Clays and Clay Minerals of Japan, #26 (Developments in Sedimentology)

DEVELOPMENTS IN SEDIMENTOLOGY 26

CLAYS AND CLAY MINERALS OF JAPAN

FURTHER TITLES IN THIS SERIES

VOLUMES 1 , 2 , 3 , 5 , 8 and 9 are out of print. 4. F.G. TICKELL T H E TECHNIQUES OF SEDIMENTARY MINERALOGY 6. L. VAN DER PLAS T H E IDENTIFICATION OF DETRITAL FELDSPARS 7. S. DZULYNSKI and E.K. WALTON SEDIMENTARY FEATURES OF FLYSCH AND GREYWACKES 10. P. McL. D. DUFF, A. HALLAM and E.K. WALTON CYCLIC SEDIMENTATION 11. C.C. REEVES JY. INTRODUCTION T O PALEOLIMNOLOGY 12. R.G.C. BATHURST CARBONATE SEDIMENTS AND THEIR DIAGENESIS 13. A.A. MANTEN SILURIAN REEFS OF GOTLAND 14. K.W. GLENNIE DESERT SEDIMENTARY ENVIRONMENTS 15. C.E. WEAVER and L.D. POLLARD T H E CHEMISTRY OF CLAY MINERALS 16. H.H. RIEKE 111 and G.V. CHILINGARIAN COMPACTION OF ARGILLACEOUS SEDIMENTS 17. M.D. PICARD and L.R. HIGH JY. SEDIMENTARY STRUCTURES OF EPHEMERAL STREAMS 18. G.V. CHILINGARIAN and K.H. WOLF COMPACTION OF COARSE-GRAINED SEDIMENTS 19. W. SCHWARZACHER SEDIMENTATION MODELS AND QUANTITATIVE STRATIGRAPHY 20. M.R. WALTER, Editor STROMATOLITES 21. B. VELDE CLAYS AND CLAY MINERALS IN NATURAL AND SYNTHETIC SYSTEMS 22. C.E. WEAVER and K.C. BECK MIOCENE OF T H E SOUTHEASTERN UNITED STATES 23. B.C. HEEZEN, Editor INFLUENCE OF ABYSSAL CIRCULATION ON SEDIMENTARY ACCUMULATIONS IN SPACE AND TIME 24, R.E. GRIM and N. GUVEN BENTONITES 25A. G. LARSEN and G.V. CHILINGAR DIAGENESIS IN SEDIMENTS AND SEDIMENTARY ROCKS

DEVELOPMENTS IN SEDIMENTOLOGY 26

CLAYS AND CLAY MINERALS OF JAPAN Edited by

TOSHIQ SUDQ Emeritus Professor, Tokyo University of Education, Tokyo 153, Japnn

SUSUMU SHIMQDA Institute of Geoscience, University of Tsukuba, Ibaragi Pref. 300-31, Japan

1978

KODANSHA LTD. Tokyo

ELSEVIER SCIENTIF PUBLISHING COMPP Amsterdam-Oxford-New

8

KODANSHA SCIENTIFIC BOOKS

Copyright @ 1978 by Kodansha Ltd. All rights reserved No part of this book may be reproduced in any form, by photostat, microfilm, retrieval system, or any other means, without the written permission of Kodansha Ltd. (except in the case of brief quotation for criticism or review) ISBN 0-444-41238-7 (series) Library of Congress Cataloging In Publication Data

Main e n t r y under t i t l e : Clays and c l a y minerals of Japan. (Developments i n sedimentology ; 26) (Kodansha s c i e n t i f i c books) Bibliography: p. Includes index. 1. Clay--Japan. 2. Clay minerals--Japan. I. SudO, Toshio, 191111. Shimcda, Susumu, 1935111. Series. QE471.3.C53 549l.6 78-8405 ISBN 0-444-99787-3

Copublished by KODANSHA LTD. 12-21 Otowa 2-chome, Bunkyo-ku, Tokyo 112 and

ELSEVIER SCIENTIFIC PUBLISHING COMPANY 335 Jan van Galenstraat, P.O. Box 211, Amsterdam, The Netherlands ELSEVIER NORTH-HOLLAND, INC. 52 Vanderbilt Avenue, New York, N.Y. 10017 Printed in Japan

Contributors

Keinosuke NAGASAWA, Geoscience Institute, Faculty of Science, Shizuoka University, Ohya, Shizuoka-shi 422, Japan Susumu SHIMODA, Institute of Geoscience, University of Tsukuba, Niiharigun, Ibaraki Pref. 300-31, Japan Haruo SHIROZU, Department of Geology, Faculty of Science, Kyushu University, Higashi-ku, Fukuoka-shi 8 12, Japan Toshio SUDO, Emeritus Professor, Tokyo University of Education, Setagayaku, Tokyo 156, Japan Hideo TAKESHI, Institute of Geological Sciences, Faculty of General Education, Osaka University, Toyonaka-shi 560, Japan Koji WADA, Department of Pedology, Faculty of Agriculture, Kyushu University, Higashi-ku, Fukuoka-shi 8 12, Japan

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Preface

Studies on clays and clay minerals have developed over a broad scope involving the basic sciences, industry and agriculture, and clay mineralogy has played an important role in clarifying the fundamental aspects. All such work is now organized into a single system, clay science, which involves a vast amount of published and collated information on an international scale. The clays and clay minerals are mostly natural materials, but include some artificial products. Clay and clay mineral synthesis is thus expected to increase in importance in the future. The properties of clays and clay minerals are more or less variable, as reflected in their crystal structures, thermal effects, and claywater systems. These variations in properties of course extend across different groups, but it is also not uncommon for species of the same group to show differences, a fact which has undoubtedly promoted academic interest in, and enhanced the industrial use of clays. The variations mostly result from the ability of clays and clay minerals to respond sensitively to changes in physical and chemical environmental conditions, both in nature as well as in the laboratory. The natural environmental conditions cover the formational and transformational processes of the clays in nature, as indicated by the results of clay synthesis and by geological and mineralogical studies on the modes of occurrence, mineral associations, textures and origins of clays. It should be noted that the modes of occurrence and origins of clays and clay minerals are essentially controlled by their geological environment, which is apt to vary geographically from region to region. Synthesized information on the geological and mineralogical properties of clays in each geographical region is thus pertinent to general studies on a regional as well as global basis. The main purpose of the present book is to provide an organized account of the geological and mineralogical properties of clays and clay minerals in Japan. Chapter 1 gives an outline of the historical development of clays and clay-mineral studies in Japan. Throughout, an attempt is made to summarize the studies putting them into perspective with the major research trends in the world, and imparting sometimes the classical but still useful knowledge as well as recent one. Subsequent chapters prepared by specialists in each field, then cover in detail the most important individual topics. Many cross-references are included so that a general view of the sub,iectcan readily be obtained. As editors, we wish to express our thanks to all authors and publishers who vii

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Vlll

PREFACE

have granted permission to reproduce published diagrams and photographs. We also acknowledge the generous help and advice of many friends and colleagues during the preparation of this book. Particular thanks are due to Mr. E. Tashiro and Mr. A.J. Smith of Kodansha for their editorial and linguistic assistance in the preparation of the final manuscript. August, 1977

Toshio SUDO Susumu SHIMODA

Contents

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Contributors Preface ........................................................................... Chapter 1.1. 1.2. 1.3.

v vii

.

1 An Outline of Clays and Clay Minerals in Japan Studies on Clays and Clay Minerals .......................................... Modes of Occurrence. Mineral Assemblages and Origins ........................ Clays and Clay Minerals ....................................................

1

20 33

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Chapter 2 Weathering of Volcanic Ash and Other Pyroclastic Materials .......................................... 2.1. Mineralogy of Volcanic Ash Soils 2.2. Deep Weathering of Pyroclastic Deposits ...................................... Chapter 3.1. 3.2. 3.3. 3.4.

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3 Wall Rock Alteration of Kuroko Deposits KurokoDeposits Alteration Patterns Clay Minerals ......................................................... Conclusion

........................................................... ....................................................... ..............................................................

105 114 127 130 136 143

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Chapter 4 Allophane and Imogolite 4.1. Chemical Composition ...................................................... 147 4.2. Optical Properties .......................................................... 151 4.3 Electron Microscopy ........................................................ 152 4.4. X-Ray and Electron Diffraction .............................................. 157 4.5. Thermal Analysis .......................................................... 160 4.6. Infrared Spectra ............................................................ 163 4.7. Charge Characteristics ...................................................... 167 4.8. Surface Acidity ............................................................ 170 4.9. Electrophoresis and Dispersion-Flocculation .................................. 172 4.10 Coordination Status of Aluminum ............................................ 173 4.1 1. Anion Sorption ........................................................... 174 4.12. Surface Area ............................................................ 178 4.13. Density and Porosity ...................................................... 179 4.14. Structure Models .......................................................... 180

.

Chapter 5.1. 5.2. 5.3.

5 Kaolin Minerals Dickite and Nacrite ........................................................ Kaolinite and Halloysite .................................................. ................................................................ Genesis

Chapter 6.1. 6.2. 6.3.

6

189 193 212

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Smectites Montmorillonite .......................................................... Saponite .................................................................. Nontronite ................................................................

ix

221 237 239

CONTENTS

X

6.4.

Stevensite

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240

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Chapter 7 Chlorite Minerals 7.1. Outline of Trioctahedral Chlorite Minerals .................................... 7.2. The FeMg-chlorites of Schists and Mg-chlorities of Serpentinites and Certain Metallic Ore Deposits ...................................................... 7.3. Fe- and FeMg-chlorites of Hydrothermal Metallic Ore Veins .................... i.4. Ferromagnesian Chlorite Minerals in Miocene Tuffaceous Sediments .............. 7.5. Magnesian Chlorite Minerals in Altered Wall Rocks of Kuroko Deposits 7.6. Dioctahedral Chlorite Minerals

.......... ..............................................

243 244 247 251 253 259

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Chapter 8 Interstratified Minerals 8.1. Modes of Occurrence of Interstratified Minerals ................................ 8.2. The Mineralogical Properties of Interstratified Minerals ........................ 8.3. Origin of Interstratified Minerals ............................................ Subject Index

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265 275 312 323

Chapter 1 An outline of clays and clay minerals in Japan Toshio SUDO

The present Chapter attempts to summarize studies on the clays and clay minerals of Japan. The first half covers the basic work up to the present, with brief comments on major trends in related work overseas. It involves research on (1) the specific properties of clay minerals as revealed by X-ray, thermal, electron optical analyses, etc., (2) some of the analytical procedures, (3) synthesis, (4) changes in the properties of clays and clay minerals on heating, grinding, and chemical treatment, and ( 5 ) miscellaneous items. The latter half of the Chapter attempts to survey the mineralogical properties, modes of occurrence and origin of the clays and clay minerals found in Japan. Throughout geological time, volcanic activity has frequently and actively occurred in Japan, resulting in an abundance of clays and clay minerals which occur as hydrothermal alteration products of various rock types, and as weathering products of volcanic ashes and glassy tuffs.

1.1.

STUDIES ON CLAYS AND CLAY MINERALS

1.1.1. Historical deve!opment

In 1899, a clay having a strong bleaching effect was discovered at Odo, Niigata Prefecture (Higashi-kambara-gun), and K. Kobayashi-a late Emeritus Professor of Waseda University-began research on the clay (the so-called “Kambara earth”) to test its importance to the petroleum industry. He first noticed that the clay had acidity, and so termed it an “acid clay”. Studies in this field, particularly on the clay chemistry and significance to petroleum engineering, then developed as his life work (Kobayashi, 1912,1929).The full range of studies undertaken by Kobayashi’s group has been described in his book, Sansei-Hakudo (Acid Clay), 1st ed., Maruzen (Kobayashi, 1919). In the early stages, Kobayashi devoted himself to the clarification of the nature of the observed clay acidity, and even in those days, he approached close to modern concepts. He extended the studies on the basis of the exchange acidity (in modern terminology) by confirming the release of alumina on treatment with neutral salt solution, and pointed out the important role of alumina in the clay acidity. At 1

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this stage, he shared common interests and aims with workers in inorganic, organic, and colloid chemistry, and with soil scientists devoted to the clarification of the nature of the acid soils in Japan. Numerous interesting properties of the acid clays were revealed as follows : (1) a strong ability to dehydrate, (2) a strong adsorptive ability for various kinds of materials such as vitamin B, (3) a catalytic ability for various organic chemical reactions involving dehydration, polymerization, isomerization, condensation, and cracking distillation, and (4) color-forming reactions with substances such as benzidine, vitamin A, and carotene. It is worthy of note also that Kobayashi, on the basis of these properties and the modes of occurrence and origin in nature, proposed his own concept for the origin of petroleum. He and his collaborators thus laid the foundation for the acid clay industry, and stimulated a broad interest in studying clays in other areas such as geology, mineralogy, and the soil sciences. The mining of bentonite is thought to have begun at Wyoming, N. America, in around 1888. About 20 yr later in Japan, exploitation of bentonite was commenced in Yamagata Prefecture. In 1930, R. Shigemune of the Government Chemical Industrial Research Institute confirmed the identity of the Japanese material with the bentonite occurring in the U.S.A. The thermobalance originally designed by K. Honda-a late Emeritus Professor of Tohoku University-set the way for work in the field of thermogravimetry (TG), and numerous thermogravimetric studies on various kinds of materials including clays and clay minerals followed (e.g. Kobayasi, 1940; Saito, 1969). S . Kozu-a late Emeritus Professor of Tohoku University-and his collaborators (Satoh, 1923; Kozu and Masuda, 1926), undertook thermal studies on kaolin clays and other related minerals, presenting DTA (differential thermal analysis) and T G curves and data for thermal expansion and contraction. Most of the curves were recorded up to temperatures exceeding 1000°C, and included data for both heating and cooling (Fig. 1.1). This work can be regarded as the pioneering thermal study on clays and clay minerals in Japan, and is widely known together with the research on the feldspar problem which Kozu and his group also performed. J. Takahashi-a late Emeritus Professor of Tohoku University-and his collaborators carried out extensive studies on glauconite, including its mineralogical properties and origin (Takahashi and Yagi, 1929;Yagi, 1929,1930,1932a). This work is regarded as the pioneering clay mineralogical study from the viewpoint of sedimentology in Japan. In the field of soil science, there was a comparatively long history of studies on soil clays in Japan. Since around 1910, work on soil acidity was actively undertaken by several soil scientists such as G. Daikubara, S. Osugi and T. Seki, contemporaneously with the work of K. Kobayashi. Seki (1913,1928) later investigated a considerable number of volcanic ash soils in Japan and pointed out several common chemical features among them, such as their remarkable deficiency of silica and base, the existence of “free” alumina and the strong “absorptive

STUDIES ON CLAYS A N D CLAY MINERALS

3

Fig. 1.1. The original DTA curve (“heating curve”) for kaolinite published by Kozu and his collaborators (Satoh, 1923). Inert material: alumina (upper graph), feldspar (lower graph).

power” for phosphoric acid. These features were considered to derive from allophane. Shioiri (1934, 1935) studied the properties of a gel-like material occurring as thin films in the interspaces of weathered pumice fragments, and reported it to be “allophane”. It is considered that this material might be imogolite. Further, Shioiri began work on the electrokinetic properties of soil clays in Japan. Kawamura and Funabiki (1936) studied the chemical composition and X-ray powder diffraction patterns of soils derived from various kinds of rocks in Japan, and pointed out the prevalent distribution of halloysite minerals in the samples studied. Attention should also be given to the work of Tamamushi on the colloid chemistry of clays and clay minerals such as acid clays, bentonite, etc., as described in his extensive reports on colloid chemistry (e.g. Tamamushi, 1937). The earlier investigations mentioned above are all regarded as cornerstones of the research on clays and clay minerals undertaken in Japan. The following sections introduce the subsequent work by Japanese workers, sometimes in collaboration with foreign workers, in relation to the major research trends in the world. 1.1.2.

X-ray studies

Since early days, studies on the crystal structure of clay minerals in the form of micron-sized flakes have been made by inspecting the X-ray powder diffrac-

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tion data and making reference to the results of crystal structure determinations of macro-crystalline analogs of the clay minerals. Advanced studies have revealed that although in many respects there are strong family resemblances, clay minerals in general show a variability in crystal structure, as illustrated by the existence of many polytypes and of order-disorder structures having distorted crystal lattices and disordered stacking of the layer lattices. This variability may affect the X-ray diffraction spots or lines, giving rise to modifications in spacing, intensity, and line profiles. Hendricks (1940), analyzing the continuous scattering of X-rays by certain clay minerals, clarified the nature of their disordered structures in terms of lattice distortion and random displacement of the layer lattices, which may occur within a wide range of order-disorder, particularly in random shifts of multiples of b/3 along the 6-axis. Brindley and Robinson (1948) analyzed the line profiles of halloysite (7A). Subsequently, studies on the disordered crystal structures of clay minerals have advanced remarkably under the influence of Brindley and MCring (1951, 1953). Nakahira (1952) analyzed the line profile of the X-ray diffraction bands of montmorillonite, and suggested that it is best explained as comprising regions of local ordering, with random displacements at multiples of b/3. The structure of dickite was refined by Neuwham and Brindley (1956) and that of kaolinite by Brindley and Nakahira (1958a). In these refined structures, the departure of the tetrahedral and octahedral sheets from the ideal structural arrangement was clearly demonstrated. Bailey and his collaborators extended our knowledge of the crystal structures, crystal chemical properties and polytypes of chlorite minerals. Shirozu (1958), in his extensive work on chlorites in Japan, provided evidence for the orthogonal type in iron-rich chlorites, as first suggested by Engelhardt (1942). The crystal structures of an orthogonal chlorite and a twolayered Mg-vermiculite have been analyzed by Shirozu and Bailey (1965, 1966). Mention should also be made of the research on the refined crystal structures of certain phyllosilicates such as brittle mica (e.g. Takeuchi, 1965) and micas as reported by Takeda and his collaborators (e.g. Takeda and Donnay, 1966). All these studies served to promote crystal structural studies on clay minerals. Hendricks and Teller (1940) first presented a general formulation for the X-ray diffraction intensity of interstratified clay minerals. MacEwan and his collaborators (MacEwan, 1956, 1958; MacEwan and Ruiz Amil, 1959) prepared many calculated X-ray diffraction patterns and peak migration curves, and proposed the Fourier transform method, facilitating the analysis of interstratified structures. Kakinoki and Komura (1965) presented the most general formulation, which is not limited to scattering in any one direction, is applicable to any number of components and total number of layers in the crystallite, and takes into account the scattering due to interlayer material. Sat0 (1969), using the Kakinoki-Komura formulation, prepared many diagrams, and his work permitted the analysis of interstratified structures in a stricter sense than ever before.

STUDIES ON CLAYS AND CLAY MINERALS

5

As a result, Sat0 and Kizaki (1972) discovered a mica/montmorillonite interstratification having “Reichweite” (range of correlation), g = 2. Recently Nakajima, Watanabe and Sudo (1972) have reported the analysis of the line profiles of certain clay minerals using the method of Warren and Averbach (1950), and the small angle scattering of some clay minerals has been reported by Watanabe (1968).

1.1.3. Electron optical studies The methodology for the crystal structure analysis of fine crystal flakes of clay minerals using electron diffraction patterns was developed by Russian workers (e.g. Zvyagin, 1967). Honjo, Kitamura and Mihama (1954) performed single crystal, electron diffraction studies of a sample of “Hong Kong kaolin” (halloysite (7A)) and reported the following significant facts. (1) The majority of about 160 crystallites had the b[01] axis as the tube axis. (2) Some three-dimensional order was indicated in the structures, which appeared to be higher than that of halloysite. (3) The c-parameter was doubled, so that the structure contains two kaolin layers in the unit cell. Among the many electron micrographs of clay minerals, particularly interesting shapes are observed in the case of imogolite and spherulitic halloysite (allophane-halloysite spherules). (p. 80) The design of electron microscopes has recently been improved remarkably, and high resolution electron microscopy now permits the observation of fine lattice images and discussion of the fine structures. Yada (1963) studied chrysotile with a high resolution electron microscope and clarified several interesting inner textures of the chrysotile fibers. He pointed out that the observed dislocation patterns suggest the c-parameter as 7.3 A instead of 14.6 A, and that the lattice images observed in cross sections of the fibers exhibit multi-spiral lattice fringes instead of concentric ones. These findings may support the model proposed by Jagodzinski and Kunze (1954). Suito, Arakawa and Yoshida (1969) revealed fine layer structures of certain organomontmorillonites, e.g. the octadodecylammonium complex, in which clear lattice images such as at 40, 27, and 15 A were observed. Dislocations were also revealed in places. Recently, Nishiyama and Shimoda (1974) have studied the oblique texture electron diffraction pattern of certain micas and their interstratifications. These authors pointed out that the polymorphs such as 2M1 and 1M can be decided by indexing the resolved arcs along ellipses. An interstratified mineral with a small amount of expandable mineral layers shows an oblique texture pattern consisting of diffused arcs which are especially diffused along an inner ellipse. Other interstratified minerals having increasing ratios of expandable mineral layers tend to show continuous scattering along ellipses with several maxima which could be assigned to the characteristic reflections of each of the polymorphs. This continuous scattering is probably due to several factors such as stacking

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disorder of dehydrated expandable layers, the superstructure, and a strained structure which may result from dehydration of expandable layers and/or mechanical bending of very thin plates of crystallites. 1.I .4.

Thermal analysis

The technique of differentialthermal analysis (DTA) has been used by scientists for many years. Since around 1945, it has been actively developed in many countries and a range of equipment of new or improved design has been produced in such countries as France, Great Britain, Hungary, Japan, the U.S.A., and U.S.S.R. In Japan, as mentioned above, excellent thermal studies on kaolin clays and related substances were carried out by Kozu and his collaborators in the period 1923-26. Since around 1945, active DTA studies have been made on broader aspects involving ceramics, the chemical industry, and mineralogy (Sudo, Nagasawa, Amafuji et al., 1952), and in Japan, DTA has subsequently been used not only in studies of clays but also in mineralogy in general. In Japan, as already mentioned, thermogravimetry (TG) originated from the thermobalance designed by Honda (1915). Since then, TG has been extensively used for studies on various kinds of materials including clays. In most cases, TG curves of clays and clay minerals are now recorded with a simultaneouslyrecording DTA-TG apparatus, or in some instances DTA-TG-DTG (delivatograph), and TG is frequently employed for the determination of the activation energy of decomposition or dehydration. The progress in thermal analysis since around 1954 stems directly from the establishment of new methods and new equipment, such as the differentialthermogravimetry (DTG) developed by Keyser (1953) and the delivatograph-a simultaneously recording DTA-TG-DTG apparatus designed by Paulik, Paulik and Erdey (1958). Recently, in Japan, apparatus such as the delivatograph (Saito, Otsuka, Iwata and Tsuchimoto, 1964), scanning calorimeter, high temperature or low temperature DTA apparatus, and simultaneously recording DTA apparatus and X-ray powder diffractometer, has been used for studies on various kinds of materials including clays and clay minerals. 1.1.5. Infrared analysis

Following the pioneering work of Keller and Pickett (1949), infrared analysis has been extensively employed for research on clays and clay minerals. In Japan, the major reports include those on the identification of kaolin minerals in the presence of chlorite (Kodama and Oinuma, 1963), interstratified minerals (Oinuma and Hayashi, 1965), and chlorites (Hayashi and Oinuma, 1965, 1967).

1.I .6. Optical studies Marshall (1930, 1935) developed a technique for measuring the mean refrac-

STUDIES ON CLAYS AND CLAY MINERALS

7

tive index and electronic birefringence of fine mineral particles. Shioiri and Fukuzawa (1951), using Marshall’s method, obtained optical data for certain soil clay minerals in Japan. They pointed out the wide difference in optical properties between the fine particles in “silicic soils” composed largely of montmorillonite and those in “aluminous soils” composed largely of halloysite (7A). 1.I .7. Thin section studies

In soil micromorphology, it is important to examine the microtexture of soils by observing thin sections under a polarizing microscope. Kubiena (1938) established a system for this purpose. Numerous reports have subsequently been published on the methodology for preparing thin sections of clays and soils. Matsui (1966) pointed out that an improved procedure based on the method proposed by Altemuller (1962) was satisfactory, and using this method, he successfully performed micromorphological studies on the “heavy soils” (pseudogley) of Hokkaido. The unsaturated polyester resin “Polylite J 8157” is diluted with an almost equal volume of monostyrol, and small amounts of methylethylketone peroxide and cobalt naphthate, a catalyst for polymerization, are added. The resultant solution is impregnated into soil specimens under near vacuum conditions. About 10-15 hr for “heavy soils” and 2-3 hr for “light soils” is required for the resin solution to penetrate into the specimens. After cessation of bubbling, the suspensions are allowed to stand at room temperature for a few days. They are then dried in an oven at a temperature below 40°C,and cooled in room air for 1-2 days to ensure complete consolidation. 1.I .8. Electrokinetic studies

Watanabe (1966) carried out research on the electrophoresis of certain clay minerals such as kaolinite, halloysite (7A) (a sample of “Hong Kong kaolin”), montmorillonite, mica, and allophane, and the data obtained were subejcted to statistical treatment. He pointed out that allophane saturated with sodium ions shows an isoelectric point at about pH 6.7. Above this value, the particles move towards the anode, and below it, they move in the reverse direction. Based on the statistical results, he concluded that the speed of allophane particles is more variable than that of other clay minerals, and suggested that allophane particles are non-uniform in terms of their particle size and zeta-potential. 1.I .9. N M R (nuclear magnetic resonance)

The magnetism of matter originates from two sources: electrons and the atomic nucleus. When an atomic nucleus is placed in a magnetic field, it absorbs energy from or discharges energy to the external electromagnetic field. This represents the basis of nuclear magnetic resonance (NMR). Kitagawa (1972) studied the NMR of adsorbed water and hydroxyl groups of minerals such as allophane, kaolinite, halloysite (10 A), and montmorillonite, and found a distinct

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difference in energy levels between the adsorbed water and hydroxyl groups in kaolinite, halloysite and montmorillonite. However, such a distinction was difficult with allophane. 1.1.10. Mossbauer eflect

Mossbauer (1958) discovered a phenomenon in which y-rays are scattered from an atomic nucleus without recoil, and are adsorbed by resonance into atomic nucleii of the same kind. This is known as the Mossbauer effect. The behavior of scattering without recoil produces absorption spectra. Two parameters indicate the position and resolution of the absorption spectra. These are the isomer shift (I.S.) and quadrupole splitting (Q.S.).They vary with the following factors : the degree of oxidation, electron configuration, coordination number, and site symmetry of the ions in the crystal structure. The Fe3+/Fe2+ratio can be obtained from the area of the absorption bands. Kohyama, Shimoda and Sudo (1973), with assistance from H. Sano, Ochanomizu University, studied the Mossbauer effect in the clay occurring as an alteration product of volcanic rock fragments in Oya-ishi. This material is composed of iron-rich saponite and ironbearing montmorillonite, and is easily oxidized when exposed to daylight. There was no marked difference in I.S. and Q.S. of Fe3+between the unoxidized and oxidizedparts. The Q.S.value of Fez+decreased with increasing degree of oxidation, suggesting that the site symmetry or structural environment of the iron ions is more symmetrical in the oxidized than in the unoxidized state (p. 46). 1 J.11. EPMA (electron probe microanalyzer)

Recently, EPMA has been developed for use in the study of clays and clay minerals. Kohyama, Shimoda and Sudo (1973) performed step-scanning analysis and quantitative analysis of the clay from Oya mentioned above. This clay gives the X-ray powder diffraction pattern of montmorillonite minerals. Under the microscope, it exhibits a vesicular texture, and the vesicules are entirely altered to clay minerals. There is a slightly difference in microscopic appearance between the marginal and core parts of each vesicule. By EPMA, Kohyama et al. clarified that the marginal part is composed of iron-bearing montmorillonite and the core part of iron-saponite (p.46). Tazaki and Tazaki (1975) analyzed a weathered product of biotite using EPMA. This material has a vermicular shape and is found in weathered pumice layers and pyroclastic flows intercalated in the Daisen Loam. 1 ts color ranges from ivory-white to brown as a whole, but on ~10s:: examination, each vermicule can been seen to consist of white and brown bands which usually exhibit rather irregularly mixed layering. Using EPMA, with the aid of X-ray and thermal analysis, they concluded that the vermicules are composed of minerals such as hydrobiotite, kaolinite, gibbsite, and probably Alinterlayer vermiculite. 1.1.12. Surnpje preparation

The methods of sample preparation of clays and clay minerals in Japan in-

STUDIES ON CLAYS AND CLAY MINERALS

9

volve the usual sieving, dispersion, sedimentation, etc. However, on detailed points such as the kind and concentration of dispersing reagents, there are some slight differences among workers in different fields. In many reports published in Japan, the fraction of less than 2 P is defined as the clay fraction, and the dispersing reagents used often include ammonia, sodium hydroxide, sodium silicate, “Calgon,” etc. Routine procedures have been proposed in some fields such as agriculture and soil engineering. As is well known, it is extremely difficult to separate the clay fraction into finer fractions each composed of one kind of clay mineral in the purest possible state. In order to circumvent this problem, a general procedure has been developed which serves to differentiate and identify each clay mineral constituent in complicated clay mineral mixtures without separation. Concerning the preparation of the clay fraction, it should be remembered that the clay minerals are in general very sensitive to chemical treatment. In the course of sample preparation, various kinds of reagents may be used to induce dispersion of the clay particles or to remove iron oxides, hydroxides, organic matter, etc. There is always the possibility that the chemicals may modify the properties of the original clay minerals themselves. Careful examination of such effects on test samples is thus important. Particular attention has been paid in Japan to sample preparation from volcanic ash soils which, in some instances, disperse well under acidic conditions, in contrast to the usual clays which tend to disperse well under alkaline conditions. Kanno (1954) has established an analytical method as described next. Abundant organic matter is commonly present in volcanic ash soils. i t is thus usually necessary to employ considerable amounts of hydrogen peroxide to remove such organic matter, and so to determine the amount of iron and aluminum in the filtrate obtained after treatment with hydrogen peroxide, since small amounts of R203 (of the order of 2-4%) tend to be dissolved by the oxalic acid formed during digestion of the sample in hydrogen peroxide. The powder obtained after treatment with hydrogen peroxide is dried in room air. A small fraction is digested in 0.002 N HC1 or 0.008 N NaOH, and its dispersingability in each case is examined. if there is better dispersion in HCl than NaOH, the following procedure is adopted. About 10 g powder is digested in 10 ml of 1 N HCI, to which water is added to make the volume up to 100 ml. The mud so obtained is allowed to stand for about 1 hr, with occasional stirring, and then successively filtered with a collodion membrane. The Si02 and AI2Q in the filtrate are determined, and the amounts are added to the wt % of the clay fraction obtained at the final stage of analysis. The powder on the filter membrane is passed through a 0.2 mm sieve, and the residue on the sieve is dried and weighed. The finer fraction passing through the sieve is made up as a suspension in water (final volume, about 200 nil), to which 2 ml of 1 N MC1 is added. The mud so obtained is transferred completely to a shaker and shaken for several hours. The contents are then transferred to a I-liter sedimenting cylinder and the volume is made up to about 500 ml with water. The resultant :uspension is

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10

shaken with an electric shaker for about 10 min, and the suspended particles are analyzed in the usual way. 1.1.13. Identification and quantitative estimation of the clay minerals in clays Clays usually consist of several different kinds of clay minerals intimately mixed with one another. In all studies of clays and clay minerals, it is of course necessary to identify the nature and determine the amounts of each constituent clay mineral. However, separation of the clay into its clay mineral constituents by mechanical means is extremely difficult. Moreover, particularly in fields such as geology, soil science and engineering, it is generally necessary to survey numerous clay samples. The method used should thus satisfy the following basic condition: to be able to identify the properties and determine the amounts of each clay mineral in the individual clay sample in detail and as rapidly as possible. In other words, it should provide basically accurate data which can be utilized for routine work. A number of suitable quantitative methods have been proposed, such as by Hathaway and Carroll (1954), Johns, Grim and Bradley (1954), Schultz (1960), etc. In Japan, from about 1950, Oinuma and Kobayashi and their collaborators have compiled and developed a general scheme for the identification of the clay minerals in clays (Table 1.1), and have proposed a new method for estimating the relative proportions (Sudo, Oinuma and Kobayashi, 1961; Oinuma and Kobayashi, 1966). The procedure for rapid quantitative analysis is described next. A calibration curve is made with a mixture of clay minerals A and B and calcite powder (less than 5 The intensity of a particular peak in each of the minerals ( I Aand Is) is determined with reference to the intensity of the 3 peak of calcite, which is admixed in specific proportions in the test samples. In most cases, the calibration curve gives a near-linear relation. Assuming linearity, the weight ratio of the minerals A and B is obtained as (IA/iA):(IB/iB),where iA:iB is the intensity ratio of A and B when existing in equal amounts. From the calibration curves of mixtures of various pairs of clay minerals taken as standards, the intensity ratio of the basal reflections of selected standard clay minerals can be summarized as

e).

: '(10L-Mo') : '(144-CU : z(104-Mi): z ( 7 i - K ) 2.6:0.9:0.5:1.0:1.2 . . . Slit system 1"- lo-0.4 mm 3.6:0.9:0.7:1.0:1.0 . . . Slit system 1/6"-1/6"-0.4mm, where (15 A-Mo) = 15 A peak of montmorillonite, (10 A-Mot) = 10 A peak of dehydrated montrnorillonite, (14 A-Ch) = 14 A peak of chlorite, (10 A-Mi) = 108,peak of mica, and (7 A-K) = 7 A peak of kaolinite. The weight ratio of these minerals can then be expressed as '(15hfO)

I(Mi) L(&!l. I(Mo') _ . _ _ .I(Ch) -. -. i(Mo)

*

i(Mo')

*

i(Ch)

*

i(Mi)

I(K) __ *

i(K)

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11

TABLE 1.1. Procedures for the identification of clay minerals (Oinuma and Kobayashi, 1966)

XRA (Mo,Mi,Ch,V,K) -Higher resolution scans of 24-26”(28) . .XRAl) K,Ch -Heated to 150, 300, 450,600 and 750°C ... .XRA Mo,Mi,Ch,V,H -Treated with ethylene glycol or Mo,H,(Ch,Mi) glycerol ......XRA Ch,K -Treated with HCI ................... .XRAz) -Treated with ammonium nitrate solution. ......... .XRA3) V Clay fraction --Treated with sodium citrate, calcium AI-V chloride and glycerol ... XRA4) DTA K,(Ch,Mo,Mi,V) Mo -Treated with piperidine ..............DTAS) Infrared spectral analysis6) K Electron micrographic observations (K) Chemical analysis Staining test?) Mo Cation exchange capacity (Mo,V)

The amount of each test sample is fixed at 0.04 g in total. The sample is placed on a slide glass and an appropriate amount of water is added to give a mud. This is gently spread over an area, 2.0 x 2.7 cm, with a matchstick, and allowed to stand in room air without disturbance. A thin clay film is then formed on the slide glass by drying. This technique is tentatively called the “natural setting method.” The addition of excess water tends to create aggregates, and these are difficult to develop into a uniform state. The alternative procedure of adding water drop-wise and stirring gently with a matchstick is usually effective for avoiding bubble formation. If bubbles are formed, they may be removed by suction in a vacuum. If difficulty is encountered in obtaining a uniform state in the clay mud, tapping lightly is often effective. Generally speaking, it is difficult to get a perfect orientation of the clay mineral flakes. Rubbing a paste strongly between two glass slides is effective in obtaining a well-oriented state, but this method gives poor reproducibility as regards uniformity of thickness. The above technique of natural setting, although not giving a perfect orientation, is thus recommended due to its good reproducibility for obtaining a uniform state.

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1.I . 14. Kinetics

Recently, Tsuzuki and his collaborators have extended their studies on hydrothermal alteration on the basis of laboratory experiments and chemical kinetics carried out on the side of an open system. The work concerns chemical reactions involving material transfer and complicated kinetic processes controlled not only by the reaction temperature but also by chemical compositional changes in the reacting solution. The process of rock alteration caused by a solution in an open system can be described in general terms as follows. The solution at a given locality reacts with thecoexistent rock. With timelapse, thecompositions of both the rock and the solution change. The solution with modified chemical composition also migrates successively to adjacent areas where it again reacts with the local rock (Tsuzuki and Mizutani, 1971). Tsuzuki, Mizutani, Shimizu and Hayashi (1974) treated potassium-feldspar with acidic solutions containing H and K at various concentrations in a silica glass tube at 210-270°C. The results were analyzed kinetically assuming A1 to be inert and silica to be mobile. The results suggest a process in which once-dissolved silica is later precipitated, when it remains after kaolinite formation. The process is able to explain many examples of rock alteration in nature. Kajiwara (1973), using the thermochemical data of Helgeson (1969), has extended the studies towards predicting possible assemblages of stable minerals in marine sediments. Concerning clay minerals, he suggested that Mg-montmorillonite, Mg-chlorite and probably talc, may be stable dependent on the activity of silica and alumina. The following concepts were developed. (1) The essentially uniform chemical state throughout the oceans as regards pH and concentrations of major cations presents certain limitations to the stable mineral assemblages. (2) The sea water is approximately in chemical equilibrium with, and thus buffered by the marine sediments due to the occurrence of rapid cation-exchange reactions. Kajiwara also suggested that the hydrothermal ore-forming solutions responsible for the so-called Kuroko type of mineralization (p. 23) may have derived essentially from cyclic coeval sea water. On the basis of the above assumptions, Kajiwara predicted the occurrence of stable mineral assemblages in the hydrothermal system of the earth’s crust under conditions where the sea water and rock-forming minerals have interacted at elevated temperature. 1.1.15. Synthesis

Studies on the synthesis of clay minerals from inorganic gels or various parent minerals under hydrothermal conditions were begun in about 1935, such as by No11 (1935) and Ewe11 and Insley (1935). Numerous reports have been published since that time. In Japan, Otsubo and Kato (1954) synthesized montmorillonite and Zn-montmorillonite using silica, alumina and magnesia gels, and zinc hydroxide as starting materials. Koizumi and Roy (1959) synthesized montmorillonites with different cation-exchange abilities employing a starting material

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consisting of gels with the chemical composition of beidellite or saponite. Iiyama and Roy (1963) synthesized an interstratified mineral (“illite-saponite”) from inorganic gels. Ueda and Sudo (1966) studied a new and interesting method for the synthesis of interstratifications of mica and expandable minerals. These authors treated micas such as fine-grained white micas and coarse-grained muscovite or phlogopite flakes, with chemicals such as aluminum sulfate and magnesium carbonate under hydrothermal conditions. They found that the micas could be converted to interstratifications which, dependent on the experimental conditions, were variable as regards the nature of their expandable mineral layers and regularity of the layer stacking, from completely regular to more or less random. They also reported that when potassium alum was used in addition to the above chemicals, a completely regular type of mineral closely resembling natural material could be produced. It is of interest to note that as the formation of these interstratifications proceeded, so the crystallization of alunite occurred in the residual liquid. Tomita and Sudo (1968) reported another interesting synthesis of interstratifications from micas. They found that micas such as fine-grained white micas and fine powders of coarse-grained muscovite flakes could be converted readily to interstratifications of mica and expandable mineral layers when the micas were heated to temperatures sufficiently high as to cause dehydroxylation, and then successivelydigested in warm HCI. The products obtained were diverse in terms of the nature of their expandable mineral layers and regularity of the layer stacking, from completely regular to more or less random. When the regular product was further digested in magnesium chloride solution, it approached closer to a natural regular interstratification in its overall properties. Tomita and his collaborators have extended such studies and reported that similar results were obtained when the micas were treated in a molten lithium salt (Tomita and Sudo, 1971), or when they were dehydroxylated and then digested in NaTPB (sodium tetraphenylboron) (Tomita and Dozono, 1972). These authors suggested that the process of formation of the interstratifications in their experiments, and also those in the experiments of Ueda and Sudo, may indicate an electric polar hypothesis for the origin of the interstratifications (see section 1.3.18). Recently, Nagasawa, Brown and Newman (1974) have carried out detailed research on the products obtained after boiling biotite flakes in 0.2 M AlCL solution. The product exhibited a 14 A spacing which was unchanged after K-saturation or ethylene glycol treatment, but gradually collapsed on heating. After removal of the interlayer material with sodium acetate, K-saturation caused a collapse to 10 A. In this respect, the product is close to the weathering product of biotite reported by Kato (1965) as trioctahedral Al-interlayer vermiculite. The structure type is two-layer monoclinic with a P-angle of 97”, and the stacking sequence is an alternation of Ia-4 and Ia-6 chlorites (notation follows that reported by Bailey and Brown, 1962). In this respect, the product accords

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with natural macroscopic vermiculite. The interlayer material is composed of A1 associated with H 2 0 and (OH), and is therefore intermediate between the interlayer materials of vermiculite and chlorite. 1.1.16 High temperature phases of Kaolin minerals

Kaolin clays represent one of the most important raw materials in the high temperature inorganic industries. The nature of the high temperature phases of kaolin minerals is thus of great importance, and numerous studies have been carried out in this field due to the complexity of the problem and the frequent lack of any broad consensus of opinion. Brindley and Nakahira (1958b) reported that the y-aIumina phase is really composed of silica and alumina in the form of a spinel structure, i.e. a silicaalumina spinel. Brindley and Nakahira (1959) on the basis of the new concept, accounted for the mullite formation occurring at 140OOC as a process in which silica-alumina spinel decomposes to mullite of the aluminum-rich type and the resultant excess silica crystallizes out as cristobalite. Tsuzuki and Nagasawa (1969) carried out detailed studies on the high temperature phases occurring in the 900-1000" C region. They concluded that several forerunning reactions, such as thermal expansion, increase in alumina with the tetrahedral coordination, and development of electron diffraction spots, took place before the peak temperature of the last exothermic peak was reached. Iwai, Tagai and Shimamune (1971) performed a crystal structure analysis of heated dickite and showed its dehydroxylated state on an electron density map. The inner (OH) tends to be dehydroxylated after the outer (OH).

I .I .17. Grinding efsects In 1953, Mackenzie and Milne (1953) gave data on the grinding effects of muscovite, biotite and vermiculite. Takahashi (1 959) also performed extensive studies on the grinding effects of minerals such as quartz, kaolinite, halloysite, (10 A), montmorillonite, mica, talc, and pyrophyllite. He followed in detail the changes in properties of these minerals with increasing grinding time, up to 200-500 hr. The findings may be summarized as follows. (1) The particle sizes gradually decreased, and the structures gradually disintegrated. (2) After grinding for 200-500 hr, the particles were finally transformed into completely spherical particles of uniform diameter, although the latter of course depended on the actual time of grinding and the kind of clay mineral used. (3) The amount of adsorptive water, and the solubility in acids or alkalies tended to increase on grinding. (4) The cation-exchange capacity also tended to increase, but approached a maximum after 50-100 hr, beyond which it either decreased (halloysite and kaolinite) or remained virtually unchanged (other minerals). 1.1.18. Clay-water systems

In the field of ceramics, soil engineering and agriculture, too many reports

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15

concerning clay-water systems exist for any simple synthesis to be made here. However, particular attention should be given to the extensive work of Y. Shiraki which has been widely reported in the literature. Also, the excellent studies of Okuda and Williamson (1964) in the field of ceramics, and of Kuwabara (1970) in the field of soil engineering, should be consulted. All these studies gave specific emphasis to clays and clay minerals. 1.1.19. Clay-organic complexes

Historically, the study of clay-organic complexes has formed one major aspect of clay research, not only in the basic but also in the applied sciences. The number of reports has continued to increase internationally, due partly to the greater diversity of research and partly to the finding of more organic materials capable of forming complexes with clays. In fact, the range of studies now encompasses such divergent topics as the origin of life on the one hand, and water pollution on the other. In the broad sense, clay-organic complexes can be divided into two types : interlayer complexes and peripheral complexes. The former, which are usually observed in expandable clay minerals such as montmorillonite and vermiculite minerals, possess some surprising properties. That is to say, these clay minerals instantaneously form crystals with certain organic molecules at room temperature.and pressure, which may be regarded as hybrid crystals of the inorganic and organic materials. The peripheral complexes may be represented by a schematic model in which the organic materials form bridges among the clay particles. Studies on clay-organic complexes are thus particularly significant in the soil sciences where it is necessary to elucidate the characteristics of associations of organic materials and soil particles. The properties of clay-organic complexes are usually quite different from those of the component clays themselves, so that their use in the chemical industry, soil engineering and agriculture has expanded, as illustrated by the creation of improved or stabilized soils and the product from bentonite known as “Bentone” (Hauser, 1950). The clay-organic complexes reported until recently were all products of reactions between an organic material and clay minerals which have been termed expandable clay minerals. However, since around 1960, it has been known that kaolin minerals, which are regarded as non-expandable clay minerals, also produce clay-organic complexes with organic materials such as urea (Weiss, 1961) formaldehyde or hydrazine (Weiss, Thielepape, Goring, Ritter, and Schafer, 1963). In Japan, one of the foremost problems concerning clay-organic complexes which has been studied is the particular tendency for organic materials (humus) to accumulate in volcanic ash soils. In recent research on fine structures using high resolution electron microscopy, Suito, Arakawa and Yoshida (1969) have observed clear lattice images with organo-montmorillonite flakes (octadodecylammonium complex, etc). Concerning industrial products, “Orben” has been developed by the Shiraishi Industrial Co. by treating montmorillonite with

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16

stea ric acid amide (a non-ionic polar compound) and trimethyloctadecylammonium chloride (Hasegawa, 1958). 1.1.20.

Intersalation

In the period 1956-59, it was noticed that various salts are specifically adsorbed within the interlayer region of halloysite (Weiss, 1956; Wada, 1958, 1959). Wada (1958) found that salts such as cesium chloride, rubidium chloride, and ammonium chloride were adsorbed as monomolecular layers within the interlayer region. In 1961, Wada (1961) discovered that kaolinite can form a complex with potassium acetate, and he later extended these studies further (Wada, 1963, 1965). The experiment was performed by grinding potassium acetate with kaolinite on an agate mortar for about 15-30 min and then allowing the ground material to stand for about 24 hr. Potassium acetate was adsorbed by the repetitive interlayer region as a well-oriented monomolecular layer, resulting in expansion the height of the unit structure from 7 to 14 A. It is surprising that the kaolinite and potassium acetate form crystals instantaneously at room temperature and pressure. When the complex is heated at about IOO’C, the 14 A spacing contracts to about 11.4 A due to the removal of water molecules from the potassium acetate (Fig. 1.2). When the complex is washed with water and then air-dried, the salt layer readily dissolvesin the water causing a contraction of the spacing from 14 to 7 A. Similar complexes are formed with dickite, nacrite, and halloysite (7 A). However, the effects of drying and wetting are not necessarily identical among all these kaolin minerals. Wetting of the halloysite (7 A) complex results in the formation of a 10A spacingcorresponding to that of halIoysite(l0A). The effect of wetting of the nacrite complex is apparently rather complex. The term “intercalation” has been used for phenomena in which there is intrusion of various kinds of materials into the interlayer region of clay minerals. For the purpose of emphasizing this particular process in the case of the for-

f

2.8A

Fig. 1.2. Crystal structural model of the kaolinite-potassium acetate complex (Wada, 1961).

STUDIES ON CLAYS AND CLAY MINERALS

17

mation of salt-clay complexes, the term “intersalation” has been proposed (Andrew, Jackson and Wada, 1960). To date, no data have been reported which indicate that serpentine minerals undergo intersalation.

1.1.21.

Clay catalysts

As stated in section 1.1.1, Kobayashi and his collaborators stressed the importance of the catalytic ability of acid clays, and demonstrated its effectiveness in various organic reactions such as the cracking distillation of fish oils, etc. He also proposed a concept for the origin of petroleum. Recently, Shimoyama and Johns (1971) and Johns and Shimoyama (1972) have discussed the role of clay minerals in the formation of petroleum on the basis of various natural facts and laboratory experiments. It is widely recognized that montmorillonite is gradually transformed into mica in thick strata at increasing burial depth as a result of diagenesis. During the transformation process, the montmorillonite dehydrates and the residual water on the clay surface probably becomes more acidic (Fripiat, Jelli, et al. 1965). On the basis of laboratory experiments, the above authors (Johns and Shimoyama) demonstrated the transformation of fatty acids associated with montmorillonite into n-paraffins through the decarboxylation and cracking of hydrocarbons at 200-300” C . They proposed a mechanism in which the decarboxylation was promoted by Fe, Al, and Mg exposed on the broken edges of the crystallites (which was effective as a Lewis acid) and the cracking of hydrocarbons was promoted by the acidity derived from dehydrated montmorillonite (which acted as a Lowry-Brmsted acid). 1.1.22.

Clay industry

The clay industry is widely developed in Japan, and makes full use of the many important and unique properties of the local clays and clay minerals. The principal uses of the kaolinite and its clay are (1) as raw materials for pottery and refractory products, (2) as fillers or coating materials for paper, and (3) as diluents for rubbers and paints. The pyrophyllite has been used (1) as a raw material for crucibles, refractory bricks and mortar, (2) as a filler and coating material for paper, (3) as a diluent or carrier of pesticides, (4) as a diluent or reinforcing filler for rubber, ( 5 ) as a diluent for paints, cosmetics and chemicals, and (6) as a filling or stiffening agent for various fabrics. The micas, particularly the fine-grained white micas (“sericite”) in Japan, have been used (1) as raw materials for ceramics, (2) as a flux for iron-welding rods, (3) as fillers for synthetic resins and paper, and (4) as admixtures to paints. The bentonite and acid clays are utilized for many purposes. Also, when the latter and their related clays are treated with acids, the useful properties of the clays are particularly improved to give so-called activated clays. Acid clays and activated clays have been used as decolorizing materials, catalysts, adsorbents and desiccants, and in the best cases, as diluents, fillers, admixtures and carriers of various kinds of materials. The principal uses of bentonite are (1) as

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a foundry sand-caking agent, (2) as a pelletizing caking agent, (3) as a component of drilling mud, (4) as a soil improvement agent, and ( 5 ) as a diluent, additive, filler, and carrier of various kinds of materials such as ceramics, medicines, paper, paint, fertilizer, etc. Okino (1967) has performed extensive studies on drilling mud with particular emphasis on its clay mineralogy. Various kinds of by-products are obtained in the process of activation of clays, such as aluminum sulfate, gypsum, silicaalumina gel, and silica-gel (Kuwata, 1957). Both vermiculite and hydrobiotite are utilized after they have been ignited and made to swell. Their properties and light weight are especially conducive to constructional uses such as in heat insulation bricks. The property of fixing ammonia also makes these materials useful in agriculture. Their application for the disposal of radioactive wastes appears promising. Talc has been used in china-ware, paper-clay, as an insectiside carrier, and as an additive for cosmetics and medicines. Serpentine is utilized as a raw material in the preparation of soluble magnesian fertilizers. These are made by crushing and mixing with phosphorus ores, calcinating and fusing at 1400-1 500" C, quenching in water, and finally grinding. Since the soil in Japan is usually relatively acidic, the use of calcium superphosphate fertilizcrs often results in the accumulation of sulfuric acid in the soil. It is then necessary to apply a complete non-sulfuric acid fertilizer in order to build up an adequate phosphorus content and to replenish the magnesia which tends to be washed out by the abundant rainfull. Ishikawa and Tanaka (1959) have performed extensive research on the use of allophane in the petroleum industry. 1.I .23.

Environmental studies

The role of clays in landslides and instances of weak ground has been discussed since ancient times. In Japan, such events tend to be prevalent due to the widespread occurrence of clayey rocks. Throughout geological time, active volcanism has frequently occurred and has produced abundant deposits of glassy tuff, tuffaceous sediments and volcanic ash. Hydrothermal solutions and hot springs resulting from post-volcanic activity have altered these various kinds of rocks to clays. Further, the generally rapid flow of the rivers due to the steep geomorphology, and the active circulation of ground water resulting from the extensive rock fissuring, have favored heavy weathering. Landslide clays, which are found along the slip planes in landslide regions, are diverse depending on the kind of wall rocks. Montmorillonite minerals are usually prevalent in regions of glassy tuffs and tuffaceous sedimentary rocks. The landslide clays in regions of crystalline schists or serpentine rocks are usually composed of such minerals as chlorite, mica, and members of the serpentine group. A considerable number of studies has been made on landslides and weak

STUDIES ON CLAYS A N D CLAY MINERALS

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ground from the viewpoint of the clay mineral assemblages and soil engineering properties of the deposits (e.g. Morimoto, Nakamura, Tsuneshi, Ossaka and Tsunoda, 1967). The name “heavy” clays and soils has been used for certain very disadvantageous clays and soils encountered in land cultivation and road repairs. In general, the materials are dense, have low porosity, and display high plasticity, viscosity, exchange acidity, hydrolytic acidity and/or water content. Mori and Sasaki (1956) have shown that the heavy soil distributed in the Komukai district, Hokkaido, is composed largely of halloysite (10 A) with subordinate amounts of allophane and quartz. Numerous reports have been published in the international literature on the role of clays in soil stabilization. The so-called soil-limeengineering method is one of the main topics. In Japan, the volcanic ash soils are composed largely of halloysite and allophane, and so tend to form weak ground. Ariizumi (1967) has performed fundamental studies on the stabilization of such volcanic ash soils using the soil-lime method. He pointed out that allophane and halloysite (10 A) react with slaked lime to give 2Ca0-Al20,.SiO,.nH,O. They also reported that when gypsum is added with the lime, ettringite (3CaO-A1,O3-3CaS0,. 32H20) is formed, resulting in rapid consolidation. Hayashi of the National Institute for Industrial Health has carried extensive mineralogical studies on dangerous airborne dusts in collaboration with his colleagues at the Institute (Sakabe as leader). Their work has particularly involved the hemolysis and cytotoxity of quartz and asbestos (silicosis and asbestosis). Hayashi (1973) developed an analytical procedure for the quantitative determination of airborne asbestos. This procedure is based on a standard curve prepared by X-analysis of standard samples using high power X-rays. Small amounts of the order of 0.01 mg on a slide glass fiber filter 3.8 cm2 in area, can be detected. 1.1.24.

Societies and publications

The Clay Research Group of Japan (CRGJ) was established in 1958. It produced three kinds of publications : Nendo-Kagaku, (Journal of the Clay Science Society of Japan), Clay Science, and Advance of Clay Science. Nendo-Kagaku was published in Japanese and included review articles, news, and some original articles (with English summaries). Clay Science set out to be an international journal giving original articles principally in English. Advance of Clay Science included the proceedings of the annual general meetings giving the papers read at the meetings in Japanese, together with English summaries. The publication of Advance of Clay Science was discontinued in 1966. In 1964, the Group was reorganized as a Society-the Clay Science Society of Japan (CSSJ), which continues to publish both Nendo-Kagaku and Clay Science.

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1.2. MODES OF OCCURRENCE, MINERAL ASSEMBLAGES AND ORIGINS

The clays and clay minerals of Japan display various modes of occurrence such as in soils, zone of weathering, recent sediments, sedimentary rocks, and hydrothermally altered rocks. Their origin involves weathering, diagenesis, hydrothermal alteration, and combinations of these processes. Crustal movements accompanying igneous activity have frequently occurred in the Japanese Islands from the Paleozoic to the Recent. As a result, clays and clay minerals formed by the hydrothermal alteration ofvarious kinds of rocks, and by the weathering of volcanic glass in rocks or soils, are particularly widespread in Japan. Concerning the clays and clay minerals in Japan, particular attention has been paid to their complicated variability in terms of modes of occurrence, assemblage, areal distribution and origin. This variability results from complicated environmental conditions illustrated in the general sense as follows:(1) original rocks are found to be variable on the small scale, e.g. sedimentary rocks consisting of tuffs, and tuffaceous sediments frequently intercalated by abundant volcanic rock sheets, and (2) such complex rocks have been altered by chemical and physical processes due to a combination of diagenesis, hydrothermal mineralization, and recent volcanic activity. It is necessary first to explain several descriptive terms such as “Green Tuff ”, “Roseki”, “Kuroko”, “Toseki”, “Gaerome clay” and “Kibushi clay”, which appear frequently in the literature on the clays and clay minerals of Japan. These names are applied to particular kinds of ore deposits (Kuroko), rocks (Green Tuff and Toseki), and clays (Roseki, Kibushi and Gaerome). Among them, the Kibushi and Gaerome are described in detail in Chapter 5. Recent advances in the study of the mineralogical and geological properties of the above rocks and clays have revealed that they are very complex and diverse in terms of their clay mineral assemblages, involving various types of interstratifications and unusual (abnormal) species. Indeed, they may be considered the “treasure houses” of clays and clay minerals in Japan, both economically and mineralogically. 1.2.1.

Green tuff

Volcanic activity was particularly violent in the Miocene in Japan, when various volcanic rocks such as basalt, andesite, rhyolite and related pyroclastic rocks such as tuffs and tuff breccias, were formed. These volcanic rocks occur as dykes, sheets and flows. Virtually all of the rocks have assumed a green color due to alteration to green-colored clay minerals. The andesite and basalt are frequently found as propylite or spilitic rocks, respectively. The green-colored rocks are known conventionally as Green Tuff, and they occur as thick beds in strata of the Miocene epoch. The clay minerals in the Green Tuff are usually very complex in terms of their properties, modes of occurrence, mineral assemblages, and origin. They are found as filling materials of amygdales, cavities and fissures, as replacement minerals of phenocrysts of mafic and felsic minerals,

OCCURRENCE, ASSEMBLAGES A N D ORIGINS

21

and as replacement materials of rock groundmass with a glassy texture. Interstratified clay minerals and unusual (abnormal) species are widespread. The clay mineral assemblages are often heterogeneous in samples collected from a small area and, in some instances, even within a single small hand specimen. The process of origin of these minerals is not necessarily local hydrothermal alteration, and is thought to involve local to regional hydrothermal alteration, sedimentation processes, diagenesis, and combinations of these processes. The earlier studies on the “lembergite” (iron-saponite) occurring in Tertiary (Miocene) iron sand beds (Sudo, 1943) (p. 38) and on the iron-rich montmorillonite minerals occurring in Oya-ishi (thick rhyolitic tuffs) (Sudo and Ota, 1952), which is a typical Green Tuff member, have been extended and refined (Sudo, 1954a; Kohyama, Shimoda and Sudo, 1973) (p. 42). These studies are still pertinent to the modern mineralogical work on the Green Tuff. Recently, the importance of carrying out detailed petrological, geological and stratigraphical work on the Green Tuff, in addition to the mineralogical studies, has been felt. Clearly also, work on the precise clay mineralogy of the deposits is essential for understanding the process of origin of the Green Tuff. Work of this nature has begun actively in recent years. Yoshimura (1964) undertook modern studies on the claymineralogy of the Green Tuff including the associated zeolites. Kimbara (1973) investigated in detail the assemblage of clay minerals and zeolites in the Green Tuff occurring in the eastern part of the Tanzawa Mountains, Kanagawa Prefecture. The rocks are composed largely of basalt and its related pyroclastics and occur as thick strata (about 10,000 m in total thickness) surrounding a quartz diorite intruded into the central part of the Mountains. On the basis of its mineral assemblages, the Green Tuff can be subdivided into several metamorphic zones, due to the contact effects of the granodiorite and to diagenetic changes with increasing burial depth. Kimbara considered that the diagenetic changes were dominant in this district, rather than the contact effects of the granodiorite. He summarized the change in clay minerals with increasing (iron-saponite and chlorite)-+ burial depth as follows : (iron saponite)+ (iron-saponite)(magnesian regular or almost regular interstratifications of chlorite and expandable mineral, associated with monomineralic crystals of chlorite)--+ (chlorite) (Fig. 1.3). The interstratifications occur in association with laumontite in the upper horizons, and with prehnite and pumpellyite in the lower ones. There are also some differences in mineralogy, such as in the interstratifications, iron-saponite and chlorite, between the upper and lower horizons, especially as regards DTA curves. The samples referred to here as iron-saponite show an X-ray peak represented by 15 and 1.53 A spacings. However, the samples occurring in the upper horizons are close to montmorillonite (dioctahedral) in respect to their DTA curves: the peak system consists of an endothermic peak between 100-200°C, a broad endothermic peak at about 500°C, a small endothermic peak at about 700°C, and an S-shaped peak.

22

OUTLINE Depth (m)

6000

I

I

5000 1

8

4000 1

I

' 3000

1000

2000

1

I

1

0 I

Heulandite. stilbite

____

c] Analcime Laumontite

j

Prehnite, pumpellyite Montmorillonite

1-1

1Chlorite

Iron-rich saponite (/Mixed-layer

(Il bp=97')

1

IChlorite(1 bp=9O')l

1

0 1 minerals

0

(Hayato ForFig. 1.3. Change in mineral assemblage with increasing burial depth in the Green Tuff mation, Tanzawa Mountains, Kanagawa Prefecture) (Kimbara, 1973). The mixed-layer mineral is essentially ferromagnesian regular or almost regular interstratifications of chlorite and expandable minerals.

The samples occurring in the lower horizons have a peak system which resembles usual iron-saponite or nontronite and consists of an endothermic peak between 100-2OO0C, a broad endothermic peak at about 500"C, and a very broad Sshaped peak or broad exothermic peak in the 800-900°C region. The assignment of the DTA peaks of the iron-saponite has not been fully established: the endothermic peak at about 500°C may be due to a "chloritized effect", as suggested by Mackenzie (1957), or it may be a characteristic peak (p. 42). All the samples termed interstratifications here show X-ray peaks represented by 30 and 1.53 A spacings, and they contain considerable amounts of magnesium and iron. However, the samples occurring in the upper horizons associated with laumontite are generally iron-rich and have a DTA peak system composed of an endothermic peak between 1O0-20O0C, an endothermic peak at about 500"C, and a small exothermic peak in the 800-900°C region. This is close to the system of an iron-rich chlorite in respect to the region between 500-1O0O0C, or close to nontronite in respect to the overall peaks. The samples occurring in the lower horizons associated with prehnite and pumpellyite are relatively magnesium-rich and have a DTA peak system close to that of a magnesium chlorite in respect to the region between 500-1000°C. All the chlorite samples show X-ray peaks represented by 14 and 1.53 A spacings. However, their DTA peaks reveal that they are not free from expandable minerals since weak endothermic peaks occur between 100-200°C. X-ray peaks, which are discernible as due to chlorite in samples associated with iron-saponite and heulandite-stilbite, have disintegrated in the 450-600°C region. The DTA curves of samples having X-ray peaks

OCCURRENCE. ASSEMBLAGES AND ORIGINS

23

due to chlorite associated with interstratifications and laumontite are close to iron-chlorite in respect to their peak system between 500-1000" C: this consists of a sharp endothermic peak between 500-600°C and a weak exothermic peak between 800-900°C. They are iron-rich and mostly of Ib (P = 90") polytype. Samples having the X-ray peaks of chlorite associated with small amounts of interstratifications in the prehnite-pumpellyite zone exhibit a double endothermic peak between 500-600°C and an S-shaped peak between 800-900°C: the intensities are weak compared with magnesium chlorite. The samples are magnesium-rich and mostly of IIb (P = 97") polytype. The above data suggest that each sample is not necessarily monomineralic. It is therefore considered that some samples are composed of a principal clay mineral accompanied by small amounts of another clay mineral which exist as randomly oriented aggregates or as an incorporated body such as an interstratification. Mackenzie (1970) has suggested that "DTA is indeed extremely useful for checking the presence of these interlayers, which may be too few and too randomly interstratified to be detected by X-ray diffraction". However, the above data, in some instances, suggest that the variation in properties of some samples may be due to the unusual (abnormal) properties of some of the clay minerals themselves. Careful examination of X-ray intensities and spacings should also help to ascertain the cause of this variation. In any case, it is very interesting that the samples display variable properties which are correlated with burial depth. The possibility therefore arises that iron-saponite may in fact transform to chlorite through the interstratification, while the chlorite tends to become rich in magnesium with increasing burial depth. 1.2.2. Kzwoko

The submarine volcanic activity occurring in the Miocene gave rise to many metallic and non-metallic ore deposits. Of these, the so-called Kuroko (lit. blackcolored ore) is of great importance. It is composed largely of sphalerite and galena with subordinate amounts of chalcopyrite, pyrite, barite and gypsum. The Kuroko, in places, grades into yellow-colored ore which consists largely of chalcopyrite and pyrite with lesser amounts of sphalerite and galena, and in other places, it grades into siliceous ore composed of quartz with disseminated pyrite and chalcopyrite crystals. The Koroko deposits usually consist of stratiform parts and stockwork parts. The former are massive but generally show zoning of their constituent minerals, while the latter consist of disseminated and network mineralizations distributed in an irregular and funnel-shaped form in rhyolite and its pyroclastics. Those metallic ore deposits which are genetically the same as Koroko deposits but have extremely high proportions of stockwork ore, are usually termed Kuroko-type deposits. The Kuroko deposits are usually accompanied by gypsum ores, as stated above. However, several large gypsum deposits are also found in Japan which are genetically identical to the Kuroko deposits but have only a trace of sulfide

24

OUTLINE

mineralization in and around the ore bodies. These are usually termed Kurokotype gypsum deposits. Concerning the genesis of the Kuroko deposits, it is unanimously agreed among Japanese geologists that they are of submarine exhalative or volcanic-sedimentaryorigin. It is considered that the stockwork type mineralization was probably formed epigenetically from hydrothermal oreforming fluids, while the bedded mineralization occurred syngeneticallyat points where the ore fluids emanated from the submarine surface. As in the case of the Green Tuff, the clays, clay minerals and other alteration products associated with the Kuroko and Kuroko-type deposits are very complex in terms of their properties, modes of occurrence, mineral assemblages and origin. The latter undoubtedly involves sedimentation processes, hydrothermal alteration diagenesis, and combinations of these processes. Iwao, Kishimoto and Takahashi (1954) first performed mineralogical and geological studies on the wall rock alteration of the deposits in the Kosaka mine. Iwao (1956) also studied the wall rock alteration of the Wanibuchi Kurokotype gypsum deposit. Sudo and his collaborators noticed that the clay mineral assemblages of the clay zones enclosing certain stockwork deposits were very close to those of Roseki (see section 1.2.3), comprising chiefly pyrophyllite, kaolinite and diaspore (Sudo and Hayashi, 1955, 1956a, 1957; Sudo, Hayashi and Yokokura, 1958). The close resemblance between the clay mineral assemblages of the Roseki and some stockwork ores was further substantiated by other work. In 1954, a new type of regular interstratification of chlorite (di.-di.-sub-group) and montmorillonite-was discovered in the Kurata Roseki deposit (Sudo, Takahashi and Matsui, 1954) (p. 93). A very similar material was also found in the clay zone developed around a stockwork ore of the Honko ore body of the Kamikita Kuroko mine, Aomori Prefecture (Sudo and Kodama, 1956). The chlorite in these interstratifications is of the di.-tri.-sub-group (p. 93), although it was the sample collected by Hayashi (1961) from the clay zone enclosing the Honko ore body which provided the first evidence in Japan of a monomineralic crystal of dioctahedral chlorite (Hayashi and Oinuma, 1964). Dioctahedral chlorite has also been found in certain Roseki deposits (Henmi and Yamamoto, 1965). Recently, many other clay minerals including interstratified types have been identified in the Kuroko areas, and they will be discussed later in this Chapter and Chapter 8. The wall rock alteration of the Kuroko deposits is described in detail in Chapter 3. 1.2.3. Roseki

Hydrothermal pyrophyllite deposits have Iong been known in many parts of Japan, especially the Chugoku district. The pyrophyllite ore has been termed Roseki ((‘Ro” literally means wax) since it occurs as dense, compact masses having a waxy touch and luster. With the advance of mineralogical studies on Roseki, kaolinite and diaspore were found as accessory minerals in many samples,

OCCURRENCE, ASSEMBLAGES A N D ORIGINS

25

and also as principal constituents in some cases (Table 1.2). The name Roseki is thus currently applied to compact clays composed largely of minerals such as pyrophyllite, kaolinite and diaspore. Recent data for Roseki also indicate the occurrence of many other kinds of accessory minerals such as corundum, mica, andalusite, quartz, boehmite, alunite, aluminian chlorite, regular or almost regular interstratifications of mica and expandable minerals, aluminian regular interstratifications of chlorite and montmorillonite, pyrite, feldspar, etc. TABLE 1.2. Chemical compositions of Roseki and Toseki 1) 2) 3) 4) 5) 6) 7) SiOz 62.20% 65.80% 59.93% 86.26% 51.21% 78.47% 81.48% Ti02 0.18 0.22 A1203 29.93 27.73 30.23 10.44 40.07 14.91 12.42 Fee03 0.11 tr 0.39 0.47 0.10 0.28 0.65 FeO MnO 0.00 MgO 0.06 0.52 0.12 0.33 0.06 tr. 0.14 0.82 1.52 0.03 0.11 0.10 tr. CaO 0.74 0.45 tr. 0.34 0.42 Na2O K2O 0.18 0.08 0.40 2.74 2.10 Ig. loss 6.20 5.01 6.57 2.38 8.51 3.26 3.05 Total 99.16 100.09 100.16 100.12 1-5) Roseki. 1) Mitsuishi, Okayama Prefecture. 2) Shokozan, Hiroshima Prefecture. 3 ) Goto, Nagasaki Prefecture. 4) Mitsuishj, Okayama Prefecture. 5 ) Shokozan, Hiroshima Prefecture. 1-3) Largely composed of pyrophyllite. 4) Siliceous part consists of pyrophyllite and quartz (Matsumoto, 1968). 5 ) Aluminous part consists of pyrophyllite and diaspore. 1)-3), Yoshiki (1958); 4),5), Matsumoto(l968). 6 and 7) Toseki, Amakusa, Kumamoto Prefecture (Takeshi and Shiraki, 1969). 6) 1st class. 7) 4th class. I

Kimizuka (1939) first reported the occurrence of kaolin minerals from the Mitsuishi Roseki deposits. Yoshiki made an extensive study of the microscopic, thermal and chemical properties of Roseki and reported dickite from the Shokozan Roseki (Yoshiki, 1944). The existence of dickite and nacrite was also reported by Iwai, Takeshi and Ossaka (1949) in certain Roseki deposits of the Hokushin area. A new type of regular interstratification of chlorite di.-di.-subgroup) and montmorillonite-was discovered in the Kurata Roseki (Sudo, Takahashi and Matsui, 1954) (p. 93). Henmi and Yamamoto (1965) reported the occurrence of dioctahedral chlorite (probably di.-di.-sub-group) in considerable proportions by weight in the Itaya Roseki, Okayama Prefecture, and suggested the following chemical reaction for its production : boehmite pyrophyllite water-dioctahedral chlorite. Recently Nishiyama, Shimoda, Shimosakaand Kanaoka (1975) have reported the occurrence of a lithium-bearing aluminian regular interstratification of chlorite and montmorillonite from the Tohoo Roseki, Aichi Prefecture, and described it as Li-tosudite.

+

+

26

OUTLINE

1.2.4. Toseki

Toseki is one of the particular rock types which have been used since ancient times in Japan as raw materials for pottery and porcelain. Among the many Toseki deposits, the so-called Amakusa-Toseki, which was discovered in Amakusa, Nagasaki Prefecture, towards the end of the 1600’s, is the largest in scale and the best in.quality. In the general sense, Toseki possesses several characteristics which are favorable for making pottery or porcelain in terms of its workability, vitrification and sintering: it is converted to porcelain if burnt at SK 10 or thereabouts, and contains small amounts of iron and titanium (Table 1.2). Previous studies on Toseki deposits have show that they are usually composed of mica, kaolin minerals, quartz and feldspar in various proportions. For example, the principal constituent minerals of the Amakusa-Toseki (elutriates) are : 5970 %quartz, 15-30 %mica, 7-21 % kaolinite, and 1-3 %feldspar. Theironcontent (Fe203)is 0.28 %, 0.30 %, 0.44 % and 0.65 % in first, second, third and fourth class material, respectively. The favorable characteristics for ceramic use mentioned above may be due in part to the mineral assemblage: the mica and feldspar may serve as a flux. Petrologically, Toseki has been considered to comprise hydrothermally altered rocks derived from rhyolite, lithoidite, perlite or other parent rocks. Recently, Kanaoka (1968) in his extensive study of the mineralogy of Toseki, indicated the following interesting facts. (1) Aluminian regular interstratifications of chlorite and montmorillonite, and regular, almost regular or random interstratifications of mica and expandable minerals, occur in many Roseki deposits in considerable proportions by weight. (2) The polytype of some of the mica in Toseki closely resembles that reported by Shimoda (1970) as 2M2(p. 54). He suggested that the presence of these interstratifications may perhaps have some bearing on the characteristics mentioned above.

1.2.5. Hydrothevinal clay minerals Hydrothermal metallic ore deposits are widely distributed in Japan, and hydrothermal clay minerals are found as gangues in the ores and as alteration products of the wall rocks. Further hydrothermal clay minerals occur as alteration products of various kinds of rocks, and some of these deposits are sufficiently large for exploitation. Studies on hydrothermal clay minerals have often concentrated on clarification of the nature of the wall rock alteration, since this should provide a powerful tool in ore exploration. Lovering (1949) studied the wall rock alteration of the metallic deposits at Tintic, Utah. In Japan, Iwao, Kishimoto and Takahashi (1954) initiated studies on the wall rock alteration of the Kosaka Kuroko deposit. Iwao further extended such work to other deposits such as the Wanibuchi gypsum deposit (Iwao, 1956) and the Ugusu alunite deposit (Iwao, 1963) (Fig. 1.4, A and B). Numerous reports have subsequentlybeen published on the

600 400

200

0 rn

8

Figs. 1.4. Mineral distributions around hydrothermal deposits. A and B. Vertical profiles of the Ugusu silica-alunite deposit, Shizuoka Prefecture (Iwao, 1963). A. Black-Silicified rocks or silica deposits; hatched-Alunitized rocks or alunite deposits; dottedArgillaceous rocks or clays : crosses-Original rocks or basic to intermediate Tertiary volcanics; R-restored surface. B. Distribution of the dominant clay minerals in the clays or clayrocks. Open circles-Kaolin, mostly dickite; double circles-Pyrophyllite; A-Montmorillonite; squuresSericite, illite; solid circles-Mixed layered minerals. C. Lateral mineral variation in amount along the principal adit of the Yonago Roseki deposit, Nagano Prefecture (Sudo, Hayashi, and Shimoda, 1962). D: Diaspore. P: Pyrophyllite. Q: Quartz. K: Kaolinite. The upper figure @,P) shows the total amount of diaspore and pyrophyllite; the blackcolored area at the left-hand side is largely composed of diaspore, and the black-colored area at the right-hand side is largely composed of pyrophyllite.

28

OUTLINE

mineralogy and geology of hydrothermal clay minerals in Japan, and, as overseas, zonal arrangements of clay minerals have often been observed. The principal studies include those on the wall rock alteration of the Nishiazuma mine (sulfur deposit) by Mukaiyama (1954), the copper deposit (veins and replacement deposits) of the Ashio mine by Nakamura (1961), Pb-Zn-Cu veins of the Mikawa mine by Nagasawa (1961), the Yonago mine (pyrophyllite deposit) by Sudo, Hayashi, and Shimoda (1962) (Fig 1.4, C), the gold deposit of the Kasuga mine by Tokunaga (1955), and the Matsukawa geothermal area by Sumi (1968). A geological survey and close inspection of many core specimens from the Matsukawa geothermal area revealed that the Miocene welded dacite tuff and welded andesite tuff, as well as the Pleistocene pyroxene andesite, have undergone complex hydrothermal alteration. It is generally true to say that the alteration zones form a series from the center outwards as follows: (alunite zone)---+(kaolin zone)--+(montmorillonite zone)-(saponite-chlorite zone). It has been reported that regular or almost regular interstratifications of chlorite and montmorillonite, as well as random interstratifications of mica and montmorillonite, tend to occur in the chlorite zone, while almost regular interstratifications of mica and montmorillonite tend to occur in the montmorillonite zone. In general, zonal arrangements of clay minerals are discernible in many alteration areas. Howcver, closer examination often reveals that the alteration features are far more complex than the overall pattern. This suggests that the alteration may not necessarily represent a single stage of alteration but rather overlapping processes of alteration which took place successively or in different stages. 1.2.6. Weathering zones and soils

Due to the widespread occurrence of volcanic ash, pumice beds and glassy tuffs in Japan, studies on the clay minerals of the weathering zones and soils derived from them are particularly important. Seki (1913, 1928) reported the presence of allophane in various volcanic ash soils in Japan, and clarified its general properties. Later, the clay mineralogy of allophane and halloysite was summarized by Ross and Kerr (1934). In about 1954, active work on allophane and related materials was initiated in Japan, as well as in certain other countries such as New Zealand (Sudo, 1954; Fieldes, 1957). Mackenzie (1963) commented that this trend led us back to an older concept, so indicating a reversal of ideas about the kind of principal constituents of clays over the history of clay research. One older concept was that kaolinite (a crystalline mineral) represented the principal constituent mineral of clays in general. Another older concept suggested that clays were largely amorphous. However, with advances in the study of crystal structures, the presence of crystalline materials in clays and soils was greatly emphasized. Then, the study of allophane, a Eon-crystalline or poorly crystalline clay mineral, became active. The present author favoured the concept of Grim (1968) that studies on the non-crystalline and poorly crystalline

OCCURRENCE, ASSEMBLAGES AND ORIGINS

29

clay minerals are of great importance, and that these materials occur not only in volcanic ash soils or clays as principal constituents but also more commonly in general clays and soils than hitherto thought, though in relatively minor amounts. It is even feasible that some of the soil engineering and agricultural properties of clays may be markedly influenced by the presence of small amounts of non-crystalline materials admixed with the clays. Concerning the clay minerals formed by weathering, it appears reasonable to suppose that the crystallites may to some extent grade into poorly crystalline or non-crystalline materials, particularly in the marginal portions. The problem of the weathering of volcanic ash soils is discussed in detail in Chapter 2. 1.2.7. Recent marine sediments Recent marine sediments are usually rich in clays minerals. Many studies have tended to concentrate on the distribution of the clay minerals in terms of their kinds, assemblages and relative amounts. Due to the need to survey many samples, rapid methods for qualitative and quantitative analysis are generally employed. Distribution maps for the clay minerals in marine sediments have been published from the U.S.A., England and U.S.S.R. (e.g. Biscaye, 1965; Griffin, Windom and Goldberg, 1968; Gorbunova, 1966). In Japan, Oinuma and Kobayashi (1966) initiated similar studies, and distribution maps have been prepared from samples collected in the North Pacific, Japan Sea, China Sea, Indian Ocean, and other areas (Fig. 1.5.). They also examined the detailed distribution of the clay minerals in Tokyo Bay, and pointed out that the proportions of different clay minerals are controlled to an appreciable extent by the movements of the sea water: montmorillonite tends to occur in lesser amounts than other clay minerals in areas of more active movement. As for the claymineralogical analysis of sedimentary rocks, they have reported various examples to show differences in clay mineral assemblages between strata of different geological ages, and between different formations of the same age, particularly those between two adjacent horizons in unconformable contact. They suggested that such analysis could help, in some cases, in the stratigraphical subdivision of strata without fossils. These maps have been refined periodically on the basis of additional samples collected and analyzed by these authors and their collaborators (Aoki, Oinuma and Kobayashi, 1975). Aoyagi (1967, 1968, 1969) performed extensive studies on the clay minerals of Tertiary sedimentary rocks found in the oil fields of Japan. Quantitative estimations of the constituent minerals were made on the basis of calibration curves for standard minerals, involving montmorillonite, mica, chlorite, kaolinite, zeolites (analcime and laumontite), cristobalite, quartz, feldspar (albite), calcite, and dolomite. He discussed the relationships between the clay mineral compositions and following factors : lithology, depositional environment, and diagenetic changes. Montmorillonite tended to be dominant in marine sedi-

6d

I 60"

1 80°

1 100"

I 120°

1 140'

I 160"

I 180"

1 160"

I 140"

I 120"

I

looo

Fig. 1.5. Distribution map of clay minerals in Recent marine sediments (less than 2 y) (Aoki, Oinuma and Kobayashi, 1975).

I 80"

OCCURRENCE, ASSEMBLAGES AND ORIGINS

31

I .6 Neogene

s

Tertiary

J

" T i 1 .m

Cretaceous

2

I

I

I

Paleogene

.+

Tertiary

d

I

Cretaceous

Neogene

2 C

Tertiary

$ 1 Cretaceous I

I

I

Fig. 1.6. Variation in mineral compositions of sedimentary rocks of various geological ages. (Abbreviated from the original figure of Aoyagi (1969), selecting the principal mineral constituents.) Mo: Montmorillonite. Mi: Mica. Ch: Chlorite. Q: Quartz. F: Feldspar.

ments, particularly those of neritic or bathyal origin. Kaolinite tended to be dominant in near-shore sedimentary rocks. To the first approximation also the total oil production in various areas composed of Quarternary and Tertiary rocks tended to increase with increasing amount of expandable clay minerals. Aoyagi reported that from the Neogene towards the Paleogene, and to older rocks, montmorillonite tended to decrease in amount, and minerals such as mica, chlorite, and their interstratifications tended to increase. He suggested that this tendency was due to diagenetic changes (Fig. 1.6). 1.2.8. Clay minerals in active volcanic areas Particular attention must be paid to the studies by Ossaka and his collaborators on the clay minerals that occur in association with active volcanoes and hot

32

OUTLINE

springs. Yamada, Iwai and Ossaka (1969) indicated that the mineral assemblages could be well explained according to the pH of the water closely associated with the minerals, i.e. involving the hot spring water and ground water. Opaline silica and aluminum or iron hydrous sulfates are found as alteration products of volcanic rocks which have been subject to attack by strongly acidic hot spring water. Montmorillonite is found as a principal constituent of mud-flows associated with alkaline water. Allophane and halloysite occur in clays associated with ground water that has a pH in the intermediate range. A new submarine volcanic eruption took place near Nishinoshima in about April, 1973. Following the eruption, the sea water became turbid with fine, suspended particles which were yellow to brown in color. Ossaka (1975) reported a DTA curve and X-ray powder diffraction pattern, and gave details of the chemical composition as shown in Table 1.3 and Fig. 1.7 A,B. The exothermic peak in the 200-300°C region may be attributable to non-crystalline iron hydrates. A strongly acidic hot spring water flows out near the seashore of the island of Satsumaiwojima. Close to the exit point, it is transparent in spite of the fact that abundant iron and alumina are dissolved in it. However, the spring water becomes turbid as it flows progressively into the sea. Fine, yellow to brown precipitates are produced probably as a result of chemical interaction with the sea water. Ossaka (1975) analyzed the precipitates chemically, and measured the pH of the sea water associated with them. He found a relationship between the pH values and amounts of Fe203,as shown in Fig. 1.7 C. It was suggested that the pH values of the sea water associated with the precipitates at Nishinoshima were more acidic than the values at Satsumaiwojima. TABLE 1.3. Chemical composition of fine particles suspended in sea water after eruption of the Nishinoshima submarine volcano. (Ossaka, 1975) Dates of collection SiOz Ti02 Ah03 Fez03 MnO MgO CaO NazO KzO Ig. loss Total

Oct. 9, 1973

Mar. 14, 1974

1) 30.20% 22.27 14.93 0.17 0.96 1.85 0.63 27.15

2) 14.97% 0.29 8.56 45.70 1.02 tr 0.50 0.21 28.38

98.16

99.63

_____

The samples were washed in water to remove sea water, and then analyzed chemically. 1) Outside the Bay. 2) Inside the Bay. (Analyst: Y. Ohira.)

CLAYS AND CLAY MINERALS

33 r-!

A

V

1 1

1

200

L

l

I

1

400 600 Temp. (“2)

1

1

800

1

1

1000

I

0

20

40

Fe2O3/(SiO~+Al203+Fe2O3)

60

80 (wt%)

Fig. 1.7. X-ray powder diffraction pattern (A) and DTA curve (B) for fine particles suspended in sea water after the eruption of the Nishinoshima submarine volcano (Ossaka, 1975). (C) Relationship between the amount of iron in precipitates resulting from chemical interaction between the hot spring water and sea water at Satsumaiwojima, and the pH value of the sea water associated with the precipitate (Ossaka, 1975).

1.3. CLAYS AND CLAY MINERALS

1.3.1. ClassiJication

The Nomenclature Committee of the AIPEA (Association Internationale pour 1’Etude des Argiles) has recommended a nomenclature and classification system for clay minerals (Pedro, 1967) which involves only the most general principles for common clay minerals. No firm recommendation is given for a group name to include the montmorillonite minerals, and the nomenclatural decision on a smectite group, or montmorillonite-saponite group is left open. No appropriate short term is recommended to replace the rather lengthy name of the kaoliniie/serpentine group. Further, it is recommended that the name “mica” be used instead of “illite” (Grim, Bray, and Bradley, 1937). The clay minerals dealt with in this book include both common and rare species. As a general principle for the descriptive accounts, the firm recommendations of the AIPEA scheme are followed, e.g. the subdivisions: Type-GroupSub-group. “Type” is defined according to the ratio of tetrahedral to octahedral sheets in one repetitive unit structure. “Group” is defined according to the magnitude of the charge density on the layer surface. “Sub-group” is defined according to the nature of the octahedral sheet. Further detailed points which lie outside the firm recommendations of the AIPEA are decided by the authors’ choice. Thus, the clay minerals discussed in this book may be summarized as follows : (1) Clay minerals having a layered structure based on sheets with 6-member-

34

OUTLINE

ed rings of silica tetrahedra. They are formed by condensation of sheets of silica tetrahedra with sheets of A1 or Mg octahedra. The tetrahedral sheet has no systematic inversion with respect to the site of Si. (A) 2:l Type Pyrophyllite-talc group Di.-sub-group Pyrophyllite Tri.-sub-group Talc Smectite group, or montmorillonite-saponite group (montmorillonite minerals) Di.-sub-group Montmorillonite, beidellite, nontronite Tri.-sub-group Saponite, iron-saponite Vermiculite group (vermiculite minerals) Di.-sub-group Al-interlayer vermiculite Tri.-sub-group Usual Mg-vermiculite, some Al-interlayer vermiculite Mica group (mica minerals or mica clay minerals) Di.-sub-group “Hydromuscovite”, “sericite”, glauconite (mica type), celadonite Tri.-sub-group Brittle mica group (brittle mica minerals) Di.-sub-group Marganite Tri.-sub-group Xanthophyllite Chlorite group (chlorite minerals) Di.-sub-group Donbassite Di.-tri.-sub-group Sudoite, cookeite Tri.-di.-sub-group Tri.-sub-group Various species (B) 1:1 Type Kaolinite-serpentine group Di.-sub-group (kaolin minerals, or kaolinite minerals) Kaolinite, dickite, nacrite, halloysite (7 A), halloysite (10 A) Tri.-sub-group (serpentine minerals) Antigorite, lizardite, chrysotile, 6-layer serpentine (2) Clay minerals with chain-like structures (essentially of 2:l type) and having a systematic inversion in the tetrahedral sheet with repect to the Si-site. Hormite group Sepiolite, palygorskite (3) Miscellaneous (varieties of dubious validity as clay mineral species, or having structures that are not yet defined). So-called garnierite, deweylite, aquacreptite (4) Non-crystalline or poorly crystalline clay minerals. Allophane, imogolite, hisingerite, penwithite

CLAYS AND CLAY MINERALS

35

(5) Interstratified clay minerals Regular type Magnesian regular interstratifications of chlorite and an expandable mineral Corrensite (the expandable mineral is “swelling chlorite” or ranges in the series, “swelling chlorite”+vermiculite--+montmorillonite (more appropriately ferromagnesian saponite) Aluminian regular interstratifications of chlorite and an expandable mineral Tosudite (the expandable mineral is essentially montmorillonite ;the chlorite involves either the di.-di.-subgroup or the di.-tri.-sub-group) Regular interstratifications of talc and saponite Aliettite Aluminian regular interstratifications of mica and an expandable mineral Rectorite Random type (involving diverse degrees of randomness) Notes: Advanced studies have revealed that, in general, the behavior of the expandable mineral tends to be unusual, and the degree of regularity of the layer stacking varies widely between completely regular and completely random. 1.3.2. Pvvoyhyllite and talc

The pyrophyllite-talc group is subdivided into an dioctahedral sub-group consisting of the pyrophyllites, and a trioctahedral sub-group consisting of the talcs. Pyrophyllite occurs as one of the principal clay mineral constituents of socalled Roseki (see Section 1.2.3), which is distributed widely as hydrothermal clay deposits mostly in Southwest Japan and in certain parts of Central and Northeast Japan. Pyrophyllite is also found in association with kaolinite and diaspore as a principal mineral constituent of the clay zones enclosing certain Kuroko ore bodies of the stockwork type (see section 1.2.2) (Sudo and Hayashi, 1955, 1956a, 1957; Sudo, Hayashi and Yokokura, 1958) (p. 93). Kodama (1958) has described the mineralogical properties of the pyrophyllite in Japan, including X-ray powder diffraction data (Table 1.4), chemical compositions (Table 1.5), and a DTA curve (Fig. 1.8). Brindley and Wardle (1970), on the basis of indexing of the X-ray powder diffraction peaks, first clarified that pyrophyllite is divisible into two types according to its crystal system; one is monoclinic and the other, triclinic. The pyrophyllite samples so far described in Japan belong to the monoclinic type. Talc is known to occur in dolomite, serpentine rocks and crystalline schists, mostly in Paleozoic and Mesozoic structural zones. Most of the Japanese talc occurs in serpentine rocks. Among the many deposits, that of Matsumae is the largest. The geology of the area consists mainly of Paleozoic chert and schal-

36

OUTLINE

TABLE 1.4. X-Ray powder diffraction data for pyrophyllite I

001 002 110

iii 02i iii;lii 112

iii 022 003 112

114

ii4 20i ;i30 13i ;200 i4i 20i;131 201 ;113 004 220;220 ii4;041 203;132 227. 222 221 ;I33 024;1% 042 ;024 042 221 222;204 005

043 1343115 etc. 222 224 24i ;025 etc. i5i;310 etc. 1343153 etc. 151 ;24i etc. .

_

____ ~

9.20 4.60 4.42 4.26 4.06 3.764 3.492* 3.454* 3.178 3.068 2.953 2.741* 2.710* 2.569 2.547 2.532 2.416 2.341 2.300 2.215 2.170* 2.152 2.135* 2.116* 2.083 2.059* 2.026 1.998 1.952 1.887 1.841 1.823* 1.812* 1.7439 1.7223 1.6894 1.6674* 1.6529* 1.6327*

**

80 30 100 80 60 5 5 5 20 100 20 3 4 30 30 40 80 10b 5 4 15 15b 2 2 20 25 3b 2 .. . ....

15nC

I

I

I

I

I

I

.......... ..-' .:...... . .............. ...... ......... . . . No.6-1' ... .... ....'7

.

...

B 0

45

;

;

. .>... . .. ..... . . .

....

1F.A

'"7 I

I

I

....... .........

.

I

I

I

I

I

.

.. ; ,.~.:,>.

.'.

0:.

.. ..;::.'

.'*

.,' '

bi.

No. 6-2

100

. 60

40

-2-1

0

1

2

3

4

5

Velocity (rnm/sec)

Fig. 1.13. Mossbauer spectra for the clay altered from volcanic rock fragments in Oya-ishi (Kohyama, Shimoda and Sudo, 1973). 6-1) Unoxidizedsample. 6-1') Partially oxidized sample. 6-2) Oxidized sample.

shown in Table 1.7. Using EPMA, chemical analysis was performed on the two different parts, Types I and 11. The chemical formula of Type I in the primary state was obtained as (NaO.

5 2 KO. 08 CaO.

26)

(MgO.90

Fei.>.5"2.52)

(si7. 66 "0.

34)020(0H)4r

indicating that the material is an iron-bearing montmorillonite-beidellite. The chemical formula of Type I1 was (NaO.60

KO.

04 CaO.

44)

(M& 04

Fet.:8

"0,

OZ)(si6.

36 "1,

64)020(0H)4,

indicating that the material is an iron-saponite. The chemical formulas of the iron-saponite called "lembergite" and the material from Oya may be compared in their ideal forms as follows; w: Na, K, Ca/2.

46

OUTLINE

TABLE 1.7. Chemical composition, X-ray powder diffraction data and Mossbauer effect of clays altered. from volcanic rock fragments in Oya-ishi, and the b-parameters of the constituent clay minerals in the clays (iron-bearing montmorillonite/beidelfite and iron-saponite) (Kohyama, Shimoda and Sudo, 1973) 6-1)

SiOz

6-2)

Color of powdered sample

brown

2.27

hk

13;20 22;04 31 ;15;24 33 :06

bo

(A)

9.300* 9.030**

brown

2.08

2.09

1::;

30

14.46

37

15b

‘2.59 12.53

1%

5b 8 11 2 3

0.36 0.96

I

brown

I

1.S. (mmisec) 0.35*** 0,s. (mmisec) 0.86*** I

10-2)

d(W)

Q.S. (mmisec) 2.86

~

50.03 % tr 13.94 9.34 2.12 0.28 3.50 1.49 1.50 tr 5.17 12.25 99.62

2.20

1.14 2.52

.

46.77% 0.02 12.47 8.27 3.07 0.20 3.20 1.55 1.50 0.40 5.23 17.92 100.60

I

I

IS. (mmjsec) 1.19

9-2)

32.83 % tr 8.41 0.93 6.75 0.20 2.58 1.38 1.42 0.21 3.46 42.04 100.21

d(A)

1.70 1.536 1.501 1.337 1.293

26 ;40

9-1)

blue

2.20

[4.46

11;02

Fe3’

13.57 9.15 1.56 0.14 4.32 1.99 1.71 0.36 5.17 16.00 100.02

blue

No. of octahedral cations*

Fez+

46.05 %

37.02% 0.02 10.90 0.90 7.61 0.12 3.48 1.61 1.38 0.29 4.86 33.28 101.47

9.216* 9.006**

1.70 1.534 1.503 1.331 1.293

I

9.300* 9.048**

6 4 6 2 2

9.204* 9.018**

6-1) and 9-1) Unoxidized samples. 6-2), 9-2) and 10-2) Oxidized samples. *Iron-saponite. **Iron-bearing montmorillonite/beidellite. ***6-1’ (Fig. 1-13).

d(A)

I

1.70 1.535 1.501 1.330 1.297

4b 4 6 2 2

I

I I

9.210* 9.012**

CLAYS AND CLAY MINERALS

47

,,Al,

Oya-material W l 6 7 (Mg,Fei+) (Si,

67)

O,,(OH),

The data strongly suggest the existence of an iron analog of saponite (an endmember) having the following ideal chemical formula :

In the diagram showing the relationship between the total Fe and Mg content

in the octahedral sheet (per unit structure) and the 6-parameter (Fig. 1.16), the composition of Type I falls within the range of the dioctahedral field, and that of Type I1 within the trioctahedral field. An iron-montmorillonite had been reported earlier by Sudo (1950b) (Table 1.8). This material is generally gray to white in color, but pale green in places, and occurs in association with mica in the clay zone enclosingthe Nisliikannondo ore body (Kuroko) of the Hanaoka mine, Akita Prefecture. Although the pale green color remains unchanged on exposed surfaces in the field, some collected samples tend to acquire a brownish tint on exposure to daylight. Small veinlets or spots of native copper occur in the pale green-colored clay. The occurrence of iron-montmorillonite in Recent marine sediments has been reported by several workers overseas. However, adequate mineralogical data are not available except in the case of the material from the Red Sea termed “ferroan nontronite” by BischofT (1972). Aoki, Kohyama and Sudo (1974) have reported that a montmorillonite mineral is the dominant constituent of a sediment core (total length, 430 cm) collected from Ihe Northeastern Pacific. In the upper half of the core, the ironmontmorillonite occurs in association with mica, kaolinite and chlorite, and occasionally with small amounts of clinoptilolite. Most of the lower half of the core is composed entirely of iron-montmorillonite which occurs as a browncolored clay. The actual site of the core was close to the Clarion Fracture Zone and to the Baja California Seamount Province. The large amounts of ferric iron in the samples could scarcely be removed by treatment with 0.05 N HCl and sodium hydrosulfite, i.e. by the method proposed by Mackenzie (1954) to remove free iron (Table 1.8). Greene-Kelly’s test confirmed that the material examined was montmorillonite. The spacing of the (06,33) peak indicates that it is of the dioctahedral sub-group. The chemical composition (without recalculating the FesOs as FeO) gave a chemical formula in which the tetrahedral sheet is almost entirely occupied by Si, and the total number of octahderal cations is close to 2.00 on the basis of 010(OH)3.These data indicate that the mineral is an ironmontmorillonite. The DTA curves and infrared absorption spectra are included in Fig. 1.14.

TABLE 1.8. Chemical composition and formulas of iron/montmorillonite 1) 46.30%

SiOz Ti02 AbOs Fez03 FeO MnO MgO CaO NazO KzO HzO(+)

2) 44.81% 0.53 7.45 14.29 0.41 1.44 5.73 2.59 0.48 0.86 8.37 12.81 99.77

18.47 6.03 0.45 3.06 2.16 1.03 0.35 6.83 14.50 99.18

HzW-1

2') 51.66% 0.58 8.13 14.08 0.51 0.29 4.21 0.15 1.21 0.71 6.74 10.13 98.40

3) 44.03 1.31 3.25 18.39 0.21 1.49 5.73 2.27

3') 51.72 0.87 7.00 14.41 0.21 0.03 4.70 0.48 1.19 0.70 6.72 10.92 98.95

0.18 0.79 7.81 14.40 99.68

Total Si 3.65 3.97 3.99 Ti 0.03 0.05 AI(1V) 0.35 Al(V1) 1.37 0.74 0.64 Fe3+ 0.36 0.81 0.84 Fez+ 0.03 0.03 0.01 Mn 0.02 Mg 0.36 0.48 0.54 Ca 0.18 0.01 0.04 Na 0.16 0.18 0.18 K 0.04 0.07 0.07 1) Hanaoka mine, Akita Prefecture (Sudo, 1950b) The (060) spacing: 1.51A. 2) and 3) Northeastern Pacific (Aoki, Kohyama and Sudo, 1974). 2 ) and 3') Samples obtained after removal of iron oxides or hydroxides from samples 2) and 3). respectively. The (060) spacing: 1.508 1.509A.

-

I I

100

I

1

l

1

1

I

I

1

500 Temp.

1

('c)

0

I

I

I

I

I

I

I

I

40 30 20 18 16 14 12 10 8 6 Wave number (em-') (X 100)

-

4

Fig. 1.14. DTA curves and infrared absorption spectra for iron-montmorillonite in a core sample taken from the Northeastern Pacific (Aoki, Kohyama and Sudo, 1974). Specimens 2 and 2': see Table 1.8.

i

9.2

-

0

0

4

Fig. 1.15. Estimation of the number of Fe3+ ions in the octahedral sheet from the b-parameter observed for dioctahedral smectite. The data in the figure are from the following sources. Circles: montmorillonit-beidellite (Radoslovich, 1962). Squares: nontronite (Radoslovich, 1962). A: Ironmontmorillonite-beidellite(Kohyama, Shimoda and Sudo, 1973). The arrow indicates the y-value estimated from the b-parameter iron-montmorillonite from the Northeastern pacific. 9.4 0

@

9.3

Montmorillonite-beidellite Nontronite

V V

v v

x Saponite-iron-rich saponite

9.2 '

V

Vermiculite v Biotite A Talc 01

V

nv

D

3

VV

x.p-l x xx

a2

bo(i)

A 3

A 4

i

9.:

9.C

8.c

I

).O

0.5

I

I

I

I

1 .o 1.5 2.0 2.5 Fe +Mg (in octahedral sheet per half unit structure)

I

3.0

Fig. 1.16. Relationship between the b-parameter and total number of Fe and Mg ions. The data in the figure are from the following sources. Montmorillonite-beidellite: Radoslovich (1962), Radoslovich and Norrish (1962), Grim (1968). Nontronite: Radoslovich (1962), Radoslovich and Norrish (1962). Saponite-iron saponite: Radoslovich (1962), Radoslovich and Norrish (1962), Sudo (1954a1, Miyamoto (1957), Midgley and Gross (1956), Quakernoat (1970), Kimbara (unpublish~ddatu). Vermiculite: Radoslovich (1962), Radoslovich and Norrish (1962). Biotite: Radoslovich (1962), Radoslovich and Norrish (1962). Talc: Radoslovich 11962), Radoslovich and Norrish (1962). 1) and 2) Iron-saponite and iron-montmorillonite-beidellite from Oya, respectively (Kohyama, Shimoda and Sudo, 1973). 3) and 4) Iron-montmorillonite from the Northeastern Pacific; samples from which iron oxides and hydroxides had been removed with HCI and sodiurn hydrosulfite; corresponding to samples 2 and 3' in Table 1.8 (Aoki, Koyhama and Sudo, 1974).

OUTLINE

50

Fig. 1.15 shows the relationship between the b-parameter and y-value (ferric iron in the octahedral sheet). The y-value for the present sample read from the diagram agrees well with that obtained from the chemical formula. Fig. 1.16 shows the relationship between the b-parameter and the total amount of Fe and Mg in the octahedral sheet. The plotted points for the present material fall in the range nearer to the trioctahedral field than those of the Oya material, but still within the dioctahedral field. Aoki et al. (1974) suggested that a colloidal mixture of iron, manganese and silica was perhaps originally formed as a result of chemical interaction between sea water and material emanating from submarine hot springs, and that the mixture gradually crystallized out as iron-rich montmorillonite on subsequent diagenesis. Thus, the iron in the material may primarily have been in the ferric state. 1.3.5.

Vermiculite

Mg-vermiculite (trioctahedral vermiculite) occurs in aggregates of green to golden yellow macroscopic flakes that are found in association with talc and chlorite in serpentine rocks which have suffered the contact effects of granites or allied igneous rocks (Table 1.9, Fig. 1.17). Al-interlayer vermiculite occurs in some soils and sedimentary rocks in Japan. Tamura’s method (Tamura, 1958) is well known as the best technique for clarifying the nature of Al-interlayer vermiculite. Sudo, Oinuma and Kobayashi (1961) have studied the Al-interlayer vermiculite occurring in certain cretaceous sedimentary rocks. The samples are composed of very complex clay mineral assemblages involving Al-interlayer vermiculite. Using Tamura’s meTABLE 1.9. Chemical compositions of vermiculite and hydrobiotite

SiO2 Ti02 A1203

Fez03 FeO MnO MgO CaO NazO KzO HzO(+) HzO(-) PZOS Total

33.42 % tr 10.44 3.66 2.34 tr 25.18 4.00 0.02 tr 14.60 6.12 tr

34.1 I % 3.52 16.87 18.84 2.69 0.19

8.04 0.09 0.40 4.06 8.01 3.18 tr

99.78 100.00 1) Vermiculite, Uzumine, Fukushima Prefecture (Shimane, unpublished darn). 2) Hydrobiotite, Onomachi, Fukushima Prefecture (Kato, 1965).

CLAYS AND CLAY MINERALS

51

A

0

E 100

500 Temp. (“C)

1000

I

0

/

I

l

l

500

I

l

l

1

1000

Temp. ( 2 )

Fig. 1.17. A: DTA curves for vermiculite (Shimane, unpublisheddatu). 1) and 2) Uzumine, Fukushima Prefecture. B: DTA, TG and DTG curves for the vermiculite from Uzumine, Fukushima Prefecture (Shimane, unpublished data).

thod, these authors suggested that one sample was composed of Al-interlayer vermiculite and another of Al-interlayer-montmorillonite. The weathered biotite flakes occurring in weathered surface rocks and soils derived from granitic rocks and showing marked exfoliation are known in Japan as “Hiru-ishi”. The material consists of hydrobiotite which is essentially an interstratification of biotite and vermiculite. Kato (1965) performed extensive studies on the weathering products of the granodiorite at Shinshiro City. He pointed out the existence of Al-interlayer vermiculite derived from biotite, which may be called trioctahedral Al-interlayer vermiculite. He also reported that the weathered biotite flakes showed variability with respect to their color, overall mineral assemblage, and chemical composition. With the progression of weathering, the biotite flakes tended to be altered to hydrobiotite (SiO2/AI203 = 3.5-3.7) (Table 1.9), then Al-interlayer vermiculite (trioctahedral) (SiOe/ AI2O3= 3 . 9 , and finally kaolinite and gibbsile. 1.3.6. Mica cla-y minerals

Mica clay minerals may be divided into dioctahedral and trioctahedral species. The Nomenclature Committee of the AIPEA has recommended that the most common name “micas” be used as an inclusive name for these minerals until the nature of so-called “illite” has been clarified. This recommendation can

52

OUTLINE

be adopted for classifying the samples reported in Japan. However, for descriptive purposes, it is necessary to introduce some of the past and present names commonly used in Japan. The term “sericite” (from the Greek for “silky”) has been commonly applied to mica minerals since early days, in mineralogy, petrology and economic geology, and by people attracted by its silky luster as a fine powder. The so-called “sericite” in Japan is all of metamorphic or hydrothermal origin, and until recently it was regarded as a fine-grained (or at least finer than muscovite) Aldioctahedral mica. However, recent studies have revealed that the samples may be divided into two classes: (1) a mica without discernible interstratifications, and (2) an interstratification of mica and rnontmorillonite ranging from random to almost regular types. Thus, broadly speaking, the term “sericite” is at present used as a field name for both (I) and (2), or for (2), only where terms such as “hydromuscovite” or “pure sericite” have occasionally been introduced. Fine-grained white-colored Al-dioctahedral micas have also been reported as principal constituents minerals of Recent sediments or argillaceous sedimentary rocks. However, in Japan, detailed mineralogical studies aimed at describing and identifying these mica minerals have lagged, and they have rather been termed “illite” or occasionally “sedimentary illite”. Recent studies on the mica minerals of argillaceous sediments have revealed that some of them are interstratifications of mica and montmorillonite. Fine-grained white micas in general show some departure from muscovite in terms of their chemical compositions, such as less potassium and more water. Descriptions of “sericite” (i.e. pure sericite) often indicate that the departure lies in the intermediate range between muscovite and “sedimentary illite”. Samples of metamorphic origin and some samples of hydrothermal origin are chemically very close to muscovite. Broadly speaking, the variation in chemical composition of fine-grained micas spreads almost continuously over the range “sedimentary illite” --+ “sericite” -+ muscovite, and the changes do not necessarily result from interstratifications. The mineralogical properties of “sericite” may be summarized as follows. The white micas in crystalline schists have often been called sericite. Such minerals are usually found in polycrystalline aggregates of flakes oriented almost parallel to the flake plane. One specimen from the crystalline schist of the Hitachi mine, Ibaragi Prefecture, is very close to muscovite except for the crystallite sizes. It may represent a macrocrystalline analog of mica clay minerals. Fine-grained white-colored mica clay minerals occur as hydrothermal alteration products of Tertiary rhyolite and its tuffs, and occasionally of granodiorite and shale. They are found in aggregates of powdery crystals having a silky luster, and have been called sericite. The following modes of occurrence are known : (1) large clay deposits without accompanying large metallic mineral deposits : these have in most cases been utilized as a source of mica clay minerals,

CLAYS AND CLAY MINERALS

53

e.g. the sericite (Murakami clay) at Osudo, Niigata Prefecture; (2) a principal clay mineral constituent of clay zones enclosing various kinds of metallic ore deposits such as Kuroko deposits, antimony deposits (the Kanbe mine, Nara Prefecture), and copper deposits (the Ashio mine, Tochigi Prefecture): in some cases, the sericite clay has been used as a source of mica clay minerals after removal of the metallic ore minerals; (3) a principal clay mineral constituent of Toseki; and (4) an accessory mineral of Roseki. Kodama (1957) studied the sericite occurring as a hydrothermal alteration product of granodiorite at Ozawa-mura, Gunma Prefecture (Table 1.lo). The 10 A spacing does not suffer any discernible change in the temperature range up to 1000°C. However, the mineral is chemically distinct from muscovite as follows: Si02/Rz03= 1.3 (1.2 in muscovite), Si02/K20= 9.3 (7.0), R203/K20 = 4.1 (3.2), H20(+) = 0.276 (molar ratio) (0.233). Kodama (1962) studied 14 samples of “sericite” of hydrothermal origin. He termed them “hydromuscovite” and pointed out that they could be divided into three groups with respect to their polytypes: 2M1, lM, and mixtures of them (Tables 1.10 and 1.1 1). He reported out that the departure from muscovite in chemical composition tended to be greater with increasing proportion of 1M type. Although no detailed discussion was made in the original paper as to whether an interstratification was present or not, X-ray powder patterns strongly suggest that no interstratified structure is in fact discernible (at least in the samples of 2M type). Shimoda (1970) reported the mineralogical properties of a fine-grained mica occurring in a hydrothermal alteration product of rhyolite and its related tuffaceous sediments near the Shakanai mine (Kuroko deposit), Akita Prefecture (Table 1.11). He described the mica as hydromuscovite. Although no detailed discussion was made of the presence or absence of an interstratified structure, the reported data strongly suggest that no clearly discernible interstratification could be confirmed. Shimoda pointed out that the X-ray powder diffraction pattern is different from those of the 2M1 and 1M types but rather closely resembled that of the 2M2 type, which is known in lepidolite. Recently, Kanaoka (unpubfisheddata)has pointed out that similar material is often found in Toseki. The DTA curve of the Shakanai material is shown in Fig. 1.18. Shirozu and Higashi (1972) studied many samples of sericite associated with Kuroko deposits, and pointed out that they may be divided into two groups: (1) sericite with no sign of interstratifications (termed by them pure sericite), and (2) interstratifications of mica and montmorillonite. They found that the sericites occurring in the siliceous ore zone or siliceous rocks consisted of pure sericite or contained small amounts of expandable minerals incorporated as interstratifications, while the sericite samples from the clay zone were usually interstratifications of mica and montmorillonite, with small but appreciable amounts of expandable layers. Most of the samples from the black and yellow ore zones tended to be intermediate between the above two (for details, cf. Chapter 3).

OUTLINE

54

TABLE 1.10. Chemical composition of sericite YO(41)

Si02 47.65% Ti02 0.10 A1203 37.03 Fez03 0.01 FeO tr MnO tr MgO 0.04 CaO tr K20 9.02 NazO 0.76 H2O(+) 4.97 HzO(-) 0.73 Pzo5 0.02 Total 100.33

GO

SR(-60)

MY(-M3) MU(-01)

47.24% 0.38 35.04 059

48.21% none 35.40

47.55% n.d. 37.78

0.21 0.16 8.75 1.37 5.52 0.32 99.58

1.53

n.d. 0.36 0.78 8.00 0.46 4.78 0.96 n.d. 100.48

tr n.d. 0.49 0.13 8.18 0.40 4.95 1.30 n.d. 100.78

47.17% none 38.04

SH

SS 48.44% tr 33.84

0.17

0.49

n.d. 0.28 0.36 6.75 0.25 6.22 0.36 n.d. 99.60

tr 0.95 0.11 9.40 0.50 5.42 0.60 99.75

47.14% 0.34 37.09 0.49 0.83 0.57 7.10 0.35 5.18 0.99 0.01 100.09

si

6.17 A1 1.83 A1 3.92

Ti 0.04 Fe3~b0.05 Mg 0.16 Ca 0.08 Na 0.09 K 1.19

Alkali content Quartz KzO Na20 Total impurity 9.02% 9.78 % YO(-01) 0.76 % 2 Mi 0.41 8.34 7.93 MY(-M4) 2 MI 8.46 SR(-60) 8.00 0.46 2 MI-1 M(2:l) (8.32) SR(-Nl7) (0.39) 2 MI-1 M(2:l) (8.71) 5% 8.86 0.43 8.43 MY(-Ml2) 2 MI-1 M(1:l) 8.58 0.40 8.18 MY(-M3) 2 M1-1 M(1:l) 7.93 2 MI-1 M(1:2) 0.37 7.56 MY(-M7) (0.31) (7.74) 10 SR(-N3) 2 M1-1 M(1:2) (7.43) 7.60 0.30 2 M1-1 M(1:2) SR(-N2) 7.30 (7.66) 10 (0.30) SR(-56) 2 MI-1 M(1:2) (7.36) 7.00 0.25 MU(-Ol j 2 M1-1 M(1:2) 6.75 (7.59) 20 (0.96) KA(-60) 1 M (6.60) Y O : Yoji Pass, Gunma Prefecture; a hydrothermal alteration product of granodiorite. GO: Goto Roseki deposit, Nagasaki Prefecture. MY: Kumanodo, Tochigi Prefecture; a hydrothermal alteration product of rhyolite and its tuffs. MY(-M7) and MY(-M10) contain diaspore and quartz as impurities. SR: Shiraishi mine, Tochigi Prefecture; hydrothermal alteration product of rhyolite. MU: Murakami, Nagano Prefecture; a hydrothermal alteration product of andesite. YN: Azumamura, Nagano Prefecture; a hydrothermal alteration product of shale. KA: A sample from the clay zone enclosing the Okunosawa ore body (stratiform type), Kamikita mine (Kuroko deposit), Aomori Prefecture. SS: Seshido mine, Fukushima Prefecture; a hydrothermal alteration product of rhyolite. SH: Shakanai mine, Akita Prefecture; a sample found in association with gypsum and anhydrite in the Kuroko deposit (Shimoda, 1470). Y O (Kodama, 1957). GO and SS (Shimoda,, Sudo and Oinuma, 1969). SH (Shimoda, 1970). Other samples (Kodama, 1962). Bracket: Alkalies contents corrected for quartz impurity. *associated with a sma!l amount of 2Mtype. Specimen

Polymorph

TABLE 1 . 1 1 . X-Ray powder diffrection data for sericite (Kodama, 1962) 2M1 YO(-Ol) Muscovite

hkl 002 004 110 111 022 112 113 023 113 114 006 144

113 025 115 116 200 202 008 131

204 133 22i 22 3

d(i)

10.1 5.05 4.50 4.31 4.12 3.98 3.89 3.74 3.50 3.35 3.21 3.13 3.01 2.88 2.81

I 35 22 12 3 2 5 5 6 10 48 11 5 12 8 6

2.57

13

2.51 2.46

5 4

] 2.38 ] 2.20

5

3b

d(i) I

s m vs w w vw m m

9.99 4.98 4.47 4.29 4.11 3.95 3.87 3.72 3.55 3,475 3.32 3.20 3.1 2.98 2.86 2.78 2.585 2.560

m vs ms vw s m m w vs

2.49 2.46 2.390 2.376 2.245 2.185

w w vw m wb w

vw

2M1+ 1M SR(-60) 2:l Mixture d(i)

I d(A) LO.1 35 10.1 5.06 24 5.03 4.50 10 4.48 4.37 3 4.31 2 4.15 1 4.11 3.98 3.91 5 3.90 5 3.75 3.73 3.67 7 3.66 3.52 10 3.50 3.35 35 3.35 3.20 12 3.20 3.06 10 3.09 3.00 8 2.99 2.94 2 2.87 6 2.86 2.82 5 2.80 2.69 2.57 17 2.57 2.52 4 2.50 2.46 3 2.46 2.44 3 2.39 3 2.38 2.24 2 2.24

1M Muscovite (Radoslovich, 1960) I hkl d(A) I 10.07 s 15 001 11 002 5.00 w-m 12 020 4.487 s 7 iii 4.342 w-m 4.093 w-rn 2 021 10 112 3.647 s 3.482 vvw 40* 003 3.337 s 3.208 ww 11 112 3.0593 s 3 113 2.9211 w 5 023 2.6772 w 2.5875 w-m 130 10 131,203 2.5585 vs(b) 3* 2.4773 vvw 2.4327 w 131 4 132 2.3918 w 2.3509 w 114

2Mz

JSA(-60)

I 80 60 14

4 12 6 6 (2M1) 6(1M) IO(2Mi) 80** 12 (2M1) 8 (1M) 14 (2M1) 12 6 4 22 8 4 8 4

d(A) 10.1 5.01 4.50 4.35 4.11 3.65 3.34 3.08 2.91 2.68 2.57 2.46 2.39

2.2440 w 2** 040 2.2096 vw 220 031,133 2.1901 vvw 2.1020 vw 1 202 2.10 1.997 8 005 2.0766 w-m 1.948 lbr 133 1.9454 vw(b) 1.6856 vvw 2.24

SH hkl 002 004 iii,110*,200* lll*.20i* lli* 202*,112* 113 113,204 114 006 114,204

d(A) 10.25 5.06 4.49 4.31 4.31

I 55 42 60 15 5

3.681 3.520 3.348 3.211

43 33 58 28

115 115*

3.066 2.946

40 15

203 116 311,116*

2.869 2.812 2.583

22 18 90

206*,008* iii* 023,314 117*,208* 22i*,118* 118,221 314*

2.513 2.450 2.426 2.402 2.285 2.252 2.210

10 16 15 14 4 8 7

(Continued)