Illite Springer-Verlag Berlin Heidelberg GmbH Alain Meunier • Bruce Velde

Illite

Origins, Evolution and Metamorphism

With 138 Figures

Springer Professor Dr. Alain Meunier University of Poitiers UMR 6532 CNRS HYDRASA Laboratory 40, Avenue du Recteur Pineau 86022 Poitiers, France E-mail [email protected]

Dr. Bruce Velde Research Director CNRS Geology Laboratory UMR 8538 CNRS Ecole Normale Superieure 24, rue Lhomond 75231 Paris, France E-mail [email protected]

ISBN 978-3-642-05806-6 ISBN 978-3-662-07850-1 (eBook) DOI 10.1007/978-3-662-07850-1

Library of Congress Control Number: '3502272 Bibliographic information published by Die Deutsche Bibliothek Die Deutsche Bibliothek lists this publication in die Deutsche Nationalbibliography; detailed bibliographic data is available in the Internet at .

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© Springer-Verlag Berlin Heidelberg 2004 Originally published by Springer-Verlag Berlin Heidelberg New York in 2004. Softcover reprint of the hardcover I st edition 2004 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

Cover Desing: Erich Kirchner, Heidelberg Typesetting: LE-TeX, Leipzig

Printed on acid free paper 32/3141/LT - 5 4 3 2 1 0 To the memory ofJohn Hower and to Bruno Lanson

This book has taken some time to assemble, bringing together much data resulting from approximately 50 years of scientific endeavour by many re­ searchers. It has been inspired by many people, although some seem more important to us than others, mostly for personal reasons. One of us (BV) began his research career in trying to answer the question "What is Illite?". We hope that in a few years we can answer it more fully than in 1965. John Hower posed this question to one of his students, one among many. John was an inspiration to many people, not only his students, and for this reason we would like to dedicate this book to him. In fact, one can observe that much of the work on clay mineralogy has been influenced by the ideas and discoveries ofJohn Hower. One needs only to scan the pages of major clay mineral journals. The present authors, finding their way towards the ends of their careers, one faster than the other, have followed the paths laid out by John Hower and other eminent clay scientists. The question of illites, however, is not yet answered completely, and the importance of using them to solve geological and environmental problems persists. Because of this we must look to the young active scientists who are better equipped than we were to solve the problems of the future. We would like then to dedicate this book also to the younger generation, especially one member, Bruno Lanson, who has shown his capacities in the recent past, and whom we would like to wish well in future endeavours. As with John Hower, we have worked with Bruno and appreciate his qualities as we appreciated those of John. Our book is therefore dedicated to the memory of John Hower and to Bruno Lanson, generations and worlds apart but both passionately engaged in clay science. Preface

It is our pleasure to present this large body of information and thoughts of many mineral scientists which has accumulated over decades. Illite is a mineral that has been discovered relatively recently, even though it has great importance in the geological cycles ofweathering, sedimentation and burial. Illite is the major potassium mineral among silicates in the surface environment. Potassium represents the only alkaline metal, to be bound in silicate structures during the great chemical reshuffling called weathering. The weathering environment is one of strong chemical segregation, where Si and AI become the resistant, residual elements of silicate rocks. Iron forms an oxide and potassium forms the stable clay illite. Then Si and Al form smectites and kaolinite. Sodium, calcium and to a large extent magnesium are extracted from the solids as dissolved ionic species of the altering fluids. Ca and Mg are reintroduced into solid minerals via carbonate precipitation, and Na remains to make the sea saline. This mineral has been difficult to study because it is of fine grain size, as are all clays: 2 pm in diameter. Illite, along with other clays, had to wait to be discovered until a useful method of X-ray detection became available. With such a tool clays, whose definition was initially based upon the resolving power of an optical microscope (2 ].lm), could be efficiently investigated. In fact the study ofillite parallels the use and development of X- ray diffraction techniques. Initial powder amounts giving rise to linear photographic film records gave rather rough indications as to mineral phase identifications, especially in cases of multi phase assemblages so common to clay mineral occurrence. Analog recording methods developed in the 1950S provided graphical representations of diffracted beam intensities which made identification much more precise. For the next three decades, X-ray diffractograms were the major tool of clay mineralogy. This was a period of enormous progress in the identification, in­ terpretation and modelling of clay mineral interaction using X-ray radiation. The geology of clays became a true discipline. It was possible to study large series of samples in order to gain a general idea of phenomena based upon spatial distribution and variations of clays as they reacted to chemical changes and temperature changes over different periods of time. These are the fun­ damental variables of geology, time-temperature-composition; it takes a large amount of information in order to understand their functions. Of course, Ralf Grim is the pioneer of illite research; John Hower and Jack Burst outlined the evolution of clays in sedimentary burial processes which VIII Preface produce illite-rich clays and Bob Reynolds provided us with the tools of cal­ culation which were used to determine the physical reality and unmask some wishful thinking in the interpretation of X-ray diagrams. These new tools kept some of us busy for several decades, until it became apparent that more infor­ mation of a more precise nature was necessary in order to interpret the X-ray signal detected by diffractometers. Bruno Lanson gave us a solid method of decomposing the different diffraction components in an X-ray diagram so that much more precise and numerically exact comparisons could be made with the modeled diffraction diagrams. Use of digital output from a diffraction spectrum and comparison with calculated X- ray diffraction spectra give us the possibility to quantify clay mineral occurrence and give viable identifications to mineral change. This is the great leap forward of the last years of the 20th century. These were the tools. Along with them we had the inspiration of work using the concepts of crystal growth; elegantly explained by Alain Baronnet, which caused us to think in another dimension, the third instead of the classical phyllosilicate two-dimensioned sheet structures. Some of the first applications of these ideas to clay series were performed by Atsuyuki Inoue, which propelled us to our present state of discovery. The present authors have participated in this rather fascinating development and have enjoyed the fruits of the research of our friends, colleagues and students. Here we have tried to focus this effort on the problem of illite: illite is a mineral that occurs over the whole range of clay mineral stability - time, temperature and chemical activity - and often in great abundance. It is frequently but not always present. At times it plays a critical role in the development of a geological system, either by its presence or absence. Illite is one of the most common clay minerals in soil clays developed under temperate climates, in the most fertile of soils. It is the end-product of burial diagenetic processes, supplanting the diagenetically formed smectites in pelitic sedimentary materials. It is the common clay mineral associated with many types of ore deposits. The correct identification and determination of the origin of illite can provide important information concerning many processes which lead to economic deposits. Illite, by virtue of its potassium content, is a key mineral concerning soil usage. Its presence, absence or instability determine much of what is called soil fertility. Thus illite is not just a nice mineral to study but an important one. We hope to convey some of this information and a sense of the significance of illite in natural and man-made environments to our readers. Quite abruptly, we decided to write this book with "four hands" (if not two full heads) in November 2002 in order to put a "milestone" in the long path (more than 30 years) which we have walked. Since a memorable afternoon of 2002 during which BV visited the "Pedologie" lab of the University of Poitiers, we worked and discussed (sometimes with more passion than necessary) to­ gether. Science is above all a debate! Our greatest satisfaction is undoubtedly to have learned so much from our students. Some of them are now our colleagues and masters in their specialities (D. Beaufort, B. Lanson, A. Bauer among oth­ ers). Perhaps it is time to say, after 30 years, that one of the greatest benefits Preface IX of our common scientific adventure was to make friends all over the world. This could be, at least, encouraging for new student generations to learn that science offers great possibilities, to meet exceptional people and to maintain enthusiasm which is more or less the equivalent of youth. Contents

Introduction 1

1 The Mineralogy of Illite - What is Illite? 3 1.1 Illite Definitions...... 3 1.1.1 Definitions of the Past...... 3 1.1.2 Definition Based on XRD Examination ...... 5 1.1.3 Examples of Pure Illites...... 10 1.1.4 Examples of Illites in Natural Soils, Sediments and Sedimentary Rocks...... 12 1.1.5 Summary of One-Dimensional Analysis of Natural Minerals by XRD ...... 17 1.2 Definition Based on Chemical Composition ...... 18 1.2.1 Solid Solutions of Illite and Glauconite ...... 18 1.2.2 Charge-Lowering Substitutions ...... 20 1.2.3 The Crystal Structure of Illite and Solid Solution ...... 23 1.2.4 The Theoretical Crystal Structure of Illite ...... 31 1.3 Thermodynamic Stability of Illite ...... 40 1.3.1 The Gibbs Free Energy of Formation of the Illite Phase... 40 1.3.2 The Stability Field of the End-Member Illite Phase ...... 45 1.4 The Growth of Illite Crystals ...... 48 1.4.1 Crystal Shapes in Diagenetic Environments...... 48 1.4.2 Growth Mechanisms of Lath-Shaped Illite Crystals ...... 52 1.4.3 Growth Processes for Plate-Shaped Crystals...... 56 1.5 A Working Definition of Illite ...... 61

2 The Geology of Illite 63 2.1 Illite in Soils and Weathered Rocks ...... 63 2.1.1 Occurrence of Illite in Soils ...... 63 2.1.2 More Recent Studies...... 64 2.1.3 Early Formation of Illite in Weathered Granites ...... 68 2.2 Illite in Diagenetic Series...... 76 2.2.1 Illite Formed During Early Sedimentary or Eodiagenetic Processes...... 76 2.2.2 The Origin of Illite in Shale Burial Diagenesis...... 79 XII Contents

2.2.3 Illite Crystallinity...... 85 2.2.4 Bentonite...... 97 2.2.5 Sandstones ...... 100 2.3 Illite in Fossil and Active Geothermal Fields and Hydrothermal Alteration Zones ...... 109 2.3.1 Sericite and Illite in Fossil Hydrothermal Systems ...... 109 2.3.2 Instability of Muscovite Relative to Illite ...... 113 2.3.3 Crystallochemical Characteristics of High-Temperature Illites (Sericite) ...... 115 2.3.4 The Smectite-to-Illite Conversion in Geothermal Fields .. 119 2.4 The Illite Age Measurement ...... 122 2.4.1 Fundamental Concepts ...... 122 2.4.2 The K-Ar Apparent Age of Authigenic-Detrital Mineral Mixtures ...... 125 2.4.3 Patterns ofK-Ar Accumulation During Illite Growth Processes ...... 129 2.4.4 Diagenesis of Bentonites ...... 136 2.5 Summary ...... 139 2.5.1 What is Illite? ...... 139 2.5.2 Where Does Illite Form? ...... 141

3 Dynamics of the Smectite-to-Illite Transformation 145 3.1 Experimental Studies ...... 145 3.1.1 The Run Products in Whitney and Northrop's Experiments Using Bentonite ...... 146 3.1.2 The Different Possible Interpretations of the Experiments ...... 149 3.2 Kinetics of Experimental Transformations (Natural and Synthetic Starting Materials) ...... 155 3.2.1 Kinetics of Illite Formation Using Synthetic, Chemical Compositions ...... 155 3.2.2 Kinetics Using Natural Smectite Minerals ...... 158 3.3 The Bulk Composition Effect (K20) ...... 160 3.3.1 Natural Minerals ...... 160 3.3.2 Multiparameter Kinetics ...... 163 3.3.3 Formation of Muscovite at High KOH Concentrations: Shape and Polymorph ...... 165 3.4 Kinetics of the Smectite-to-Illite Conversion Process in Natural Environments ...... 166 3.4.1 Burial Diagenesis ...... 167 3.4.2 The Dual Reaction Kinetic Model (Velde and Vasseur 1992) ...... 168 3.4.3 Changes in Reaction Kinetics ...... 170 3.5 Success and Failure of the Multiparameter Models ...... 172 3.5.1 The Kinetic Model of Pytte and Reynolds (1989) (Thermal Metamorphism) ...... 172 Contents XIII

3.5.2 Drawbacks of Multi-Parameter Kinetic Models ...... 172 3.6 Stability Controls (T, t, Jlx) ...... 174 3.6.1 Comparison of Experimental Models and Natural Systems ...... 174 3.6.2 Kinetic Parameter Values ...... 174 3.6.3 Importance of Mineral Reactions ...... 175 3.7 Summary ...... 176 3.8 Application of Kinetics to K-Ar Dating ...... 176 3.8.1 The Problem for K-Ar Dating of Illite from Shales ...... 176 3.8.2 K-Ar Age and Mass Transfer During Smectite-to-Illite Conversion ...... 178 3.8.3 An Example: The Balazuc Series (Renac 1994) ...... 182

4 Applications 189 4.1 Exploration and Exploitation of Natural Resources ...... 190 4.1.1 Geothermal Resources ...... 190 4.1.2 Clays and Petroleum ...... 198 4.1.3 Illite Crystallinity and Organic Matter ...... 210 4.1.4 Ore Resources ...... 212 4.2 Environmental Problems ...... 226 4.2.1 Illite and Mixed-Layer Minerals in Soils: Questions of Fertility ...... 226 4.2.2 Some Effects of Agricultural Practice and their Bearing upon the Loss of Illite Content in Soils. 230 4.2.3 Nuclear Waste Barriers - Strategy and Illite Mineralogy ...... 240

Glossary 249 References 263 Index 283 List of Abbreviations

CEC cation exchange capacity (meqflOO g or cmolkg-1)

FWHM full width at half maximum intensity (°28 Cu or Co Ka) HIS hydroxy-AI interlayer smectite HIV hydroxy-AI interlayer vermiculite liS MLM illite-smectite mixed layer mineral. In case of coexistence of sev- eral liS MLM, they are distinguished as follows: IISil illite-rich liS MLM I/Ssm smectite-rich liS MLM PCI poorly crystalline illite R=O or RO randomly ordered mixed layer mineral (see glossary) R=l or Rl ordered mixed layer mineral (see glossary) weI well-crystallized illite XRD X-ray diffraction

LlGO free energy of formation (kcalmol-1 or kJ mol-I)