However, all den Tex (1958) was able to prove was that the present-day fabric was epigenetic, as shown by its previously (re)crystallized almost random gangue258 fabric of quartz crystals (E. den Tex, pers. comm. 1998). He later provided the appendix on structural petrology (den Tex 1963) for the updated edition of Hills' textbook, Elements of Structural Geology. Petrofabric work in Australia was, as elsewhere, discouraged for a time by the lack of an unequivocal interpretation of common

quartz fabrics, and because so much of the continent was still awaiting primary mapping, even at the 1: 250 000 scale, structural petrology was largely regarded as an entirely academic subject. Nevertheless, those few who did become involved, following Phillips' initial stimulation, became extremely influential in the international development of structural petrology. In 1962, Paterson organized a conference at ANU on 'Structural Analysis and Rock Deformation'. The participants included Bruce E. Hobbs, T. P. Hopwood, Winthrop D. Means, J. L. Talbot, B. Wood and Spry, Paterson and Weiss. A second conference was held in 1965, and these eventually led to the formation of the Tectonics and Structural Geology Specialist Group of the Geological Society of Australia (Cox 1994). The generation trained and encouraged to do fabric work by Phillips and then Paterson, in turn led to structural petrologists of note, such as Hobbs, M. A. Etheridge and G. S. Lister. The influential text An Outline of Structural Geology by Hobbs, Means & Williams (1976) was but one of the subsequent publications that ultimately derived from the stimulation provided by Phillips. Thus, the visit to Australia was in the end fruitful and underlies some of the more important work in structural petrology to come out of Australia, in particular: Lister's work on the relationship of strain, shearing and quartz c-axis fabrics (e.g. Lister & Williams 1979); the work of Paterson, Hobbs and others on the experimental deformation and recrystallization of geological materials (e.g. Paterson 1958; Lister et al 1978); and Cox and Etheridge's ideas (e.g. Cox & Etheridge 1983) on the development of preferred orientation by sheet-silicates.

10. Background to controversy

Developments in understanding of Moine geology during the 1950s and 1960s During World War II, and immediately thereafter, the study of Moine geology languished. After Sutton and Watson had completed their PhD studies of the Lewisian foreland under Read (Sutton & Watson 1951), they remained at Imperial College and turned their attention to the still vexed question of the exact relationship between the Moine metasediments and the Lewisiantype rocks enclosed within them. Were the Lewisian-type rocks in inliers underlying unconformable Moine metasediments, or were they part of the Moine succession, or were they thrust-slices into it? The Geological Survey and many others believed the views of Peach et al. (1907) that the Lewisian rocks were in inliers, whereas Read (1934b), as we have seen, took the opposite view. With their recent familiarity with the Lewisian complex, Sutton and Watson were well qualified to examine the problem. Moreover, the use of cross-bedding, which occurs in the Moine metasediments (Wilson et al. 1953), to indicate stratigraphic way-up in metasedimentary successions, was by now established. This tool was able to show way-up direction even in tightly folded Moine rocks. Under Read at Imperial College, for the first time in British university geological research, teams of researchers, staff, research students and research fellows systematically examined areas of regional geology. One team, under Read and Pitcher (to 1955), concentrated on the geology of Donegal and the Donegal granite (1947-1963),259 while another, initiated by Sutton and Watson, examined the Moine succession. The Moine work started with the reinvestigation of the Scardroy and Fannich areas in Ross-shire (Fig. 5.2) by Sutton & Watson (1953, 1954) and attempted to unravel the complex fold-geometry of the Moine rocks. They identified major north-south folds with overturned axial planes, eastwards at Scardroy, and westwards at Fannich Forest. They also recognized NW-SE trending folds but categorically stated that the two fold sets (north-south and NW-SE) developed at the same time and were comparable with the 'double system of folding' already described by the Geological Survey from the Lewisian (Peach et al. 1907) and Moine rocks (Peach et al. 1913) and interpreted by Cecil Burleigh Crampton (1871-1920) in the latter memoir as forming simultaneously. Petrofabric work by Sutton and Watson at Scardoy revealed the same girdles as had been earlier described by Phillips, with the lineations and the b-axes of the girdles being coincident, but with both plunging to the south instead of the SE. Their published account thanks Phillips for introducing them to petrofabrics and for examining their completed diagrams. The same girdles as those which occurred in definite Moine rocks were also found in rocks which had been previously mapped as Lewisian. Both studies led Sutton and Watson to emphatically reject the Lewisian-type rocks as being inliers, concluding that they were part of the Moine succession. There were no basal Moine conglomerates, metamorphic differences, discordances nor, particularly important, consistent younging away from Lewisian-type rocks. In places, cross-bedding showed that the Moine rocks appeared to become younger upwards, towards the Lewisian-type rocks. This uncompromising conclusion, that the Lewisian-type rocks were part of the Moine succession, was welcomed by Phillips (1954a) in a written contribution to the discussion of the Fannich Forest paper, and he also emphasized the corollary that

the Moine succession could not then possibly be correlated with the Torridonian. However, this view of the Lewisian rocks as part of the Moine succession precipitated bitter disagreement between the Imperial College school and those elsewhere, who retained the Lewisian inlier interpretation. Thus, Kennedy not only defended the original Geological Survey view, but produced a detailed structural and stratigraphical synthesis, including the use of cross-bedding, of the Moine and Lewisian rocks of Morar (Kennedy 1955) that showed the Lewisian to be in thrust-sheets, nappes and in anticlinal cores,260 rooted to the SE and refolded by north-south folds with the Lewisian below the stratigraphical bottom of the Moine succession. Kennedy's views were the carefully considered distillation of nearly 30 years of intermittent work, which had begun in 1936 (Kennedy 1955), and were influenced by his familiarity with the structure of the Swiss Alps, obtained in 1927-1928, during his post-doctoral year in Zurich. The existence of two contrasting interpretations of the nature of the Lewisian-like inliers led to some unrestrained, sharp, and sometimes rather angry, exchanges at the Geological Society when papers were read which supported the existence of Lewisian inliers. In caricature, did these inliers extend down to the scale of single hornblende crystals contained in the Moine metasediments? A rather intimidating group from Imperial College, led by Sutton, would press the Read dogma, and speakers such as Kennedy (on 4 November 1953) and his student Tom Clifford (on 12 January 1955) received far more verbal criticism than the relatively restrained published discussion records, although such criticism is quite evident in the published record (Kennedy 1955; Clifford 1958). Phillips shunned such meetings and expressed himself to his Bristol colleagues as strongly opposed to such behaviour. In fairness, it must be added that later, when Kennedy's (1955) hypothesis of a series of thrusts and nappes intercalating Lewisian and Moine slices became accepted, and the concept of Lewisian inliers was restored, Sutton (1980) was very willing to admit that Kennedy had been right and himself wrong. After gaining his BSc at the University of Birmingham in 1949, Weiss had studied for his PhD at the University of Birmingham, where he worked on the structure of parts of the Mona Complex in Anglesea. Stimulated by the publication of Turner's (1948) memoir on the Mineralogical and Structural Evolution of the Metamorphic Rocks, Weiss also included petrofabric studies as part of this work. However, his PhD dissertation was not submitted until late in 1953 (L. E. Weiss, pers. comm. 2000) because, in the summer of 1951, he took part in the second Birmingham University expedition to Svarlbard (having been on the first as an undergraduate in 1948), where he carried out structural studies (Weiss 1953). He then joined Turner at the University of California in Berkeley on a Commonwealth Fund Fellowship (1951-1953), undertaking field studies in the Mojave Desert and related petrofabric analysis (Weiss 1954).261 In a subsequent publication based on part of his PhD dissertation, Weiss (1955) discussed the nature of the occurrence of non-coaxial quartz and mica girdles262 with dissimilar orientations, which he had encountered in the rocks of southern Anglesea.263 He believed that the phenomenon was the same as that previously described by Phillips (1945) from the Moine metasediments and by Kvale (1953) from Norway. Weiss concluded that the girdles were produced during a single phase of movement. The kinematic Baxis of this movement is most clearly defined by the preferred

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orientation of quartz; whereas the slip plane ... is defined by the preferred orientation of the mica and to a lesser extent quartz. The megascopic fabric considered alone gives no guide to the orientation and significance of the kinematic B-axis. Neither of the two lineations visible in the foliation is parallel to B, although movements normal to it have produced them It is commonly assumed that the B-axis of a both deformed fabric lies in the foliation. This may be a general rule for rocks deformed by proved slip upon the foliation; but it cannot apply to many rocks which have suffered solid flow during plane deformations in which the B-axis transects structures inherent in the initial fabric. For this reason current procedure of selecting tentatively the most prominent surface in the rock as 0ft, and the most prominent lineation as B, is liable to give rise to a basically two dimensional interpretation of the orientation data, governed by foliation The constant orientation of quartz girdles, regardless of the megascopic fabric, recorded in Bergsdalen by Kvale and in Anglesey .. . suggests the presence of a constantly orientated B-axis in these two areas (Weiss 1955, p. 235; quoted with permission of the author). On 27 June 1956, Ramsay read a paper on his PhD work on the Loch Monar area, which lies south of Scardoy (Fig. 5.2), to the Geological Society of London. This paper (Ramsay 1958a) was a milestone, for he not only recognized two distinct major sets of folds, but he analysed the quite complex geometry of both the earlier and later sets in detail. The earlier folds trended east-west and were distorted by a later set of NE-SW trending folds. The Lewisian-type rocks were regarded as an 'integral part of the Moine series' (Ramsay 1958a), but the interpretation of the structural geometry considered was not dependent upon the original nature of the Lewisian-type rocks because the earliest structures, which might have emplaced them, were not recognized or considered. This paper opened the door to the systematic recognition and analysis of refolding. The petrofabrics revealed girdles and 'cross-girdles' but was held to show that Lewisian-type rocks had only suffered the same deformation as the enclosed Moine rocks. During the next few years, the complex geometry of superposed folding would become better understood through studies like those of Weiss (1959b) and Ramsay (1962a). Within a year of the reading of his Loch Monar work, and before it was even published, Ramsay (1958ft) reported to the Geological Society on 15 May 1957 that the Moine-Lewisian relationship at Glenelg (Fig. 5.2) showed that early thrust slicing (of the kind envisaged by Kennedy (1955), but in even thinner strips) had brought together alternating bands of indubitable Lewisian and Moine rocks, perfectly parallel. These had then been tightly folded about original NNE-SSW axial planes, followed by later folding with approximately NE-SW trending axial planes. These two major fold episodes deformed the assemblage as if it were a single stratigraphic succession. As a result of this work, the effects of deformation in erasing discordances were more fully appreciated than ever before, and immediately the lack of discordance between the structures in the Lewisian sheets, within the Moine metasediments, and the Moine foliation became explicable - the original discordances had been deformed into near parallelism. As a result, the concept of Lewisian inliers was revived (although initially rather hesitantly as regards those in central Ross-shire), but by 1960 was regarded by

the main protagonists (e.g. Ramsay 1960; Sutton 19600) as firmly established, and it has remained an agreed fact since. By December 1961, the accumulated structural information from many studies enabled Ramsay (1963), at a symposium held in Edinburgh, to categorize four sets of folds in the Moine rocks. He showed these were produced sequentially, with the first set being isoclinal or possibly (especially in central Ross-shire) in the form of thrust-sheets. In general, Ramsay (e.g. in discussion of Sutton & Watson 1959), had changed his thrust model for the early interleaving of Moine and Lewisian rocks to one involving isoclinal folding, because of the symmetry of the Moine stratigraphy about the Lewisian rocks. Also, the isoclinal folds could be traced upwards into recognizable folds in less deformed areas. Initially, it was thought that the Lewisian lay in isoclinal folds rooted to the east or SE (e.g. Kennedy 1955); later it was supposed to be in downward- and eastward-facing264 folds rooted to the west or NW (e.g. Ramsay 1963; Powell 1974). The Lewisian rocks occur at two levels: one at and near the base of the Moine metasediments (in the Morar Group); and the other much higher up in the succession. Although the detailed description of the Moine stratigraphy started with Richey & Kennedy's (1939) account of the lower part of the succession resting on the Lewisian at Morar, south of Skye, little further progress could be made until there was understanding of the geometry of the main fold phases. First, Ramsay & Spring (1962) using their new understanding of the folding, then Powell (1964) and Dalziel (1966), who described the upper parts of the Moine stratigraphy, enabled Johnstone et al (1969) to define and subdivide the three main Moine groups of Morar, Glenfinnan and Loch Eil (in upward succession) over much of the Moine outcrop (Fig. 5.1). By this time, the existence of important slides265 was well recognized in the Moine succession, e.g. the Sgurr na Cairbe slide of Fleuty (1961) and the Sgurr Beag slide of Tanner (1971). Such slides cut out parts of the original stratigraphy, by moving the rocks vertically or laterally away. The Sgurr Beag slide separates much of the Morar and Glen Finnan Groups and in places contains impersistent slices of Lewisian material. This emphasizes its major importance as a structural discontinuity, which brought in Lewisian basement before the second phase of folding (F2) in the Moine fold sequence, the slide plane overall dipping eastwards and thus suggesting to these authors major westward movement of the rocks to the east of the slide onto the Morar Group to the west (Tanner et al. 1970). So, by 1970, it was generally agreed (e.g. Kennedy 1955; Ramsay 1963; Tanner et al. 1970) that an early (i.e. D2 and pre-Moine Thrust) major eastward, or possibly westward, movement had affected much of the Moine metasediments and clearly this could have important implications for the origin of the quartz petrofabric girdles identified by Phillips (1937ft). It was also becoming established (e.g. Lindstrom 1961; Bryant & Reed 1969; Sanderson 1973) that in regions of intense ductile266 shearing, the rotation of fold hinges to approach the transport direction could bring fold hinges which were initially at high angles to the movement direction, into parallelism with it.267 In practically all the papers noted above, stereograms are used to depict structural data and there is no doubt that this was, in part, due to the success of Phillips' (1954ft) book (discussed below) on the use of the stereographic projection as a tool in structural geology.

11. Bristol (1953–1967)

Stereograms for macroscopic data The above-noted developments in the 1950s and 1960s in Moine geology show the growing recognition of the importance of combining lithological mapping with shrewd and careful observations in the field of folds, lineations and schistosities in order to unravel the geometrical history of deformed rocks. The increase in the field data collected, dips and strikes of bedding, cleavage or schistosity and the axial planes of folds, plunge amounts and geographical directions of folds and lineations (Fig. 11.1) led to an explosion of data and the need to be able to manipulate, display and synthesize such data at a time before computers were generally available (Howarth 1999). The process was enormously facilitated by the gradual extension of the use of the stereographic projection from crystallography (in which, as has been seen, upper hemisphere plotting is used), to structural geology (in which lower hemisphere plotting is conventional, presumably because folds and lineations are normally considered in their down-plunge attitudes, not the reverse).

There is no doubt that the widespread use of the stereogram in structural geology in Britain was promoted, more than any other factor (Sutton 1960b), by the publication of Phillips' (1954b) textbook The Use of Stereographic Projection in Structural Geology, following his return from Australia. In the preface, Phillips paid tribute to the usefulness of Cotton & Garretty's (1945) report.268 Phillips' chapter entitled Tectonic synthesis in stereographic (and related) projection', illustrated how the Lambert equal-area projection (Fig. 4.4) could be applied to summarize the orientation of joints, lineation and planes of schistosity, using examples from the schists of Start Point, Devon (Fig. 11.2) and the Moine schists. The book received particularly favourable reviews from Ingerson (1955, p. 782) and Harland (1955), although Flinn (1956a) expressed a little disappointment that Phillips had not mentioned some of its more controversial uses in structural geology, such as determining the symmetry of orientation data, unrolling folds269 and dating phases of deformation. Nevertheless, this outstandingly successful book, which was (and still is, even today) widely used by teachers and students of

Fig. 11.1. Lineation on a fold (plunging to the lower left of the picture) in Moine schist, Kinlochmoidart. Reproduced with permission of the author from figure 64b of L. E. Weiss, 1972, The Minor Structures of Deformed Rocks, Springer, Berlin.

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conclusion was indeed correct (M. R. W. Johnson, pers. comms 1998, 1999), and it was not to be long before Christie (1956, 1960, 1963) provided further confirmatory evidence from the Lough Assynt area (Fig. 5.2). A session on 'Structural petrology and problems of the Caledonides', held at the British Association meeting in Bristol on 2 September 1955 (Phillips 1956b), saw the presentation of the results of some of the first 'modern' detailed structural work in the Highlands by Christie (1956), Colin Crampton (1956), Johnson (1956), P. Wilkinson (1956) and, in Antrim, by Goldring (1956). Following the presentations, Phillips said that he was naturally gratified that so much support was forthcoming for some of the chief contentions of his earlier work. There appeared to be complete agreement that the typical Highland lineations represented true B-structures, which could not be directly correlated with the northwesterly forward thrust movements. Further evidence had been presented, too, that the regional Moine fabric was progressively modified by later movements near the thrust zone, and that the double girdle fabrics arose from this overprinting (Phillips 1956b, p. 577; quoted with permission of Mr W. F. C. Phillips).

Fig. 11.2. Lower hemisphere equatorial equal-area projection of observations of normals to schistosity (open symbols) and poles to lineation (solid), Start area, South Devon; broken line shows best-fit average foliation plane. Redrawn with permission of Mr W. F. C. Phillips from figure 80 of F. C. Phillips, 1960, The Use of Stereo graphic Projection in Structural Geology, Edward Arnold, London.

structural geology, put the final seal on Phillips' reputation as a superbly clear pedagogue. It stimulated many to make measurements of lineations and foliations because they could be conveniently plotted and used to obtain fold plunges, etc., integrating structural data over large and small areas. For example, even the measurement of the Donegal Granite 'intrusive lineations', and mullion structures in the aureole (Pitcher et al. 1959; Pitcher & Read 1960), were prompted by Phillips' book (W. S. Pitcher, pers. comm. 1998). Phillips visited the Abisko area in Swedish Lapland in August 1954, but no results relating to this trip were ever published.270

New petrofabric difficulties Over the next few years, Phillips continued his classes in structural petrology for final-year students (Fig. 11.3) and supervised, or gave advice to, a number of PhD students (e.g. Colin B. Crampton, Denis C. Goldring, Santi Kumar Gosh and K. A. Jones). In 1955, Phillips was the examiner of the successful PhD dissertation from Imperial College (supervised by Wilson), in which Johnson (1956, 1957, 1960) described the microfabrics in the Torridonian rocks from the thrust belt. In the inverted limb of the Loch Alsh fold at Loch Carron (Fig. 5.2), Johnson had found that movement of a Lewisian slice over inverted Torridonian along the Strome Thrust had induced a visible ESE to SE lineation (and a tectonite fabric with NE-SW girdles) and a steep easterly dipping cleavage, in the inverted Torridonian. This finding considerably surprised Phillips, because he maintained that the widespread NNE-SSW girdles, which he had found in the Moine metasediments, were both pre-Cambrian and pre-Torridonian in age, and he therefore expected that only NW-SE orientated quartzgirdle fabrics would be present in the Torridonian rocks involved in the Moine Thrust belt (Phillips 1957a). Nevertheless, following examination of the evidence, Phillips agreed that Johnson's

This view was probably influenced by Christie's (1956, p. 573, 1963) assertion, later strongly contested by Johnson (1965), that in the Assynt area there was transport of the Moine schists towards the SSW along the Moine Thrust. Johnson (1956, p. 575) argued, on the basis of evidence from the Moine Thrust Zone in the Coulin Forest, Wester Ross (Fig. 5.2), that the widespread ESEplunging lineation was first imposed on the Moine, Lewisian and Torridonian rocks of the Moine Thrust Zone. He believed that, rather than indicating transport in a direction perpendicular to the lineation, it was consistent with the rocks being 'subjected to an all-round uneven squeezing rather than directional shearing stress' induced by subsidiary stresses set up 'during major tectonic transport westwards along the Moine Thrust'. He also suggested that the accompanying ESE-orientated folds post-dated the formation of the fabric and were concentrated in areas of thickening in the nappes. The second phase consisted of late-stage post-crystalline movements on the thrusts which impressed localized north-south trending linear structures (Johnson 1956). Following the meeting, Phillips led a three-day field trip to examine the structural petrology of the Start Point schists. As stated earlier, although it is uncertain exactly when Phillips first began his study of the Funzie Conglomerate, it is known that he visited Fetlar to collect specimens in August 1951, July 1954 and 1955.271 Meanwhile, Derek Flinn (ft. 1922), a mature student who studied in Read's department at Imperial College following the end of World War II, realized the enormous potential for further work in Shetland. He first visited Unst in 1949 in the course of research for his BSc dissertation on its geology. This work was followed by a PhD on the metamorphic rocks of the north of Mainland (Flinn 1952). He subsequently continued his research on Fetlar, unaware of Phillips' interest, although he did know of James Phemister's, as the latter had apparently asked Read (without success) to stop Flinn working there (D. Flinn, pers. comms 1998, 2001). The subsequent publication of Flinn's (1956b) paper 'On the deformation of the Funzie Conglomerate' (Fig. 8.3) came as an unwelcome surprise for Phillips, as he had not been consulted by Read over Flinn's intention to work on the topic. Moreover, Flinn's work threatened to raise another whole controversy, because his study of the petrofabrics of the quartz in the deformed quartzite clasts yielded similar results to those obtained by Strand (1945) from the Bygdin Conglomerate (Fig. 8.1) in Norway.272 Both studies showed that there was a partial girdle of quartz caxes around the lineation, as defined by the long-axes of the pebbles. This was, therefore, a comparable relationship between lineation and the quartz girdle to that which Phillips had found in

BRISTOL (1953-1967)

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Fig. 11.3. Field excursion of final-year students from Bristol University to Start Point, Cornwall, 1955. Phillips is standing, fifth from left; also standing, first and second from left, are lecturers Ian H. Ford (geology, d. 2002) and Dr Cecil Reginald 'Bill' Burch (1901-1983, FRS 1944; physics), both of whom worked with Phillips on microscope development. Photograph courtesy of Professor G. Evans (front row, third from left).

the Moine metasediments but, in this case, the pebble shapes enabled Flinn (1956b, p. 480) to conclude that 'compression in the plane normal to the elongation direction has forced the pebbles to elongate by flow'. This was in direct contrast to Phillips' (1951b) interpretation of the phenomenon (echoed by the views he expressed at Kalgoorlie and Yankallila Bay, during his Australian visit), as a relict pre-tectonic feature of the original sedimentation.273 It is of interest that Flinn (19566, pp. 502-504) began his explanation of the 'quartz-cake' deformation of the clasts in the conglomerate by citing Sander's (1948, p. 70, 1970, p. 72) Einengung (constriction) mechanism, particularly as it does not seem to have figured in Sander's writings as a mechanism of much importance. This mode of deformation was envisaged by Sander as a static compression in the ac-plane (i.e. without tectonic transport), resulting in flattening with extension parallel to the 6axis (Fig. 11.4). Sander (1948, 1950; 1970, pp. 41, 194, 435, etc.) likened it to the effect of squeezing a rod (e.g. of clay) held across the palm of the hand with the fingers wrapped round its circumference.274 Such a mechanism, he believed, would produce a resultant extension in the direction of the minimum compressive stress (Fig. 11.4), exactly the explanation for 'rodding' of quartzites given by Clough (in Peach et al 1912, p. 49) which was quoted previously. Flinn (19566, pp. 502-503) argued that the observed fabric of the pebbles of quartzite, granitic rocks, and the metasedimentary rocks of the Funzie Conglomerate (which resemble the finergrained matrix which encloses the clasts) conforms to that of the matrix and also to that of the neighbouring non-conglomeratic rocks. This cannot be adequately explained by either simple shear (as the pebbles show triaxial deformation) or pure shear (as the

Fig. 11.4. Sander's (1948, p. 70, 1970, p. 72) Einengung constriction deformation mechanism, illustrated by change of shape of plastically deforming cylinder of rock in response to differential stress; solid arrows indicate directions of maximum compression (size indicates relative magnitude); open arrows show resultant extension.

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pebbles do not exhibit the expected shear-plane orientation, and pure shear alone cannot explain the triaxial fabric). Rather, Flinn (1956b, p. 503) envisaged the pebbles being deformed by plastic or viscous flow, once the elastic limit of the rocks was exceeded. Such a process cannot be described in terms of either simple or pure shear, both of which are inherently two-dimensional mechanisms.275 He showed that the deformation varied progressively: from elongation parallel to the lineation, and constriction normal to it, in the northern part of the outcrop; to flattening (X > Y >> Z) in the SW part of the outcrop. The consistency of direction of the pebble axes was accounted for by flow of the matrix against the pebbles, and the relatively high symmetry of both the constricted and flattened rocks was taken as evidence that the forces causing the deformation acted parallel to the symmetry axes of the rock fabric (Flinn 1961, p. 248). The intensity of deformation by constriction increased towards the contact of the conglomerate with the overlying rocks, which are separated from it by a thrust plane.276 Phillips never published a fuller account of his own study of the conglomerate, probably as a result of Flinn's publication. Flinn (pers. comm. 1998) says that he only learnt of Phillips' continued interest in the area and of his annoyance ('he was furious'; R. Bradshaw, pers. comm. 1998), from James Phemister, when they happened to meet by chance on Fetlar, following the publication Flinn's 1956 paper. At first sight, it seems curious that Phillips should have regarded the fabric in the Funzie Conglomerate pebbles as being dominated by a pre-sedimentary texture, when Flinn was able to show a systematic progressive deformation, elucidated simply by comparing clasts in the least deformed areas with those in the most deformed areas. But it must be remembered that this was only discovered by detailed mapping and sampling of the whole outcrop of the conglomerate, which covered several square kilometres (Fig. 3.5; for details see Flinn 1956b, fig. 2), whereas Phillips had only collected a few samples. Phillips' work on the Moine rocks undoubtedly also suffered from the fact that he neither mapped the rocks himself nor collaborated with a structural geologist undertaking such mapping, as would have certainly been possible by the 1950s. It was clearly ironic that Flinn's work on the Funzie Conglomerate (which in part ultimately laid the basis for the solution of the Moine petrofabric problem) should have been laid aside by Phillips, at least partly on the grounds of a supposed pre-sedimentary fabric in the pebbles, but perhaps also because Phillips regarded the 'shearing movements' as parallel to the length of the pebbles and therefore perpendicular to the quartz girdles and thus demonstrating the 'revised interpretation': in effect continuing the confusion between the directions of the externally applied forces and those of internal movements in response to those applied forces. This was the confusion which lay at the heart of the Moine controversy. Cornish sea-floor studies In 1957, the second edition of Phillips' (1956a) Introduction to Crystallography again received favourable review (Faust 1957). That same year, Phillips began, at the invitation of Whittard, a long-term study of the petrology of the metamorphic rocks exposed on the sea-floor of the English Channel, off the southern Cornish coast. These are only visible above water at the Eddystone Rocks (Fig. 2.1), which form a reef 80 km WSW of Plymouth.277 Phillips accompanied Whittard278 and staff from the Marine Biological Association on the Research Vessel Sarsia in July 1957. According to the businessman, geologist and palaeontologist, Dennis Curry (1912-2001), who participated in several of these voyages, although the ship was perfectly seaworthy, it tended to pitch and roll very heavily even in a moderate sea. Consequently, all the scientists on board suffered from seasickness. Although Whittard was an indifferent sailor, he did not allow this

fact to interfere with his work, even when he was 'obviously ill', and he evidently expected his colleagues to do the same (Curry, quoted in Bulman 1966, p. 536). It seems that Phillips did not enjoy the rough sea conditions and, having experienced little sympathy from Whittard, he did not participate in the subsequent voyages. Nevertheless, the July expedition (and a subsequent trip in September) provided useful samples of garnetiferous amphibolite, obtained by dredging and diving in the vicinity of the Eddystone Rocks and adjacent sea-bed, which Phillips subsequently examined. Some of Phillips' findings were later incorporated by Whittard (1962, p. 658) into his description of the geology of the whole of the Western Approaches. In this account, Whittard mentions that 'Dr Coles Phillips reports' that the phonolite279 9 km ENE of the Wolf Rock (Fig. 2.1) was nosean-bearing, whereas immediately SE of the Wolf Rock, it became an aegirine-sanidine280nepheline281 alkali rock.282 Further controversy In December 1958, Phillips 'communicated' to the Geological Society a paper by his student, Colin Crampton, which summarized the findings of his PhD dissertation. In the course of this work, Crampton had analysed the fabrics of quartzites lying both below and above the plane of the Moine Thrust. He concluded that below, and distant from, the thrust-plane there was evidence of preservation of an original sedimentary fabric consisting of 'a girdle of quartz axes parallel to the bedding', and that this fabric was destroyed 'with the onset of granulation near the thrustplanes' which yielded a new preferred orientation. While above the thrust new preferred orientations of quartz axes are developed, including crossed girdles, the girdle intersection being directed parallel to the regional [south-easterly plunging] lineation, and, rarely, simple girdles parallel to the lineation. Quartz fabrics . . . show a transition from the simple girdle normal to the lineation to one parallel to lineation, intermediate members of the transition being various styles of crossed girdles.... It is concluded that the simultaneous deformation of both Moine and Cambrian rocks by a somewhat discontinuous system of penetrative movements about a common B-axis directed north-east occurred after the regional deformation of the Moines by penetrative movements about a B-axis directed south-east. .. . The simultaneous deformation .. . about a common B-axis directed north-east involved some lateral NE-SW movement immediately beneath the overriding thrust slices (Crampton 1959, pp. 33-34; quoted with permission of The Geological Society, London). Crampton's claims regarding the presence of an original sedimentary fabric, and an ordered transition between simple girdles both normal to, and parallel to, the predominant lineation with crossed-girdles as intermediaries, were greeted with considerable scepticism (Johnson 1959; Ramsay 1959; Rast 1959), particularly in view of the fact that he had not made any measurements of cross-bedding direction from the foresets (which are widely preserved in the Cambrian quartzites). Furthermore, Ramsay (1959) asserted that more detailed structural field investigation, confined to small areas where the major structures were understood, was needed before the fabric patterns could be related to the Caledonian movement phases and that the era of 'reconnaissance surveys' (by implication, such as Crampton's work) was outmoded. Crampton's study does not seem to have been published in the Society's journal, as would normally be expected, presumably as a result of its critical reception.283 In 1959, Phillips began work on rock fabrics using an X-ray texture goniometer developed by Wooster (1950).284 This interest

BRISTOL (1953-1967)

was, in part, stimulated by John Starkey, a Liverpool University research student who was studying the geology of part of Connemara, western Ireland, and who spent the academic year of 1958-1959 at Bristol University with Leake. Starkey and his father were also building an X-ray texture goniometer, and Starkey (1960) consulted with Phillips about many of the details of the construction. Phillips' grasp of both the crystal and X-ray theory, and workshop practice, proved invaluable. The potential rewards of X-ray-determined quartz orientations were that the crystal lattice orientation could be measured whereas, using optics, only the attitude of the quartz c-axes could be found and the crystal lattice could be in any orientation rotated about the c-axis. To discover whether the forces orientating the quartz did so partly by causing slip along certain planes of weakness within the quartz lattice needed a full three-dimensional orientation of the crystal. However, problems of grain-size variation, the presence of minerals other than quartz, and a whole series of technical difficulties resulted in Phillips publishing nothing in this field apart from a study of growth fabrics in fibrous calcite and haematite in kidney ore (Bradshaw & Phillips 1967), and a comprehensive historical review of the apparatus, interpretative techniques and applications of X-ray goniometry in geology and mineralogy, which appeared well after his retirement (Bradshaw & Phillips 1970). The criticisms levelled at the work of Phillips and his students by Anderson and others, discussed earlier, continued to be a source of irritation. Phillips now replied to his critics in a review paper The interpretation of petrofabric diagrams' (Phillips 1960a), which partly concerned the identification of patterns of 'significantly' non-random orientation in a set of orientation data; but this turned out to be an equally contentious, although highly statistical, issue (Pincus 1953; Vistelius 1957, 1958, 1966; Flinn 1963; Vistelius & Flinn 1964; Watson 1966). This review paper was almost his last on petrofabrics. It summarizes both the 'orthodox' and 'alternative' positions on Wineations (one perpendicular to the movement and one parallel to it) and the resulting quartz girdles, while clearly revealing that Phillips maintained essentially the same view as he had in 1937.

The Moine fabric debate almost fizzles out After this, Phillips' dislike of controversy must have finally got the better of him, and he appears to have gradually distanced himself from the on-going studies in Scotland to concentrate his research (and that of his students, e.g. Chris Bowler and Brian Marshall) on the somewhat less contentious topic of the metamorphic rocks of Devon and Cornwall (Phillips 1961, 1962a, 1964a, b). Even so, Phillips became increasingly unwilling to interpret petrofabric diagrams about which others consulted him. While the loss of so many tens of thousands of measurements in the Liverpool fire may have still weighed heavily with him, the more likely reason for this reluctance was growing doubts regarding the interpretation of petrofabric diagrams, for in his (19600) review paper, despite again rejecting Anderson's 'alternative' hypothesis, Phillips wrote that while the symmetry of the diagrams could be interpreted in terms of the symmetry of the movements in the genetic process, it would not necessarily reveal the system of forces which gave rise to the movements (Phillips 19600, p. 663). Furthermore, he emphasized that the measurement of the orientation of the crystallographic optic axes was essentially a matter of convenience, as they could be determined using the universal stage but they need not necessarily be related in any sense 'other than a purely geometrical one, with the genetic vectors which are immediately concerned in the orienting process' (Phillips 19600, p. 664). This suggests a recognition by Phillips that some petrofabric patterns might not be uniquely related to the causative mechanisms, i.e. different causative mechanisms might sometimes give

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rise to the same pattern. However, in view of the regularity of the girdle pattern and its orientation that he had demonstrated in the Moine rocks, it would seem unlikely that this did not arise in the same way everywhere. More importantly, his comments echo those of Kvale (1953, pp. 70-71), already quoted, that petrofabrics inconclusively determine major tectonic transport directions, and indicate disillusionment with the practical value of petrofabrics. This presumably came about partly as the result of the continuing controversy of earlier years, but was more certainly prompted by the flood of multiple refolded structures being documented from the late 1950s, which showed that movement directions in most metamorphic rocks varied enormously over time. At least three major phases of folding, plus additional minor ones, were recognized in the Moine succession (Ramsay 1960). Identifying one single movement phase did not usually characterize any particular rock, nor was any petrofabric pattern necessarily related to the movement phases which controlled the main geometry of the rock (F. C. Phillips, pers. comm. to B. E. L., c. 1962). Rapid advances in structural geology showed that the study of small folds and their accompanying schistosities, combined with the mapping of lithostratigraphy,285 revealed far more about the overall history of the rock than the study of petrofabrics could decipher. Crucially, Ramsay (1960) showed that fold axes, and the linear structures parallel to them, may form at any angle to the movement direction; they may be parallel to b or to 0 or, quite commonly, in some direction between 0 and b in the schistosity plane. At one stroke, the controversy dissolved, and with it disappeared much of the original motivation for undertaking petrofabric studies. At about the same time Flinn (1958), perhaps ironically using data from Shetland, also demonstrated that extension lineations could be both parallel to fold axes as well as normal to them. Shortly afterwards, in a most important paper (Flinn 1962), he showed how lineations and planes rotate under progressive threedimensional strain and that neither fold-axes nor axial planes are indicators of movement directions or of directions of flow in rocks, and that to use them for these purposes involves arbitrarily assuming a particular orientation of the folds in relation to the eventual flow directions in the rock. As a result, he recommended abandonment of Sander's (in Sander & Schmidegg 1926; Sander 1948) {a, b, c} kinematic coordinate system (Figs. 4.8 and 4.9). Although Wilson (1961, p. 530, f.n.) continued to support the 'orthodox' interpretation, so far as the minor structures in the Moine rocks were concerned, and the view (also held by Phillips) that the eastward-plunging folds and minor structures 'are older than, and entirely unrelated to, the post-Cambrian movement towards the WNW on the Moine Thrust', the controversy had essentially disappeared. As Ramsay (1963), in truthful but rather generous words, concluded in discussing the rocks of the Scottish Highlands: these regions are of great structural complexity as a result of the superposition of several sets of folds; their apparent homoaxial286 character [which Phillips had observed in 1937b, figs 2 and 3] is entirely the result of the tight nature of the earlier folds, the intensity of the later deformation, and the strength of re-crystallisation of the rocks during the later deformation (Ramsay 1963, p. 152). The problem remained, however, of what had caused the regular NE-SW quartz girdles over so much of the Moine outcrop.

Gemstones Phillips had continued to be active on the council of the Mineralogical Society (1952-1955) and when the mineralogist George Frederick Herbert Smith (1872-1953) died,287 Phillips was invited

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to undertake the preparation of a completely revised edition of Smith's Gemstones. This book was widely regarded as the gemmologists' 'bible'. First published in 1912, it was so successful that 12 editions were published during the lifetime of the author, the last appearing in 1952 (Smith 1952). It described the nomenclature of gemstones and their physical characters, such as refractive indices, specific gravity, colour and hardness; the occurrence and properties of natural precious, semi-precious and ornamental stones and pearls, how to identify them non-destructively and how to distinguish them from similar or manufactured stones; a little on 'imitation' stones and cultivated pearls; together with an account of the most important historical diamonds and the modes in which they were cut. Within three years, Phillips had written a substantially modernized 13th edition (Smith & Phillips 1958) which went on to be reprinted throughout the 1960s, until he produced the 14th edition (Smith & Phillips 1972). Phillips did not, however, find it an easy task, as retaining the 'character' of a 'classic' book whose roots went back to 1912, while modernizing it, was difficult. However, no doubt it was a relief to return to work of a non-controversial nature in which his expertise in crystallography and optical mineralogy was employed. Phillips' amendments included a chapter on the polarizing microscope; a more precise account of the principal crystal systems, including drawings of crystals in identical style to those in his Introduction to Crystallography (Phillips 1963a); deletion of the distinction between 'precious' and 'semi-precious' stones, and also of the monetary values of gemstones (because they continually changed); the addition or elaboration of some of the more sophisticated analytical methods of identifying gemstones (e.g. absorption spectra, and X-ray discrimination between natural and cultivated pearls); information on the natural formation of gemstones; and a much expanded section on synthetic and imitation stones which were becoming much more common than previously. The difficulties in producing the revised version caused Phillips a good deal of stress (W. F. C. Phillips, pers. comm. 1997). This throws some light on the nature of his character: almost overconscientious and often rather worried about matters others would have rapidly resolved - after all, the whole revision for the 13th edition took him less than three years. The following extract from a review of the 14th (1972) edition summarizes the roots of the difficulties: In undertaking the revision of a book there is a natural tendency to think first of the additions that must be made to bring it up to date and make it more useful to the present-day reader. What is far less easy is to eradicate the signs of old age which often lie dormant in the text for a generation, or can even be seen in some of the illustrations . .. [e.g.] the 1907 model of the Herbert Smith refractometer ... One recognizes the piety that urged these retentions, since both the book and the refractometer were Herbert Smith's greatest contributions to gemmology, but one feels that he himself would have recognized the need for change (B. W. A. 1973). Nevertheless, Phillips need not have worried: No small part of the book's . . . standing as a classic has lain in the scholarly, authoritative and academic vein in which it was written,... [pjassages of Dr Phillips'... own writing differ from those of the original author in being more succinct and more clearly comprehended, but the general flavour and feel of the book has not been marred in any way [It is] a worthy successor to the previous editions of this famous and essential classic (B. W. A. 1958; quoted with the permission of the editor, Journal of Gemmology). In 1960, Phillips served as President of the Bristol Naturalists' Society and shortly after began writing the centenary history of

the society (Phillips 1962b). The second edition of his book on stereographic projection (Phillips 1960b) was published the same year. Shackleton (R. M. S. 1961) noted: 'Its success is apparent not only from the sales of the work but also from the extensive use of stereograms in papers on structural geology. It would be unjust to complain that Dr Phillips has been too successful; it is no fault of his that stereograms have sometimes been substituted for geology'. Sutton (1960b) complemented this by remarking 'it is largely because of the work of Dr Phillips that such methods are now more widely used by geologists than when this book first appeared'. At the Ninth Inter-university Geological Congress, held at the University of Exeter in early January 1961, Phillips reviewed the application of stereographic methods to the interpretation of orientation data for megascopic fabrics (such as fold-axes, lineations, bedding-cleavage intersections and jointing, etc.) in the rocks from the Variscan fold-belt288 of mainland Europe and SW England (Phillips 1962a). He now placed emphasis on these rather than the study of microfabrics 'which never seems to make much appeal to structural geologists' (Phillips 1962a, p. 110). It is interesting that in his final section of this paper, concerned with lineation, Phillips comments on the difficulty of distinguishing in practice between 'a-lineation' parallel to the direction of movement and 'b-lineation' normal to this and parallel to the fold axes. He also stated that 'to describe a lineation as "a direction of stretching" . . . carries a genetic implication which may be quite unfounded' (Phillips 19620, p. 125). Citing a number of different examples, including slickensides and Wilson's (1950) study of fold-axes and boudinage289 in Cornwall, as examples of 0lineation, Phillips (19620, p. 126) then reiterated his view that the mullion structures of the Moine metasediments 'lie parallel to the b-direction of the generating movements, though there has probably been later movement parallel to their length (Phillips 1937b; Wilson, 19530a)'. However, Phillips avoided any discussion of structural petrology in this paper, on the grounds that the generally low-grade metamorphism of the metasediments in SW England meant that there was little preferred orientation in the coarser-grained rocks and study of the slates would require the use of X-ray techniques 'to which structural petrologists have so far paid little attention' (Phillips 19620, p. 126).290 Presumably the lack of further comment implies that little in the way of useful results had emerged from his own X-ray studies to date. Perhaps the most telling remark was that 'there is still considerable reluctance on the part of many structural geologists to accept [structural petrology] interpretations unless they are supported by evidence of the kind with which they are more familiar' (Phillips 19620, p. 126). Quite understandably, perhaps Phillips no longer wished to risk precipitating further unwishedfor controversy. Later in the year, Phillips (1961, published in abstract only) presented a synthesis of his petrofabric study of the Start and Bolt mica-schists of the Start Point area (Fig. 2.1) at a conference of geologists working in the SW of England, held in Camborne and hosted by the Royal Geological Society of Cornwall. He had found that poles to the westerly plunging visible lineation were concentrated about an axis which suggested the presence of an anticlinal structure plunging slightly south of west. Petrofabric analysis showed that the lineation corresponded to well-defined girdles of quartz and mica. The major system of joints was in the 0c-plane, perpendicular to the lineation; a second system of conjugate joints striking on average N 50° E and N 50° W was also present (Fig. 4.6) and he concluded that the northern boundary of the (?Palaeozoic) schists, the Start Boundary, was probably a vertical fault.291 At its meeting of 14 September 1962, following a proposal by Dr K. F. G. Hosking, seconded by Mr Halford, the Council of the Royal Geological Society of Cornwall unanimously elected to award the William Bolitho Gold Medal to Phillips for his work on the geology of Devon and Cornwall. It was presented to him

BRISTOL (1953-1967)

on 15 December at the 148th AGM of the venerable society, (D. Freeman, pers. comm. 1997). This was particularly fitting, as the SW was Phillips' first love, although he also had a great affection for the people and natural history of the Orkneys (which he had visited in 1954) and the Shetlands (Anon. 1982). Phillips' crystallographical and mineralogical interests were maintained with book reviews and publication of the third edition of his Introduction to Crystallography (Phillips' 1957b, 1962c, 1963a, b). In 1964, Phillips was elected to a personal chair as Professor of Mineralogy and Petrology at Bristol University (he was particularly supported in this by the physicists, on the strength of his crystallography book; R. J. G. Savage, pers. comm. 1997) and held the position of Deputy Dean of the Science Faculty. Phillips' study of the metamorphic rocks of the sea-bed between Start Point and Dodman Point, Cornwall (Fig. 2.1) was at last published that same year (Phillips 1964a), based on the material collected (mainly by dredging) on cruises in 1957, 1958 and 1963.292 It was doubtless with some satisfaction that Phillips (1964a, p. 658) was able to record that a sample of garnetiferous amphibolite in a dredge haul taken (at his request, by his Bristol colleague, the economic geologist Ian H. Ford, aboard R. V. Sarsia in September 1963) NNW of the Eddystone Rocks (Fig. 2.1), closely resembled 'a specimen of Worth's material (FCP coll. 105) which has long been in my possession'. Phillips suggested that the metamorphic rocks of Eddystone and nearby Hand Deeps (Fig. 2.1) differed to some extent in their mineralogical composition from the schists found on the sea-floor to the west of Start Point, and that this might be accounted for by a previously unsuspected southeasterly extension of the Portwrinkle Fault offshore, which brought the two different facies into relatively close spatial proximity. Phillips (1964b) subsequently summarized his views on the nature of metamorphism in SW England at a conference held to celebrate the 150th anniversary of the inauguration of the Royal Geological Society of Cornwall. In 1965, Phillips was elected as Vice President of the Mineralogical Society (1965-1968). He still persisted with some petrofabric work including a study (Phillips 1965) of the quartz and mica girdles in a strongly lineated quartzite which he had collected from the Broken Hill district of New South Wales during his 1953 Australian tour. The planes of the mica and quartz girdles were 25° apart and he compared these 'crossed-girdles' with similar ones, obtained by new measurements, from the strongly lineated Moine schist from Oykell Bridge, northern Scotland (Figs 5.2 and 6.3). He attributed the crossing of the girdles to polymetamorphism, i.e.

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overprinting, just as he had explained such relationships in his 1945 account. The understanding of divergent quartz and mica girdles was clearly still a matter of interest to him, partly as a result of Weiss's (1955) paper,293 but he felt that in these cases the noncoaxial quartz and mica fabrics294 were more likely to have been produced as a result of more than one period of strong deformation, rather than Weiss's (1955) postulated mechanism of a single phase of deformation affecting an initially layered fabric whose symmetry did not conform with that of the deforming movements. Following Whittard's death in 1966 (Phillips 19660), Phillips was annoyed when the university made him Head of Department, as he felt he was being forced into the job as a quid pro quo for having been given a personal chair, rather than money being spent on refilling the Chaning Wills Chair of Geology which Whittard had occupied (G. Evans, pers. comm. 1997). However, Desmond Donovan (pers. comm. 2000) comments that as Whittard died before he was due to retire, no search for a successor was in place and it was almost inevitable that Phillips would become acting Head in these circumstances. During this final year of employment (1966-1967), Phillips repeatedly stressed the 'caretaker' nature of his position with evident distaste and was reluctant to make decisions. This made apparent a characteristic which in retrospect can be seen to have run through his professional career, namely that he was best and most comfortable with implementing, as a deputy, the policy decisions of others (e.g. Tilley, Whittard, the Dean of Science, etc.) rather than being responsible for making the decisions, which caused him worry. As he approached retirement, Phillips' efforts went mainly into university teaching and administration, and reviewing books (Phillips 1966b,c). The year 1966 also saw the publication of Structural Diagrams (Vistelius 1966), a translation from Russian by R. Baker, edited by N. L. Johnson and Phillips, of a book (Vistelius 1958) by the leading mathematical geologist Andrei Borisovich Vistelius (1915-1995) on the statistical analysis of three-dimensional orientation data. Phillips had made his own translation of Sander's two-part work Einfuhrung in die Gefugekunde der geologischen Korper (An Introduction to the Study of Fabrics of Geological Bodies; Sander 1948, 1950) in 1958-1959, although he had never intended it for publication (translators' preface, Sander 1970, p. xi). He now bowed to pressure from Sander and many other geologists (N. R. 1970), to produce a complete translation of a book regarded by many at that time 'as a classic contribution to the literature of petrology' (Sander 1970, p. xi).

12. Retirement

In 1967 Phillips retired to Wains Way, Butt's Lawn, Meerut Road, Brockenhurst, Hampshire. Apart from acting as an external examiner to King's College London, he now had the time to give another short course on structural petrology (on 21-22 March 1968), and to see his 1970 translation of Sander's book through to publication. Reviewers of this text were agreed that few geologists not unusually fluent in German would ever have read a significant proportion of the original (N. R. 1970; Weiss 1970; Johnson 1971; Ramsay 1971) and for this reason alone, the translation of the embodiment of the philosophy underlying Sander's (and Schmidt's) life work was desirable. The task of translation was made particularly difficult because of the combination of Sander's convoluted style, local dialectal terms, and new words not previously used elsewhere and not always used as initially defined. Phillips enlisted the help of George Windsor of the Department of German, Bristol University, to assist him with the onerous task. Several times Phillips almost gave up on the Herculean task of producing a text suitable for publication, and the book was probably only completed because of the personal urgings of Weiss, Paterson and others who encouraged him to persist (Weiss 1970). Phillips took the opportunity to add a second bibliography of 168 books and papers (covering the years 1950–1967) to update Sander's original. Rather surprisingly, although Phillips' additions to Sander's bibliography include Flinn's papers on the statistical testing of petrofabric diagrams for non-randomness (e.g. Flinn 1963), there is no mention of the papers of Flinn (1956b, 1962), Weiss (1955, 1959a [which had already been cited in Phillips' (1960a) review of the interpretation of petrofabric diagrams], 1959b) or Ramsay (1958b, 6, 1959, 1960), all of which are relevant

to the interpretation of fabrics in areas which have been subjected to multiple deformations. Unfortunately, Phillips' heroic translation of Sander's work received a rather mixed reception and was very little read or referred to. As noted by one of the reviewers, Nicholas Rast (d. 2001) (N. R. 1970), had the translation appeared some ten years earlier, it might have had more impact on the structural debate. On the one hand, the 'strict adherence to the German text, although essential in a translation of this kind, is a mixed blessing for the reader: the English text remains formidably difficult . .. [although] if the work is long and tiring, the reward is great' since it gives 'an insight into the ideas of one of the most original minds in the earth sciences' (Weiss 1970). However, others did not agree that Sander's influence had necessarily been beneficial: '[his] lack of understanding of the statistics of preferred orientation and Achsenverteilungsanalyse,295 [and] his coordinate system bogged down structural geology for years and the resultant transport direction, a and B lineations controversy is still with us to some extent' (D. Flinn, pers. comm. 1996; see also Siddans 1972, pp. 222-224; Flinn 19940). Unfortunately, by the time Phillips' translation appeared, it was really chiefly of historical interest, as Sander's methods had become superseded.296 Phillips subsequently wrote a joint review article with Bradshaw on X-ray petrofabric studies (Bradshaw & Phillips 1970), completed new revisions of his ever-popular textbooks (Phillips 1971, 19726; Smith & Phillips 1972) and undertook more book reviews (19720, 1975), but his health gradually began to decline, and he died of broncho-pneumonia at the Forest Oaks nursing home, The Rise, Brockenhurst, Hampshire, on 11 September 1982.

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13. Benefits of hindsight

The true significance of Sander's b-axis In 1937, Phillips concluded that the regional-scale pattern of lineation which he had observed at both micro- and macroscales in the Moine metasediments, trending broadly NW-SE and plunging to the SE, was attributable to 'movements along southwest to north-east lines, earlier than the post-Cambrian displacements' (Phillips 1937b, p. 597). It appeared to post-date the intrusion of the Carn Chuinneag igneous complex (Phillips 1937b, p. 595, 1945, p. 210), to pre-date the isoclinal folding (Phillips 1945, p. 211), and the associated fabric was broken down by the 'dislocation-metamorphism' of the Moine Thrust Zone (Phillips 1945, p. 212).297 Furthermore, Phillips agreed with Read's interpretation that although the pervasive NW-SE 'stretching lineation' (Read et al. 1926, p. 121) pre-dated the Moine Thrust itself, 'it is the lineation parallel to the b-axis of the fabric which has provided the direction of yield during the later thrustmovements' (Phillips 1937b, p. 597). As Flinn put it (pers. comm. 1998), Phillips' interpretation was 'right (to some extent) for the wrong reasons.' Although the style of Phillips' (1945) composite petrofabric diagrams (e.g. Figs 6.8-6.10) has recently been found by Richard D. Law to be particularly helpful as an aid to kinematic interpretation,298 much of the controversy which dogged Phillips' petrofabric research was attributable to the fact that in his own work Phillips followed Sander's usual kinematic interpretation of the 'b-axis' as being orthogonal to the principal compressive stress and, hence, to the 'direction of transport', a view which, as has been seen, unfortunately became increasingly controversial. Figure 13.1 contrasts the Sanderian interpretation of the girdle fabric (Fig. 13.la, c), in which the 'direction of movement' was taken to be perpendicular to the 'b-axis' in the plane of the girdle, with the modern interpretation (Fig. 13.1b, d), as applied by Law and his co-workers (Law et al. 1984, 1986; Law 1987, 1990; Law & Potts 1987), in which the 'direction of movement' is regarded as being perpendicular to the girdle, i.e. parallel to the direction of the lineation. Ramsay (1963, p. 146), Flinn (pers. comm. 1998) and others have pointed out that with the passage of time it became increasingly apparent that lineation can develop parallel to fold axes (i.e. Sander's 'b = B'), normal to fold axes (parallel to Sander's 'a-axis'), or in any other direction. In his classic paper 'On folding during three-dimensional progressive deformation', Flinn (1962) proved computationally that neither fold axes nor axial planes bear any special relation to the {X, Y, Z} axes of the three-dimensional deformation ellipsoid and, consequently, to use them as indicators of movement directions, or of the direction of flow in rocks, is quite misleading.299 For example, after Christie (1956, 1960, 1963) interpreted the ESE-plunging linear structures in the Moine Thrust Zone as a B-axis, concluding that the thrust was a strike-slip fault with transport towards the SSW, Johnson (1965, p. 673) asked 'how can Christie be so confident that he has identified the transport direction using only fold axes?' and cited Flinn (1962), Ramsay (1963) and Turner & Weiss (1963), all of whose studies agreed in concluding that fold axes could lie at any angle to the direction of maximum compressive stress. Modern work makes use of 'strain-markers' (Simpson & Schmid 1983), i.e. small-scale phenomena in the rocks, such as shear-bands, garnets with curved inclusion trails, pressureshadows of porphyroblasts and oblique grain-shape fabrics which record the effects of strain. However, now that better

Fig. 13.1. Schematic diagram contrasting the Sanderian (a, c) and 'modern' (b, d) interpretation of the relationship between quartz c-axis fabrics as they appear when plotted (stippled field) on a lower hemisphere equal-area projection, and the inferred kinematic 'b-axis' of Sander (b) and 'movement direction' (m.d.). Lineation (1) and plane of foliation (f) are also shown. The upper figures (a, b) are plotted in a geographical frame of reference, with north at the top. The lower figures (c, d) are plotted in a specimen frame of reference: in (c) the plane of projection is perpendicular to both foliation and lineation (the 'b-axis' is vertical); in (d) the plane of projection is perpendicular to the (horizontal) plane of foliation and parallel to the lineation (as in Fig. 6.8b). Reproduced with permission of Professor R. D. Law and Cambridge University Press from figure 11 of R. D. Law & G. J. Potts, 1987, The Tarskavaig Nappe of Skye, northwest Scotland: a re-examination of the fabrics and their kinematic significance', Geological Magazine, 124, 231-248, copyright © 1987 Cambridge University Press.

understanding of the genesis of quartz crystallographic fabrics has emerged, the techniques of structural petrology are also being used effectively for this purpose (Law 1990). Direct measurement of the three-dimensional shape of the deformation ellipsoid from measurements of deformed pebbles in conglomerates (Flinn 1956b, 1962) has already been mentioned. More recently, Coward & Kim (1981), Fischer & Coward (1982) and Coward et al. (1992) have made use of measurements of the ellipticity of the crosssections of fossil worm-tubes300 in the Pipe Rock sequence of the Cambrian quartzites of the Durness succession (Fig. 5.2), as well

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as the deflections of the tubes from their original perpendicularity to the bedding, to make quantitative estimates of the shear-strain in thrust-sheets within the Moine sequence. We agree with Flinn (pers. comm. 1998) that the a- and b-axis controversy was both unnecessary and extremely unfortunate, since it resulted from erroneous assumptions on both sides. In interpreting the petrofabrics, Phillips followed Sander's ambiguous rules regarding the kinematic interpretation of the {a, b, c} tectonic axes as well as he could. His error was to adopt Sander's theories unquestioningly, whereas Phillips' opponents set out to determine the deformation [which] the Moines have undergone by making the tacit and unspecified assumption that the deformation is simple shear (because the lineation is at least approximately parallel to the direction in which the Moine Thrust is thought to have moved) and that it represents the continuation of simple shear movement on the Moine Thrust (or vice versa). 301 Having already made up his mind about the nature of the deformation, Anderson then applied the {a, b, c} axes so as to fit his interpretation of what 'transport direction' and 'rotation axis' meant.302 In both cases, the result had nothing to do with what had actually gone on in the rocks (D. Flinn, pers. comm. 1998).303 Recent work in the Durness and Loch Eriboll [Erieboll] regions (Fig. 5.2) of the Moine Thrust Zone (Ramsay 1997) has shown a direct geometric linkage between the folds in the Cambrian coverrocks and those of the Lewisian basement, even though the axial directions of the linked folds are almost at right angles to each other. This difference in fold-axis orientation is interpreted (Ramsay 1997, pp. 463-464, fig. 24.11) as having been controlled by fundamental differences which existed in the orientations of the dominant planar structures in the basement rocks and in the cover. He found that in zones weakly affected by the Caledonian deformation, the Lewisian linear structures plunge to the ESE or SE, more or less as in the original foreland regions, whereas in the highly Caledonized zones, these linear features are less prominent and tend to plunge to the W or SW (Ramay 1997, p. 464). On the basis of detailed field evidence, Ramsay concluded that the sequence of deformation events can be shown to comprise early contraction of the cover (and perhaps the basement also) followed by folding of both, with the formation of schistosity and local ductile mylonites. The strikes of the basement rocks then became reorientated to conform with NNE-SSW 'Caledonian' structures. As a result, the original linear fabrics of the basement were overprinted by ESE- to SE-plunging folds and the development of lineations caused by the alignment of mineral grains. Finally, the development of major brittle thrusts (with some localized ductile deformation close to thrust planes)304 sliced the previously folded units and mylonite fabrics into a series of nappe sheets. Furthermore, Ramsay concluded that many of the structural features within the overlying Moine Nappe linked the Caledonian deformation southeastwards, across the Moine Thrust, into the more metamorphosed parts of the orogen305 (Ramsay 1997, p. 468). He emphasizes (Ramsay 1997, p. 470) that the folds and thrusts were formed at quite different periods of time within the overall Caledonian deformation, when the rocks possessed quite different rheological properties. This understanding of the complexity of the relationships which can develop between folding and pre-existing lineations simply did not exist at the time that Phillips was undertaking his pioneering studies. However, it does explain the 'apparent coincidence' remarked on by Phillips (1949, 1951b) of the presence of ESE-plunging lineation in both the Moinian and Lewisian rocks, and confirms his hypothesis (Phillips 1937b, 1939, 1945, 1951b) that the folding pre-dates the development of the Moine Thrust Zone. Phillips (1937b, p. 583) echoed Sander's (1934, p. 37) plea that 'there ought not to be microtectonists and megatectonists working

independently of each other, but rather one group of workers investigating the correlations between processes in large and small units'. Had such collaboration taken place, much of the subsequent argument might well have been avoided. The explanation of 'crossed-girdles' Even in the 1960s, after nearly 20 years of experimental work, Turner & Weiss (1963, p. 430) noted that 'experimental evidence bearing on the possible significance and mode of evolution of quartz subfabrics ... is somewhat meagre' and that consequently their interpretation still remained equivocal. However, a continuing programme of experimental rock-deformation studies by, for example, Griggs & Miller (1951), Paterson (1958), Heard (1963), Tullis et al. (1973) and Tullis (1977) led to an improved understanding of the deformation mechanisms of mineral crystals. This eventually gave rise to computer simulation studies of the development of preferred crystallographic orientations in the quartz fabric of a deforming rock (e.g. Lister et al. 1978; Lister & Hobbs 1980), involving three-dimensional deformation under conditions of rigid-plastic flow and with five independent crystallographic glide-systems. The results of these studies revealed how the girdle fabric of a model quartzite develops as a result of axial extension, and that 'crossed-girdles' occur naturally in the course of a single phase of deformation under plane strain (Fig. 13.2),306 contrary to the assumptions of all the early structural petrologists that one of the pair must be the result of 'overprinting' during a later phase of deformation. Note that each of the equal-area stereographic plots in Figure 13.2 is rotated by 90° counterclockwise with respect to the standard orientation used by Phillips in Figures 6.9 and 6.10. The nature of the Moine Thrust Deep seismic profiling has revealed that the Moine Thrust rises from a depth of some 27 km in the lower crust (Soper & Barber 1982) and near-surface dips are at 11-15° to the ESE (Coward 1980). The cessation of ductile deformation and general initiation of imbrication307 within its footwall308 has been dated at c. 430 Ma, with plastic deformation associated with shearing continuing to 408 Ma (van Breeman et al. 1979; Freeman et al. 1998). Evidence from slickensides and listric faults309 has established that the general transport direction is directed at 290-300° towards the WNW (Coward 1980; Coward et al. 1992). The Moine Thrust is now recognized to be the oldest, but structurally highest, of a number of thrusts which together form the NNE-SSW trending Moine Thrust Zone. Detailed petrofabric and X-ray texture goniometry studies by Richard Law and his co-workers (Law et al. 1984,1986; Law 1987) of quartz fabrics in the mylonites associated with the Moine Thrust plane have established (e.g. at the Stack of Glencoul, Fig. 13.3) that the asymmetrical single-girdle fabric, which is only found within a few centimetres of the thrust-plane, reflects strongly non-coaxial flow (which they interpret as indicative of simple shear) in the direction of transport towards the WNW; whereas, as strain increases a crossed-girdle fabric develops310 at depths of 30 cm or more below the thrust-plane (Fig. 13.4). This fabric is believed by Law and his co-workers to reflect the presence of conjugate, mutually interfering sets of shear bands which are symmetrical about the plane of foliation and lineation, and are presumed to have developed under conditions intermediate between the flattening and plane-strain fields. Unravelling the 'Tarskavaig Moines' It is now known that Phillips (1938b, 1939, 1947a) was misled in his interpretation of the structure of the problematic Tarskavaig

BENEFITS OF HINDSIGHT

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Fig. 13.2. Computer simulation of the development of quartz optical c-axis fabric under strain attributable to coaxial deformation (Lister & Hobbs 1980). Each diagram is a lower hemisphere equal-area projection of 500 c-axes. The original random c-axis fabric is shown at the origin (lower left). The individual equal-area diagrams are placed in the context of a Flinn (1962) deformation plot. As used here, the horizontal reference axis corresponds to an increasing ratio Y/Z and the vertical reference axis to an increasing ratio X/Y, where X, Y and Z are the principal axes of finite strain: X is the axis of extension, Y is the axis of intermediate strain, and Z is the axis of shortening; X>Y>Z. The equal-area projections are all orientated with the X-plane vertical, the Z-plane horizontal, and the Y-axis vertical (i.e. out of the plane of the paper). In terms of natural rocks, this is equivalent to an anti-clockwise rotation of Figure 6.8b by 90°, so that the plane of foliation (XY) is vertical with the lineation in the plane of the paper. Note how the skeleton of the pattern of maximum point concentrations is symmetrically related to the finite-strain axes and that crossed-girdle fabrics similar to those in natural quartzites develop under plane strain. Reproduced with permission of Professors G. S. Lister and B. E. Hobbs, from figure 8 of G. S. Lister & B. E. Hobbs, 1980, 'The simulation of fabric development during plastic deformation and its application to quartzite: the influence of deformation history', Journal of Structural Geology, 2, 355-370.

Moines' on the Isle of Skye by the presence of local folding. Modern work by Law & Potts (1987) suggests that, by mischance, four of Phillips' localities (including his sites 6, 7 and 8 shown in our Fig. 6.5) lay close to what is now known to be the hinge-zone of the Tarskavaig synform, and consequently reflect a locally modified lineation trend. Broadly speaking, the Tarskavaig Nappe and the Moine Nappe in this area both show the regional SE-pitching lineation and Phillips' apparently 'anomalous' locality (site 10, Fig. 6.5) in fact corresponds to the norm. As a result of his unlucky choice of sampling localities, Phillips' (1951b, p. 234, table II) favoured solution for the stratigraphy, arising from his petrofabric study of the Tarskavaig Moines', was to assign both the Lewisian and Moine successions to the pre-Torridonian. He believed the Tarskavaig rocks to be younger than these, predating 'thrust Torridonian' and then 'thrust Cambrian'. Although modern work has established that the Tarskavaig Moines' have some petrographical and geochemical affinities with the Sleat Group of the Torridonian, their exact stratigraphic position is still essentially unknown (Stewart 1991; G. Potts, pers. comm. 2000).

The cause of Kvale's confusion Modern re-examination of the tectonics of southern Norway (and the area containing the Bergsdalen quadrangle in particular; Fossen 1992, 1993), paying particular attention to small-scale structures and strain-markers, suggests why Kvale may have found the structure of the region so difficult to understand. He believed that all the structures were related to a single phase of Caledonian movement which emplaced the Bergsdalen Nappes. However, Fossen (1992, 1993) has now shown that there was an initial phase of contractional regional deformation (Dl) in Ordovician-Silurian times when, following the destruction of the lapetus Ocean, the continent of Laurentia311 first collided with Baltica312 (Fig. 13.5). The Bergsdalen Nappes were emplaced in this period, moving (possibly hundreds of kilometres) with top-to-the-SE thrusting, to end up lying on top of the Baltic Shield. Next came a phase of extensional deformation (D2) in which the shear-sense initially reversed (moving some 25 km, with top-to-the-NW) and this was followed by the development of

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Fig. 13.3. (a) Exposure of the WNWdirected Moine Thrust in cliffs at the Stack of Glencoul, Assynt, Northwest Highlands of Scotland. Mylonitic Cambrian quartzite (Q) underlying similarly deformed Moine rocks (M). The Moine Thrust plane (M. T.) is shown by the broken white line; note the boudin necks (b) in the quartzites adjacent to the thrust plane which also deform the thrust surface itself (the boundary of the necking in the area of shadow is discernible in an enlarged version of the original print). R. D. Law (pers. comm. 2000) interprets this as direct evidence that crystal plastic deformation and mylonitization continued during the very last moments of the thrust surface and that all the features from this area are consistent with late extensional collapse of the orogenic pile, (b) Contact between the Moine rocks (M) and mylonitic Cambrian quartzite (Q) at handspecimen scale. Polished surface cut perpendicular to foliation and parallel to lineation. The Moine Thrust is marked by an arrow. Photographs courtesy of R. D. Law; slightly modified from versions originally published as figures 3a and 3b of R. D. Law, M. Casey & R. J. Knipe, 1986, 'Kinematic and tectonic significance of microstructures and crystallographic fabrics within quartz mylonites from the Assynt and Eriboll regions of the Moine thrust zone, NW Scotland', Transactions of the Royal Society of Edinburgh: Earth Sciences, 77, 99-126. Reproduced with permission of the Royal Society of Edinburgh.


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found over the decollement zone is believed by Fossen to reflect local variations in the slip direction of nappe transport and/or reworking during D2.315 The abrupt change in orientation of the Dl structures in the basement rocks in the NW of the quadrangle (Fig. 8.4) may be a result of partitioning of the deformation into orogen-parallel (strike-slip) and orogen-normal (transverse) thrusting (Gilotti & Hull 1991; Fossen 1993). Fossen et al. (1994) and Fossen & Hoist (1995) have subsequently modelled the tectonics of this region as transpressional, i.e. undergoing deformation as a result of the oblique motion of plates (Harland 1971), where a simple shear zone subjected to strike-slip (vertical simpleshear deformation) is accompanied by a simultaneous component of pure shear (plane-strain contractional deformation) in a plane perpendicular, or possibly oblique, to the shear zone.

Modern understanding of the cause of the lineation and fabrics measured by Phillips in the Moine rocks

Fig. 13.4. Schematic diagram showing the relationship of quartz c-axis fabrics in mylonitic Cambrian quartzites relative to vertical distance away from the Moine Thrust plane at the Stack of Glencoul, Assynt, Northwest Highlands of Scotland. The lower hemisphere equal-area projections are viewed towards the NNE, rotated such that they are parallel to the lineation and the plane of foliation is horizontal (Fig. 6.8b). Foliation and lineation are parallel to the surface of the thrust throughout the mylonite sequence. The asymmetric fabric developed within the first 10 cm below the thrust gives way to a relatively sharp crossed-girdle fabric which persists down to at least 8.5 m, but which then becomes much more diffuse at depths of 40 m and 70 m (Law et al. 1986, figs 5-7). However, deformed quartz veins within phyllosilicate-rich mylonitic Moine metasediments above the thrust are all characterized by asymmetrical single-girdle fabrics (Law 1990, p. 341). Redrawn with permission of the author and The Geological Society, London, from figure 6 of R. D. Law, 1990, 'Crystallographic fabrics: a selective review of their applications to research in structural geology', in R. J. Knipe & E. H. Rutter (eds), Deformation Mechanisms, Rheology and Tectonics, Geological Society, London, Special Publications 54, 335-352.

major, oblique, extensional shear zones313 and stretching of the basement. Weijermars (1997) has recently suggested that the presence of SW-NE elongation of pebbles in the Bygdin conglomerate at Barnesodden (i.e. elongation in a direction perpendicular to the general NW-SE lineation found elsewhere in the conglomerate, which is parallel to the overall direction of shear transport), occurs as a result of local lateral spreading within the movement zone beneath the Jotun Nappe. Weijermars (1993, 1997) explains this by a mechanism of pulsating prolate strain.314 In the context of Kvale's interpretation of movement parallel to Sander's tectonic a-axis, it is of particular interest that Fossen (1993, p. 107) found that the Dl fold axes were rotated to become parallel to the dominant Dl lineation, probably as a result of a combination of simple shear thrusting and horizontal pure shear, with shortening perpendicular to the thrusting direction, whereas the fold axes associated with D2 are at a high angle to the D2 extensional lineations. These patterns are broadly reflected in Kvale's structural map (Fig. 8.4). However, Flinn ( 1 9 9 4 a ) is of the opinion that it is a constrictional pure shear zone and that Fossen provides no evidence for the presence of a significant simple shear component. The general curvature in the lineation directions which Kvale

Following a deepening understanding of the mechanisms involved in global plate tectonics in the years since the concept was first proposed (Morgan 1968), Shackleton & Ries (1984) have argued, on the basis of a world-wide review, that since destructive plate boundaries are shear zones on a crustal scale, and shear zone geometry involves extension in, or close to, the direction of shear (Ramsay & Graham 1970), then, at a regional scale, 'stretching' (extension) lineations should reflect the direction of the relative motion of the lithospheric plates. Shackleton & Ries (1984) concluded that high-angle convergence of plates produces transverse extension lineations and that large extensions cause the development of sheath folds316 (discussed in more detail below) whose acutely curved axes tend to approach the stretching direction. Furthermore, the pre-existence of a strong linear fabric predisposes towards the development of later folds with axes parallel to the earlier linear fabric. They suggested that 'in the Caledonides, transverse and longitudinal ductile shearing was followed by brittle shearing, the longitudinal displacements being consistently sinistral' 317 (Shackleton & Ries 1984, p. 114), a view supported by Soper & Hutton (1984) and Seranne et al (1991). At the same time as the Scandinavian Caledonides were being formed by the continental blocks of Laurentia and Baltica moving towards each other, the Caledonides of northern Scotland were formed by the collision of the microcontinental blocks of Avalonia and Cadomia (Eastern Avalonia)318 with Laurentia (Fig. 13.5).319 The area which now forms the British Caledonides lay on the northern side of the NW-dipping suture line which marks the locus of the site of closure (as a result of these continentcontinent collisions) of the former lapetus Ocean, whereas the area of southwestern Norway, investigated by Kvale, lay on its southern side. Consequently, the NW-directed crustal imbrication of northern Scotland is the counterpart of the SE-directed thinskinned thrusting of southern Scandinavia (Soper & Hutton 1984, p. 788). It has been suggested by Chauvet & Seranne (1994) that continued sinistral wrenching between the newly accreted continental blocks eventually led to late-stage extensional collapse in Devonian times,320 manifested in SW Norway by large-scale folding developed parallel to, and contemporaneously with, a pattern of regional east-west trending lineation. These authors propose that the folding may have been caused by buckling resulting from horizontal regional north-south compression perpendicular to the extension direction (as a result of continued northward movement of Avalonia), and that this regime affected the Devonian sediments which had by then infilled the system of basins covering the region between northern Scotland, Shetland and southern Norway. We are grateful to Richard D. Law (pers. comm. 2000) who summarized for us the modern understanding of the genesis of the lineation and quartz fabrics measured by Phillips, in the context of

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Fig. 13.5. Reconstruction of the North Atlantic Caledonides in mid-Silurian times (c. 430 Ma BP). Collision has already taken place between Baltica and Laurentia, but within-plate deformation is continuing with crustal imbrication (short arrows). Cadomia has yet to collide with northern Britain-southern Baltica, and Avalonia with the Appalachians. Reproduced with permission of Professor N. J. Soper and the American Geophysical Union from figure 4 of N. J. Soper & D. H. W. Hutton, 1984, 'Late Caledonian sinistral displacements in Britain: implications for a three-plate collision model', Tectonics, 3, 781-794, copyright © 1984 American Geophysical Union.

the geology of the region involved, which can be divided into three structural domains: (1) the relatively high metamorphic grade Moine rocks to the east of the Moine Thrust Zone; (2) the mylonitic rocks adjacent to the Moine Thrust itself (Fig. 13.3), including plastically deformed Cambrian age quartzite in the immediate footwall and plastically deformed pelitic321 and psammitic322 Moine rocks in the hanging wall323 to the Moine Thrust (dominantly at greenschist facies); and (3) the thrust sheets exposed to the west of the Moine Thrust. Here, deformation is dominantly by brittle fracturing, and there is little crystal plastic deformation (and hence crystal preferred orientation; cf. Fig. 6.2b), except in local areas such as the Tarskavaig Nappe of SW Skye. If the name Moine Thrust is confined to the dislocation associated with crystal plastic deformation exposed from Eriboll southwards to the Stack of Glencoul and the Allt nan Sleach stream section in

southern Assynt (Law et al. 1984, 1986; Law 1987, 1998a, b) and is not used for the brittle feature exposed from Knockan Crag southwards (see Fig. 5.2 for locations), then the modern understanding of the WNW lineation and its attendant quartz fabric in both the mylonitic Moine rocks above the Moine Thrust examined by Phillips and the mylonitic Cambrian quartzite in the immediate footwall to the Moine Thrust (e.g. Christie 1963; Law et al. 1984, 1986; Law 1987, 1998a, b), is that it is the result of WNW-directed Caledonian movements which also formed the Moine Thrust and other underlying thrusts. Within the underlying thrust-sheets, deformation was at lower temperatures (Knipe 1990), and hence crystal plastic deformation and crystal fabric development is more limited. Locally, however, strong crystal fabric development was recorded by Phillips in the underlying thrust-sheets, e.g. in the Tarskavaig Nappe of Skye (Phillips 1938b; Law & Potts 1987). The pattern of crystal preferred orientation is also consistent with WNW-directed stretching. The crystal fabric diagrams published by Phillips (1937b) also


indicate that the domain of penetrative WNW-directed stretching extends for some considerable distance eastwards into the higher metamorphic grade Moine rocks lying above the Moine Thrust Zone. If any earlier grain shape and crystal fabrics were originally present in these rocks, they have now been largely overprinted by penetrative deformation associated with the WNW-directed thrusting and stretching (Holdsworth 1989, 1990). This main phase of penetrative deformation was Silurian in age (van Breeman et al. 1979) and consequently very late in the history of the Moine rocks. It was therefore much more widespread (especially to the east of the Moine Thrust) and pervasive than was appreciated when Phillips undertook his study. At that time, it was considered that the deformation related to the thrusting was confined to the vicinity of the obvious thrusts. The regularity of the lineation and its attendant fabric is primarily a function of the lateness of the structure, which ensured that it has avoided being folded by the earlier deformations. Thus Barr et al. (1986), Holdsworth (1989) and Holdsworth et al. (1994) have shown that a continuity of structures exists between the Moine Thrust Zone and the overlying Moine Nappe rocks, so that far more of the structures and fabrics in the Moine Nappe are Moine Thrustrelated than was originally realized. Phillips was the first to recognize the continuity of the lineations across the Moine Nappe and into the Moine Thrust Zone, but the correct interpretation as to why this was so eluded him. One of the longstanding problems in orogens everywhere, and central to the Moine petrofabric controversy, has been gaining an understanding of the mechanisms which can lead to the parallelism of fold hinges and mineral lineations. As has been seen, this was touched on in the criticism of Phillips' work by Anderson (1948) and others, and underlay the fundamental difference of opinion between Sander and Heim in the 1920s as to which of the [a, b, c] kinematic axes should be regarded as being parallel to the

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'direction of movement'. By the late 1970s, it had begun to be apparent that there was an overall similarity of style and orientation of minor folds and their relation to mineral lineation in thrust zones associated with orogenic belts as far apart as NW Scotland, Norway, West Greenland, the southern Appalachians (USA) and Australia (Lindstrom 1961; Bryant & Reed 1969; Cobbold et al. 1971; Sanderson 1973; Escher & Watterson 1974; Bell 1978): as strain increased, fold axes which had initially formed at an angle approximately perpendicular to the mineral elongation (transport) direction appeared to rotate towards it. In a study of quartz mylonites from a shear zone in the Cap de Creus peninsula (NE Spain) Carreras et al. (1977) suggested that as a result of mineralogical inhomogeneity in the various lithologies present, internal buckling instability could develop within a shear zone. As a result, folds initially formed at approximately 90° to the transport direction would become progressively flattened and stretched so that their axial planes became approximately parallel to the foliation plane (which is itself subparallel to the ductile thrusts), and their fold axes would gradually rotate into parallelism with the mineral elongation lineation (Figs 13.6, 13.70). Consequently, 'the three dimensional outline of the folds increasingly resemble sheaths extended parallel to the extension direction as the shear strain increases' (Carreras et al. 1977). These structures (sometimes likened to a 'test tube' in shape), characterized by their extremely curvilinear hinge lines (Fig. 13.7b), consequently became known as sheath folds. Cobbold & Quinquis (1980) subsequently demonstrated experimentally how such folds could develop. When most intensely developed, a transverse cross-section through their complex conical geometry can give rise, at the scale of an outcrop, to the appearance of concentric banding (Fig. 13.7c), referred to as an 'eye-structure' (Ramsay 1962b). However, as recent work (discussed below) has shown, sheath folds are also formed with dimensions of kilometres.

Fig. 13.6. (a-d) Sketch to illustrate the progressive rotation of parts of an original fold hinge into parallelism with lineation which is itself parallel to the (thrust) transport direction (arrowed), as curvature develops under progressive deformation; thick dashed line indicates both axial trace of the developing (kilometre-scale) sheath fold and orientation of the lineation. Note progressive development of divergence of facing directions on the limbs of the sheath fold.

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Fig. 13.7. (a) Sketch to illustrate the relationship of the sheath fold geometry to the Caledonian ductile thrusts in west Sutherland; thrust transport direction towards WNW. (b) Sketch to illustrate the geometry of (?Precambrian; R. E. Holdsworth, pers. comm. 2001) sheath folds exposed in Garry quarry (National Grid ref. NH 196 023), Glen Garry, west Sutherland. The folds have flat-lying axial planes and locally show nearly 180° of hinge curvilinearity over a few metres about a north-south axis and lineation. (c) Eye-structure in Moine psammites, Creag Mhor, Sutherland. Parallel white lines show trend of mineral lineation plunging down the central axis of the sheath fold. Lens cap is 5 cm across, (a, c) Reproduced with permission of Dr R. E. Holdsworth from figure 5 and (original of) figure 2b of R. E. Holdsworth, 1990, 'Progressive deformation structures associated with ductile thrusts in the Moine Nappe, Sutherland, N. Scotland', Journal of Structural Geology, 4, 443–-452. (b) Reproduced with permission of Dr R. E. Holdsworth and The Geological Society from figure 3b of R. E. Holdsworth & A. M. Roberts, 1984, 'Early curvilinear fold structures and strain in the Moine of the Glen Garry region, Inverness-shire', Journal of the Geological Society, London, 141, 327-338.

Before methods for the field interpretation of large-scale sheath folds were fully developed (e.g. Alsop & Holdsworth 1999), Carreras et al. (1977, p. 16) suggested that it was the rotation of fold axes associated with sheath fold structures (Fig. 13.6) which lay at the root of some of the controversy in interpretation of structures in the Moine, citing the debate between Christie (1963, 1965) and Johnson (1965) as an example. Furthermore, Carreras et al. (1977) found that sheath folding can modify the existing

microfabric by (i) pseudo-passive rotation without altering the existing microstructure, as well as (ii) formation of a new fabric, similar to the old but in grains elongated along the axial plane. This leads to the formation of a crossed-girdle consisting of an old and a new element, yet formed as a result of a single phase of deformation. As mentioned above, this possibility was confirmed by the computer simulations of Lister et al. (1978) and Lister & Hobbs (1980). Traces of pre-thrusting (?Precambrian) 'Dl' deformation structures in the Moine Nappe of Sutherland are preserved as a bedding-parallel foliation, a weak N- to NNE-trending mineral lineation, and rare minor folds in rocks which were, at that time, still largely the right way up, although towards the east they reached at least garnet-grade metamorphism (Holdsworth 1989). The presence of kilometre-scale sheath folds and flow perturbation patterns in the 'D2' structures related to the Caledonian ductile thrusting has been recognized in the Moine rocks in studies, particularly in the A' Mhoine-Ben Hutig [Beinn Thutaig] region of Sutherland (Fig. 5.2), by Holdsworth & Roberts (1984), Holdsworth (1990), Alsop & Holdsworth (1993) and Alsop et al. (1996). These authors have demonstrated that, as a result of ductile shearing associated with the initiation and propagation of the thrusts, fold axes in the Moine have been rotated into within 20° of the transport direction, as marked by the ESE- to SEplunging 'stretching' lineation. The sheath fold facing patterns, as elucidated by Holdsworth (1988, 1989) and Alsop & Holdsworth (1999), show that the original facing direction of the folds is consistent with their initial development as WNW- to NW-overturned buckles, with hinges at high angles to the transport direction, during the NW-directed thrusting of the Moine Thrust movements. Holdsworth (1990), Alsop & Holdsworth (1993) and Alsop et al. (1996) have found that, in some places, these F2 sheath folds are themselves deformed by metre- to kilometrescale eastward-plunging 'F3' buckle folds. These may be either asymmetric, with relatively straight hinge lines subparallel to the main phase (D2) mineral lineation, or sheath folds about an ESEplunging axis, overturned towards the WNW and refolding both the F2 folds and the mineral lineation (Holdsworth 1990). Both these later 'F3' fold types are interpreted as being formed as a result of differential shear in regional flow perturbation patterns generated within the underlying detachments, and have been influenced in their location and orientation by the presence of the slightly earlier F2 sheath folds, as a result of their effect on the flow patterns (Alsop et al. 1996; Holdsworth, pers. comm. 2001). Such rotation of fold axes and lineations, which was not envisaged at all during the time Phillips worked - and would not have been even if he had collaborated with Moine mappers, goes a long way to explaining how and why fold hinges and mineral transport lineations are so often parallel. A crucial part of Phillips' contribution was his early recognition that the lineations and fold axes were parallel in the Moine rocks. Flinn (1994a; pers. comm. 1998) has made the point324 regarding early criticisms of Phillips' work that his opponents 'set out to determine the deformation the Moines have undergone by making the tacit and unspecified assumption the deformation is simple shear . .. [and] . . . that it is the continuation of the simple shear movement on the Moine Thrust (or vice versa)'. Recent interpretations (e.g. Law et al. 1984, 1986; Law 1987, 1990; Holdsworth & Roberts 1984; Holdsworth 1989) invoke a mechanism in which WNW-directed boundary-parallel shortening took place with both coaxial deformation (approximately pure shear) and non-coaxial deformation (involving a component of simple shear) taking place at various levels relative to the thrust planes (cf. Fig. 13.4) as a result of strain partitioning. This early phase of 'active' (F2) folding was followed by a later boundary-parallel extension phase during which these folds switched to a 'passive' mode and became modified into sheath structures; as a result, the simple shear component became the common deformation factor throughout D2 (Holdsworth 1989). The recent work on the sheath folds and


(to a lesser extent) the flow-perturbation folds gives independent verification of the assumed subparallelism between the transport in the Moine Thrust Zone and that in the Moine, as it shows that the D2 fold geometries and the facing directions are consistent with the top-to-the-NW thrusting, thereby providing the proof which Flinn felt was lacking in the early work (Holdsworth, pers. comm. 2001). Despite the advances in the understanding of such fabrics and the improvements in radiometric dating which have taken place in the years following Coles Phillips' death, controversy over the deformational history of the Moine and Dalradian rocks of Scotland continues. A review of recent literature (Bluck 2000, p. 99) concludes that study of this topic is still 'beset by claims and counter claims, and the division of opinion mostly centres on the significance of age determinations, the interpretation of metamorphic fabrics, and the relationships of dated rock-units to

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structure and metamorphism'. This appears to be particularly true as regards the existence of the so-called 'Knoydartian' (Bowes 1968) Neoproterozoic325 tectono-thermal event, which may or may not have taken place between 850 and 700 Ma ago. Although radiometric dating appears to provide some evidence in its favour, Soper & Harris (1997), Dewey & Mange (1999) and others, strongly believe that there is no firm evidence to support such an early period of regional ductile folding. Indeed, as noted by Bluck (2000) in his discussion, the occurrence of such an event seems to be inconsistent with the gradual development of the extensional basins which are believed to characterize the Laurentian margin elsewhere. These workers suggest that this process culminated in the opening of the lapetus Ocean (c. 600 Ma ago) which was eventually followed by a single, short-lived orogenic episode in the Middle-Late Ordovician, associated with the subduction of the northwestern side of the lapetus Ocean (discussed above).

14. Conclusion

Phillips was, first and foremost, a superb teacher and his main legacy lies in the students he trained and in the influence of his textbooks, An Introduction to Crystallography and The Use of Stereographic Projection in Structural Geology. His revision of Herbert Smith's Gemstones is much less well-known, because the study of gemstones does not form a significant part of any degree course. He excelled at the exposition of factual, logical, noncontroversial mathematically based material in the visual, nonmathematical way sought by geologists. His translation of Sander's book was difficult to understand simply because Sander's obscure writings were themselves 'impenetrable' and replete with technical phrases invented by Sander which had no equivalents in English. Moreover, the subject of petrofabrics was never in the mainstream of geology degree courses, so Phillips' last book would not have become familiar to most geology students even if it had appeared ten years earlier. However, despite the controversy which surrounded the petrofabric approach, Phillips' pioneering studies in the Scottish Highlands certainly were early developments in the use of increasingly sophisticated field and laboratory methods in which graphical manipulation of three-dimensional structural data, using Stereographic techniques, helped to unravel the complex structure of the Moine rocks. Despite the fact that Sander's kinematic axes, 'movementpicture' and 'symmetry principle' have become discredited,326 petrofabric studies undoubtedly provoked thoughts about the mechanisms of crystal deformation and recrystallization during

metamorphism. This stimulated early experimental rockdeformation studies (particularly of marbles), by Griggs & Miller (1951), Paterson (1958), Heard (1963), Tullis et al (1973), Tullis (1977) and others, to determine crystal response to known forces. It also led to looking at the already quite detailed knowledge available about deformation and recrystallization in metallurgy (e.g. McLean 1965) even though, in the end, the heterogeneity of rocks, the low symmetry of silicates, the long times available in geology, the large fluid and gaseous fluxes, and the multi-episodic nature of geological events, generally frustrated meaningful comparisons with metallurgical knowledge. Despite some continuing interest in petrofabrics, especially using the less laborious X-ray texture goniometry, first attempted by Sander & Sachs (1930), Fairbairn (1943), Ho (1947), Trommsdorf & Wenk (1963, 1965), Starkey (1964), Wenk (1965a, 1965b) and Bradshaw & Phillips (1967),327 and more recently revived by Law et al. (1986), Law (1987) and others, the mantle of the British master of the subject never passed on to any of the many students at Phillips' courses, or those he supervised in research. Petrofabrics in Britain became sidelined in the direct study of fold episodes, their geometry and sequence, but abroad (especially in France, Germany, Australia and the United States), a modern generation of structural petrologists is pursuing work that is quite fundamental to understanding the mechanisms of deformation and recrystallization that accompany fold and thrust structures. Many of these workers, particularly those with Australian connections, can trace their petrofabric initiations to those trained by Phillips.

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Notes

1

2

3

4

5

6

7

8

9

10

Someone who studies the systematic description of rocks and the mineralogical and textural relationships within them, based on field observations, the study of hand-specimens and examination of thin-sections under the microscope. Someone who studies what might be called the 'natural history' of rocks on the basis of their petrography, mineralogy, geochemistry and their origin and mode of formation; a structural petrologist specializes in the interpretation of the textural fabric of the rock with a view to determining the nature of the dynamic forces which gave rise to it. A small piece of rock, ground to have a flat base, mounted on a glass microscope slide with Canada balsam, and then ground down until it is thin enough to be transparent (a standard thickness of 0.03 mm is used) and therefore suitable for examination of the mineral compositions and texture of the rock. An anecdote illustrating this appears in the section on 'Departmental reorganization' in Chapter 3. A special microscope stage to enable the observation and measurement of the optical properties of a mineral in thin-section with regard to a ray of light passing through it not only normal to the plane of the thin-section, but at an oblique angle to it. It was first introduced to enable the measurement of the complete optical orientation of any transparent biaxial mineral in a rock in thin-section with sufficient accuracy for the determination of the mineral (e.g. finding the exact composition of a plagioclase feldspar, in which there exists a continuous series of possible compositions intermediate between the albite (NaAlSi3O8) and anorthite (CaA12Si2O8) end-members). Now in the archives of the Department of Geology, University of Bristol. Notebook: # 1-258. It should be noted that the pre-1949 entries in this record were written up by Phillips in 1949 following the loss of much of his research material in a fire, the circumstances of which are discussed in Chapter 7, and it is not clear to what extent the pre-1949 entries are recalled from memory as opposed to being copied from earlier written records. Thompson, an Oxford classics graduate subsequently became a barrister in the Middle Temple. A man of private means, described by his contemporaries as ' a fine elocutionist' and 'capital arguer,' he could afford to give up his life at the Bar for a career he found more rewarding, and he consequently came to the school as a new master in 1893. This remarkable man subsequently gave very considerable assistance to the school (which became a public trust c. 1908), including financing the building of a new science block and swimming pool, and setting up a leavers' university scholarship, to enable its successful future development. When the house system was introduced, Thompson became the first housemaster of North Town House, appointing Phillips one of his two House Captains in 1918 (Jeffery, pers. comm. 1997). Although Phillips' Notebook records a spilite (a basaltic lava, containing albite in which the primary dark-coloured minerals have been altered to chlorite and epidote; Notebook # 8, no collection date) from 'Eylesbarrow Tin Mine, E. of Sheepstor, Dartmoor', this ceased production in 1826 (Dines 1956). The comprehensive information on the mines of the Liskeard, Callington and Tavistock, and Dartmoor districts given in Dines (1956) suggests that the only two mines still extracting the tin-ore cassiterite at the time Phillips was at school were: (i) Trewint and Halvana, near Altarnun in the Liskeard District; and (ii) the larger Birch Tor and Vitifer warren, near North Bovey on Dartmoor (although there was minor tin production from reworking mine dumps elsewhere during World War I). Since the latter is located not far from the Eylesbarrow mine and continued production until 1928, it seems to be the more likely of the two to have been the subject of Phillips' lecture. Both the Devon Association and Plymouth Athenaeum were lively

11 12

13 14

15

16

17

18 19

20

21

22

23 24

25 26 27

28

29

30

31

32

learned societies at that period and it is possible that Phillips may have attended some of their meetings (although he is not known to have been a member of these organizations). Notebook # 105, no date (n.d.). A metamorphic rock showing pronounced layering (foliation) caused by alternations of quartz-feldspar grains and mica; and also containing the dark-coloured magnesium-, iron-, manganese- or calcium-bearing silicate mineral, garnet; and hornblende, a member of the amphibole family of aluminosilicate minerals. Notebook, # 3834. Described by Robert Evans (pers. comm. 1999) as 'a College in those days with rather snobbish dons, a strong public school background, and some contempt for the sciences'. It seems probable that the majority of the early hand-specimens recorded in his Notebook (# 1–258, n.d.), which mainly come from SW England, the Lake District and Wales, were collected either during his time at Plymouth College and/or during these early Cambridge years. Phillips would later carry out the chemical analysis of five of his rock samples in Hutchinson's department. Read joined the Geological Survey in 1914 and was posted to their Edinburgh office. Three months later, he joined the army and saw active service in Malta, Gallipoli and on the Somme. Invalided out in 1917, he rejoined the Survey and for the next fourteen years mapped in the Highlands of Scotland and the Shetland Islands in the company of Peach, Home, Bailey and Anderson. It was these years which gave rise to his lifelong interest in the nature of metamorphic rocks and granites (Williams 1963). Appointed Senior Geologist in 1926, he resigned in 1931 to become Professor of Geology at Liverpool University. T. C. Phemister's elder brother. A thin sheet of igneous rock injected either near-horizontally (sill) or near-vertically (dyke) into a suite of pre-existing igneous, metamorphic or sedimentary rocks. A non-marine (i.e. continental) succession of sandstones, red shales and conglomerates conventionally assigned to the Devonian period, although the base of the Lower Old Red Sandstone has recently been determined as c. 410–415 Ma (Armstrong 1991), i.e. late Silurian. A sodium- and iron-bearing silicate mineral, one of the alkaliamphibole series. A fine-grained granitic rock with a typical 'micrographic' texture in which the crystals of quartz and alkali-feldspar are intergrown in such a way as to give the quartz crystals in rock the appearance of cuneiform characters. Veins or dykes which are offshoots of larger intrusions. The Ronas Hill granophyric granite is now considered to be a sheetlike intrusion emplaced in a number of stages; see Flinn (1985, p. 1169) for further discussion. A calcium- and iron-bearing alumino-silicate mineral. The sodium-bearing end-member of the plagioclase feldspar series. A mineral which has assumed the external form of a pre-existing mineral. Large crystals (in this case of a calcium-magnesium alumino-silicate, such as tremolite or actinolite) set in a fine-grained matrix. Relatively low-temperature aqueous fluids produced late in the process of crystallization of an igneous melt. This was before the advent of radioactive dating, which now suggests that this is the youngest (358 8 Ma) of four intrusions of Devonian age on Mainland in the Shetland Isles (Miller & Flinn 1966; Harris 1991). That is, the same age as the volcanic region of the inner Hebrides comprising, Mull and the Isle of Skye, etc. Rocks made up predominantly of the magnesium-silicate mineral serpentine, often formed as a result of the hydrothermal alteration of

73

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33

34

35

36

37 38 39

40 41 42 43 44 45 46 47

48

49

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pre-existing basic and ultrabasic rocks, through the breakdown of the ferromagnesian silicate minerals olivine (Mg, Fe)SiO4 and pyroxene (Mg, Fe)SiO3. A coarse-grained basic igneous rock characterized by the presence of labradoritic feldspar and augite. Photographs taken through the microscope to illustrate the texture and mineralogy of a thin-section of rock. A dark chromium-iron-oxide mineral, Cr2O3.FeO; Phillips (1927c) noted that some of the Shetland chromite was a translucent brownish colour while some was opaque and black in colour. An ultramafic rock characterized by the presence largely of olivine with other ferromagnesian minerals and a complete lack of feldspar. A fibrous variety of amphibole. A magnesium-iron-silicate mineral of the amphibole group. A green-coloured iron-magnesium-silicate mineral, often formed as an alteration product. A magnesium-carbonate mineral. A magnesium-silicate mineral with a mica-like layered structure. A calcium-magnesium-carbonate mineral. A calcium-iron-carbonate mineral. A magnesium-iron-carbonate mineral. A calcium-carbonate mineral. A magnesium-carbonate often formed as an alteration product. A process leading to progressive change in the composition of an igneous melt, leading to the separation of the magma into various fractions of different composition. Olivine forms the major constituent of the peridotite- and duniteserpentine. A structure characterized by the parallelism of linear elements in a rock, typically a preferred orientation of particular minerals observable at the scale of a hand-specimen and outcrop. However, in the introduction to his own PhD dissertation, Flinn (1952) similarly stated with regard to the nineteenth century work (Hibbert 1822; Heddle 1878a, b, c, 1879; Peach & Home 1879) that 'these pioneer studies are today largely of historical interest only'. Original material; Phillips recognized that the segregations of chromite were the first constituent to crystallize from the magma. This may perhaps have been partly a result of Phillips not having sufficiently detailed topographic maps, but Phillips (1927c) stated that because of poor inland exposure, some of the boundaries were extremely hard to trace (a fact corroborated by subsequent workers). Nevertheless, compare Figure 3.4 with the map of the 'serpentine' complex of Unst in Flinn (1958, reproduced as our Fig. 3.5), which is virtually identical to Read's 1930 map (reproduced in Wilson et al. 1931 and Read 1934a). However, although Read's map did show 'pyroxene-rock' between the serpentine and the gabbro ('greenstone'), he did not show any subdivisions of the serpentine body. For later maps, see Flinn et al. (1979), Flinn (1985; which appears to have been updated in Johnson 1991), and Pritchard (1985); and for modern 1:50 000 maps of Yell, Unst and Fetlar, see Flinn (1994b, 1999). Phillips felt that the boundaries on Peach & Home's (1879) map were often to be preferred to those of Peach & Home (1887) since despite 'greater detail [which] is presumably the result of greater fieldwork, the accuracy of the boundaries seems to have suffered considerably' (Phillips 1927c, p. 623). It is therefore rather surprising to find that if Phillips' two maps of Unst (Figs 3.2 and 3.4) are superimposed at the same scale, the western boundary of the serpentine does not coincide exactly. An ultramafic rock composed solely of olivine (Phillips 1927c, p. 652). However, note that at the time of Phillips' work, it was also defined as 'a peridotite consisting essentially of olivine, and often containing chromite' (Holmes, 1928, p. 85; our italics). Gneiss is a coarse-grained, high-grade metamorphic rock of igneous or sedimentary origin in which lenticles or irregular bands of quartz and feldspar generally predominate, alternating with thinner schistose layers in which mica and amphiboles predominate. A calcium-iron-cerium-bearing alumino-silicate accessory mineral. An yttrium-phosphate accessory mineral. An alumino-silicate mineral generally found in metamorphic rocks of pelitic (argillaceous) composition; according to Flinn (pers. comm. 1999) this was a misidentification of the related iron-rich aluminosilicate staurolite.

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Albite-bearing basaltic lavas in which the primary mafic minerals have been altered to epidote and chlorite. A massive, impure, flinty rock mainly composed of silica. The series of plutonic igneous rocks consists mainly of ferromagnesian minerals: Iherzolite, mainly olivine with orthopyroxenes and clinopyroxenes; harzburgite, mainly olivine together with orthopyroxenes and a trace of clinopyroxene; dunite, solely olivine; wehrlite, consisting of olivine and clinopyroxene (augite); pyroxenite, solely clinopyroxenes; finally, gabbro, consisting of clinopyroxene and plagioclase (see Pritchard 1985, fig. 13, for more details of the inferred compositional changes). A term introduced by Greenly (1919, pp. 65-66, 193-195, 306) when describing the geology of the island of Anglesey, Wales, to denote a chaotic assemblage of rocks. Wells had recently co-authored with Frederick Henry Hatch (18641932) the revised (8th) edition of the volume of Hatch's Text-book of Petrology on igneous rocks (Hatch & Wells 1926). See Pritchard (1985, fig. 1) for a map showing the spatial occurrence of these rocks. A pseudomorph is a mineral which assumes the external shape of another, older, mineral. In this case, the bastite (a hydrous magnesiumsilicate) results from the replacement of pre-existing ortho- and clinopyroxenes. 'The fact that in liquids of the system MgO-SiO2, forsterite, if any forms at all, will necessarily separate before clino-enstatite, has been used to explain the observation that ordinarily in rocks olivine, even when present in very small amount, has evidently separated at a very early stage and especially before pyroxene. This relation can be expected to hold even more rigidly the more our natural olivine and pyroxene approach a highly magnesian composition' (Bowen & Schairer, 1935, p. 212). This view would also be consistent with what he had probably learnt from Harker as an undergraduate: 'in the banded peridotites . . . and gabbros of the Scottish isles, the heterogeneous character was the result of incomplete differentiation' (Harker 1909, p. 341). Metamorphism is the process by which the composition of a preexisting sedimentary or igneous rock is changed as a result of the imposition of new physical and chemical conditions (often associated with a greatly increased pressure and/or temperature regime); once chemical equilibrium has been established, the mineral assemblage will reflect both the original chemical composition of the altered rocks and the imposed conditions of pressure and temperature. A group of dark green iron—magnesium alumino-silicates characteristic of pelitic sediments affected by low-grade metamorphism. The zone of contact-metamorphosed rocks surrounding an intrusion. Metamorphism resulting from the intrusion of a hot granite body into the country rocks. A metamorphic rock resembling a slate but of coarser grain size. Crystals which are significantly larger than the groundmass of a metamorphic rock. Metamorphism caused by the imposition of sufficient pressure as a result of large (regional) scale movement at the prevailing temperature so as to induce extensive changes owing to crushing and shearing at low temperatures, and extensive recrystallization at higher temperatures. The plagioclase feldspars are minerals in which there exists a continuous series of possible compositions intermediate between the pure albite (Ab; NaAlSi3O8) and pure anorthite (An; CaAl2Si2O8) endmembers. The subspecies are defined compositionally as: anorthite, An100Ab0-An90Ab10; bytownite, An90Ab10-An70Ab30; labradorite, An70Ab30-An50Ab50; andesine, An50Ab50-An30Ab70; oligoclase, An30Ab70-An10Ab90; and albite, An10Ab90-An0Ab100. The exact composition of a plagioclase feldspar has traditionally been determined on the basis of measurement of the optical properties of the crystal. Grade of metamorphism represents the degree of metamorphic change undergone by a rock, as indicated by the presence of characteristic suites of 'index' minerals. A dark brown iron-rich form of mica. The results of a chemical analysis for the 'major elements' of a rocksample are generally expressed in terms of the weight-percentage of the oxides of silica, titanium, aluminium, ferrous and ferric iron, manganese, magnesium, calcium, sodium, potassium and phosphorus, plus water and carbon dioxide.

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This is because the increasing SiO2 content induces a negative correlation with the other major elements as a result of the constant-sum (100%) property of the major-element analyses. Chemical studies of the Green Bed rocks, again using Niggli numbers, were resumed in the mid-1960s by Peter van de Kamp as part of his Bristol PhD (supervised by Leake), and he remembers the considerable assistance and interest shown in this work by Phillips. A plot based on the representation of a composition in terms of the proportions of three end-members. It uses a coordinate system based on an equilateral triangle and, in its usual usage, each corner represents a 100% contribution of one of the three end-members. The orientation of the triangle in Figure 3.7 will seem odd to modern readers, accustomed to a ternary diagram being drawn with its base horizontal, but this type of presentation was common in early work; see Howarth (1996b) for a history of the ternary diagram. That is, there was little or no change in the overall chemical composition of the rocks despite the mineralogical changes induced as a result of the metamorphism. The plate which supports the microscope slide. See Howarth (1996a) for details of how such a net is constructed. See Medenbach et al. (1990) and Lima-de-Faria (1990) for further discussion. See, for example, Johannsen (1918), Winchell (1958) and Winchell & Winchell (1959). Campbell Smith had himself been a student at Corpus Christi, and was a non-resident fellow of the college from 1921 to 1924. He had been taught mineralogy and petrology in 1906-1910 by Hutchinson and Harker and had been working in the Department of Mineralogy at the British Museum (Natural History) since 1910, where he became Deputy Keeper of Minerals (1931-1937) and Keeper (1937-1952). He learnt universal stage methods under the guidance of Marcel Gysin in the Geneva laboratory of the Swiss petrologist, crystallographer and economic geologist Louis Claude Duparc (1866-1932), shortly after World War I (Duparc & Reinhard 1923; A. C. B[ishop] 1989). Twin crystals may be defined as the intergrowth of two or more individuals in such a way as to yield parallelism in the case of certain parts of the different individuals, and at the same time other parts of the different individuals are in reverse positions in respect to each other (Dana & Ford 1958). The terms 'pericline' and 'acline-A' describe different types of twinning which can occur in plagioclase crystals. Enstatite is a magnesium-silicate member of the pyroxene family of minerals; anthophyllite is a magnesium-iron-silicate and a member of the amphibole group of minerals. For a modern discussion of this zonation pattern, which suggests pressures gradually increasing from 3.5 to at least 6.5 kbar, and temperatures in the range of 300 to 700°C consistent with depths of burial of up to 40 km, see Johnson (1991) and Bluck (2000). Kyanite and sillimanite are (like the mineral andalusite) aluminiumsilicates found in metamorphic rocks of argillaceous composition. Kyanite is stable at higher pressures than andalusite and is found in intermediate- to high-grade rocks; sillimanite is stable at higher temperatures than either kyanite or andalusite and is found in the highestgrade metamorphic rocks. A rock derived from the low- to medium-grade metamorphism of a basic igneous sock, such as gabbro or dolerite. A zoned crystal is one which has grown in such a way that it exhibits successive shells of different composition; these can often be detected under the microscope as each layer will have slightly different optical properties from its neighbours, showing up by changes in colour or extinction angle when examined in polarized light. The experimental study of the composition of rock-forming minerals by means of subjecting mixtures of suitable mineral end-members to conditions of high temperature and pressure for a long time, followed by chemical examination of the resulting reaction products to determine the mineral phases present. The Geophysical Laboratory of the Carnegie Institution of Washington, principally under the leadership of Norman Levi Bowen (1887-1956), was a leader in this type of research from 1905 into the 1960s (Eugster 1980; Geschwind 1995). As a newcomer to the laboratory in 1933, Evans was never invited to Phillips' home (whereas he went frequently to the Wooster's) and up to the time he left for war service in 1940 he 'knew nothing of

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[Phillips'] wife and family or whether he had either' (G. Evans, pers. comm. 1999). Which had been donated to the Russell-Cotes Art Gallery and Museum, Bournemouth. Present views would be that the anthophyllite replaced the enstatite in spear-like crystals due to metamorphism of the pyroxene with entry of water. This is the usually accepted English-language equivalent of the term Gefugekimde after Knopf's translation used by Sander (1934); however, in his translation of Sander (1948) Phillips uses the words 'the study of fabrics'. A term first published in Knopf (1941) although Fairbairn (1949) says that she used it as early as 1934 in lectures at Yale and Harvard universities. See Fairbairn (1949) or Turner & Weiss (1963) for further details of procedures. A penetrative surface of discontinuity in a metamorphic rock, often visible as a banded or laminated structure resulting from segregation of minerals into compositionally different layers parallel to the schistosity. A crystallographic plane of weakness along which a specimen can be split; in the case of a large mica crystal, it can be split into very thin plates parallel to the base of the crystal; the same term is also used for the planes of fracture along which a metamorphic rock may be split. Numerous examples are discussed in Turner & Weiss (1963, pp. 425-427). Even at this time, the nature of the exact relationship between the fabric at microscopic and mesoscopic scales was often 'ambiguous' (Turner & Weiss 1963, p. 468). See Fairbairn (1949) or Turner & Weiss (1963) for further details of procedures. There are exceptions in the literature (e.g. Sahama 1936; Flinn 1952, 1956b; Law et al. 1992). A typical Schmidt net is 20 cm in diameter and is used in conjunction with a counting circle of 2 cm diameter, i.e. one-hundredth of the total area of the net. Special techniques are used to ensure correct counts at the edges of the plot; early English-language accounts of the methods used include Haff (1938), Knopf & Ingerson (1938), Fairbairn (1949), Billings (1954), Phillips (1954b) and Turner & Weiss (1963). In his writing he apparently attached little importance 'to being read and understood by those who take in his ideas superficially, but [his veracity] led him to write only for a limited number of men' (MullerSalzburg 1980). See Wiesender (1980) for further details. Sander himself may not have cared for this degree of attention. Apparently an excessively modest man, he never gave lecture-tours, and this may be one of the reasons why so many foreign geologists visited his laboratory (Muller-Salzburg 1980). Schmidt's PhD dissertation was also based on work in the Tauern Window of the Austrian Alps (Cornelius 1949) and he subsequently used material from the Tauern in his petrofabric studies. The change in shape or volume of a body of rock as a result of stress (force per unit area). The strain ellipsoid (a term originally introduced in physics by Thomson & Tait 1879) is the shape taken by an original spherical volume of rock deformed under homogeneous strain. Although Harker dealt with the problem in only two dimensions, he showed how the orientation of the principal axes of the strain ellipsoid could be deduced from measurements on distorted fossils. However, Mclntyre (1953), who met Sander in 1948, commented 'it was not always realised that Sander's work began with field determination of the geometry and kinematics, and that the petrofabric interpretations followed. The present theoretical and experimental knowledge of the mechanism of quartz orientation was quite inadequate; usually quartz diagrams had to be interpreted in the light of megascopic structures rather than vice versa'. See also Paterson & Weiss (1961). Pollard (2000) argues that Sander's symmetry principles and the 'movement picture' were vague qualitative concepts which, because they were not founded on quantitative, mechanical principles involving displacement and velocity, were ultimately bound to fail to adequately provide a means to deduce strain and stress.

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Small grooves or striations which develop on the surface of a faultplane. The surface of a slickenside is smooth in the direction of movement and rough in the other. 116 A force tending to deform a rock mass through the movement of one part of it relative to another. 117 This point seems to have first been made by Anderson (1948). 118 For example, in discussion of recent work on the eastern Tauern Window, Wallis & Behrmann (1996) note that within the last ten years, the view that the Austroalpine domain was emplaced as an essentially rigid sheet over the underlying Pennine domain (which forms the northern edge of the Alps and is exposed in the Tauern Window) in a north-south or NE-SW direction has been modified. This has occurred as a result of the recognition of west-east to NW-SE orientated stretching lineations in the eastern Alps, which suggests emplacement of higher units to the west and not to the north. Furthermore, extensional deformation (possibly at a convergent plate margin, pre-dating the northward-directed continental collision) causing crustal thinning, was also an important process in the development of polyphase deformation of the region 'which is consistently oblique to the documented general E-W trend of the facies boundaries and former continental margins . .. [which] implies that the Austroalpine domain cannot be treated as a rigid sheet emplaced rapidly during a single event' (Wallis & Behrmann 1969, p. 1468). Lammerer & Weger (1998) comment that while the Tauern Window is best explained by a dextral transpressive regime in which north-south shortening by folding and thrusting reduced its initial length by about 50%, this was completely compensated by lateral material transport and the most uniform structural element today is an extension parallel to the long-axis of the Tauern Window and its major fold axes. 119 Typically segregations of quartz 'varying in dimension from those of telegraph poles down to walking sticks' parallel to the lineation in metamorphic rocks (Peach et al, 1907). 120 'Like a rod, which can be rotated when pressed between parallel palms, by sliding the hands in opposite directions, for which we can use the short term "to noodle"' (Sander 1970). Despite this, his discussion of the origin of rodded gneisses (Sander 1970, pp. 435, 496–498) strongly suggests that because of his certainty that the deformation fabric could be completely accounted for by one- or two-dimensional shearing, he simply did not seriously consider an alternative model in which extension parallel to the transport direction could be a dominant mechanism. 121 Sander published his first study of the orientation of quartz crystals in 1911, fourteen years before he and Schmidt began universal stage methods, and their first textbooks on the methods were published in 1930 and 1932 respectively. However, as recently pointed out by Wenk & Christie (1991, pp. 1091-1092), these two investigators approached the problem from entirely different points of view. While Schmidt tried to base his interpretations on physical principles, Sander used a more empirical approach. It seems ironic that Schmidt's well-meaning attempt to use an oversimplified physical model, that a densely packed crystal lattice direction will orientate itself into the macroscopic shear direction, was to prove so misleading. It would be another 40 years before a real understanding was gained of the role of intercrystalline slip and mechanical twinning in the development of preferred orientation during ductile deformation of rocks. 122 A type of constant volume change of shape characterized by a fixed orientation of one of the circular sections of the strain ellipsoid. Sander believed that most folds form as a result of a combination of flexure and slip, with the slippage occurring in a direction orthogonal to the fold axis. In Sander's time (1948), a common analogy was a sideways unidirectional slippage of a deck of cards. Indeed, Flinn (1994a, p. 281) has commented that, even today, despite the fact that rock deformation should be regarded as an inherently three-dimensional phenomenon, simple shear is widely invoked as the dominant rockdeforming process, 'possibly because of the ease with which a pack of cards can be deformed in the imagination'. 123 A particular type of irrotational strain in which the body is elongated in one direction and shortened at right angles to this. It is important to realize that, in contrast to simple shear, pure shear is a three-dimensional deformation. 124 Hence 'the use of simple-shear/two-dimensional deformation in rocks

should never be assumed but proved in every case' (D. Flinn, pers. comm. 1998; see also Flinn 19940). 125 Flinn (pers. comm. 1998), however, suggests that Sander never intended his 'transport direction' and 'rotation axis' to be taken literally. 126 Metamorphosed quartzofeldspathic sandstones. 127 Metamorphosed sandy shales. 128 High-grade metamorphic facies formed under high temperature (450-700°C) and moderate to high pressure (3-11 kbar) conditions; it includes the staurolite (quartz-muscovite-biotite-garnet-oligoclasestaurolite), kyanite (quartz-muscovite-biotite-garnet-oligoclasekyanite) and sillimanite (quartz-muscovite-biotite-garnet-oligoclasesillimanite) Barrovian zones, and the cordierite (quartz-muscovitebiotite-oligoclase-cordierite-garnet) and sillimanite (quartz-muscovitebiotite-oligoclase-sillimanite-garnet) Buchan zones in NE Scotland. 129 A gneissose rock which has been partly melted and often shows signs of injection by many dykes and veins of granite. 130 Low-grade metamorphic facies formed under moderate temperature (200–400°C) and moderate pressure (2-10 kbar) conditions; it includes the chlorite (quartz-muscovite-chlorite-albite), biotite (quartzmuscovite-chlorite-biotite-albite) and garnet (quartz-muscovitechlorite-biotite-garnet-albite/oligoclase) Barrovian zones, and chloritebiotite (quartz-muscovite-biotite-chlorite-albite) Buchan zone in NE Scotland. 131 An unconformity is a time-gap, attributable to a period of non-deposition or erosion of pre-existing sediments; in this case, it is represented by the surface where the original sedimentary cover rests on the Lewisian rocks of the basement. The beds above and below this surface differed in their angles of dip and strike, forming an angular unconformity which was itself folded during later periods of deformation (Ramsay 1963). 132 The rocks which make up the Lewisian complex show an Archaean and Proterozoic history of deformation and metamorphism which spans the period c. 3000-1000 Ma BP (Friend & Rollinson 1996). They are unconformably overlain by the Moine, Torridonian and Cambrian successions (McClay & Coward 1981). 133 A succession of reddened sandstones, shales, feldspathic sandstones (arkoses) and conglomerates of Precambrian age (c. 995 Ma BP, Stoer Group, and 810 Ma BP, Torridon Group) which are unconformable on the Lewisian basement. Their exact relationship to the Moine succession is uncertain (McClay & Coward 1981). 134 Deposited unconformably on both the Lewisian basement and the overlying Torridonian, these Cambro-Ordovician sediments consist of a succession of sandstones and grits (Basal Quartzite; and the Pipe Rock, which contains bioturbation and fossil worm burrows), c. 550 Ma old at their base, which pass upwards into a thin dolomitic shale (Fucoid Bed, which contains worm burrows and the trilobite Olenellus), and quartzite (Serpulite Grit, which contains worm burrows and the fossil Salterella) then the thick sequence of limestones and dolomites which form the Durness Limestone (McClay & Coward 1981). 135 Internal layering (cross-stratification) of primary origin within a single sedimentation unit, most commonly developed in sandstones. It is inclined at an oblique angle to the bedding plane at the base of the unit and indicates the direction of sediment accumulation. 136 A fining-upward sequence of grain-sizes within a single sedimentary unit; the coarsest material is at the base. 137 Way-up structures are used to identify the direction of the top of a sedimentary unit at the time it was originally laid down, and hence the direction of stratigraphic younging of the rocks. This is particularly useful when the body of rocks has been subjected to later deformation. 138 The post-depositional processes by which newly deposited sediments lithify to become rock. 139 A conglomerate is a cemented sedimentary rock containing rounded fragments, ranging from coarse sand occasionally up to boulders in size, set in a finer matrix, and associated with deposition in a stream or beach environment. 140 Sequences containing a high proportion of sand-sized material in the original sediments. 141 A high-grade metamorphic rock made of the minerals plagioclase and hornblende, a calcium-magnesium-iron amphibole. 142 Areas of exposed rock surrounded by stratigraphically younger strata.

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The metamorphic rocks were believed to contain an assemblage of minerals formed under conditions of lower-grade metamorphism as the intensity of the metamorphic event waned. Notebook, # 830-1022. Rather surprisingly, the university had no policy to retain copies of the prize essays and, regrettably, no copy of Phillips' essay now seems to exist (Waller, pers. comm. 1998). The downward angle of tilt in the vertical plane of the axis of a fold, or a lineation, with respect to the horizontal plane (see Fig. 11.1). The direction of dip of the axis of a fold or the angle measured in some specified plane between a lineation and the horizontal direction of strike of the plane. An exception is in a boudinage situation, where in higher crustal levels the rocks fracture or neck (see Figs 8.2 and 13.3a). The form of the ellipsoid which results from the deformation of an originally spherical portion of the rock being deformed. Following Flinn (19566, 1978), the major axes of the ellipsoid are designated X, Y and Z, where X > Y > Z by definition; but note that Flinn (1962, p. 386 et seq.) used Z > Y > X (in order to conform to the practice of optical mineralogists in describing the optical indicatrix). A chert-like banded or streaky rock found associated with major thrust-planes; a product of dynamic metamorphism, it results from the extreme granulation and shearing of rocks pulverized during the overthrusting process. Notebook # 495–496. Metamorphism developed as a result of the mechanical deformation of pre-existing rocks, generally associated with thrust-planes and shear zones. A rock whose fabric is dominated by planar features (Sander 1930). Notebook # 1100-1308. A nappe is a sheet of rocks tens of kilometres in extent (which may be in the form of a large, sheared, recumbent fold) which has travelled for several tens of kilometres, moving over the underlying formations on a thrust-plane. A structure produced by the crushing of the minerals in the rock. The pitch of a lineation is the angle between the (horizontal) direction of the strike of the dipping plane on which the linear element appears and the direction taken by the lineation on the plane. Indeed, it is still not certain whether the 'Tarskavaig Moines' are part of the Moine metasediments, part of the Torridonian, or even whether the unmetamorphosed 'Torridonian' rocks of the foreland and the Moine metasediments of the central fold belt belong to same supergroup or not (Stewart 1991); their age is still problematical (G. J. Potts, pers. comm. 2000). A monomineralic rock made up entirely of olivine crystals. One unexplained mystery is that the first edition of the textbook (Hatch & Rastall 1913), written when both Hatch and Rastall were at the Sedgwick Museum, states in its preface; The book is illustrated by numerous figures, for the most part from original photographs, taken by Mr F. C. Phillips of the Sedgwick Museum, Cambridge, from rocksections partly belonging to the authors and partly to the Museum.' However, Phillips (who is unambiguously acknowledged as such in the preface to the third edition) would only have been 11 years old at the time of publication of the first edition! It is therefore presumed that, by curious coincidence, there was some other F. C. Phillips, possibly a student or technician. Unfortunately, it has not proved possible to trace any information regarding Phillips' apparent namesake. The photomicrographs in the second edition are the same as those in the first, but no comment as to their source appears in its preface. Specimens from this trip are recorded as Notebook # 1315-1664. However, no notes exist for most of the specimens; the original details are presumed to have been lost in the Liverpool fire, described in Chapter 7. A rare pyroxene-garnet rock which has the chemical composition of basalt but is believed to have been formed under conditions of high temperature, in the range 200-750°C and very high pressures, exceeding 10 kbar. Where he met F. O. S. Dobell, E. Golding (chemist) and N. E. Barlow (mineralogist). Probably the Golden Kopje gold mine, located less than 20 km to the SE of the Alaska mine (P. L. Lowenstein, pers. comm. 2001). Phillips' material from the Great Dyke and elsewhere in Zimbabwe (in

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the collection of the former Department of Mineralogy and Petrology) is still retained in the collection of the Department of Earth Sciences, Cambridge. 166 Some 590 Ma in age (Rogers et al. 1989). N.B. The part titles are abbreviated in the thesis title. 167 It has not been possible to reproduce these figures for copyright reasons. 168 A hornfels is a rock produced by the contact (thermal) metamorphism of rocks intruded by a magma. 169 The effect on the fabric and mineralogy of pre-existing metamorphic rocks of recrystallization during a later phase of metamorphism. 170 Hans Cloos's philosophy is described in Cloos (1947) and its subsequent English translation by E. B. Garside (Cloos 1954). 171 Notebook # 1665-1834. 172 Law and his co-workers (Law et al 1984, 1986, 1992; Knipe & Law 1987; Law 1987, 1990) realized that this view corresponds with that frequently used in modern work to represent the results of experimental (and computational) studies of quartz and calcite grain orientation under conditions of controlled deformation, and that the asymmetry of the pattern corresponds to the shear-sense of the imposed stress-field. 173 A silvery-white potassium-rich mica. 174 That is, tension cracks lying in the plane orthogonal to the direction of lineation, assumed to represent the b-axis (see Fig. 4.9). 175 Now dated at c. 550 Ma (Brown 1991). See Wilson & Shepherd (1979) or Brown (1991, pp. 235-236 and figs 8.5, 8.6) for geological maps of the intrusion and further discussion. 176 Folds with parallel or nearly parallel limbs. 177 A rock which has a fabric dominated by linear features (Sander 1930). 178 It is now known that both single and cross-girdle c-axis fabrics can occur as a result of a single phase of deformation, depending on the nature of the local stress regime imposed (Lister et al. 1978; Lister & Williams 1979; Lister & Hobbs 1980; Law 1990). 179 Geological Survey map sheets 1:63 360 (1 in:l mi) 101, 102, 107 and 108. 180 Notebook # 1842. 181 The Notebook also records a number of other ore-specimens (# 1836-1841) and Phillips appears to have been careful throughout its compilation to distinguish between those specimens which had been presented to him, and those collected by him personally. 182 An instrument used to measure the interfacial angles of crystals (Medenbach et al. 1995). 183 The 'space-group' is a descriptor of the symmetry with which the atoms within a crystal are arranged. The structure of these atoms (as distinct from the form of the exterior of the crystal) will possess a number of symmetry elements, such as rotation axes, symmetry planes and symmetry centres, which all exist as an extended pattern in space, quite independent of the particular nature of the atoms which form the crystal lattice. They collectively form a self-consistent set of symmetry operations, termed a space-group. The development of space-group theory was pioneered by the German physicist, Leonhard Sohncke (1842-1897), the Russian mineralogist Evgraf Stepanovich Federov (1853-1919) and the German mathematician Arthur Schoenflies (1853-1928). Following the discovery of the diffraction of X-rays by crystals in 1912, it became recognized that space-groups could be a useful tool in the determination of crystal structure and their nomenclature became standardized in the 1920s (Ewald 1962). 184 A zenithal projection of normals to the crystal faces. The normals originate at the centre of the hemisphere, and are projected onto a plane parallel to the equator which touches the top of the hemisphere at the (nominal) north pole. 185 In 1948 Westoll was appointed to the J. B. Simpson Chair of Geology at King's College, Newcastle, where (despite a marked dislike of filing and a reputation for procrastination) he was a successful head of department for 29 years. He established an outstanding reputation as a vertebrate palaeontologist and stratigrapher and was elected to Fellowship of the Royal Society in 1952 (Murchison 1997). 186 Gneisses resulting from igneous rocks or metamorphosed igneous rocks. 187 A calcium-magnesium-iron amphibole mineral. 188 At which Read lectured to the Society on 'Granite'. 189 R. Bradshaw (pers. comm. 1996) saw some of these in storage during Phillips' time at Bristol University; unfortunately, they no longer seem to exist.

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This took place in 1950. Fragments of broken rock which have been eroded and transported to a different site; they may range in size from sand-grade to boulders, depending on the type of sedimentation involved. 192 The field trip to Strathspey followed the 1951 meeting of the British Association for the Advancement of Science in Edinburgh; other participants included Wilson, Fairbairn, Turner and Robin Hamley Clark (1921-1987). 193 Whose comments were based on his unpublished dissertation results. 194 At Harvard under the leadership of Knopf and David Tressel Griggs (1911-1974), and at Berkeley under the New Zealand-American geologist, Francis John Turner (1904-1985) (Wenk 1979). 195 Although it is possible that Phillips had not seen Turner's (1948) memoir by the time of the submission of his 1949 manuscript, curiously, he does not cite it in any of his later publications. 196 Mclntyre (1953) subsequently pointed out that Clough had mapped a 'relatively inconspicuous but definite lineation' which crossed the small NE-SW trending axial traces of the folds 'parallel to the [macroscopic] a direction, and hence trending NW-SE'. As the rocks 'show intense megascopic folding, the plunge is too variable to be mapped, but since the plunge of the fold-axis is low, it is possible to map the trend of the lineation' (Mclntyre 1954). Accordingly, Clough did not put a barb on his mapping symbol to indicate the sense of plunge, whereas Hinxman's lineation was parallel to the fold axes, and the barbs on his map symbols showing the direction and sense of 'stretching' (Mclntyre 1950) were directed up-plunge 'apparently solely on the basis of a supposed connection with the Moine Thrust' (Mclntyre 1954). 197 Presumably by Phillips (1937b, 1947a). 198 When the Lewisian was subsequently subdivided into the Laxfordian and Scourian metamorphic episodes by Sutton & Watson (1951), the rocks which Phillips had examined in detail were assigned to the Laxfordian. 199 Notebook #3000-3016. 200 Notebook # 660, 664, n.d. 201 Notebook #3122-3189. 202 Pronounced 'fenny' (Flinn 1956b). 203 William Phillips recalls accompanying his father to Fetlar and assisting him in making measurements of the 'stretched' boulders; he also accompanied Phillips on a second visit (?1954), at which time they also went to Orkney. 204 A copy in the library of the Geological Society of London is dated as having been received on 9 August 1951. 205 At that time it was not uncommon for Survey staff to continue 'in post' until they were 63 or 64 (P. A. Sabine, oral. comm. 1999). 206 There is a gap in the record between specimen # 3224, collected July 1949, and specimen # 3512 collected in August 1951. 207 Specimens # 3512- 3557, collected from Fetlar in August 1951. 208 Manuscripts concerning James Phemister's fieldwork on Fetlar (British Geological Survey National Geological Records Centre, collection LSA/169; R. Gillanders, pers. comm. 2000) show that he collected specimens of the Funzie Conglomerate in 1929-1930; however, there is no record in these papers that he ever made the specimens available to Phillips. Phemister also mentions that his attention was first drawn to the nature of the formation by an anonymous 'student' who worked on Fetlar in the summers of 1926 and 1927. While it is initially tempting to think this person could have been Phillips, by the summer of 1927 he would have been fully engaged in writing up his PhD dissertation and the three publications derived from it. There is no mention of the conglomerate in his dissertation, nor is there any record that he collected specimens of it at that time. Furthermore, there are no strong similarities between the handwriting in the two exercise books written by the anonymous 'student' and extant examples of Phillips' own handwriting. It seems probable that the two exercise books preserved in the Geological Survey collection are a record of work undertaken by an undergraduate student and possibly subsequently passed on to Phemister by a supervisor. Peter Sabine (pers. comm. 2000) suggested that the student might have been James Phemister's younger brother, Thomas (1902-1982), but this is ruled out by the fact that although he was an undergraduate at St John's College, Cambridge, he joined the staff of the University of British Columbia in 1926. 209 The lecture notes taken by Paterson show that he still maintained this stance in 1953.

210

191

211

212

213 214

215

216

217

A structure in which a highly deformed suite of rocks has slid over a crystalline basement. See Howarth (1999) for further details of the work of the Cloos brothers and Balk. Although at this time, Ernst Cloos had only very recently acquainted himself with Sander's methods and had relatively little experience of their application; see Howarth (1999) for further details. Summarized in Ramsay (1963) and McClay & Coward (1981). Kleeman also took the opportunity to study the latest apparatus for X-ray crystallography, the preparation of rock slides, and methods of chemical analysis of rocks. He visited Durham, Oxford and Cambridge universities and the various colleges making up London University. Phillips' Notebook records a number of specimens which he had collected from the Scottish Highlands in earlier years and which he also made available to Kleeman for universal stage work (unpublished correspondence, 22 April 1952, University of Adelaide Archives; Percival, pers. comm. 1998). The attendees on the 1952 course included Clive Bishop, Malcolm Brown, Frank Moseley, Timothy Whitten, Enayr Williams and Gilbert Wilson (Bishop, pers. comms 1996, 1997). The syllabus for a presumably similar two-day short-course (but apparently without an accompanying field trip) given by Phillips in March 1968 listed the following topics: Introduction: the study of rock fabric; importance of the microfabric. Macroscopic fabric features. Lineation: field measurements. Laboratory study. Orientation of sections, U[niversal]-stage measurements. Treatment of scatter diagrams. X-ray methods. Typical fabrics; girdle diagrams, fabric axes. Grain elongation. Joints. Homogeneity and symmetry of fabrics: component and collective diagrams, A. V. A. [Achsenverteilungsanalyse: i.e. axial distribution analysis (Sander 1950; see Knipe & Law (1987) for a modern application of this technique to a quartz mylonite associated with the Moine Thrust Zone)]. Tectonites. Componental movements. Symmetry of strain. Translation-gliding in metal fabrics. Flexural gliding. Twin-gliding. Gliding in rock-forming minerals: quartz; mica; carbonates and dynamic interpretation. Indirect componental movements: recrystallisation; time relationships (internal fabrics etc.). More complex fabric patterns: crossed strains, oblique girdles. Overprinting and re-orientation. Structural petrology, and the microfabric in particular, in relation to tectonic problems - illustrated from Start Point and the Scottish Highlands. The two practical periods . . . will be concerned chiefly with some additional manipulations on the stereographic (and equal-area) net, and the examination of some typical metamorphic fabrics in hand-specimen and thin section.

218

219 220

221

222

223

224 225 226 227

228

His impression is verified by notes taken by M. S. Paterson at Phillips' lectures in Australia in 1953. Notebook # 3585-3605. Phillips visited Dudley Senanayake, who had become Premier of Ceylon following the death of his father the previous year. Details of Phillips' Australian trip are summarized from his manuscript account (Phillips 1953ft). Supplementary biographical information is principally based on material in Branagan (1973), Glenister (1953) and Johns (1976). Phillips (1953ft) records 'mentioned the stereo ms.' during a meeting on 4 October with Emeritus Professor Leo Arthur Cotton (1883-1963) at the University of Sydney. Including the Government Geologist, the economic geologist H. A. 'Matt' Ellis (fl. 1934-1961); the Government Chemist, H. P. Rowledge, and Government Mineralogist, P. E. LeMesurier. Notebook # 4000-4047. Notebook # 4075-4090. Notebook # 4093–4100. Graham Chinner (pers. comms 1997, 1999) writes of his comment T liked the stiff upper lip description of trying to cross the flooded Tanunda Creek - in actual fact I came close to ending his career, and five others too, at that point!' The notes taken at Phillips' lectures by M. S. Paterson have been tran-

NOTES

229

230 231 232 233 234 235

236

237

238 239

240 241 242

243 244

245

246

247 248 249

250 251 252

253 254 255

scribed and will be placed on file with the Geological Society of London and the British Library Document Supply Centre, Boston Spa. Reginald Claude Sprigg (fl. 1919-1993), at that time head of regional mapping with the Geological Survey of South Australia, is not specifically mentioned by Phillips as a participant but appears in a group photograph of the attendees. Early Precambrian. Notebook # 4101–4124. Notebook #4125. Notebook # 4126–4133. Notebook # 4134-4142. Phillips' diary entry for Sunday 30 August notes 'Sent off a syndicate ticket to the Tasmanian Lottery, "Stretched Pebble"1. Phillips was certainly aware of the early work by the American sedimentologist and stratigrapher William Christian Krumbein (19021979) on sedimentary fabrics (Krumbein 1939) since he cites this paper in his bibliographies in both Phillips (1954b) and Sander (1970). Internal bedding, within a sedimentation unit, which is inclined to the principal surface of accumulation and dips in the direction of sediment transport. Notebook # 4143-4160. First recognized as uranium-bearing by the English-Australian geologist and Antarctic explorer Sir Douglas Mawson (1882-1958), in 1906 (Alderman 1966). Notebook # 4161–4172, 4192–4202. Notebook #4173–4188. The structural petrology of these specimens is discussed in Phillips (1965). Notebook #4203–4218. A sodium-rich pyroxene (ferric-silicate) mineral often found in igneous rocks. Non-departmental attendees included the economic mineralogist Dr Leo Koch (b. 1904), and economic geologist L. J. Lawrence (School of Mining Engineering and Applied Geology, New South Wales University of Technology, renamed the University of New South Wales in 1958; Dillon, pers. comm. 1998), A. S. Richey (Newcastle University), and N. C. Stevens (Mining Museum, Department of Mines, New South Wales). Koch had studied under Professor Kalb at the University of Cologne and emigrated to Australia in the 1930s. After the war he held a Commonwealth (of Australia) research fellowship at the University of Sydney, under Professor Cotton, during which time he devised a new system for mineral determination, which he called 'Tetraktys' (Koch 1949), which was both 'philosophical' and scientific. Reputedly a fine teacher, he was appointed lecturer at the NSW University of Technology in 1951 and at the time of Phillips' visit, held the position of Research Lecturer. He regarded Phillips' Introduction to Crystallography as 'a masterpiece' and, as a result of his own work on Tetraktys, was at the time particularly interested in 'the definition of symmetry,' which it seems he discussed with Phillips. Lawrence's PhD dissertation was concerned with studies of the ore deposits of the New England district (Dillon, Koch and Lawrence, pers. comms 1998). Stevens was working on the stratigraphy and structure of the Palaeozoic rocks of central-western New South Wales. Red aluminium-oxide and iron-oxide deposits which result from the weathering of rocks under humid tropical conditions Notebook #4219–4231. Notebook # 4232-4253. After taking her PhD at Cambridge, she had become curator of the University of Sydney Geological Museum (1931-1935) before becoming a lecturer. Notebook # 4254-4259. Notebook #4260–4281. Opick had emigrated to Australia in 1948. He subsequently built up a large collection of Cambrian trilobites and had just lost his manuscript descriptions of them, in a fire, together with another manuscript describing the geology of the Canberra district, which he had painstakingly compiled during four years of work at weekends (A. W. A. R. 1984). Phillips (1953ft) must have had considerable fellow-feeling for his loss. Notebook # 4282–4285. Notebook # 4286–4290. Although alkali-aggregate reaction in concrete had been described

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from the United States in the 1940s, its potential for causing concrete damage was not widely appreciated in Britain until the 1970s (Mason 1994). 256 Ore-minerals formed at the same time as the rocks within which they occur. 257 Ore-minerals formed later than the rocks within which they occur. 258 The non-metalliferous mineral aggregates associated with ores in a mineral vein. 259 The idea of the Donegal project, an integrated study of a major granite body and its surrounding metamorphic rock, was apparently suggested to Read by W. W. Watts in the late 1930s, but because of the lack of students during the Depression, when Read was at Liverpool, and the war years, it was not until 1947 that he was able to initiate the study. Imperial College students involved with this work included G. J. H. McCall, A. R. Gindy and S. V. P. lyengar (Williams 1963). 260 An anticline is an arch-shaped fold with the oldest rocks at its centre. 261 It is incorrectly stated in Howarth (1999) that Weiss studied for his PhD at the University of California, Berkeley. We are grateful to Professor Weiss for clarifying (pers. comm. 2000) the details of his career in the early 1950s. 262 That is, they do not share a common axis of symmetry or rotation. 263 In the same paper, Weiss (1955) also proposed the use of ka more descriptive primary nomenclature: S1 S2 and so on for surfaces and planes, L1 L2 and so on for lineations, and F1, F2 and so on for the axes of folds'. This rapidly became the norm in subsequent structural studies (although recent convention is that these abbreviations are no longer written using subscripts). 264 Fold facing (Shackleton 1958) refers to the direction, normal to the fold hinge-line, along the axial plane in the direction of younger beds. It is a useful concept for geologists working in structurally complex areas as it links the most important stratigraphic and structural elements. 265 Ductile faults lying close to the bedding or foliation which slid during the metamorphism and folding. The term was first introduced by Bailey (1910, p. 593). 266 A ductile solid is one which responds to stress of sufficient magnitude by flow, as opposed to failure by fracture as is the case with brittle behaviour. 267 See also Rhodes & Gayer (1977), Bell (1978), Williams (1978), Kirschner & Teyssier (1992), Fossen (1993) and Fossen & Hoist (1995); this phenomenon is further discussed in Chapter 13. 268 Comparison of the examples and discussion in Cotton & Garretty (1945) with the exercises in Phillips' book suggests that the methods of solution for his questions 4, 5a, 7, 8a, 11, 13, 18 and 20 may have benefited from material in the earlier publication. 269 A technique originally developed by Sander (1948, 1970) to determine the original attitude of structures subjected to later deformation. 270 William Phillips (pers. comm. 1999) suggests that on this occasion, he was a member of a general party (possibly from the Bristol Naturalists Society) on an essentially non-professional visit and his specimens of the metamorphic rocks were collected for interest only. 271 Notebook # 3512–3557, August 1951; 3690-3704, 3712-3725, July 1954; 3855-3860, 1955. 272 Flinn (1959, 1961) re-examined the Bygdin Conglomerate and concluded that the deformation of the clasts was due to flow caused by pressure differences developed in the sole of the advancing nappe, and possibly due to extrusion from beneath it; and that a similar mechanism probably also explained the genesis of the Funzie Conglomerate. A study of the Bygdin Conglomerate by Hossack (1968) concluded that most of the pebble deformation was produced by a static flattening of the conglomerate under the weight of the crystalline rocks of the overthust Jotun Nappe (which also seems to have undergone a similar flattening deformation). The maximum elongation strain has a NW-SE trend and the conglomerate seems to have flowed in this direction. Flinn (1994a, p. 282) has recently pointed out, in view of 'the widespread uncritical acceptance by devotees of kinematic analysis that all deformation is by simple shear', that both the Bygdin and Funzie conglomerates provide excellent evidence for three-dimensional deformation having taken place and that the shear zones are therefore zones of pure-shear deformation. 273 Strand had suggested that the quartz fabrics were due to a later event than that which had elongated the pebbles.

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As Weiss (1954) pointed out, when he adopted a similar model to explain the deformation of marbles in southern California, the Canadian-American structural geologist George William Bain (fl. 1901-1971), writing at about the same time as Sander's first text on structural petrology, envisaged a similar mechanism in his discussion of the development of flow folds in Appalachian marbles. He wrote that the deformation 'occurs at depths where pressure from all sides upon the rock renders even crystalline substances incapable of transmitting stress in any definite direction. Any differential pressure causes movement of the crystal mass by fracture flowage' (Bain 1931). 275 See also his later discussion of this topic in Flinn (1994a). 276 Flinn et al. (1979) suggested the flow occurred under a thrust nappe moving to the WNW. More recently, Shackleton & Ries (1984) have suggested that the geometry is that of a classic shear zone in which the overlying mass was sheared towards the SSW relative to the Funzie Conglomerate. 277 As remarked earlier, Phillips' first contact with the Eddystone gneiss was almost 50 years earlier, when he was presented with a specimen from Worth's collection. 278 whittard was said by Curry (in Bulman 1966) to prefer to be addressed as 'Prof.' by his sea-going colleagues, while he expected to call them by their given-names. 279 An alkaline igneous rock characterized by the presence of nosean, a blue feldspathoid (a sodium-sulphate alumino-silicate mineral, which forms as the equivalent of feldspar in silica-deficient rocks). 280 A potassium alkali feldspar. 281 A white feldspathoid mineral. 282 whittard added that it was hoped to land on the Wolf Rock at a later date 'in order to determine in orientated samples the fabric of the rock (which is known to be fissile)' (Whittard 1962, p. 658). This was evidently successfully accomplished during a voyage, without Phillips on board, in September 1963; Notebook # 4382-4391. 283 Modern work (McClay & Coward 1981; Butler 1982; Law et al. 1984, 1986; Law & Potts 1987; Coward et al. 1992) has concluded that although detrital grains are present in the quartzites, the fabric is attributable to layer-parallel shear; and there is now a complete understanding of the relationships between the 'simple' and 'crossed'girdles. This is discussed in Chapter 13. 284 Letter from F. C. Phillips to N. F. M. Henry, Department of Mineralogy and Petrology, University of Cambridge (communicated by G. A. Chinner, pers. comm. 1999). 285 Establishing the stratigraphic sequence and spatial relations of the rocks purely on the basis of their lithological features. 286 An assemblage of folds at all scales related to the same longitudinal axial direction. 287 On the strength of a double first in mathematics and physics from the University of Munich, Smith joined the British Museum (Natural History) as an assistant in the Mineral Department in 1897 and eventually rose to become Keeper of Minerals (1935-1937). He was also Vice-President of the Mineralogical Society (1929-1932); principal examiner in gemmology for the Gemmological Association of Great Britain (1913-1949) and its President (1942-1949). 288 A late Palaeozoic (Permian) phase of mountain building c. 225-300 Ma BP (Harland et al. 1990). 289 A structure found in deformed rocks in which a relatively stronger 'competent' bed, the material of which is resistant to flowage, is surrounded by material which can flow more easily. As a result, when the competent bed suffers extension, it breaks into strips whose crosssections resemble 'boudins' or sausages (Fig. 8.2, centre). 290 This seems a rather surprising remark, in view of his own interest in such techniques since 1959. 291 See also Hobson & Sanderson (1983). 292 Notebook # 3923-3936, 3993-3999 and 4382-4391. 293 Which Phillips (1960a) refers to both here and in his earlier review of the interpretation of petrofabric diagrams. 294 The orientations of the b-axes of the quartz and mica fabrics are not coincident. 295 Achsenverteilungsanalyse (or AVA) is axial distribution analysis (Sander 1950), a structural petrology technique for studying the fabrics of different phases of mineral growth within the same specimen. 296 However, interest in petrofabric analysis per se would be reawakened in the 1980s as a result of greatly improved understanding of the

297

298

299

300

301

302

303

304

305 306 307

308 309

310

311

312

313

314

mechanisms of quartz orientation, following experimental and computer-simulation studies (Lister et al. 1978; Lister & Hobbs 1980). Johnson (pers. comm. 1998) comments that Phillips' erroneous perception of 'a low degree of preferred orientation' in the overthrust zone arose as a result of a lack of sufficiently representative samples - had he sampled the strongly lineated Cambrian quartzite in parts of the Moine Thrust Zone, then he would have realized that one cannot separate the Moine (and Lewisian) with preferred orientation in the microfabric from the Cambrian and Torridonian without. This mistake was subsequently rectified by Christie (1956, 1960) and Johnson (1956, 1957, 1961). Compare, for example, Sylvester & Christie (1968) with Law et al. (1992). 'To use them is to assume that at the start of the deformation the layering had a special orientation relative to the future pattern of flow, which is thereby fixed in direction quite arbitrarily' (Flinn 1962). TI^ ellipticity of the tube cross-sections may reach up to 2:1, with the long-axis striking NNE, normal to the tectonic transport direction where layer-parallel shortening has occurred near Loch Eriboll; and 5:1, with the long-axis orientated ESE, parallel to the transport direction at Glencoul (Coward & Kim 1981). This view persisted despite the fact that Flinn (1956£>, 1961) showed that the movement on megathrusts does not (necessarily) continue into the adjacent rocks in Shetland and Norway. A similar point was made by Weiss (1954). 'The truth is that the Moines are the Moines, and the Moine Thrust is the Moine Thrust, and they are unrelated until they are shown to be related, which requires more than the assumed paralleity of the Moine Thrust movement to the extension lineation in the Moines' (Flinn, pers. comm. 1998). There are at least two 'Moine thrusts' - an early ductile thrust extending from Loch Eriboll southwards through the Stack of Glencoul to central Assynt, and a later cross-cutting brittle structure that also puts Moines on the Cambrian-Ordovician succession and outcrops southwards from central Assynt. The famous Knocken Crag outcrop is associated with this later feature, it could be extensional.... It was largely the work of Mike Coward and Rob Butler [Butler & Coward 1984; Coward 1985, 1988] that resulted in our current understanding of the structural geometries and cross-cutting relationships, and offered a simple solution to the old argument between John Christie [1963, 1965] and Mike Johnson [1965] over whether the 'Moine thrust' was a ductile structure (associated with mylonites - Christie) or a brittle feature associated with cataclasites (Johnson). It was no great surprise to find out that both these eminent gentlemen were correct in their own field areas, but that they extrapolated their findings over too wide a geographic area (R. D. Law, pers. comm. 2000). A major linear region in the crust which has been subjected to intense deformation, eventually resulting in the formation of a mountain belt. The success of the computer models can be gauged by comparison of Figure 13.2 with a similar set of plots for naturally occurring quartz caxis fabrics, such as those in Law et al. (1984). The formation of a series of thrust sheets, all dipping in the same direction and displaced by the same order of magnitude. The body of rock beneath the thrust plane. A listric fault is a curved, generally concave and downward-flattening fault. See, for example, White et al. (1980) for a more general discussion of the properties of mylonites in ductile shear zones. Now represented by Greenland and the northeastern seaboard of Canada and the United States. Now represented by Norway, Sweden, Finland, Denmark, the Baltic states and western Russia. A shear zone is a tabular body of rock cut by many parallel, large-scale fractures. Weijermars (1997, pp. 39–40) gives the following physical analogy to explain what he believes happened at Barnesodden. The stretching of a pebble perpendicular to the direction of shear can be simulated by moulding a sphere out of a high viscosity material such as modelling clay, loading it under a flat plate, and subjecting it to vorticity by rolling the sphere between a flat base and the parallel plate, while pulling the plate at a slow constant speed, while keeping it parallel to the base. The distance between the plate and the base will be found to decrease periodically and increase, while the sphere pulsates in the XZ

NOTES

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316

317 318

plane parallel to the transport direction. Simultaneous stretching of the sphere into a prolate spheroid occurs, with its major axes normal to the transport direction. It will ultimately be found to deform into a thin cylindroidal object with the radial cross-section reducing as the pulsating deformation continues. See Weijermars (1993, 1997) for details of the numerical model. However, Tikoff & Greene (1977) have suggested that there is evidence from the Sierra Nevada Batholith that different orientations of stretching lineations may form concurrently in some shear zones, and have suggested that stretching lineations may not form parallel to the direction of the simple shear component of deformation, the "tectonic transport direction', as often as has been assumed in the past. A fold with an isoclinal profile whose hinge-line curves smoothly through an angle of at least 90°. Movement is to the left relative to the position of the observer. Comprising the present-day landmasses of England, Wales and southern Ireland, northern France and the Low Countries, north Germany and Poland, and the northern margin of Spain and Portugal.

319

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This reconstruction (Soper & Hutton 1984) is for early Llandovery time (c. 430 Ma BP); see Soper et al. (1987) for a series of reconstructions from mid-Ordovician to early Devonian time. 320 See Bluck (1990) for further discussion of the possible terraneaccretion history of the Scottish Caledonides from the Precambrian to the Devonian. 321 Pelite is a metamorphosed sedimentary rock originally composed of silt or clay size-grade material. 322 Psammite is a metamorphosed sedimentary rock originally composed of quartzofeldspathic sandstones. 323 The surface of the rock above the thrust plane. 324 Alluded to in earlier text and in notes 124, 272, 303. 325 A time-division of the youngest Precambrian (1000-540 Ma BP). 326 See Wenk & Christie (1991), Jiang & Williams (1999), Marrett & Peacock (1999), Fletcher & Pollard (1999), Pollard (2000) and Peacock & Marrett (2000) for further discussion. 327 See Bradshaw & Phillips (1970) for a comprehensive review of work to 1969.

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Index

Page numbers in italics refer to Figures. [a, b, c}kinematic axes (Sander) 20, 27, 59, 63, 64 Achsenverteilungsanalyse (A.V.A.) 62, 78, 80 Agrell, S. O. 22, 32–34, 33, 43 Alderman, A. R. 50 Allison, A. 24 Alsop, G. I. 70 'alternative' kinematic interpretation 34, 43, 45, 59 Amy Mary Preston Read Scholarship 5 An Introduction to Crystallography 38, 39, 58, 72 An Introduction to the Study of Fabrics of Geological Bodies 17, 61, 62 An Outline of Structural Geology 52 Anderson, E. M. 41-43, 59, 69 Andreatta, C. 31 Assistant Director of Studies in Natural Sciences 13, 38 Australia Kleeman's work 47 lecture tour 2, 49-52, 61 awards and prizes Cambridge University Amy Preston Read Scholarship 5 Bishop Green Cup 5 Manners Scholarship 5 Open Exhibition 4 Sedgwick Prize 22, 26 Wiltshire prize 5 City of Plymouth Joan Bennett Scholarship 4 Corpus Christi College (Cambridge) Caldwell Research Studentship 5 Cowell Scholarship 5 Exhibitioner 4, 5 Foundation Scholarship 5 Research Fellowship 10 Geological Society of London Daniel Pidgeon Fund award 5 Murchison Fund award 31 Plymouth College Brown Prize 3 Form prizes 3 Murch Memorial Prize 3 Royal Geological Society of Cornwall William Bolitho Gold Medal 60 B tectonites 35, 41 b-axis and B-axis problems 20-21, 26, 27, 34, 42, 43, 45, 60, 53–54, 63–64 BA degree 5 Bailey, E. B. 24 Baker, G. F. U. 49, 50 Balk, R. 34,41,45 Barker, R. B. S. 2

Barlow, N. E. 77 Barr, D. 69 Barrow, G. 10, 25 Becker, G. F. 18 Ben Vurich granite 32-34 Bergsdalen Nappes 45-46, 65-67 Bernal, J. D. 10 Billings, M. P. 21 Birkenhead home 39, 40 Bishop, C. 78 birth 1 Black, M. 31 book reviews 25, 38, 39, 55, 58, 60, 61, 62 books written, translated or revised An Introduction to Crystallography 38, 58, 60, 72 An Introduction to the Study of Fabrics of Geological Bodies 61, 62 Gemstones 59–60, 72 The Use of Stereographic Projection in Structural Geology 49, 51, 54, 55, 60, 72 Bowen, N. L. 9, 10, 31, 75 Bowes, D. 47 Bowler, C. 59 Bradshaw, R. 1, 48, 58, 59, 72, 77, 81 Bristol home 41 Bristol Naturalists' Society 48, 60 Bristol University Head of Department 61 lectureship 41 personal chair 60 readership 43, 47 British Association for the Advancement of Science 25, 31, 44, 56 British Control Commission 38 British Council funding 49 British Rheologists' Club 39 Brown, M. 78 Bullard, E. C. 26 Burch, C. R. 57 Bygdin Conglomerate 42, 56, 67 c optical axis of quartz defined 15 Cambridge Civil Defence Services 32 Cambridge University positions held 5, 10, 13–14, 38 postgraduate work 5-10 undergraduate days 5 Campana, B. 50 Campbell, J. D. 49 Cam Chuinneag granite 33, 35, 63 carpentry skills 1 Chair of Geology Bristol 60 Liverpool 39-40

character 1, 2, 60, 61 children 2 Chinese language skills 1 Chinner, G. A. 2, 49 Christie, J. M. 56, 63, 70 church work 2 Clark, R. H. 78 Clifford, T. 53 clocks, interest in 1-2 Cloos, E. 34-35, 37-38, 43, 45 Cloos, H. 27, 33, 34-35 Clough, C. T. 23, 26, 27, 30, 31, 43, 57 Coleman, R. 7 composite stereographic plots 27, 35, 36, 37 constriction deformation mechanism 57 contours in equal-area projection 17 Cornwall 3 field courses 2, 48, 57 Kenidjack hornfels 43 post-doctoral studies 10 Royal Geological Society of 60, 61 seafloor studies 58, 61 Corpus Christi College (Cambridge) Exhibitioner 4, 5 Research Fellowship 10 Cotton, L. A. 51, 55, 78 Coward, M. P. 63, 64 Crampton, C. B. 53, 56, 58 Crook, T. 31 crossed girdles 17, 79, 37, 56, 58, 64 curating 14, 39 Curry, D. 58 Dalradian 77, 24 Green Group (Bed) 10–77, 12–13 Dallwitz, W. B. 49, 51, 52 Daubree, G.-A. 18-19 Deans, T. 33 death 62 Debating Society 3 decision-making ability 61 deformation ellipsoid 26, 63 degrees awarded 5, 7 Demonstrator in Petrology (temporary) 5 Den Tex, E. 50-51,52 detrital mineral properties 31 Devon 3 field courses 48 post-doctoral studies 10 Start Point studies 43, 48, 55, 56, 57, 60, 61 Dobell, F. O. S. 77 Dollar, A. T. J. 33 Donegal granite 53, 56 Donovan, D. T. 61

92

93

INDEX

ductile shearing 54 dunite fabrics 31 Duparc, L. C. 75 Dyson, F. 4 Eddington, A. E. 4 Eddystone Rocks 2, 4, 58, 61 equal-area projection 17 Einengung (constriction) mechanism 57 Ellis, H. A. 78 Ernst, T. 31 Eskola, P. 10, 43 Etheridge, M. A. 52 Evans, R. C. 1, 10, 14, 33 Evans, G. 1, 48, 57, 61 extension lineation 26 eye-structure 69, 70 fabric defined 15 flow 39-40 facing direction 54, 70, 71 Fairbairn, H. W. 18, 21, 51, 72 family 1, 2 Fankuchen, I. 33 Federov, E. S. 12, 20, 77 fieldwork 2, 6, 10, 15, 31, 34–35, 43, 55, 58, 80 finite strain analysis 18 Finlay, T. M. 5 fire at Liverpool 40, 59 Fisher, N. H. 51 Flinn, D. 6, 7, 21, 26, 55, 56-58, 62, 63, 64 flow fabric 39-40, 59 foliation plane 15, 27, 26, 27, 35 Forbes, B. G. 49 'forbidden' sector or zone 21, 30 Ford, I. H. 57, 61 Fossen, H. 65, 67 foreign language skills 1, 61, 62, 72 French language skills 1 Funzie Conglomerate 9, 43–44, 50, 56, 57, 58 gardening interests 2 Garretty, M. D. 51, 55 Gass, I. G. 7 gemstone collecting 2 Gemstones 59–60, 72 Geological Society of London 5, 29, 46, 53, 58 Fellowship 10 Daniel Pidgeon Fund award 5 Murchison Fund award 31 Geologists' Association membership 5 George Herdman Chair of Geology 39-40 German language skills 1, 61, 62, 72 Germany 38 Gindy, A. R. 79 girdle defined 17, 19 petrofabrics 26-27, 29-30, 35, 43, 44-45, 52, 53, 59, 62 Goldring, D. C. 48, 56 Goldring, E. 77

Gosh, S. K. 56 Green, J. F. N. 25, 29 Green Group (Bed) studies 10-77, 12-13, 15, 21 greenstone 7 Gregory, J. W. 25 Griggs, D. T. 43, 64, 72, 78 Gunn, W. 23 Halford, Mr 60 Hall, A. J. 33 hand specimen collection 2 Harker, A. 5, 10, 13, 18, 33 Hatch, F. H. 31, 74, 77 Headland College 3 health problems 40, 58, 60, 62 Heard, H. C. 72 Heddle, M. F. 6 Heim, A. 20, 69 Henry, N. R M. 1,33 Hermann-Mauguin notation 38 Hibbert, S. 6 Higher Certificate results 4 Hill, D. 51 Hills, E. S. 51 Hinxman, L. W. 23, 30 Hipparchos 12 historical interests 38 hobbies 1, 2 Hobbs, B. E. 52, 64, 70 Holdsworth, R. E. 69-71 Home Guard service 32 Hopwood, T. P. 52 Home, J. 6, 23, 25 Hosking, K. F. G. 60 Hutchinson, A. 5, 10, 13 Hutton, C. O. 33 Inchbae Gneiss 45 Inchbae granite 33 index minerals 10 Ingerson, E. 18, 51, 55 Inter-university Geological Congress 60 Intermediate BSc (London) 4 International Geological Congress Organising Committee 39 intrusive lineations 56 isograd 10 Italian language skills 1 lyengar, S. V. P. 79 Jaeger, J. C. 50, 51 Johnson, M. R. W. 56, 58, 62, 63, 70 Joklik, G. F. R. 51, 52 Jones, K. A. 56 Jones, O. T. 21–22, 31, 39 Joplin, G. A. 51 Kennedy, W. Q. 41, 53 kinematic axes [a, b, c] 20, 27, 59, 63, 64 King's School (Bruton) 2 King's College (London) external examiner 62 Kleeman, A. W. 47, 49, 50, 52 Knopf, E. F. 18, 20, 43

Koch, L. 79 Krumbein, W. C. 79 Kurrang Conglomerate 49 Kvale, A. 34, 37, 41, 42, 45-46, 53, 59, 65, 67 Lapworth, C. 23 Lambert equal-area net 17, 55, 56 composite plots 35 rotated projections 35, 63 Law, R. D. 63, 64, 66, 67, 68, 72 Lawrence, L. J. 79 Lector in Mineralogy (Cambridge University) 38 Lecturer in Mineralogy and Petrology (Cambridge University) 14 lecture tour of Australia 49-52 lecturing skills 1 Lemesurier, P. E. 78 Lewisian rocks 23, 24, 29, 45, 53 lineation 7, 20, 21, 26, 35, 39, 45, 46, 55, 56, 59 a v. b interpretation 43, 46, 48, 52, 60, 64 modern work on fabric 67-71 Lister, G. S. 52, 64, 70 Liverpool Geological Society 39, 40 Liverpool University Chair of Geology 39–40 locality map Australia 47 Cornwall 3 Devon 3 Northwest Highlands (Scotland) 24 Shetland Islands 5 South Africa 34 Southern Rhodesia (Zimbabwe) 34 Loupekine, I. S. 41 MA degree 5 McCall, G. J. H. 79 Mclntyre, D. 31, 42, 45 Marr, J. E. 10 marriage 2 Marshall, B. 59 Marshall, C. E. 51 Martin, H. 27, 29, 34, 41 Mawson, D. 79 maximum density, defined 17, 27, 30 Means, W. D. 52 mechanical skills 1 Meldon aplite 4 metamorphism, post-doctoral studies 10-11 mica 75 fabric studies 15, 28, 36, 37, 53-54, 61 Moine studies 26–31, 35–38 Miller, W. H., collection 14 Mineralogical Society 1, 10 Council Member 14, 31, 35, 48, 59 Membership 5 Vice President 61 Moine Supergroup (Moines) 7, 23-24, 29, 55 Christie's work 56 Crampton's work 56, 58 Holdsworth's work 69-71

94

Moine Supergroup (Moines) (continued) Johnson's work 56 Law's work 63-64, 67-68 microfabric 26–31, 35–38 modern research 64-65, 67-71 Peach and Home interpretation 24-25 Phillips' work 24-25, 26-31, 35-38, 41-45 plate tectonic setting 67, 68 Ramsay's work 54, 59, 64 Sutton and Watson's work 53-54, 47, 60 Moine Thrust 23, 25, 27, 28, 29, 37, 56, 58, 64, 66, 67, 68 Moine Thrust Zone 25, 29, 45, 56, 64, 67 monoclinic fabrics 20, 43 Moseley, F. 78 Moye, D. C. 51 mullion structures 26, 28, 29, 42, 56, 60 munitions factory work 32 Natural History Society 3 Natural Science Society 3 Nicholas, T. C. 39 Niggli, P. 11, 41, 51 Niggli values 11 Nockolds, R. S. 33 normal, definition 12 Northwest Highlands of Scotland 23, 24, 27 Norway 34, 41, 53 Bergsdalen Nappes 45–46, 65–67 Bygdin Conglomerate 42, 56, 67 olivine crystal fabrics 31 opaque/ore mineral studies 6, 14, 31, 38, 49, 50 ophiolites 7-8 Opick, A. A. 51,52 ore/opaque mineral studies 6, 14, 31, 38, 49, 50 'orthodox' kinematic interpretation 34, 41, 43, 45, 59 orthorhombic fabrics 20 Oxford and Cambridge Higher Certificate 4 Oxford and Cambridge School Certificate 3 Oykell Bridge 27, 28, 29, 61 parents 1 Paterson, M. S. 1, 2, 49, 50, 52, 62, 64, 72 Peach, B. N. 6, 23, 25, 53 petrofabrics applied to Moines 25, 26–31, 35–38, 41–45, 63–64, 67–69 basic principles 15-18 kinematic interpretation 18-21 Phillips develops 21 Petrology of Sedimentary Rocks appendix 31 PhD students 1 examined 51, 52, 56 supervised 22, 32-33, 56, 58, 59 PhD studies 1, 5, 6–7 Phemister, J. 5, 7, 44, 56, 58


Phemister, T. C. 39, 78 Photographic Society 3 photographs of F. C. Phillips 1, 33, 49, 50, 57 photomicrograph skills 6-7 physical appearance 1 Pitcher, W. S. 40 Plymouth College 3 pole, definition 12 post-doctoral studies Cornish metamorphism 10, 31 Green Bed study 10–11, 12–13 Prider, R. 33, 49 Professor of Geology (Liverpool University) 39-40 Professor of Mineralogy and Petrology (Bristol University) 60 pure shear 20, 57–58 pyroxenite 7, 8 quartz 15 fabric studies 15, 19, 26–31, 32, 35-38, 43–44, 53-54, 61, 63-64, 65, 67 Moine studies 26-31, 35-38 X-ray studies 58-59, 60, 62, 72 Ramdohr, P. 38 Ramsay, J. G. 40, 54, 59, 62, 63, 69 Rast, N. 58, 62 Rastall, R. H. 5, 31, 14, 33, 77 Read, H. H. 5, 7, 25, 26, 29, 30, 39, 40, 53, 56 Reader in Geology (Bristol University) 43, 47 refractive index measurement in liquids 31 Relativity article 4 retirement 62 Reynolds, D. 1 Richey, A. S. 79 Richey, J. E. 24, 30 Roberts, A. M. 70 Robinson, E. V. 49 rock collection 2 rodding 26, 29, 42,57 Rowledge, H. P. 78 Royal Geological Society of Cornwall 60, 61 William Bolitho Gold Medal 60 Rudd, E. A. 50 Ruger, L. 41 Rum dunites 31 Russian language skills 1 Rutledge, H. 51 Sander, B. H. M. 16, 19, 20, 26, 27, 30, 41–43, 49, 57, 69, 72 book published 17-18 Phillips translates 61, 62, 72 petrofabric method 15-18 kinematic interpretation 18-21, 63, 64 Sander's b-axis 20, 21, 57, 63-64 Sando, M. 49 Schmidt, W. 15, 16, 17, 18, 20, 26, 41 Schmidt net 17

School Certificate results 3 schooling 2, 3–4 seafloor studies, Cornwall-Devon 4, 58, 61 Senanayake, D. 78 Seranne, M. 67 serpentine and gabbro complex 8-10 serpentine rock studies 6, 7, 8-10, 31 Shackleton, R. M. 40, 43, 45, 60, 67 Shearman, D. J. 47 sheath folds 67, 69, 70 Shelley, D. 48 Shetland Island studies 5-10, 31, 43–44 final paper 14 Funzie Conglomerate 43–44,56,57,58 Geological Society paper 8 PhD studies 5-7 short courses in structural petrology 47, 49, 62 siblings 1 simple shear 20, 57-58, 64 Skye dunites 31 slaty cleavage 18 slickensides 20, 27, 43, 60 slide 54 Smith, C. 12 Smith, G. F. H. 59-60 Smith, W. C. 10 smoking habits 1 Sohncke, L. 77 Soper, N. J. 25, 64, 67, 71 South Africa visit 32,34 Southern Rhodesia (Zimbabwe) visit 32,34 space-groups 38 Sprigg, R. C 79 Spry, A. H. 50, 52 Stack of Glencoul 66, 67 Stanton, R. L. 51 Starkey, J. 58-59, 72 Start Point (Devon) studies 3, 10, 43, 48, 55, 57, 60, 61 Steinmann, G. 7 stereographic projection 12,13 in crystallography 12, 55 in (macroscopic) structural geology 16, 75, 79, 51, 54, 55 Stevens, N. C. 79 strain markers 63 Strand, T. 37, 41 stretching lineation 26 structural petrology courses short 47 undergraduate 48 vacation school in Australia 49 definition 1, 15 Student Demonstrator in Mineralogy 5 Suess, E. 20 Summers, Mrs 49 Sutton, J. 40, 53, 54, 47, 60 Sweden 27, 41, 56 Talbot, J. L. 52 Tarskavaig Moines 31, 32, 45, 64-65 teaching ability 1, 55-56, 72 tectonic transport direction (Sander) 20, 21

95

INDEX

tectonite 19, 35 The Plymouthian 3 The Use of Stereo graphic Projection in Structural Geology 49, 51, 54, 55, 60, 72 Thomas, H. H. 7 Tilley, C. E. 5, 10, 13, 14, 29–30, 33, 38, 39, 43 Torridonian rocks 25, 31, 34, 45 Traill Mineral Collection 39 translation work 61, 62, 72 triclinic fabrics 20 Trinity College (Cambridge) Lector in Mineralogy 38 twinning study 12 Tullis, J. 64, 72 Turner, F. J. 43, 51, 53, 63, 64, 78 Tyndale-Biscoe, R. Mel. 32 ultrabasic rock nomenclature 8 undergraduate distinctions 5 universal stage 1, 11–12,13,16,17, 21, 32, 34, 39, 48, 51, 59

invention of 12 teaches techniques 52 University Demonstrator in Mineralogy 10 University lectureships Bristol 41 Cambridge 14,38 Unst Intrusion 8-10 Vistelius, A. B. 61 Vogt, T. 24 Walker, F. 33 war effort 32 Watson, J. V. 40, 47, 53-54 Watts, W. W. 79 way-up structures 24, 53 Weiss, L. E. 41, 47, 52, 53, 61, 62, 63, 64, 79, 80 Wells, A. K. 8 Wells, B. 49 Westoll, T. S. 39 Weymouth, J. 49

White, A. J. R. 49, 52 White, D. A. 49, 50 Whittard, W. F. 41, 43, 47, 58, 61 Whitten, E. H. T. 78 Whittle, A. W. G. 50 wife 2 Wilkinson, P. 56 Williams, E. 78 Wilson, A. F. 52 Wilson, G. 40, 42, 45, 46, 59, 60, 78 Wiltshire Prize 5 Windsor, G. 62 Wood, B. 52 Wooster, W. A. 10, 14, 33, 58 Worth, R. H. 4 X-ray petrofabric studies 40, 62, 72 texture goniometer 58-59, 72 {X, Y, Z) axes (Flinn) 26, 62 Zimbabwe (Southern Rhodesia) visit 32, 34

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