Clay Minerals: A Physico-Chemical Explanation of their Occurrence

432 Pages·1985·4.767 MB·ii-vii, 1-427\432

by  B. Velde (Eds.)

FURTHER TITLES IN THIS SERIES
VOLUMES 1.2.3,5,8 and 9 are out of print
4 F.G. TICKELL
THE TECHNIQUES OF SEDIMENTARY MINERALOGY
6 L. VAN DER PLAS
THE IDENTIFICATION OF DETRITAL FELDSPARS
I 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 Jr.
INTRODUCTION TO 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
THE CHEMISTRY OF CLAY MINERALS
16 H.H. RIEKE I11 and G.V. CHILINGARIAN
COMPACTION OF ARGILLACEOUS SEDIMENTS
11 M.D. PICARD and L.R. HIGH Jr.
SEDIMENTARY STRUCTURES OF EPHEMERAL STREAMS
18 G. V. CHILINGARIAN and K.H. WOLF, Editor8
COMPACTION OF COARSE-GRAINED SEDIMENTS
19 W. SCHWARZACHER
SEDIMENTATION MODELS AND QUANTITATIVE STRATIGRAPHY
20 M.R. WALTER,E ditor
STROMATOLITES
21 B. VELDE
CLAYS AND CLAY MINERALS IN NATURAL AND SYNTHETIC SYSTEMS
22 C.E. WEAVERa nd K.C. BECK
MIOCENE 0.F THE SOUTHEASTERN UNITED STATES
23 B.C. HEEZEN, Editor
INFLUENCE OF ABYSSAL CIRCULATION ON SEDIMENTARY
ACCUMULATIONS IN SPACE AND TIME
24 R.E. GRIM and GUVEN
BENTONITES
25A G. LARSEN and G.V. CHILINGAR,E ditors
DIAGENESIS IN SEDIMENTS AND SEDIMENTARY ROCKS, I
26 T. SUDO and S. SHIMODA, Editors
CLAYS AND CLAY MINERALS OF JAPAN
21 M.M. MORTLAND and V.C. FARMER, Editors
INTERNATIONAL CLAY CONFERENCE 1978
28 A. NISSENBAUM, Editor
HYPERSALINE BRINES AND EVAPORITIC ENVIRONMENTS
29 P. TURNER
CONTINENTAL RED BEDS
30 J.R.L. ALLEN
SEDIMENTARY STRUCTURES
31 T. SUDO. S. SHIMODA, H. YOTSUMOTO and S. AITA
ELECTRON MICROGRAPHS OF CLAY MINERALS
32 C.A. NITTROUER, Editor
SEDIMENTARY DYNAMICS OF CONTINENTAL SHELVES
33 G.N. BATURIN
PHOSPHORITES ON THE SEA FLOOR
34 J.J. FRIPIAT, Editor
ADVANCED TECHNIQUES FOR CLAY MINERAL ANALYSIS
35 H. VAN OLPHEN and F. VENIALE, Editors
INTERNATIONAL CLAY CONFERENCE 1981
36 A. IIJIMA, J.R. HEIN and R. SIEVER, Editors
SILICEOUS DEPOSITS IN THE PACIFIC REGION
31 A. SINGER and E. GALAN, Editors
PALYGORSKITE-SEPIOLITE: OCCURRENCES, GENESIS AND USES
38 M.E. BROOKFIELD and T.5. AHLBRANDT, Editors
EOLIAN SEDIMENTS AND PROCESSES
39 B. GREENWOOD and R.A. DAVIS Jr., Editom
HYDRODYNAMICS AND SEDIMENTATION IN WAVE-DOMINATED COASTAL ENVIRONMENTS
DEVELOPMENTS IN SEDIMENTOLOGY 40
CLAY MIN E RALS
A Physico- Chemical Explanati on
of their Occurrence
B. VELDE
Ecole Normale Supgrieure, Laboratoire de Ggologie, 46 Rue d’Ulm, 75230
Paris Cgdex (France)
ELSEVIER
Amsterdam - Oxford -New York - Tokyo 1985
ELSEVIER SCIENCE PUBLISHERS B.V.
1 Molenwerf
P.O. Box 211,1000 AE Amsterdam, The Netherlands
Distributors for the United States and Canada:
ELSEVIER SCIENCE PUBLISHING COMPANY INC.
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Library of Congress Cataloging in Publication Data
Velde, B.
Clay minerals.
(Developments in sedimentology ; 40)
Bibliography: p.
Includes index.
1. Clay dnerals. I. Title. 11. Series.
w38g.m.v43 1985 5491.6 84-21204
ISBN 0-444-42423-7 (U. S. )
ISBN 0-444-42423-(7V ol. 40)
ISBN 0-444-41238-(7S eries)
0 Elsevier Science Publishers B.V., 1985
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V
BIBLIOGRAPHICAL DATA
Bruce Velde, Directeur de Recherche in the Centre
National de la Recherche Scientifique, now works in the
Laboratoire de G&ologie, Ecole Normale Supgrieure in Paris.
He began his undergraduate work in the University of Illi-
nois in 1956 and obtained a PhD from the University of Mon-
tana in 1962. He was a fellow at the Carnegie Geophysical
Laboratory, Wash. D.C. in' 1962-1964 and 1976. His career in
C.N.R.S. began in the Sorbonne, Laboratoire de Pgtrographie
in 1965.
VII
PREFACE
This book follows another which must be considered
as a first attempt to put some order in the house of clay
petrology. Its limited success was encouraging enough to
begin again the long process of reviewing the current lite-
rature, extracting the pertinent data, summarizing and fi-
nally analyzing the information at our disposal. A certain
number of the questions posed then can now be answered, yet
many others await investigation by clay mineralogists. What-
ever the short-comings of this book are, they reflect those
of the author and not those of his many helpful colleagues
and friends. I would like to express my gratitude to John
Hower for his guidance and patience over the years, to Alain
Meunier for bravely attempting to make sense of my enthu-
siasm, to Jacqueline Beauquin for calmly accepting and cor-
recting persistent inconsistency.
1
-
I INTRODUCTION
The study of clay minerals has made a series of ad-
vances which were due to new methods of investigation ; such
as X-ray diffractometry, or new ideas concerning their ori-
gin and evolution, such as the concept of clay petrology pro-
posed by C.E. Weaver (1959) and the concept of clay mineral
association proposed by G. Millot (1964). In fact, as has
been the case in many other disciplines, progress in under-
standing the fundamentals of clay mineralogy has come in un-
even steps. The essential work in the 19th and early 20th
century was that of discovery, isolation and identification
of the minerals. Later work in the mid-twentieth century
concerned a definition of the structure of clays and their
chemistry which is related to this structure. The Geological
Survey in the United States produced a number of fundamental
papers which defined the chemistry of clay minerals and the
mineralogy of phyllosilicates. The next endeavor was to de-
termine the geology of clays-developed by Weaver in the Uni-
ted States and Millot in France among others. Meanwhile ex-
periments were conducted, mainly in France and the United
States which attempted to quantify the chemistry of clay mi-
neral genesis by experiment or calculation. These two themes
have continued sporadically until the present. In 1977, I
attempted to summarize the available data, interpret and
sort out the major evident "truths" and then propose a se-
ries of geochemical and petrographic systems which might
explain why many clay assemblages are found commonly in na-
ture. Since that time, the electron microprobe has come on
the scene. This tool permits one to determine, in favorable
circumstances, the spacial and chemical factors which result
in the genesis of clay minerals. This new information allows
one to make a further stride in the science of clay minera-
logy. However, the era of electron microprobe studies is
just beginning which means that we have much more to learn
in the immediate future.
The new information, and that resulting from subse-
quent more "classical" studies , has changed the ideas which I
had developed in certain cases but in a general way they
2
have served to amplify and extend the domains of investiga-
tion which can now be analyzed. For example, we can now look
at the problems of clay mineral genesis during weathering in
a mineralogical and chemical way which was previously
impossible. The same is true for hydrothermal alteration as
well as sandstone diagenesis. A new field of endeavor has
occurred recently, that of the deep-sea alteration of
basalts, which allows one to consider the major chemical
transfers which influence the composition of the upper
oceanic crust as well as that of the sea. These new fields
of investigation will be covered in this book using the "old
methods" which were applied to the previously available data
for clays in sedimentary and sedimentary rock environments.
What then are these old methods ? First, it is consi-
dered necessary to determine which clay phases are commonly
present and which phases have been sufficiently studied to
give an idea of their chemical composition limits. These
limits are defined according to the results published in the
literature. Most data used appeared between 1950 and 1982.
These studies are based upon pure mineral samples which were
analyzed by classical methods and which could be identified
by X-ray diffraction methods. These are "well characterized"
minerals. Microprobe data are compared to these data
because, in most instances, X-ray diffraction information is
not available for the exact mineral analyzed. Also,
classical analysis methods allow one to distinguish Fe2+
from Fe3+, a very important measurement as we will see.
One must stop here a moment to consider the processes
that are involved in a mineral analysis. Most important,
when one makes a classical determination either for X-ray or
chemical analysis, a large amount of material is necessary,
several hundreds of milligrams, which almost by definition
involves material of several different compositions. The mi-
croprobe has shown us this. Thus classical analyses are fre-
quently average values for mineral mixtures. However, avera-
ges are only useful as long as they are considered as such.
The author feels, that adequate X-ray data are absolutely
necessary to assure that one knows which mineral species is
present. Thus microprobe data must be compared, in most
cases, to data gathered by other means. Once the types of
chemical substitutions are determined for a mineral species,
it is possible to extend the limits of our knowledge with
electron microprobe data.
3
The next step is to determine the mineral associa-
tions of the different clay minerals. This is the method of
facies used in metamorphic petrology with such great suc-
cess. Which minerals occur together and where ? Using these
generalizations one can attempt to construct a chemiographic
framework for clay petrology. The major problem with such an
approach 1s the possible metastable persistence of a phase
or its crystallization outside of its stability field. These
problems occur in metamorphic petrology and even more fre-
quently in igneous petrology but the practitioners of these
arts have not yet been severly hampered by them. There is no
reason why clay mineralogists should be. However, we will
use possibly more caution in our pronouncements since we
know that kinetic problems are great at lower temperatures
(which are relative anyway) and that the domains of clay
mineral stability are notably difficult to determine at low
temperatures, at least as far as geological conditions are
concerned.
The phase diagrams established in this way will be
useful to interpret clay mineral assemblages found in nature
with regard to their geological significance. Certain short-
comings will be pointed out (others will undoubtedly remain
and will be pointed out by the interested reader). The
object of this book then is to propose a method for
considering the geology of clay minerals which will be
modified and perfected as time goes on. Science means re-
interpretation of the past. One can never expect to
formulate eternal truths in all their detail - at least not
in the natural sciences during the latter part of the
twentieth century.
What then will be used here for the foundations of
the analysis ?
4
1 - Choice of Information
The information which is used to construct this
petrologic interpretation of clay mineral assemblages is
essentially of three types : chemical analyses of natural
minerals, assemblages of minerals reported in the literature
and experimental determinations of clay mineral stabilities.
In using data from the literature one is forced to select
from the mass available, that which seems most accurate and
that which is most directly applicable to a given problem.
Inherent in such a process is the problem of personal bias
and unintentional oversight. It is certain that pertinent
studies have been omitted from the compilation presented
here, but it is hoped that these omissions do not prevent an
understanding of the petrology of clay minerals. Basically
only studies posterior to 1950 have been considered, because
information before this time could not be correctly
characterized due to relatively poor X-ray diffraction
techniques. The main criterion for using studies reporting
natural mineral compositions is the quality of X-ray dif-
fraction data permitting the verification of the presence of
single phase or multiphase samples. Low angles of 2 8 are
especially critical where the detection of highly expandable
phases is concerned. Thus certain chemical analyses have
been arbitrarily eliminated for lack of assurance that a
given sample is monomineralic. Nonetheless this problem can-
not be discounted even in the analyses selected.
Each chemical analysis thus chosen has been calcu-
lated into a chemical structural formula using a computer
program. The method of calculation is that used by Foster
(1953 ; 1962) where a given number of oxygens and hydroxyls
is assumed to be present ; Olo(OH)2 for a 2:l structure, Ol0
(OH)8 for a 2:2 chlorite type structure and 05(OH)4 for a
1:l structure. The following site occupancies disqualified
an analysis from use : > 3.05 octahedral ions, > 4.05 sili-
con and > 1.10 interlayer ions for non-chlorite structures.
Calcium contents above 0.20 ion in low temperature micas and
in chlorites were considered to be excessive. Trioctahedral,
low-alkali phases are considered in the vermiculite-corren-
5
site group. The possibility of significant secondary iron
oxidation in numerous samples is considered to be small and
in any event inconsequential to the general trend of mineral
compositions, thus water contents were not calculated into
the structural formulas.
The experimental studies have been chosen mainly
for the completeness of reported experimental conditions and
for their apparent approach to an equilibrium assemblage.
These criteria are difficult to adhere to in that experimen-
tal data are not abundant and frequently one must make do
with what is available in order to gain an understanding of
a given problem. However, where several studies overlap,
that with the longest experimental durations or reversal
equilibria is chosen by preference. Nevertheless a certain
amount of caution is necessary to interpret the available
experimental results.