Green Marine Clays (Developments in Sedimentology)

DEVELOPMENTS IN SEDIMENTOLOGY 45

Green Marine Clays Oolitic Ironstone Facies, Verdine Facies, Glaucony Facies and Celadonite-Bearing Facies - A Comparative Study

FURTHER TITLES IN THIS SERIES VOLUMES 1-1 1, 13-1 5 and 2 1-24 are out of print 12 R.C. G. BATHURST CARBONATE SEDIMENTS AND THEIR DIAGENESIS 13 H.H. RlEKE Illand G. V. CHlLlNGARlAN COMPACTION OF ARGILLACEOUS SEDIMENTS 17 M .0. PICARD and L . R. HIGH Jr. SEDIMENTARY STRUCTURES OF EPHEMERAL STREAMS 18 G. V. CHlLlNGARlAN and K.H. WOLF, Editors COMPACTION OF COARSE-GRAINED SEDIMENTS 19 W . SCHWARZACHER SEDIMENTATION MODELS AND QUANTITATIVE STRATIGRAPHY 20 M.R. WALTER, Editor STROMATOLITES 25 G. LARSENand G. V. CHILINGAR, ,Editors DIAGENESIS IN SEDIMENTS AND SEDIMENTARY ROCKS 26 T. SUDOand S. SHIMODA, Editors CLAYS AND CLAY MINERALS OF JAPAN 27 M . M . MORTLANDand V.C. FARMER, Editors INTERNATIONAL CLAY CONFERENCE 1978 28 A . NISSENBAUM, Editor HYPERSALINE BRINES AND EVAPORlTlC ENVIRONMENTS 2 9 P. TURNER CONTINENTAL RED BEDS 3 0 J.R.L. ALLEN SEDIMENTARY STRUCTURES 3 1 T. SUDO,S. SHIMODA, H. YOTSUMOTO and S. AlTA ELECTRON MICROGRAPHS OF CLAY MINERALS 3 2 C.A. NITTROUER, Editor SEDIMENTARY DYNAMICS OF CONTINENTAL SHELVES 33 G.N. BATURIN PHOSPHORITES ON THE SEA FLOOR 3 4 J.J. FRIPIAT, Editor ADVANCED TECHNIQUES FOR CLAY MINERAL ANALYSIS 35 H. VAN OLPHENand F. VENIALE, Editors INTERNATIONAL CLAY CONFERENCE 1981 36 A . IIJIMA, J.R. HElN and R. SIEVER, Editors SILICEOUS DEPOSITS IN THE PACIFIC REGION 37 A . SlNGERand E. GALAN, Editors PALYGORSKITE-SEPIOLITE: OCCURRENCES, GENESIS AND USES 3 8 M.E. BROOKFlELDand T.S. AHLBRANDT, Editors EOLIAN SEDIMENTS AND PROCESSES 3 9 B. GREENWOODand R.A. DAVIS Jr., Editors HYDRODYNAMICS AND SEDIMENTATION IN WAVE-DOMINATED COASTAL ENVIRONMENTS 4 0 B. VELDE CLAY MINERALS - A PHYSICO-CHEMICAL EXPLANATION OF THEIR OCCURRENCE 4 1 G. V. CHlLlNGARlAN and K.H. WOLF, Editors DIAGENESIS, I 42 L.J. DOY’ E a i d H.H RORERTS, Editors CARBONATE-CLASTIC TRANSITIONS 43 G. V. CHlLlNGA RIA N and K. H. WOLF, Editors DIAGENISIS, II 4 4 C.E. WEAVER CLAYS, MUDS AND SHALES

DEVELOPMENTS IN SEDIMENTOLOGY 45

Green Marine Clays Oolitic Ironstone Facies, Verdine Facies, Glaucony Facies and Celadonite-Bearing Facies - A Comparative Study

Edited by G.S. ODlN Mairre de Recherche - CNRS Universire Pierre er Marie Curie, Paris

ELSEVIER Amsterdam - Oxford - N e w York - Tokyo

1988

ELSEVIER SCIENCE PUBLISHERSB.V. Sara Burgerhartstraat 25 P.O. Box 21 1, 1000 AE Amsterdam, The Netherlands Distributors for the United States and Canada: ELSEVIER SCIENCE PUBLISHINGCOMPANY INC. 655, Avenue of the Americas New York, NY 10017, U.S.A.

Library of Congress Cataloging-in-Publication Data

Oolitic ironstone facies, verdine facies, glaucony facies, and celadonite-bearing facies. (Developments in sedirnentology ; 4 5 ) Bibliography: p. Includes index. 1. Clay minerals. 2. Facies (Geology) 3 . Submarine geology. I. Odin, Gilles S . 11. Series. QE389.625.055 1988 552l.5 88-3 1042 ISBN 0-444-87120-9

ISBN 0-444-87 120-9 (Vol. 45) ISBN 0-444-4 1238-7 (Series) 0 Elsevier Science Publishers B.V., 1988

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier Science Publishers B.V./ Physical Sciences & Engineering Division, P.O. Box 330, 1000 AH Amsterdam, The Netherlands. Special regulations for readers in the U.S.A. -This publication has been registered with the Copyright Clearance Center Inc. (CCC), Salem, Massachusetts. Information can be obtained from the CCC about conditions under which photocopies of parts of this publication may be made in the USA. All other copyright questions, including photocopying outside of the USA, should be referred to the publisher. No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Printed in The Netherlands

V

CONTENTS

Contributors Detailed contents of the volume Foreword (in French) by Georges Millot, de 1' AcadCmie des Sciences English translation

VIT IX XVII XXI

Introduction to the study of green marine clays

1

Part A THE OOLITIC IRONSTONE FACES

Introduction and contents of Part A *A1 Chamosite, the green marine clay from Chamoson by M.F. Delaloye and G.S. Odin *A2 Green Marine Clays from the oolitic ironstone facies by G.S. Odin, R.W.0.B' Knox, S . Guerrak and R.A. Gygi

5 7 29

Part B THE VERDINE FACES

Introduction and contents of Part B *B1 The verdine facies from the lagoon off New Caledonia by G.S. Odin *B2 The verdine facies from the Senegalese continental shelf by G.S. Odin and J.P. Masse *B3 The verdine facies off French Guiana by G.S. Odin, I.D.R. Mackinnon, and M. Pujos *B4 The verdine facies deposits identified in 1988

53

by G.S. Odin, J.P. Debenay and J.P. Masse *B5 Mineralogy of the verdine facies by G.S. Odin, S.W. Bailey, M. Amouric, F. Frohlich and G.A. Waychunas *B6 Geological significance of the verdine facies by G.S. Odin and B.K. Sen Gupta

131

57

83 105

159 205

Part C THE GLAUCONY FACES Introduction and contents of Part C *C1 Glaucony from the Gulf of Guinea

22 1

by G.S. Odin *C2 Glaucony from the margin off northwestern Spain by G.S. Odin and M. Lamboy *C3 Glaucony from the Kerguelen Plateau by G.S. Odin and F. Frohlich *C4 Geological significance of the glaucony facies by G.S. Odin and P.D. Fullagar

225 249

277 295

VI

Part D THE CELADONITE-BEARING FACES

333 Introduction and contents of Part D *D Nature and geological significance of celadonite by G.S. Odin, A. Desprairies, P.D. Fullagar, H. Bellon, A. Decarreau, 337 F. Frohlich, and M. Zelvelder Conclusion to the study of green marine clays Acknowledgements

399 405

Glossary

407

References

419

Index of collaborators

44 1

Geographical index

443

VII

CONTRIBUTORS

M. Amouric

Centre de Recherche sur les mCcanismes de la croissance cristalline, Case 913, F13288 Marseille Cedex 9, (France) S.W. Bailey Department of Geology and Geophysics, University of Wisconsin 1215W, Dayton St, Madison, WI 53706, U.S.A. H. Bellon Laboratoire de GCochimie, G.I.S. OcCanologie , 6 Avenue Le Gorgeu, F29287 Brest Cedex, France. J.P. Debenay Laboratoire de GCologie, UniversitC du Maine, F72017 Le Mans Cedex, France. A. Decarreau Laboratoire de PCtrologie de la Surface, UniversitC, 40 Avenue du Recteur Pineau, F86022 Poitiers Cedex, France. M. Delaloye DCpartement de MinCralogie, UniversitC de Genkve, 13, rue des Maraichers, CH 1211 Genkve, Switzerland. A. Desprairies Laboratoire de GCochimie sedimentaire, UniversitC de Pans Sud, B2timent 504, F91405 Orsay Cedex, France. F. Frohlich Laboratoire de GCologie, MusCum National d'Histoire Naturelle, 43 rue de Buffon, F75005 Paris, France. P.D. Fullagar Department of Geology, The University of North Carolina, Mitchell Hall CB 3315, Chapel Hill, NC 27599, U.S.A. S . Guerrak Institut de GCologie, UniversitC de Rennes I, Campus de Beaulieu, F35042 Rennes Cedex, France. R.A. Gygi Naturhistorisches Museum, Augustinergasse 2, CH 405 1 Basel, Switzerland. R.W.O'B. Knox British Geological Survey, Keyworth, Nottingham, NG 125GG, England, U.K. M. Lamboy Laboratoire de GCologie, UniversitC de Rouen, BP 118, F76134 Mont-Saint-Aignan Cedex, France. I.D.R. Mackinnon Department of Geology, The University of New Mexico, Northrop Hall, Albuquerque, NM 87131, U.S.A. J.P. Masse Laboratoire de Stratigraphie,UniversitC de Provence, Centre St-Charles, F13331 Marseille Cedex 3, France. G. Millot Institut de GCologie, UniversitC Louis Pasteur, 1, rue Blessig, F 67084 Strasbourg Cedex, France. G.S. Odin DCpartement de GCologie dynamique, UniversitC P. et M. Curie, 4, Place Jussieu, F75252 Paris Cedex 05, France. M. Pujos DCpartement de GCologie, UniversitC de Bordeaux I, Avenue des FacultCs, F33405 Talence Cedex, France. B.K. Sen Gupta Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, U.S.A. G.A. Waychunas Center for Materials Research, 105 McCullough Building, Stanford University, Stanford, CA 94305, U.S.A. M. Zelvelder DCpartement de GCologie dynamique, UniversitC P. et M. Curie, 4, Place Jussieu, F75252 Paris Cedex 05, France.

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IX DETAILED CONTENTS OF PARTS A, B, C, and D:

CONTENTS of PART A *Introduction to the oolitic ironstone facies *Contents of Part A *Chapter A1 Chamosite the green marine clay from Chamoson by M.F. Delaloye and G.S. Odin 1. Introduction 2. Petrography of the Swiss oolitic ironstone 2.1. Elements of the sediment 2.2. The groundmass of the oolitic sediment 3. Mineralogical data on the green clay 3.1. X-ray diffraction study 3.2. Chemical study 3.3.Thermal study 4. Discussion and conclusions on the genesis of the facies 4.1. Environment of deposition of the oolitic ironstone 4.2. Mineralogy of the green clay 4.3.Discussion on the genesis of the green clay from Chamoson 5. summary

5 6

7 9 9 14 15 15 19 22 24 24 25 26 28

*Chapter A2 Green marine clays from the oolitic ironstone facies: habit, mineralogy, environment by G.S. Odin, R.W. O'B. Knox, R.A. Gygi, and S. Guerrak 1. Introduction 29 30 2. The problem of the ooids 30 2.1. Interpretations of the ooids 31 2.2. The extra-sedimentary accretion hypothesis 32 2.3. The intra-sedimentary concretion hypothesis 34 2.4. The mid replacement hypothesis 2.5. The non-oolitic hypothesis 38 39 3. The green clay in the groundmass 4. Mineralogy of the ironstone green clays 40 40 4.1. Green clays of the ooids 42 4.2. Presumed initial green clays 5. Discussion of the environmental factors 44 44 5.1. General environment of oolitic ironstone formations 47 5.2. Microenvironment of green clay genesis in ooids 6. Summary 51

CONTENTS of PART B * Introduction to the verdine facies * Contents of part B

53 54

X

*Chapter B1 The verdine facies from the lagoon off New Caledonia by G.S. Odin 1. Geological setting 57 2. Sampling and sample treatment 59 3. Distribution and habit of the green pigment 62 3.1. Abundance and distribution 62 63 3.2. Habit of the green pigment 4. Mineralogy of the green pigment 66 4.1. X-ray diffraction study 66 69 4.2. Acid treatments of green pigment 4.3. Chemical study 73 5. Mineralogical nature and geological significance 75 75 5.1. Ease of alteration of the green pigment 77 5.2. Mineralogical nature of the green pigment 77 5.3. Environment of genesis of the phyllite V 79 5.4. Geological significance of the phyllite V 6. Conclusions 80 *Chapter B2 The verdine facies from the Senegalese continental shelf by G.S. Odin and J.P. Masse 1. Introduction 83 2. Sedimentology 85 85 2.1. The southern shelf (Baie de Rufisque) 2.2. The northern shelf 86 3. Study of the green pigment 89 89 3.1. Separation, proportion, and habit 93 3.2. Mineralogy of the green pigments 4. Discussion and conclusions 100 100 4.1. Sedimentology of the verdine facies off Senegal 101 4.2. Mineralogy of the verdine facies off Senegal 102 4.3. Microenvironment and genesis of the 'phyllite V' mineral 4.4. Conclusions 103 *Chapter B3 The verdine facies off French Guiana by G.S. Odin, I.D.R. Mackinnon and M. Pujos 1. Introduction 2. Geological setting of the shelf off French Guiana 3. Authigenic green grains 3.1. The glaucony facies 3.2. The verdine facies 4. Mineralogy of the verdine facies 4.1 .X-ray diffraction study 4.2. Analytical electron microscopy 4.3. Chemical study 5. Geological significance of the verdine facies 5.1. Age of the neoformation

105 106 109 109 110 112 112 115 123 124 124

XI

5.2. Recent history of the shelf 6. Summary and conclusions

125 129

*Chapter B4 The verdine facies deposits identified in 1988 by G.S. Odin, J.P. Debenay and J.P. Masse 1. Introduction 131 2. The Ogooue River mouth (Gabon) 131 3. The Orinoco River mouth and eastern extension (northern South America) 134 4. The Niger delta (Nigeria) 136 5. The Konkoure River mouth (Guinea) 138 6. The verdine off Sarawak (N. Borneo, Malaysia) 142 7. The Congo River mouth 145 8. The shelf off Ivory Coast (Comoe River and other rivers) 149 9. The verdine facies from Mayotte (Comoro Islands) 152 10 The Casamance estuary (Senegal) 153 156 11 Conclusions 6

*Chaper B5 Mineralogy of the verdine facies by G.S. Odin, S.W. Bailey, M. Amouric, F. Frohlich and G. Waychunas 1. Introduction 159 2. Mineralogical data on the grains of verdine by G.S. Odin 159 3. X-ray diffraction study of the verdine facies by G.S. Odin 162 162 3.1. The green clay with a dominant peak near 7.2 A: phyllite V 169 3.2.The green clay with a dominant peak near 14 A: phyllite C 4. High resolution transmission electron microscopy on verdine by M. Amouric and G.S. Odin 171 4.1. Verdine from New Caledonia 172 4.2. Verdine from Guinea 172 4.3. Verdine from Senegal (phyllite V) 174 4.4. Verdine from Senegal (phyllite C) 176 4.5. Conclusions on the TEM studies 177 5 . Chemical study of the minerals from the verdine facies by G.S. Odin 178 5.1. Chemical composition of phyllite V 178 5.2. Chemical composition of phyllite C 182 6. Physico-chemical study of the verdine minerals by G.S. Odin, S.W. Bailey, F. Frohlich and G.A. Waychunas 183 6.1. Thermal study of phyllite V 183 6.2. Infra-red study of phyllite V 185 6.3. Mossbauer study of phyllite V. 188 7. The clay minerals from the verdine facies by S.W. Bailey and G.S.Odin 189 7.1. The diffraction peak near 14 %, for phyllite V 189 7.2. Mineralogical interpretation of phyllite V 191

XI1

7.3. Mineralogical variation of phyllite V as a function of time 7.4. Mineralogical interpretation of phyllite C 7.5. Comparison between phyllite V and chlorites 8. Conclusions

198 200 20 1 202

*Chapter B6 Geological significance of the verdine facies by G.S. Odin and B. Sen Gupta 1. Broad features of the environment 2. Localsettings 3. Substrates and microenvironment 4. Recent verdine facies versus ancient ironstone facies 5. Synopsis

205 205 205 212 215 217

CONTENTS OF PART C *Introduction to the glaucony facies *Contents of part C

22 1 223

*Chapter C1 Glaucony from the Gulf of Guinea by G.S. Odin 1. Introduction 2. Geological setting 2.1. Hydrology 2.2. General data on glaucony 3. Habit and nanostructure of glaucony 3.1. Morphological data 3.2.Nanostructure of the faecal pellets from the Congolese shelf 3.3. Morphological evolution of the faecal pellets 4. Mineralogy of the green grains 4.1. X-ray diffraction study 4.2. Chemical study 4.3. Stable isotope study 4.4. Radioactive isotope study 5. Geology of the glaucony from the Gulf of Guinea 5.1. Age of the glauconitization process 5.2. The glauconitization process 5.3. Environment of glauconitization 6. Summary and conclusions

225 225 225 227 229 229 232 232 233 233 236 237 238 240 240 242 245 246

*Chapter C2 Glaucony from the margin off northwestern Spain by G.S. Odin and M. Lamboy 1. Introduction 2. Distribution of glaucony 3. Morphological features 3.1. The verdissement of echinoderm fragments 3.2. The verdissement of bored shell fragments

249 249 252 252 254

XI11

3.3. The verdissement within the foraminifera1 tests 3.4. The verdissement of detrital mica flakes 3.5. The verdissement of quartz grains 3.6. The verdissement of non-bored shell fragments 3.7. Other morphological features 4. Mineralogical study 4.1. X-ray diffraction sudy 4.2. Chemical study 4.3. Isotopic study 5. Discussion 5.1. Morphological features and glauconitization process 5.2. Mineralogical features and glauconitization process 5.3. Age of the glauconitization process 5.4. Mechanism of glauconitization 5.5. Environment for glauconitization 6. Summary

256 257 260 262 264 266 266 268 269 27 1 27 1 27 1 272 272 273 274

*Chapter C3 Glaucony from the Kerguelen Plateau by G.S. Odin and F. Frohlich 1. Pi-esentation 1.1.Glauconies from high latitude deposits 1.2. The Kerguelen Plateau 2. Sedimentology 2.1. The sedimentary cover 2.2. Glaucony 3. Nature and origin of the green grains 3.1. Detailed data on the northeastern shelf sediments 3.2. Substrates of verdissement 3.3. Electron microscopy of evolved grains 3.4. Mineralogy of the green grains 4. Discussion 4.1. History of the glaucony from the Kerguelen Plateau 4.2. Factors of the glauconitization process 5. summary

277 277 27 8 279 279 280 282 282 283 289 29 1 29 1 29 1 292 294

*Chapter C4 Geological significance of the glaucony facies by G.S. Odin and P.D. Fullagar 1. Introduction 2. Habits of glaucony 2.1. Classification of habits 2.2.The granular habits 2.3.The film habits 2.4. Discussion of the habits of glaucony 3. Mineralogy of glaucony 3.1. Substrate components 3.2. Authigenic marine clays

295 296 296 297 300 301 305 305 309

XIV

3.3. Post-genesis components of green grains 4 . Genesis of glaucony: the verdissement process 4.1. The layer lattice theory 4.2. The mechanism of verdissement 5 . Environment of glauconitization 5.1. Microenvironment 5 . 2 . General environment 6 . Summary

316 318 318 3 19 323 323 324 33 1

CONTENTS of PART D *Introduction to the celadonite-bearing facies *Contents of part D

333 334

*Nature and geological significance of celadonite by G.S. Odin, A. Desprairies, P.D. Fullagar, H. Bellon, A. Decaneau, F. Frohlich and M. Zelvelder 1 . Presentation of celadonite by G.S. Odin

337

2. Occurrence and geological setting of celadonite by G.S. Odin and A. Desprairies 2.1. Examples of celadonite-bearing outcrops 2.2. Morphological features of celadonite 2.3. Petrographic environment of celadonite

337 337 340 342

3. Mineralogical properties of celadonite 3.1. Physical properties of celadonite by G.S. Odin, A. Desprairies and M. Zelvelder 3.2. Physico-chemical properties of celadonite 3.2.1. Infra-red absorption spectra of celadonite and related minerals by F. Frohlich and M. Zelvelder 3.2.2. Mossbauer spectra of celadonite and related minerals by A. Decaneau 3.3. Chemical properties of celadonite by G.S. Odin and A. Desprairies 3.3.1. Major element analyses on large samples 3.3.2. Discussion of chemical analyses on macro-samples 3.3.3. Micro-chemical analyses for major elements 3.3.4. Trace and rare earth elements 4. Environment of formation of celadonite 4.1. Environment of formation of celadonite based on petrography by G.S. Odin and A. Desprairies

345 353 362 365 365 368 369 374

375

xv 4.2. Environment of formation of celadonite based on mineralogy by G.S. Odin 4.3. '*O isotopic study on celadonite by A. Desprairies and G.S. Odin 4.4. Time of formation of celadonite after basalt emplacement by G. S . Odin, H. Bellon, P. D. Fullagar, A. Desprairies and M. Zelvelder 4.4.1. Radiometric dating applied to celadonite 4.4.2. Formation of celadonite in young oceanic basalts

376 379 382 382 392

5. Nature and geological significance of celadonite by G.S. Odin and A. Desprairies 5.1. General characteristics of celadonite 5.2. Comparison between celadonite and glauconitic minerals

393 393 395

6. Acknowledgements

398

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XVII

PREFACE

par Georges Millot, de 1'Academic des Sciences

Nous devons toujours &re reconnaissants aux scientifiques qui prennent le temps d'Ccrire un livre. En fait, le prCsent livre n'est ni un manuel ni une fresque pour le grand public, mais un truite'; ce qui nkcessite un travail beaucoup plus considCrable. Et ce trait6 fait dflCchir. J'ai retenu quelques thkmes de rkflexion. a a .

La couleur Ce livre ttudie les argiles marines vertes. La couleur est leur apparence, mais quelle est leur nature? Voici un demi-sikcle, les gCologues ignoraient la nature des roches argileuses: ils distinguaient les argiles grises, bleues, noires, rouges, bariolCes... 11s commenckrent alors l'inventaire min6ralogique de leurs constituants: seuls ou en melanges, une vingtaine desp5ces furent inventorides, ainsi que leurs interstratifiks. I1 en fut de meme pour les glauconies en grains, connues depuis longtemps. h i s on dktermina que le constituant principal Ctait la glauconite, variCtC fine de mica ou illite verte, riche en fer ferrique; la cCladonite des altkrations de basaltes fut confondue avec la glauconite. Peu A peu, une systdmatique rigoureuse de ces minCraux verts s'est enrichie. Le present trait6 nous donne 1'Ctat actuel de cet inventaire. Et nous voyons venir au moins cinq espkces, la smectite glauconitique, la glauconite et la cCladonite, aujourdhui distingukes, la phyllite V A 7 %, et la phyllite V B 14 8, du faciks verdine. A ces pales s'ajoute la population des interstratifiks. Enfin, sont traitkes avec prdcision deux espkces diagCnCtiques et ferreuses: la berthikrine et la chamosite.

Pour un mindral, la couleur est une apparence. Sa structure rdvdle sa nature. Les couleurs peuvent "converger" comme l'oiseau et la chauve-souris convergent dans leur apparence. Au contraire, la structure est propre d une espke: elle est une signature gdndtique. Faciks et mineral Ce livre insiste sur une distinction trks importante: il sCpare categoriquement faciks et minCral. On avait montrC voici 30 ans que les "glauconitic pellets", bien reconnaissables comme faciks, pouvaient contenir toute une variCtC de minCraux. C'est pourquoi, il a CtC proposC de distinguer le faciks sous le nom de gluuconie et le mineral type sous le nom de glauconite. C'est la meme exigence qui impose de distinguer dolomie et dolomite, calcaire et calcite. Ce trait6 dkmontre la grande importance gkologique de cette distinction, mais aussi son importance pratique en

XVIII

gkochronologie. En effet, plus l'kchantillon, analysC en spectromktrie de masse, sera riche en un minkral authigknique et trks potassique, la glauconite, plus les dkterminations isotopiques seront significativeset fidkles, et non pas erratiques. La mEme distinction "catkgorique" est menke pour le facibs verdine. Et ce faciks prksente deux espkces principales singulikres: une phyllite V B 7 qui est une kaolinite ou serpentine trks ferrique, et une phyllite V B 14 A, qui est une chlorite trks ferrique. Leurs caractkres cristallographiques s'accumulent en vue d'une reconnaissance par le ComitC international de nomenclature. Faciks gkologiques et espkces miniralogiques sont, tous deux et Cgalement, importants B connaitre pour reconstituer les conditions de genkse. Le faciks indique l'environnement avec ses particules en mouvement, les conditions de dkpbt, les traces de la vie. La paragenkse minkrale dkpend de la composition des solutions qui ont cristallisk ou recristallisk.

La dife'rence entre f a c i b et mine'ral est celle de deux kchelles dbbservation. De plus, la premikre est bioge'odynamique,la seconde est gkochimique.

Les miniiraux argileux interstratifiiis Les minCraux argileux ont "inventd" un type dorganisation particulier, qui est celui des minkraux interstratifiks. Ce sont des Cdifices oh alternent dans un meme cristal des feuillets ou parties de feuillets de natures diffkrentes. Cette invention est prkcieuse. En effet, le caractkre propre du monde minCral est discontinu. Au contraire, les solutions et les magmas fondus prisentent la suite continue des melanges en toutes proportions. C'est pourquoi, quand les magmas et les solutions cristallisent, ils donnent un mClange de minCraux diffkrents: ce sont les roches et les minerais. A la suite continue des magmas et des solutions, correspond une r6ponse discontinue par le mklange de minkraux diffdrents en proportions diffirentes. I1 en est de meme pour les argiles, mais elles sont plus souples pour deux raisons. D'abord, elles sont plus tolkrantes aux substitutions stoechiomktriques. Ensuite, elles peuvent donner des cristaux mixtes, interstratifiks rCguliers ou irrkguliers, o i ~ alternent des feuillets de minQaux argileux diffkrents. Le rksent trait6 illustre cette propriktk des argiles: on peut citer l'interstratifik (7A-14 ) ou le composk nommk phyllite C (interstratifid smectite-chlorite) tous deux propres au facibs verdine et l'interstratifik (smectite-glauconite) dans le facibs glauconie. Cette capacitk de s'organiser en edifices mixtes (mixed-layers) ou interstratifiks est trks intkressante. Elle donne une grande souplesse dans la cristallisation des microcristallites argileux, en fonction de la variation infinie des solutions naturelles. De meme, dans les recristallisations successives d'un materiel andrieur, des ktapes intermkdiaires sont reconnaissables.

K

A la varie'te' continue des milieux de genbse peuvent re'pondre en me'lange ou bien les mine'raux argileux types, ou bien leurs mine'raux interstrat@e's.Ces derniers jouent le r6le des diphtongues dans une langue, ou des di2zes et

be'mols dans une me'lodie.

XIX

Microenvironnement et ntioformations Les premiers travaux sur les relations entre milieux de genkse et argiles sddimentaires n'avaient pas un grand "pouvoir skparateur". On Cvoquait les milieux marins, sursalks, lacustres... Aujourdhui, et ce trait6 en donne un be1 exemple, le progrks de toutes les microscopies (optique, Clectroniques...) coup16 avec les progrks de la systkmatique des minCraux argileux permet de distinguer des microenvironnements. On comprend que le micromilieu qui se trouve au coeur d'un grain ou dun pellet prisente des caractkres physicochimiques et biochimiques diffkrents de ceux de l'eau de mer oh circulent les crabes et les turbots. Et ceci est de grande consQuence. En effet, la plupart des modkles thermodynamiques disponibles nous donnent les conditions dCquilibre "minCraux-solutions", en solution diluCe, oh 1'activitC de l'eau est considCrCe comme Cgale h l'unitC. Or, les travaux rkcents nous montrent que dans les petits pores, une partie de l'eau est like aux parois et l'activid de l'eau baisse: la prkcipitation d u n grand nombre despkces minCrales en est facilitde et leurs domaines de stabilid changCs. Ces precipitations diminuent encore le diamktre des pores et I'activitC de l'eau baisse encore. Ainsi les milieux microporeux, par rapport aux milieux environnants oh l'eau est libre, vont fonctionner comme "puits" et favoriser les minCralisations. Ceci s'effectuera avec ou sans dissolution des parois, ce qui correspond 2 deux mCcanismes distinguCs dans ce livre: cristallisation dans les microvides ou cristallisation avec contribution des minQaux de la roche. Aux extremes, on se trouve devant la nCocristallisation ou devant la recristallisation; on comprend les cas interm6diaires.

La notion de microenvironnement,largement utiliske dans le prksent trait&,est tr2s importante: elle pennet d'envisager des microsites avec leurs micromilieux difkrents. Et ces microsites sont autant de "pi2ges"pour les cations environnants alimentant la croissance de cristaux difkrents. VarititC des mintiraux et milieux de gen&se G r k e B une systdmatique raffinCe des "Argiles marines vertes", griice B l'observation distincte des faciks et des minCraux, griice h l'examen minutieux des microenvironnements, ce trait6 prisente une discussion serrCe sur les relations entre les minCraux argileux verts et les milieux de genkse. De cette faqon, ce livre est un livre de giologie aussi bien que de minkralogie. En effet, son but ultime est de comprendre l'origine et l'histoire de ces minCraux, histoire qui s'kclaire aujourdhui de faqon decisive, parce que 1'Ctude gCologique des faciks et 1'Ctude minCralogique des constituants sont menCes toutes les deux de faCon approfondie. Et puis, aprks la sedimentation et la diagenkse prCcoce qui se produit dans les vases, vient la diagenbse d'enfouissement. Lh, les contraintes thermodynamiques augmentent, et les minCraux recristallisent. Les trois termes de ma rkgle d o r augmentent en m6me temps: ordre, puretC, taille. L'ordre est caractCrisC par la cristallinid. Parce que chaque mintral tend vers un minimum dCnergie interne, les ions Ctrangers sont chassis dans le mineral voisin, et "la puretd", comme l'ordre, augmente. Enfin, parce que l'ordre et la puretC augmentent, la taille des minCraux

xx augmente. On parvient aux minCraux de la diagenkse, puis du mCtamorphisme. L'Ctude comparke des "ironstone facies" B chamosite et berthikrine et des "verdine facies" est trks suggestive dune diagenkse denfouissement. Quund l'alpiniste quitte la vallke et s'klhe sur les versants puis sur les hauteurs de la montagne, il voit la vkgktation changer: changement des caracttres dune esptce, passage d des sow-esplces puis des esptces diflkrentes, puis trts diflkrentes. La gore change avec l'environnement. I1 en est de m&meici pour les milieux skdimentaires. 0 0

.

Depuis un demi-sikcle, j'ai CtC le tCmoin de l'aurore, puis des progrks de la "GCologie des Argiles". Plus gCnCralement, au cours de ce long voyage, j'ai CtC admiratif des renouveaux des connaissances en "GCochimie de la Surface de la Terre". C'est un honneur pour moi de prksenter ce livre sur les "Argiles marines vertes". J'en remercie les auteurs et le principal dentre eux, Monsieur G.S. Odin et ceci pour deux raisons. D'abord parce que ce livre nous Cclaire de lumikres nouvelles sur un vieux problkme: ceci est trks utile pour sortir de la confusion. Mais aussi et surtout parce qu'il nous fait rCflCchir sur les Cquilibres dClicats qui, dans les micromilieux des sCdiments marins, nous conduisent B des nCoformations minCrales par croissance des cristaux. Faciks et minCral: une nouvelle fois, il existe une relation entre la composition et le milieu de genkse des roches argleuses. Ce trait6 est un exemple significatif de la mCthode B suivre, en Sciences de la Terre: combiner les arguments gCologiques et gComCtriques et les arguments mindralogiques et gbochimiques. Ces deux familles d'arguments doivent etre combinks de facon entrelacee, come serpenti in m o r e . Strasbourg, au jour du printemps le 21 Mars 1988 Georges Millot

XXI

FOREWORD

by Georges Millot de 1' Academic des sciences

We should always be thankful to scientists who take the time to write a book. In fact, this volume is neither a manual nor a vulgarization, but a treatise; and that entails a considerably greater amount of work. And this treatise is thoughtprovoking. I have taken note of some of the themes upon which to reflect. 0 0

0

The colour This book is about green marine clays. Such is their appearance; but what is their nature? Half a century ago, geologists knew little of the nature of clayey rocks: to them they were grey, blue, black, red, smped ... A mineralogical list of their components was then begun, and twenty or so kinds were recognized, alone or combined, as well as their interlayerings. The same went for glaucony grains, which had long been known. It was then found that the principal component was glauconitic mica, a fine variety of mica or green illite, rich in f e m c iron; the celadonite produced by alteration of basalts was confused with glauconitic mica. Little by little, the rigorous inventory of these green minerals was added to. The actual state of this inventory today is presented in this treatise. We note the arrival of at least five types, glauconitic smectite, glauconitic mica and celadonite whose differences are recognized today, and the 7 A and 14 A phyllite V of the verdine facies. Between these extreme falls a sequence of mixed-layers. Finally, two diagenetic and ferrous types: berthierine and chamosite, are discussed with precision.

With minerals, the colour is superficial. I t is their structure which reveals their nature. Colours may "converge" in the manner of the shape of a bird and a bat. In contrast, the structure remains proper to each species: it is a genetic signature. Facies and mineral This book dwells on a very important distinction: it categorically separates the mineral from the facies. Thirty years ago, it was shown that glauconitic pellets, while recognizable as a facies, could contain a wide variety of minerals. It was for this reason that the suggestion was made to distinguish the facies with the name glaucony (in French, glauconie) from the mineral, called glauconitic mica (in French, glauconi&& The same difficulty obliges us to distinguish the magnesian limestone (in French, dolomie) from the mineral dolomite (in French, dolomitg), and limestone from calcite. This treatise demonstrates the great geological impor-

XXI I

tance of the terminological distinction, as well as its practical contribution in geochronology. Indeed, more a sample destined for mass spectrometry analysis is found to be rich in the highly potassic authigenic mineral, glauconitic mica, more the isotopic determinations will be reliable and less erratic. The same "categorical" distinction is made for the verdine fucies. Now this facies presents two singular princi al types: a 7 8, phyllite V which is a highly femc serpentine or kaolinite, and a 1 4 phyllite V which is a highly ferric chlorite. Their increasingly well-understood crystallographic characters make them likely to be recognized by the ad-hoc International Committee on mineralogical nomenclature. The nature of both geological facies and mineralogical types are each equally important in determining the conditions in which the rock was formed. The facies indicates the environment with its free-moving particles, depositional conditions, and traces of life. The mineral paragenesis depends on the composition of the crystallizing or recrystallizing solutions.

f

The difSerence between facies and mineral is that of two scales of observation. Furthermore, the first is biogeodynamic, the second is geochemical. The mixed-layered clay minerals Clay minerals have "invented" a particular type of organization, that of mixed-layered minerals. These are constructions where sheets in whole or part of different natures, alternate within the same crystal. This invention is invaluable. In fact, the very character of the mineral world is discontinuous. In contrast, solutions and molten magmas present a continuous suite of mixtures in varying proportions. And so, when these magmas and solutions crystallize, they give a mixture of different minerals: these are the rocks and the ores. To the continuous suite of magmas and solutions corresponds a response made discontinuous by the mixture of minerals in different quantities. The same goes for the clays, but they are more flexible for two reasons. First, they are more tolerant towards stoechiometrical substitutions. Secondly, they may give mixed crystals, with regular or irregular mixed-layering, where different clay mineral layers alternate. An illustration of this property in clays is given by the present treatise: we may cite the 7 A-14 8, mixed-layer, or the compound called phyllite C (smectite-chlorite mixed-layer) both of which are found in the verdine f a c i e s , and the smectite-glauconite mixed-layers of the gluucony fucies. This capacity for mixed-layer organization is most interesting. It lends a great flexibility to the crystallization of the clay microcrystallites, as a function of the infinite variation of natural solutions. In this way, the intermediate stages in the successive recrystallizations of earlier material may be shown to exist.

From the continuum of varying milieux may come a mixture either of clay mineral types, or of mixed-layering of these minerals. These last serve in the same way as diphtongs in language, or sharps andjlats in a melody.

XXIII

Microenvironment and neoformations The early work done on the relationship between sedimentary milieux and sedimentary clays was of rather low "resolution". Terms were invoked such as marine, brackish, lacustrine ... Nowadays - and this treatise is a good example - progress in all the microscopies (eg. optical, electronic ...) associated with the extended inventory of clay minerals, allows different microenvironments to be distinguished. We understand that the micromilieu found at the centre of a grain or pellet presents physicochemical and biochemical characteristics different from those of sea-water where crabs and turbots swim. Now this is of great consequence. For most available thermodynamic models provide for mineral-solution conditions in equilibrium, in diluted solution, where the activity of the water is taken as unity. Now, recent work has shown that in small pores, part of the water is attached to the wall, and the waterk activity is diminished; the precipitation of a great number of mineral species is thereby made easier and their stability domains are changed. Such precipitations further diminish the diameter of the pores and the activity of the water diminishes even more. Thus microporous milieux, as against the surrounding regions of free water, will act as "sinks" favourable to mineralizations. This will occur with or without dissolution of the walls, which corresponds to two mechanisms distinguished in this book: crystallization in microcavities or crystallization wherein the minerals of the host rock contribute. In extreme cases, we thus observe neocrystallization or recrystallization. We understand the cases that lie between.

The notion of the microenvironment, widely used in the present treatise, is very important: it allows the conception of microsites each with their different micromilieu. And these microsites will be so many traps for neighbouring cations which feed the growth of different crystals. Variety of minerals and formation milieux Thanks to a greatly perfected inventory of the "Green Marine Clays", thanks to the separate observation of mineral and facies, thanks to the examination in minute detail of microenvironments, this treatise presents a close discussion of the relations between the green clay minerals and the formation milieux. The book thus is as much about geology as it is about mineralogy. Its ultimate aims, indeed, is to understand the origin and history of these minerals, a history which today becomes decisively clearer, because the geological study of the facies and the mineralogical study of the components are both undertaken in depth. Then, after the sedimentation and the early diagenesis produced in the ooze, comes the burial diagenesis. Here, the thermodynamic constraints increase, and the minerals recrystallize. The three terms of my golden rule: order, purity, size increase at the same time. The order is characterized by the crystallinity. Since each crystal tends towards a minimum internal energy, external ions are chased away to neighbouring minerals, and the "purity" increases with the order. Finally,

because order and purity increase, the size of the minerals increases. We reach the diagenetic minerals, then those of metamorphism. The comparative study between the ironstone facies (which include chamosite and berthierine) and the verdine facies, is very suggestive of a burial diagenesis.

When the alpinist leaves the valley to climb the mountain-sides and then the mountain-tops, he sees the vegetation change: change in the characters of a species, passing to sub-species, to diferent species and then to very digerent species. The flora changes with the environment. It is the same here with sedimentary milieux.

* * Over the last half century, I have witnessed the beginnings and then progress of "Geology of Clays". In more general terms, I have, during this long journey, admired the increase in knowledge of the "Geochemistry of the Earth's surface". It is for me an honour to present this book on the "Green Marine Clays". For it I thank the authors, and the major contributor, Dr. G.S. Odin and I thank them for two reasons. First, because this book sheds new light for us on an old problem: this is very useful for getting out of the confusion. But also and above all because it causes us to reflect upon the delicate balances which, in the micromilieux of marine sediments, brings us to mineral neoformation by crystal growth. Facies and minerals: once again there exists a relation between the composition and the formation milieux of clays. This treatise is a significant example of working methods in the Earth Sciences: to combine geological and geometric arguments with mineralogical and geochemical arguments. These two families of arguments must be combined as though they were interwoven, come serpenti in amore. Strasbourg, the first day of Spring March 2lSt,1988 Georges Millot

1

INTRODUCTION TO THE STUDY OF GREEN MARINE CLAYS by G.S. Odin About twenty years ago, the studies of the present editor were mostly devoted to glauconitic sediments. To obtain a better understanding of the conditions and process of genesis of the facies before diagenetical alteration (glauconitization),particular attention was paid to the unburied sediments lying on the continental shelves of present oceans (Odin, 1975a). In the course of that study, it became clear that some green grains were formed of authigenic clay minerals, with a dominant X-ray diffraction peak at 7 8, (Odin, 1985a). This sort of 7 8, clay mineral is known from preQuaternary series e.g., oolitic ironstones (Orcel et al., 1949). However, substancially different environmental or mineralogical characteristics have been observed for the following three facies namely 1) glaucony, the most frequent ancient and recent marine facies characterized by the formation of green clay minerals at comparatively high depth; 2) verdine, the facies encountered in recent sediments at shallow depth; and 3 ) oolitic ironstone, the facies described from shallow depth pre-Quaternary sediments. The three facies correspond to three specific combinations of different green clay minerals with particular habits, and therefore, must be identified using specific names. Incidentally, amongst the diverse aspects of the study of the glaucony facies, one was the use of crushed green grains for paint pigments during Roman times and later (Odin and Delamare, 1986). However, detailed studies of the green pigment of wall paintings showed that the main natural pigment used was a celadonitic clay mineral (a green clay found in volcanic rocks). The search for the possible geographical source of the green pigment led to a study of the celadonite-bearing facies, which showed sufficient points in common with the glaucony facies to allow a fruitful comparison from an environmental point of view. The four facies quoted above have sometimes been confused in the past literature i.e., ironstone green clays for verdine green clays, verdine facies for glaucony facies, and some glauconitic minerals for the celadonitic mica. The common point is that green clays are involved, and all of them are iron-rich. Partly for that reason, the order of presentation chosen in this volume follows the geochemical path of iron from continent to ocean (Odin, 1975b): ancient ironstone facies is known to form at the boundary between land and ocean; recent verdine facies appears to develop at a similar location but is essentially marine; glaucony facies occurs farther from continental water input in an open marine environment; in the celadonite-bearing rocks, iron appears dominantly "oceanic" in the sense that many of these rocks are found in volcanic series formed in deep waters where oceans are opening. The general organization of each of the four parts of the volume (detailed

2

content at the beginning of each part) has been varied to avoid monotony in the form and to take into account the present state of knowledge as discussed below. The oolitic ironstone facies is mostly discussed here for the purpose of comparison and as it is widely described in the literature, this part is short comprising two chapters. The first chapter (Al) concerns a selected example of outcrop which is interesting both because it shows many of the main characters of the facies and because it is little known to English speaking readers (most literature on these Swiss sediments from Chamoson area is in other languages). The second chapter (A2) discusses the diverse hypotheses on the origin and process of formation. A new interpretation of the green marine clays of the oolitic ironstone facies is proposed in the light of knowledge of recent verdine facies: the ironstone clays would be essentially diagenetic in origin. The verdine facies is presented at length because previously little known; many new data are gathered. This part gives what is intended to be an exhaustive view. Four chapters describe the presently known deposits for this facies, three deposits are considered in details from the most recent deposit (Chapter B 1, New Caledonia) to the presumably oldest and relict (Chapter B3, French Guiana) deposit. Others are shortly described in Chapter B4.A detailed mineralogic study constitutes a fifth chapter where a variety of green marine clays are precisely identified for the first time. A sixth chapter summarizes the geological significance of that facies in comparison to the formerly discussed one (oolitic ironstone facies) as well as to the following one (glaucony facies). The glaucony facies is discussed in part C; new data have been obtained from the present sea-bottom. Three chapters give examples of unburied glauconitic sedimentary deposits from different latitudes and different ages and illustrate the variety of the initial substrates favourable to glauconitization. A fourth chapter summarizes the general characteristics of the facies; this chapter is not intended to be exhaustive since many data have been published in the literature especially from the mineralogical point of view; but the geological significance is considered in detail and new data obtained since ten years from isotopic analyses are particularly fruitful for this discussion. The fourth part on celadonite-bearing rocks, is arranged as a multiauthored single monograph which reviews the data recently gathered on a subject which is extensively discussed in the literature of the last decade because celadonite occurs frequently in deep-sea basalts. New unpublished results are added in this review; for example, results of isotopic studies which allow both a better knowledge of the environment of formation to be obtained and the geological significance of celadonite to be understood. Following a general conclusion on green marine clays, a glossary is proposed; it might be useful to consult this glossary before reading the main text because a certain number of new or uncommonly used words have been used in order to designate some of the concepts frequently referred to in the volume. This glossary may serve as a subject index. In short, the present volume concerns clay formation in more or less close contact with sea-water i.e., synsedimentary processes; the central part of this

3 volume is the discussion of two facies, verdine and glaucony, observable in the present oceans; each of these two facies has been compared to a brother facies, mineralogically different and environmentally apparently similar for ironstone facies versus verdine facies; or environmentally apparently different and mineralogically close for celadonite-bearing facies versus glaucony facies. The study of these four facies in a single volume was a good opportunity to derive general ideas on the relationship between the marine environment and clay minerals. Two leading ideas were constantly present when writing analytical discussions regarding examples of sedimentary deposits as well as chapters of general discussion. The first leading idea is that authigenic marine clays are widespread and diverse in oceans. Although quantitatively more restricted than inherited clays, the authigenic clay minerals are a more precise reflection of their environment of sedimentation and deserve more study. Moreover, the geological significance of authigenic clay minerals can be precisely discussed thanks to the study of sediments of the present-day sea-bottom. The variety of authigenic clay and other minerals formed at the sea-bottom still needs to be investigated, but appears wider than commonly known. In particular, all clay mineral groups are present. The present volume only gives a limited view on the question with authigenic serpentinic (7 A), smectitic to illitic (glauconitic minerals), intermediate smectitic-chloritic, and purely chloritic clay minerals; this first set of data should be supplemented in the future. The second leading idea results from the observation that the diverse clay minerals observed are all formed following a similar fundamental process which is crystal growth. Therefore, the fashionable hypothesis developed during the sixties and seventies, and according to which the sea was essentially the site for a transformation process (moderate modification in a permanent inherited crystal structure) of inherited clays, is considered obsolete here. The marine environment entirely creates its own suite of clay minerals. It is one of the most interesting aspects of the study of these green marine clays, to have been, in some aspects, the first instance in which this revision of a fundamental idea of the sedimentology of clay was made necessary.

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5

Part A

THE OOLITIC IRONSTONE FACIES INTRODUCTION TO THE OOLITIC IRONSTONE FACIES The oolitic ironstone facies has been described from sedimentary formations of Cambrian to Pliocene age (James, 1966). It can be regarded as absent from modern sea-bottom sediments, with one possible exception reported from Scotland (Rohrlich et al., 1969). The present part intends to summarize what is known (or suspected) about the environment of formation of the ancient oolitic ironstones and the general mineralogy of the authigenic clay minerals present in this facies. These clay minerals are green, iron-rich, and occur in a shallow marine facies; therefore, the data summarized will allow a comparison with the modern, apparently equivalent facies, i.e. the verdine facies described in the following Part B of this volume. Part A comprises two chapters. The first describes a single case study initially considered by M.F. Delaloye in his thesis. This example has been selected because the concerned outcrop is 1) historically important, 2) comparatively little quoted in the English literature, 3) well preserved, and 4)really representative of the facies. This outcrop is located near Chamoson and was the source from where chamosite was defined by Berthier (1820). Based on the information provided by this and other related outcrops in Switzerland, the second chapter discusses the diverse hypotheses proposed in the literature about the process and environment of formation of the oolitic ironstone facies. Central to these hypotheses is the question of the puzzling original oxido-reduction factor. A new hypothesis concerning the original nature of the green marine clays will be proposed in order to suggest a new approach at the Eh problem. This hypothesis proposes that the iron cations in the original synsedimentary green marine clays were initially ferric in contrast to their present ferrous state. This implies that all oolitic ironstone clay minerals analysed today result from diagenetic reactions. This fundamental, previously non-considered evolution of clay minerals formed during sediment deposition, would have taken place during early burial diagenesis; the hypothesis is supported by several observations including the comparatively good crystallinity observed today for these green clays, which is unusual for marine authigenic clay minerals, and the common occurrence of authigenic ferric marine clay minerals in recent unburied sediments.

6

CONTENTS of PART A *Introduction to the oolitic ironstone facies *Contents of Part A

5 6

*Chapter A1 Chamosite, the green marine clay from Chamoson; a study of Swiss oolitic ironstones by M.F. Delaloye and G.S. Odin 1. Introduction 7 9 2. Petrography of the Swiss oolitic ironstone 9 2.1 .Elements of the sediment 14 2.2.The groundmass of the oolitic sediment 15 3. Mineralogical data on the green clay 3.1 .X-ray diffraction study 15 3.2.Chemical study 19 3.3.Themal study 22 24 4. Discussion and conclusions on the genesis of the facies 24 4.1 .Environment of deposition of the oolitic ironstone 25 4.2.Mineralogy of the green clay 26 4.3.Discussion on the genesis of the green clay from Chamoson 5 . Summary 28 *Chapter A2 Green marine clays from the oolitic ironstone facies: habit, mineralogy, environment. by G.S. Odin, R.W. O'B. Knox, R.A. Gygi, and S. Guerrak 1. Introduction 29 30 2. The problem of the ooids 2.1.Interpretations of the ooids 30 31 2.2.The extra-sedimentary accretion hypothesis 2.3.The intra-sedimentary concretion hypothesis 32 2.4.The ooid replacement hypothesis 34 2.5.The non-oolitic hypothesis 38 39 3. The green clay in the groundmass 40 4. Mineralogy of the ironstone green clays 40 4.1.Green clays of the ooids 4.2.Presumed initial green clays 42 44 5. Discussion of the environmental factors 44 5.1.General environment of oolitic ironstone formations 47 5.2.Microenvironment of green clay genesis in ooids 6. Summary 51

7

Chapter A1 CHAMOSITE, THE GREEN MARINE CLAY FROM CHAMOSON; A STUDY OF SWISS OOLITIC IRONSTONES by M.F. Delaloye and G.S. Odin INTRODUCTION

Previous studies of Swiss oolitic ironstones The sedimentary oolitic ironstone near Chamoson (Western Swiss Alps) allows the presentation of the historical, sedimentological and mineralogical significance of the term "chamosite". Berthier (1820) proposed the name chamoisite after the name of the village erroneously written "Chamoison" in his study. The correct spelling of "Chamoson" for the locality led to the term of charnosite which now designates the mineralogical component first identified by Berthier (Lacroix, 1895). Berthier undertook an optical and chemical study. He correctly identified the green component as a new (nearly pure) mineral: a dominantly ferrous and slightly aluminous silicate which he ascribed to the chlorite family. DCverin (1945) published a detailed petrographic study on the oolitic ironstones of Switzerland. In the sixties, this problem was resubmitted to one of us for his Ph. D. thesis (Delaloye, 1966).

Geological setting The geological setting of the iron ore of Chamoson, and of equivalent outcrops in Switzerland, is shown in Figure 1. The sediments have been locally submitted to a light metamorphism which provoked an induration of the formations. Therefore, the sediments appear generally more cemented than the iron ores of northern France or Great Britain which are also of Jurassic age. The historical outcrop is located 6 km NE of Chamoson; DCverin (1945) quotes this outcrop after the local name of Chamosentze nearby; the sediments are regarded as Callovian in age, like the Erzegg and Planplatte wid-bearing iron-rich sediments and those in the northernmost outcrop of the Glarnisch Mount. In Urbachtal, the age is upper Bathonian; and in Windgale, the oolitic ironstone formation seems to cross the Bathonian-Callovian boundary. The lithological sequence is mainly schistose and limy with ammonites as common stratigraphic fossils. Near Chamoson, the oolitic facies has the form of a restricted lens, 250 m wide, and a few metres thick. Elsewhere, the facies appears as irregular, 1 cm to 10 cm thick layers, or as series of oolitic lenses gradually passing into schists or limestones. Often, the limy sediments underlying the iron-rich oolitic lenses are composed of bioclastic debris of crinoids

8 (calcaire 3 Entroques) typical of a shelf environment. At the top of the iron-rich sediments, DCverin has reported localized concentrations of belemnite and ammonite remnants. Due to its influence on the mineral assemblage, it is of interest to note here that the area near Chamoson has been more affected by tectonics and related low-grade metamorphism than the well preserved area near Erzegg and Planplatte, but less affected than the area of Windgalle, and similarly affected compared to the area of Urbachtal.

Figure 1. Geological setting and location of the Jurassic oolitic ironstones in Switzerland. 1) Chamoson; 2) Urbachtal; 3) Planplatte; 4) Erzegg; 5) Windgillle; 6) Glmish Mount. The outcrops are located in the Helvetic Nappes and were more or less slightly metamorphosed during Alpine events.

Mineralogical nomenclature Since the original proposal by Berthier (1820), the term "chamosite" has been assigned to the silicate of Chamoson. Because it has been strictly defined only on optical and chemical grounds, the name has been used for other more or less green clays with an oolitic facies. This is a source of confusion because it is now known (Orcel et al., 1949) that crystallographically different minerals have been designated by this name. In this sense "chamosite" took the meaning of a facies: any green ferrous clay in an oolitic ironstone formation. The situation was considered inadequate by several authors including Orcel et al. (1949). Millot (1964, p. 246) suggested to define chamosite sensu strict0 as a 14 8, mineral, i.e. a chlorite. This suggestion was later approved by the Nom-

9 enclature Committee of the Clay Mineral Society (Brindley et al., 1968). Therefore, chamosite designates a ferrous chlorite like the one found in the sedimentary iron ore outcropping near Chamoson. The 7 A clay mineral that has been called "chamosite" by English writing authors (for example Yerskova et al., 1976) does not have priority for this name and the term berthierine should be prefered. The mineral name berthierine was first proposed by Beudant (1832, in Lacroix, 1895) for the green oolitic clay collected from the Jurassic ironstone of Hayange (Lorraine, France). These ooids are purely made of a 7 8, iron-rich clay mineral. Berthierine is therefore a highly femferous clay of the serpentine family. However, the correct use of these two terms is not easy due to the difficulty in distinguishing whether the mineral has a periodicity at 14 A or not. In the natural feniferous chlorites, the first diffraction peaks of odd order in the 001 series, are indeed frequently of very low intensity (Orcel et al., 1949). Specific treatments may however reveal the 14 8, periodicity poorly expressed on untreated samples (Tomita and Takahashi, 1986). If a detailed mineralogical study is not available, we will quote ironstone green clay for the clay minerals of the iron-rich oolitic sediments. PETROGRAPHY OF THE SWISS OOLITIC IRONSTONES

The main characteristic of the studied sediments is their high iron content; these formations are therefore easy to observe in the field where they appear as brownish lenses due to meteoric oxidation. In thin section as well as in the field, the most typical criterion is the presence of ooids locally reaching 1 mm or more in diameter. These ooids are irregularly distributed and usually draw clouds or irregular bands of more or less dense spheroidal or ellipsoidal elements in a fine-grained, cemented groundmass. This distribution as well as the general sedimentary structure (lens) clearly results from deposition in presence of bottom currents.

Elements of the sediment

Carbonate remnants Excluding the cement and the ooids, the only important constituents of the iron ore lens near Chamoson are bioclastic carbonate grains, in addition to very little detrital quartz. Ninety percent of the biodetrital fraction is made of crino'id fragments. Most are strongly eroded and can be observed in all thin sections either as free grains or as nuclei in the ooids. Spines or other skeletal parts of echinids are not rare; like the crino'id fragments, they can be identified by their characteristic structure delineating a regular lattice: the stereom. The rest of the carbonate fraction consists of pieces of molluscs (bivalve shells or belemnite rostra), sponge spines, tests of brachiopods or ostracodes. According to Dkverin (1945), the small (pelagic) foraminifers were probably abundant in the initial sediment; their present abundance, when preserved by silicification in pyrite or in a few oolitic nuclei, supports this view. Planktonic fossils are abun-

10 dant in the ironstone of the G l b i s c h Mount where DCverin (1945) observed the presence of foraminifers, ostracodes, microcephalopodes and microgastropodes. These fossils indicate an open marine environment of deposition. In thin sections, the relationship between the carbonate grains and the green clays is of three types in the outcrop near Chamoson: the clays 1) fill the voids, 2) impregnate and replace, or 3) surround and coat the previously deposited clasts of carbonate. The latter case leads to the oolitic structure. DCverin (1945) illustrated green clay in the pores of the echinoderm stereom as well as fillings in ostracode tests. The partial or complete replacement of carbonate by green clay minerals includes echinoderm and mollusc fragments, belemnite rostra and brachiopod tests in the outcrop near Chamoson. It is very frequent in Erzegg or Planplatte regions. From the relationships observed in thin section, it is difficult to conclude whether the replacement process took place before burial or later on during diagenesis (Bradshaw et al., 1980).

Well preserved ooids Oolitic structures are illustrated by DCverin (1945). A discussion of the formation of the green material is based on those oolitic structures. The problem in interpreting the thin sections is the difficulty to locate the time at which the present aspect of the rock has been reached because the presently observed paragenesis is a combination of cumulated geochemical reactions which occurred before or at the time of deposition, during early burial, diagenesis and dynamic metamorphism. Noneless, the sediments show distinct and unambiguous oolitic structures and the material forming their layers is a light-green clay resembling chlorite (Fig. 2). The size of the ooids is frequently homogeneous in a given thin section. The mean diameter varies from 0.2 to 1.0 mm. Usually of regular, ellipsoidal form when correctly preserved, the ooids show a restricted variation of the maximum versus minimum diameter ratio between 1.5 and 1.3. These characters strongly suggest a dynamic deposition and reject a strictly in situ intra-sedimentary genesis of the ooids. The nuclei of many ooids are comparatively small, and numerous green

----3-+----3

on the form and size of the initial nucleus. Photomicrograph 2 shows a large triangular calcitic nucleus (shell fi-agment) surrounded first by black and green layers followed by purely green layers. The nucleus of the darker mid is made of an angular layered fragment of broken ooid (broken ooids are present on Photo.1). The light-green layers are underlined by black sheets representing interlaminae of diagenetic iron oxide additions to the initial grain. Photomicrographs 3 and 4 ( crossed and parallel nicols, respectively) show an mid of which the nucleus is an already rounded piece of echinoderm. The carbonate stereom voids are filled with green clay and the stereom itself has begun to be replaced by the green clay. Only a few of the calcitic nuclei have partly turned to green before the coating process. Photomicrographs 5 and 6 (parallel and crossed nicols respectively) show another green mid of which the nucleus is a fragment of the layered coating of a previously formed and broken mid. Photo. 6 and 3 show that the layered coating is formed of concentrically oriented clay particles because the optical figure of a black-cross appears under crossed nicols.

11

Figure 2. Thin sections of pieces of iron ore from Chamoson. The large majority of the elements are coated nuclei, i.e. ooids. Photomicrograph 1 shows abundant ooids cemented by calcite. The cement is locally green. The general form of the ooids is ellipsoidal but appears much less regular than it is usual for carbonate ooids. The form of the ooids depends... (Figure caption follows p. 10)

12 clay layers surround it. A moderate proportion of grains shows a large nucleus and a thin envelope which presents only 3 or 4 clay layers. The maximum number of more or less distinct laminae was counted for an ooid illustrated by DCverin; the ninety laminae have a constant thickness of about 4 to 5 pm for that ooid of about 0.8 mm in diameter. The colour of the clay varies from a very light bluish-green to a bright-green. The pleochroism is more or less obvious between the above quoted colours and a more yellow one. According to us, the evolution from a piece of crinoid toward an mid comprises three steps: 1) the pores of the stereom fragment are filled with green clay; 2) the clay replaces the carbonate skeleton which sheltered the first crystallization of green clay; 3) this element acts as a nucleus around which the authigenic clay concentrically crystallizes forming an mid growing with time (Fig. 3). This interpretation differs from that suggested by DCverin (1945,p. 34,45 and 47) who considers that the fragment of substituted carbonate is progressively and structurally modified (digested) from the exterior to the interior. The total volume of the grain being time-constant, the thickness of the oolitic aspect increases by centripetal rearrangement and recrystallization of the already present green clay. This was called by Dtverin "metamorphose". In other words, according to DCverin, the oolitic structure would develop itself at the expanse of the preliminary substrate, previously substituted for green clay (Fig. 3); we believe that the oolitic structure results from the accretion of green clay layers around a nucleus and this phenomenon increases the size of the initial nucleus (Fig. 3). We reject the hypothesis of DCverin mostly because the substituted fragments of echinodermal stereom have no reason to have a regular ellipsoidal shape before the "metamorphose". However, the mechanism proposed by DCverin would be possible if the initial carbonate substrate had already an oolitic structure (Fig. 3); in other words, if the green clay would form by substitution of carbonate ooids. This is the heart of the problem and this third hypothesis is difficult to reject definitely. However, we feel that it is difficult to accept a hypothesis implying primary carbonate ooids in a sediment where no carbonate ooids have never been quoted nor any trace of carbonate remnants is present in the now observed oolitic structure. A large majority of the nuclei is bioclastic carbonate fragments but other possibilities have been described. The most frequent is the re-use of pieces of brocken ooids (Fig. 2). This indicates that already hard ooids were present and were used again as nuclei for the growth of new ooids. In other words, favourable conditions for growing green clay ooids are also compatible with an in situ reworking of previously deposited hard ooids of similar composition. Therefore, the genesis location of some ooids is similar to that of deposition of others and consequently, the two environments are not far from each other. In summary, in the less modified ironstone sediments, the ooids are green; limy ooids have never been reported; the nucleus of the ooids is preferably made of biodetrital carbonate or broken pieces of previous argillaceous ooids. Pieces of already cemented sediment have also been observed. The green clay

13

presently observed in the ooids seems to result from three different processes: 1) filling the voids of a preliminarily deposited carbonate bioclastic grain; 2)replacing the carbonate fragment itself; and 3) oolitic accretion of clay around a nucleus. The last process appears predominant and common to most of the green grains. This point makes the initial oolitic clay mineral a result of geochemical reactions at or near the sea-bottom and, therefore, directly concerns the subject of the present volume.

nCARBONATE

G E E N CLAY

SEDIMENT

Figure 3. Three mechanisms could explain the internal structure observed in green ellipsoidal grains of Swiss oolitic ironstones. 1) the mechanism proposed here; 2) the mechanism suggested by Dtverin (1945); 3) the mechanism of intra-sedimentaryreplacement of previous carbonate ooids. In 1, the green clay successively fills, replaces and surrounds the carbonate fragments by an accretion process. In 2, the last stage is replaced by a centripetal recrystallization of the previously formed clay and this might occur either above or, preferably (according to Deverin), below the sea-water/sedimentinterface (bold line).

Evolution of the o o i h The evolution of the green clay ooids after burial may be of diagenetic or tectonic origin. According to DCverin (1945), the green oolitic material can be

14

substituted for siderite or feldspar; ooids can be silicified and pyrite or magnetite may grow on their margin. Carbonate is sometimes introduced between the argillaceous laminae. The tectonic effect is a deformation of the ooids which become more and more elongated despite their toughness. This deformation presumably favours the mineral substitutions quoted above (these descriptions are interpretative however -i.e. subjective-; in fact the sediments show different structures, and the observer tries to arrange them in a manner which presumably reflects the chronologic evolution). Thus three conclusions have been obtained from the Swiss ironstone study. The first conclusion accepts the fact that the formation of ferric oxides and hydroxides occurs after the genesis of the green clay which will be shown later to be ferrous. This is of great importance because several authors have reversally suggested that the first process of iron accummulation during ironstone genesis was the formation of iron oxide ooids (see Chapter A2, p. 36). The latter suggestion is not supported by observations made in the Swiss Alps. A second conclusion still concerns the chronological succession of the paragenesis. Here again, when carbonate is present in the ooids, its formation follows the accretion of green clay i.e., no carbonate ooids can be suspected before the formation of the green clay (hypothesis 3 in Fig. 3 is not supported). A third conclusion is related to the habit of the ooids. When the present form of the ooid is not ellipsoidal, this is not due to an initially soft nature; the ooids are assumed to be hard very early in the sedimentogenesis. But their deformation (flattening, lengthening) is linked to the numerous laminae allowing the clay layers to shift one onto the other under an important dynamic pressure.

The groundmass of the oolitic sediment Between the grains studied above, there is always a certain proportion of calcite which is locally interpreted as the fine crushing of bioclasts where and when ooids have been formed. For the ironstone near Chamoson, the presence of siderite makes the rock difficult to break and the oolitic grains difficult or impossible to separate and purify. A further interesting component of the groundmass is a green clay. This is a fourth habit of this component in the rock (besides the former three described from within the ooids). This diffuse green pigment is frequently darker green than the ooids themselves. It is very difficult to identify the time of genesis: it could be synchronous with the deposition or early burial time, or the result of a late diagenesis. We did not find strong arguments supporting the formation of the green clay together, before or shortly after the genesis of the green ooids. However, E v e r i n (1945) quotes the presence of pieces of cemented green clay reworked in the groundmass or used as a nucleus for some ooids. If this is correct, the green clay of the groundmass is penecontemporaneous with the formation of ooids. Elsewhere, the same author states that the diffuse green clay really seems to originate from an exudation out of the ooids. This would imply a diagenetical origin.

15 Finally, the outcrop near Chamoson is known to show numerous fissures filled with a mixture of calcite and green clay. In that case, the green clay is diagenetic and no longer indicative of the environment of deposition. In our opinion, a large proportion of green clay is formed during the time of deposition or during very early burial; this clay forms the angular, hard pieces of clay in the groundmass. But the later diagenetical processes frequently remobilize the green clay of the groundmass as well as the one from ooids. This material either recrystallizes in situ or fills the voids of the sediment. The resulting clay minerals are diagenetic products probably not related to sea-water fluids from the environmental point of view. MINERALOGICAL DATA ON THE GREEN CLAY

Only hard sediments are available in the Swiss outcrops. The ooids have been mechanically concentrated by gentle crushing of the whole-rock, by sieving, and by magnetic separation. After removal of most of the carbonate by this treatment, decinormal acetic or hydrochloric acids have been used by adding them drop by drop in a Becher containing the rock and constantly stimng. The ooids have been then concentrated by rolling the dried grains on an inclined plane and finally purified by hand picking. After crushing the selected material in an agath mortar, moderate acid leaching followed by several (up to ten) distilled water cleanings and centrifugation, glass slides were used to obtain oriented clay preparations.

X-ray diffraction study The green clay from the ooi& A particular attention was paid to ooids which represent an early step of genesis: a primary component. The purified ooids from the well-preserved sediments from Chamoson were selected, crushed, liberated of their calcite, and cleaned with distilled water. Oriented slides were prepared; Figure 4 shows two of many X-ray diffraction patterns. At first sight, the material appears somewhat complex, especially considering the number of peaks present between 7 A and 20 A. The X-ray diffraction peak at 12 A is due to stilpnomelane a mineral previously observed in thin section. However, the most developed peaks indicate the dominant presence of a chlorite: 14 A, 7.05 A, 4.68 A, 3.50 A. The 001 and 003 reflections are clearly smaller than the 002 and 004 ones, which shows that the chlorite is very rich in iron. The precise location on the diagrams of the 001 peaks for I equal to or above 5 is difficult. The nature of the peaks between 7 A and 20 A has been understood after several conventional treatments of the oriented slides. Ethylene glycol treatment shows that a mixed-layer chlorite-smectite is probably present. This smectite has been interpreted as a nontronite by Delaloye (1966).

16 Si

UNTREATED OOLITHS

30'

100

KaCu

Figure 4. X-ray diffraction patterns of well preserved ooids from Chamoson. The green clay appears to be a mixture of chlorite with other clay minerals. Foreign minerals as stilpnomelane (St), siderite (Si) and quartz (Q) are also present. (Redrawn from Delaloye, 1966)

Progressive heat treatments have been undertaken on several series of oriented clay specimens. An interesting observation is that the peak at 7.05 8, evolves and yields a doubZe peak: one portion remains at 7.01 A and the other shifts toward 7.68 A when the temperature goes up. Delaloye (1966) considers that the shifting peak characterizes the mineral berthierine ("ferrokaolin" of this author). Therefore, Delaloye (1966) considers that chlorite and berthierine are present in the green clay of the well preserved ooids; a mixed-layer chloritesmectite would complement the composition of that clay.

The clay from veins Near Chamoson the presence of 2 cm thick veins filled with pure clay minerals makes this sediment useful to easily prepare the material for analysis. The clay sampled there results from a secondary process of genesis. Oriented slides have been prepared and Figure 5 shows one of the diagrams obtained. It shows the characteristic 001 reflections for a nearly pure chlorite. The compara-

17

tively high 001 diffraction peak remains smaller than the 002 and 004 reflections. The 001 reflections have been carefully measured both in position and relative intensity in order to calculate the structural factors (F). Table 1 gives the results for the diagram of Figure 5 and for an other one not shown here. The position and intensity of the peaks are not reproducible from a diagram to another. Furthermore, the real "recognition" of the 005 reflection and higher orders is very tentative. CHLORITE from a fissure (sample 8 0 )

r-

(0

2

0

I

0 0 0

0

0

50.

40'

0

Ir)

N

0

0

0

0

300

0

-

0 0

20"

Figure 5. X-ray diffraction pattern of a clay from a vein collected near Chamoson. (Redrawn from Delaloye, 1966)

Table 1. Positions and relative intensities for the series of 001 reflections of two "chamosites"from veins collected near Chamoson. (Data from Delaloye, 1966) d

(A)

1

(%I

d

(A)

1 (%I

001

14.25

40

14.13

29

002

7.10

100

7.02

100

003

4.68

10

4.69

11

004

3.537

50

3.528

46

005

2.931 ( ? )

5

2.818

7

006

2.272 ( ? )

12

2.334

1

007

2.008

15

2.008

10

008

-

0

009

-

0

0

0

00.10

-

0

1.408

2

1.691 ( ? )

(?) Question marks indicate inaccurate estimates for the location of the reflections.

1

18

: 2 e T k.

R

T

$4 CHLORITE from a f i s s u r e

Figure 6. Electronic density of the green clay along the C, axis computed according to the 001 diffraction peaks. The curve obtained corresponds perfectly to the chlorite structure shown on the left hand side.

In order to verify the purity of the analysed material and its identity as a chlorite, oriented slides have been heated to different temperatures between 400" and 650°C before X-ray diffraction. Heating leads to a progressive decrease of all the 001 reflections but two of them; the 004 reflection remains stable until 550°C and disappears later; the 001 reflection remains similar or increases slightly after heating, its top becomes wider at 600°C. The chamosite of the veins appears to be pure, but the absence of a 7 A mineral, still remains to be proved at that stage.of the study. In order to test again the purity of the material, the calculation of the electronic density was undertaken. Projection of the electronic density of a set of planes separated by increments of 0.025/C0 on the C, axis of the elementary cell undertaken by Delaloye (1966) have been improved using computer facilities. It permitted a slightly different reconstruction of the electronic density projection on the C, axis. It is presented in Fig. 6 along with a normal chlorite structure. Very good matching indicates that the secondary iron silicate is a pure chlorite. In summary, the green clay from the ooids (primary clay) appears to be composite and the green clay of the fissures (secondary clay) is pure and strictly chloritic.

19

Chemical study Well preserved pure ooids were obtained from four samples and analysed using the classic wet chemical methods. Table 2 summarizes the data. If we except the presence of calcite and possibly iron carbonates (the two known possible impurities) the chemical results could well be used for characterization of a chlorite and a structural formula of ferrous chlorite would result. However, this exercise would not be correct since the X-ray diffraction study has proved the presence of some nontronite. This may be presumed from the chemical data because, compared to other pure chlorites (Foster, 1962), the silica contents appear rather high. Chemical analyses are also available for the clay from the veins sampled near Chamoson and at Windgtille (wet chemistry). They are given in Table 3. The two analyses published by Everin (1945) were widely quoted in the literature amongst the very few chemical data available for "chamosite". They were obtained after acid treatment which explains the absence of CaO. Amongst the three new analyses published by Delaloye (1966) for the locality of Chamoson, the one for sample 8a showed about 10% of CaO and the presence of about 7% of CO,. Therefore, the values measured were recalculated in order to eliminate calcite; the recalculated values alone are given in Table 3. Compared to the data available for the ooids, it is evident that the clay from the veins contains less silica and more alumina, FeO and MgO. This corresponds better to a ferrous chlorite composition. Amongst the clay from the veins themselves, the green clay from Chamoson is richer in silica and the Fe 0, content is 3 or 4 times less compared to the other green clays from Windghle. This may result from an oxidation process; however, the ferrous iron content does not decrease concurrently. Table 2. Chemical analyses of the green clay from purified ooids of the ironstone near Chamoson. The composition of recent green clays referred to phyllite V (Part B) is given for comparison. (G. Krummenacher analyst; data reproduced from Delaloye, 1966) ~

001 i t hs

Si02

93

44

94

60d

35.29

34.22

34.41

38.67 16.00

6

5 -

*lZ03 FeO

16.96 32.87

14.67

16.00

33.56

33.49

32.94

Fe203

0.00

3.97

0.00

CaO

1.12 0.79

8.22

0.63

0.07

MgO

2.98

2.71

2.39

2.45

H20'

9.05

6.00

8.89

8.69

99.06

99.38

99.78

98.82

Phyllite V 34 - 38

- 12 7

18 - 22 8.5 - 13.5

20 Table 3. Wet chemical analyses of the clay from Jurassic ironstone veins of Switzerland. (1) J. Jakob and (2) G. Krummenacher analysts; after (1) DCverin (1945) and (2) Delaloye (1966). Sample b is from Windgiillele;other samples from Chamoson.

Si02

28.86

26.20

27.50

30.07

22.43

*l203

18.49

20.12

19.14

17.26

14.27

Fe203 FeO

1.44

2.39

5.9

3.66

11.98

36.51

35.36

33.20

37.61

37.63

4.73

4.93