Atlas of micromorphology of mineral alteration and weathering

516 Pages·2009·36.08 MB·English

by  Delvigne, Jean

Micromorphology
of Mineral Alteration
and Weathering
Also in this series
if
EDCJclopedia Mineral Names
VI/.H. Blackburn & VI/.H. Dennen
Special Publication 1
if
Glossary Mineral Synonyms
J.
de Fourestier
Special Publication 2
icromorphology
of Mineral Alteration
and Weathering
Jean E. Delvigne
- 9 NOV. 1998
The Canadian Mineralogist
-~"",r-i
CR51l~
MIneralogical editions
ABsod.iltlonofcanada
Associallonmln~ralogique
duC~nada
Caption (!.j'the phntnmi roHraph
on thcfronl or r
TJ11 1'11'"1111'I11l 1'1",I; 1'1J illustrates some of the
most common patterns of weathering observed
within partly weathered primary minerals. A subhe
clral crystal of ol1:hopyroxene is partly weathered to
greenish yellow sme,tite arrangcc..l in a subparallcl
banded texture" The rtrst·rormed smectite is devel- EDITOJ\
Rub(;!"t F. Martin
aped from transverse fractures; numerollS denticulate
COVERM~DTEXT DESIGl'ER
remnants oforthopFoxenc are still preserved writh.in PouliotGlIayI:,'raphistes
the alteromorph. Further weathering induces the DE,KTOP PUBLISHER
Inl"o 1000Mot.~ine.
developmeJlt ofiron oxyhydroxides, either by de.gra
PHOTOCNGJ\AVER AND PRINTER
dation ofthe prev;ously Formed smectite or by ciirect
Litho Acml~ Prescom
weathering of' the orthopyroxene residues. Further
PUBLISHER
jVlint~r'llogical Association ofCanada
explanations are given in the caption to photomicro-
P.O. Box 78087
anu
graphs 141 142. Mcriline Postal Outlet
1460 Merivale Road
Ottawa, Ontario, Canada K2E 1B1
e-mail: c-anmin.mac.ottawa@••ympatico.ca
11' C()LL'\BOR.~·nON WITH
ORSTOM
lnsLitut fran~-aisde recherchescientiJlgllc
pOW" le Je\'doppemenLen Cooperation
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e-mail: [email protected]
All rights n>sen'ed. No partofthis book may bereproduced
or traosmjtted in an)' form and means, electronic or
mechanical, including photocopy, recording. or any infor
maLion ~torage and retrieval system, without permission in
wriLingfrom U)cpublisher.
Printed in Canada
Copyright 1998 Mi.neralogical AssociationofCanada
ISBN 0-921294-43-3
(Mineralogical AssociationofCanada, Canada)
ISBN 2-7099-1420-4 (ORSTOM, FranCt')
Preamble
TIrl I'·\1/<' .\\1 I Ius emerged as a major blages. A non-genetic terminology is developed to
locus of research in the natural sciences. In facilitate textural classifications and communication of
many universities, for example the one in findings. To a student of mineralogy and petrology,
which I teach, multidisciplina.ry teams arc the book i1lustntes the passage from familiar territory
busy developing new curricula in the emiron.mental to uncharted "vaters, the field ofactivity ofsoil scien
sciences to meet the challenges of modem society. tists and agronomists. Ofcourse, to the secondgroup,
Mineralogy is at the fordi-ont in these programs, it is the beginning ofthe book that is less familiar ter
because of the focus on near-surface interactions ritory. But to both audiences, trUlleralogy evidently
involving rocks, soil, water, air and livingorganisms. play.s akey role and is acommon language.
Mineralogists and petrologists in general have an The Mineralogical Association of Canada, in col
excellent understanding ofthe way igneous and meta laboration \Vitll ORSTOM, is proud to bring you tll.is
morphic rocks form, at temperatures as high as Aliasif,l-JicromorpholoBYc:FMineral I1heraUon and Weath
12000C and at pressures representative ofthe middle erins. It represents the distilled pearls of wisdom ofa
or lower crust. On the contrary, by and large, miner master in the fIeld. Ihave learoedagreatdeal in work
alogists and petrologists have a poor grasp ofthe way ing with Jean Delvigne to make this book a reality. I
rocks and mjnerals respond to their near-sUI-face envi now look at igneous and met.lf11orphic rocks in thin
ronment. Once these rocks begin a trajectory toward section from anew perspective, and with new insight.
the surface as a result of tectonic forces, the rock I acknowledge thein.flueoce ofFran~oisSoubies, envi
forming mineralsgenerally leave their field ofstability, ronmental mi.neralogist and mineral collector extraor
and important adjustments set in. Secondary minerals dinaire, an employee of ORSTOM formerly at the
appear, but Inineralogical research is fraught with diJ Laboratojre de Mineralogk, Universitc Paul-Sabatier,
ficuJty. The newly fOI-mea assemblages commonly are in Toulouse. Thanks to him, and to his enthusiasm, I
very ADe grained, and thus diHlcult to investigate fIrst met the author, and learned about tlle wealtll of
guantjtatively except by high-resolution microbl~aru information in the completed manuscript that became
technigues. The rocks are flsslIred, and the geochcmi. tllis book. Vicki Loschiavo helped me to cope with
cal systems involve circulating water; the stage is set chapters and figure captions, and to deal withcompet
for open-system behavior, with all the complexities ingcommitments. Iwas ver)'fortunate to counton tlle
that an open system entails. The tl"mpn'ature of reac same creati.ve team that produced our SpeCial Publica
tion is so low that non-eguilibrium assemblages of (;on Number I: PielTetteTremblay, Publicity Coordina
minerals are H~ry mucb the norm. torofthe Mineralogical Association ofCanada, Michel
Guay, and Jean-Claude Cote. I hope that whoevel-is in
Each rock-fol-mingmineral has astory to tell. Fur
tllC audjencc, soil scientist, clay mineralogist, eco
thermore, much information about the starting point
nomic geologist, agronomist, or petrologist, wi1l find
in these transformations emerges from a study of the
here new insight into the multifarious paths that rocks
rock's textural attl-ibutes. One mustsimply be shown
take to adjust to tllcir new surroundjngs near the
what to lookfor in Ol-del"to l"Ccognizethe clues. In this
Eal1:h's sUI-face.
book, Jean Delvigne patiently t;]kes the reader along
unfamiliar paths. At tllt' beginning of this atlas, the
rocks all look veil' familiar, as the adjustments are Robert F. Martin
incipient. Then, as one progresses through tllC book, Professor, Department ofEarth
the roch look less and less familiar, until virtually and Planetary Sciences, McGi11 University
nothing is left ofthe original high-temperaturl' a~sem- Editor, The Canadian .Mineralogis(

Preface
1'1' :It/m ofMicromorpho/"8J' ~rk/ineral it/tcrarion ofthis field have occurred in tJle last few years, But in
and Jf'emherina, Jean Delvignc pw\,jdesa compre most instances, geochemists operate "bUndJy" in that
hensh'e statement of problems and a swmnary of they typically do not take petrographic descriptions
present understanding of weathering, applied to into consideration, an approach that can lead to incon
some remarkable West Amcan and Brazilian exam sistent inferences, TIleinconsistencies arise because of
ples, His complete coverage is representative of the thefailure toproperly observeand W1derstand textural
petrographic- approach in the study of lateritic and mineralOgical modifications in the microenviron
alterites, The book ditfers from others in the study of ments of weathering profiles, This book thus also
the petrography of weathering by presenting first the shou.ld enlighten geochemists working on weathering
rocks, with their inheritance of hydrothermal alter processes,
ation, Then he describes ingreat detail therelationship
A single voltU11e cannot possibly cover all the
between parent minerals and the products of their
facets of the complex problems involved, However,
weathering, He makes useofabW1dantand exceptional
with the help ofthe excellent examples chosen by the
illustrations ofthin sections, Thi~documentation is of
autJlOr, the book gives a good overview of the main
paramow1t importance for students and non-special
problems of weathering, and speciJ:ically provides
ists; it allows them (0 wlderstand the complexity of
insight into the way parent minerals weather, the
such near-surface phenomena, The terminology used
nature ofweathering products, and their variability in
in this book is simplified for microscopicdescriptions,
a venica.l profile and in alateral sequence, In my opin
At first glance, it may appear esoteric, but it seIV'es to
ion, this book will serve as a guide to students, geo
characterize structures, textures and interrelations
chenlists, geologists, soilscientists, geomorphologists,
among minerals in altelites and soils,
and environmental scientists concerned with the basic
Every method starb with a few simpJe concepts, conceptsand recent trends in research on the processes
proceeds through a period ofgrowth with increasing ofweatJ1ering, especially in humid tropical areas,
sophistication, and finally reaches a stage ofsynthesis,
at which pointcase historiescan bediscllssed and com Daniel Nahon
pared, So it is ,..-ith the geochemistry of weathering, Professor, University ofAix-Marseille III
Several important developments in our W1derstilnding