Karst Bauxites: Bauxite Deposits on Carbonate Rocks

440 Pages·1982·67.658 MB·2-441\440

by  GYÖRGY BÁRDOSSY (Eds.)

Further titles in this series
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GEOCHEMICAL EXPLORATION 1974
2. P. M. D. BRADSHAW (Editor)
CONCEPTUAL MODELS IN EXPLORATION GEOCHEMISTRY
The Canadian Cordillera and Canadian Shield
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WORLD MINERAL SUPPLIES
Assessment and Perspective
4. R. T. SHUEY
SEMICONDUCTING ORE MINERALS
5. J. S. SUMNER
PRINCIPLES OF INDUCED POLARIZATION FOR GEOPHYSICAL
EXPLORATION
6. R. A. RICH, H. D. HOLLAND and U. PETERSEN
HYDROTHERMAL URANIUM DEPOSITS
7. J. G. MORSE (Editor)
NUCLEAR METHODS IN MINERAL EXPLORATION AND
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GEOCHEMICAL EXPLORATION 1976
.10. G. B. FETTWEIS
WORLD COAL RESOURCES
Methods of Assessment and Results
11./?. G. TAYLOR
GEOLOGY OF TIN DEPOSITS
12. H. K. GUPTA
GEOTHERMAL RESOURCES: AN ENERGY ALTERNATIVE
13. C. R. M. BUTT and R. E. SMITH (Editors)
CONCEPTUAL MODELS IN EXPLORATION GEOCHEMISTRY, 4:
Australia
Developments in Economic Geology 14
KARST BAUXITES
BAUXITE DEPOSITS ON CARBONATE ROCKS
by
GYÖRGY BÁRDOSSY
HUNGARIAN ALUMINIUM CORPORATION, BUDAPEST
ELSEVIER SCIENTIFIC PUBLISHING COMPANY
Amsterdam-Oxford-New York 1982
This book is the completed and translated version of
KARSZTBAUXITOK
First published in 1977 by AKADÉMIAI KIADÔ, Budapest
Translated by B. BALKAY
Joint edition published by
Elsevier Scientific Publishing Company, Amsterdam, The Netherlands and
Akadémiai Kiadó, The Publishing House of the Hungarian Academy of
Sciences, Budapest, Hungary
The distribution of this book is being handled by the following publishers
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for all remaining areas
Elsevier Scientific Publishing Company
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Library of Congress Cataloging in Publication Data
Bárdossy, György.
Karst bauxites.
(Developments in economic geology; 14)
Translation of: Karsztbauxitok bauxittelepek
karbonátos közetekben.
Bibliography: p.
Includes index.
1. Bauxite. 2. Karst. 3. Rocks, Carbonate.
I. Title. II. Series.
TN490.A5B3413 553.4'926 81-12508
ISBN 0-444-99727-X AACR2
ISBN 0-444-99727-X (Vol. 14)
ISBN 0-444-41250-6 (Series)
© Akadémiai Kiadó, Budapest 1982
AU rights reserved. No part of this publication may be reproduced, stored in a retrieval system,
or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise,
without prior written permission of the publishers.
Printed in Hungary
INTRODUCTION
A description of all the karst bauxite regions of the world would require a multi-
volume monograph whose great bulk would hamper the highlighting of the main
features of interest. For this reason, the writer has striven above all to compare bauxite
regions on a quantitative basis wherever possible, relying in doing so on the methods of
mathematical statistics. This quantitative processing and assessment of the infor­
mation available is the most essential novel feature of this book.
The first part of this volume presents observational and analytical evidence
concerning karst bauxites. The typical features of bauxites were analysed from a
variety of aspects and results from different bauxite regions were compared. Much
attention was paid to Hungarian bauxite deposits and it is these that figure in the
greatest detail in the comparative assessment. More or less metamorphosed karst
bauxites were also considered, as there is no sharp limit between metamorphic (emery)
and non-metamorphic bauxites: the transition being gradual, any delimitation would
be arbitrary.
The second part is concerned with the conditions of formation of karst bauxites and
with the factors controlling their geographic and stratigraphie distribution. The
treatment is of a synthesising type, intended to elucidate the interaction in space and
time between all the known factors.
The writing of this book was much facilitated by the fact that, in recent years, the
writer has had occasion to visit the principal karst bauxite regions of Austria, Bulgaria,
France, Greece, Iran, Italy, Jamaica, Rumania, Spain, the USA, the USSR, the
Socialist Republic of Vietnam, and Yugoslavia. Bauxite samples from all other karst
bauxite regions of the globe were made available to the writer by courtesy of bauxite
specialists at home and abroad. Comparisons with lateritic bauxites were made
possible by visits to the principal bauxite zones of Brazil, the Guiñean Republic and
India.
Over and above the viewpoint of scientific research, the writer has paid special
attention to aspects useful for practical bauxite prospecting and processing.
The writer wishes to express his sincere gratitude to Academician Elemér Szádeczky-
Kardoss who authorised the research and supported him with his advice. In the
analytic work, in data processing and in statistical calculations, the writer was assisted
by Miss Mária Tóth, Miss Ilona Buday and Miss Olga Komoróczy. The photos were
prepared by Mr Lajos Klinda. Thanks are due to Miss Anikó Tóth for the painstaking
preparation of the drawings.
The scientific readers of the book were Dr. Kálmán Balogh and Dr. Vilma Széky-
Fux; the author takes this opportunity to express his gratitude to them.
14
INTRODUCTION
He is indebted to Bálint Baikay, György Komlóssy, Péter Ottlik and Ferenc
Zenkovics for reading chapters of this book, for their helpful advice and remarks. Last
but not least, it would be quite a task to enumerate all those geologist, mineralogist and
technologist colleagues who have contributed ideas, remarks and friendly assistance in
the preparation of this book, but sincere thanks are expressed to them all.
No international consensus has as yet evolved concerning the terminology of
bauxite geology. The writer therefore deems it necessary to specify the meaning of the
principal terms as they are used throughout this book.
Bauxite. A residual or sedimentary rock in which the aggregate content of the oxide
and/or hydroxide minerals of aluminium, iron and titanium is greater than 50 %, and
aluminium minerals are more abundant than the minerals of the two other elements
together. The question as to what is a bauxite, then, must be decided on the strength of
the quantitative mineralogical composition. The definition of bauxite as an ore of
aluminium is equivocal because the limit between ore-grade and sub-grade bauxites is
in continual change, depending on the development of refining technology and of
demand. The types of bauxite encompassed by this broad definition are discussed in
§4.1.
Bauxite ore body. That part of the bauxite complex (see below) which is made up of
ore grade or potentially ore-grade material (bauxite, clayey bauxite, bauxitic clay).
Bauxite genesis. The totality of those processes of alteration and sedimentation
which lead to the formation or rocks enriched in aluminium, including processes of
weathering, transportation, and deposition.
Bauxitisation. That phase of bauxite genesis by which the material of some rock is
converted into bauxite or by which the conversion into bauxite of a rock already
partially bauxitised is continued.
Lateritisation. A form of superficial weathering resulting in an increase of
aluminium and titanium contents, also frequently but not invariably of iron contents,
and in a decrease of alkali, alkali earth and silica contents. Bauxitisation is a special
case of lateritisation, characterised by a prevalence of aluminium enrichment. Latérite
is a generic term for the rock products of lateritisation.
A hierarchy of four bauxite geological/depositional units in ascending order of size
is distinguished:
(1) Bauxite deposit. A spatially coherent (uninterrupted) depositional unit of
uniform genesis, composed of bauxite and bauxitic rocks (e.g. the bauxite lens
Darvastó VI). In certain depositional types, several bauxite ore bodies can be
distinguished within a bauxite deposit; these may be separated by bauxitic rocks, and
possibly by clay, sand or lignite. Even in this case, however, the bauxite deposit must be
genetically coherent.
(2) Bauxite deposit group. Several bauxite deposits lying close together in the
horizontal sense but separated by a comparatively broad barren zone from any bauxite
deposits not belonging to the group (e.g. Nyirád bauxite deposit group). Typical
deposits have an areal extent in the range 10-100 km2. In a bauxite deposit group
featuring a largish number of deposits, it is usual to distinguish subgroups for better
orientation. In the extreme case, even a single bauxite deposit may be regarded as a
15
INTRODUCTION
'group' if it is geologically separate and geographically remote from some other
groups. In some areas, bauxite formation repeatedly took place in different geological
periods. In the writer's experience, deposit features and genetics in each of these
periods tend to differ rather substantially; they are accordingly regarded here as
separate groups (e.g., in the Obrovac-Novigrad-Drnis region of Yugoslavia, a
Paleocene and a Middle Eocene deposit group are distinguished).
(3) Bauxite region. A complex of geologically related bauxite deposit groups,
separated from neighbouring bauxite regions, if any, by a barren zone or by a change in
geology (e.g. the Transdanubian Hills bauxite region of Hungary). Their areal extent is
in the range of from several hundred to several thousand km2. Kirpal' (1977)
distinguished bauxitic zones within bauxite regions, comprising deposit groups that
constitute elongate bands or zones. In the writer's opinion, this hierarchic sub-unit is
unnecessary except in some bauxite regions of exceptional extent. A bauxite region, as
a unit of higher rank both in the spatial and in the temporal sense, may encompass
several bauxite deposit groups of different ages.
(4) Bauxite belt. A coherent group of bauxite regions in a second- or third-order
geotectonic unit (e.g. the Mediterranean bauxite belt), characterised by a uniform
geostructural history. The areal extent is from some hundred thousand to a few million
km2 with a length or width of several thousand km. Somes bauxite belts have had a
single episode of bauxite formation; in others, two or more such episode may have
taken place.
Bauxite complex. A term coined by Vadász (1951) for the rocks making up a bauxite
deposit; it includes in addition to bauxite also all other rocks genetically connected
with it.
Bauxitic formation. A stratigraphie succession, one or more horizons of which
include one or more bauxite deposits. The faciès of the bauxitic formation are
genetically related to the bauxite deposit and, in fact, control its depositional features.
1. CLASSIFICATION OF BAUXITE
DEPOSITS
A much debated issue, the classification of bauxite deposits has not as yet produced a
consensus. This is due to the manifold features of the deposits which can thus be
classified from a number of different aspects. What the specialists cannot agree on is the
relative importance of these features.
The most striking difference recognised early in this century is between bauxite
deposits overlying silicate rocks on the one hand and carbonate rocks on the other. It
was on this basis that Harrassowitz (1926) divided bauxites into silicate bauxites and
calcareous bauxites. Rather widely accepted since, this subdivision is still current
especially in textbooks written in the German language (Petrascheck and Petrascheck
1950, Schneiderhöhn 1962, Cissarz 1965).
Fox (1932) subdivided bauxite deposits on a genetic basis. In his opinion, lateritic
bauxites ('aluminous latérites') are the products of the lateritic weathering of silicate
rocks, whereas terra-rossa bauxites derive from terra rossa, the weathering residue of
limestones and dolostones. His subdivision was adopted also by De Weisse in his
monograph of 1948.
Vadász (1951) rejected the terms 'silicate' and 'calcareous' bauxite as conducive to
misunderstandings, and introduced instead the terms 'lateritic bauxite' and 'karst
bauxite', appreciating in the latter them of the role played by the karstification of a
carbonate bedrock in the evolution of some deposits. This simple and easy-to-apply
subdivision became fairly widely accepted in the literature (cf e.g. Zans 1959, De Weisse
1964).
Roughly at the same time, some other classifications were also elaborated, without
eliciting much response. For example Harder (1952) proposed the following
classification based on parent-rock composition:
(1) Deposits derived from alkali- and aluminium-rich silicate rocks.
(2) Deposits connected with limestones.
(3) Deposits connected with sedimentary clays.
(4) Deposits connected with intermediate and basic eruptives.
(5) Deposits due to the vigorous weathering of rocks of medium aluminium
content.
The groups thus defined cannot be unequivocally distinguished; the place of a given
deposit in this or that group is often debatable.
Hose's (1960) classification rests on a morphological basis:
1. CLASSIFICATION OF BAUXITF DEPOSITS 17
(1) Deposits developed on peneplains.
(2) Deposits formed on volcanic domes and plateaux.
(3) Deposits on karsted limestone plateaux.
(4) Sedimentary reworked deposits.
This classification also failed to gain broad acceptance, owing to the uncertainty
inherent in separating the first group from the second.
Valeton ( 1972) pointed out that some deposits fit neither into the latérite nor into the
karst bauxite group. In view of this fact, she developed the following classification
based on bedrock lithology:
(1) Bauxite deposits overlying igneous and metamorphic rocks.
(1.1) Slope type.
(1.2) Plateau type on basic igneous rocks.
(1.3) Plateau type on variable rock types.
(2) Bauxite deposits on sedimentary rocks.
(2.1) Bauxites on clastic sediments.
(2.2) Bauxites on carbonate rocks.
(2.3) Bauxites on phosphate rocks.
Although consistent, Valeton's classification is one-sided, paying attention neither to
the abundance of the types of deposits, nor to their depositological features.
Concentrating on depositological features, Patterson in his turn (1967) proposed the
following classification:
(1) Blanket deposits: flat-lying layers of variable thickness.
(2) Interlayered deposits: discontinuous layers and lenses interstratified in
sedimentary and/or volcanic rocks. Some are residual; some are redeposited.
(3) Pocket deposits: fillings of depressions, most often in dolomite and limestone, but
sometimes in other rocks too. This group includes a subgroup of 'interlayered
pocket deposits' (pockets intercalated in a sequence of sedimentary deposits).
Patterson's groups offer no clear-cut distinction either in the depositological or in
the genetic sense. The use of his classification would therefore lead to numerous
ambiguities.
The classification proposed by Grubb (1973) is based on the altitude at which .
bauxitisation has taken place:
(1) High-level or upland deposits.
(2) Low-level or peneplain-type deposits.
Grubb placed into the first group the residual deposits formed above the ground
water table under fair drainage conditions, including among others the lateritic bauxite
deposits of Guinea, Ghana, India and Hawaii.
He placed into the second group the residual, redeposited and allochthonous
deposits characterised, according to him, by repeated fluctuations of the ground water
table, citing as typical examples the deposits of Gove and Weipa in Australia, and those
in Guyana and Surinam. Deprecating the distinction of a separate karst bauxite group
2 Bárdossy
18 1 CI ASSíFirATlON OF BAUXITE DEPOSITS
as superfluous, he placed the bauxites of Jamaica and Hispaniola into the high-level
group and all other karst bauxites into the low-level group.
The distinction of high- and low-level deposits among the lateritic bauxites is
doubtless justified and is not a novel idea either. The rejection out of hand of the karst
bauxite group, however, is entirely unjustified. The Jamaican bauxites have
incomparably more in common with the European karst bauxites than with the high-
level lateritic bauxites. It is extremely difficult to decide in the case of a buried deposit of
a past period whether bauxitisation in its time took place on an elevated or on a low-
lying topography. Last but not least, there are deposits which, in the course of their
long history of evolution, alternated between high and low positions as a result of
vertical (epeirogenic) movements in the region. Grubb himself cites some such deposits,
including those of Malaysia and of the Darling Range in Australia. All in all, such a
classification cannot possibly be sufficiently unambiguous. The present writer
accordingly sees no point in adopting it, particularly in extending it to the karst
bauxites.
In the USSR, the classification of bauxite deposits took a course different in many
respects from the above. Deposits were classified on a purely genetic basis early on.
Malyavkin (1937), for example, distinguished lateritic, metasomatic, organogenic and
metamorphic deposits. Likewise on a genetic basis, A. D. Arkhangelsky (1937} who,
remarkably enough, denied the existence of lateritisation and of lateritic bauxite
deposits—classified bauxite deposits into groups of (1) marine, (2) lacustrine and/or
marshy origin. He assumed all the deposits of the Mediterranean region to be of marine
origin.
Vikulova (1946) distinguished five types of deposits according to their sites of
accumulation: (1) deposits on plateaux forming watersheds, (2) valley-floor deposits,
(3) deposits filling karst depressions, (4) lacustrine deposits, (5) lagoon and seashore
types.
It was Peive (1947) who first recognised the importance of geotectonic position and,
on this basis, distinguished two types of deposits: (1) those of the géosynclinal zones,
and (2) those of the platform regions. According to him, the former deposits are all
marine, and all overlie carbonate rocks; the latter ones are all residual or lacustrine or
marsh-deposited. He placed all the deposits of the Urals and of the Mediterranean
region into the first group. Peive's classification was adopted by Goretsky et al (1949),
Rukhin (1958) and by many others. Sapozhnikov (1970,1971 ) identified karst bauxites
with the deposits of the géosynclinal zones.
The geotectonic classification was in fact based on the recognition of objectively
existing, important relationships. In the form cited, however, it represents something of
an oversimplification: in addition to géosynclinal zones and platforms, there also exist
other types of geotectonic units, which do not lack bauxite deposits, either. Nor is the
relationship postulated by Peive of a general validity: bauxite deposits overlying
carbonate rocks do exist also on platforms, and latérite bauxite deposits are known
also from géosynclinal zones (e.g. in Oregon State, US).
Aiming to eliminate these contradictions, Goretsky (1960) developed the following
geotectonic classification, which is more detailed than those cited above:
1. CLASSIFICATION OF BAUXITE DEPOSITS 19
(1) Deposits in stable zones of platforms.
(1.1) On anteclises.
(1.2) On syneclises.
(2) Deposits on mobile parts of platforms.
(2.1) In the borderlands of syneclines.
(2.2) In intramontane and foreland depressions.
(3) Deposits of géosynclinal belts.
(3.1) In zones of transition between platforms and geosynclines.
(3.2) In the outer part of géosynclinal zones.
(3.3) In median masses.
Goretsky subdivided each of these groups into two or three subgroups on the basis of
bedrock morphology, obtaining a total of 16 subgroups. Goretsky's classification does
account for almost every geostructural type, and is self-consistent but its application in
practice is fraught with a great deal of uncertainty. Different authors tend to hold
different views concerning the structural position of this or that region, particularly the
question as to what parts of a platform are to be regarded as stable or mobile. Goretsky
himself, for example, characterised the South Ferghana bauxite region as a
géosynclinal zone, whereas on the geotectonic map of the USSR, published in 1962, it
figures as a gently folded platform. Another deficiency of Goretsky's classification is
that—following A. D. Arckhangelsky—he pays hardly any attention to lateritic
bauxite deposits. He places them in the same group with the allochthonous lacustrine
and marshy bauxite deposits, confining them to the stable platform regions.
KirpaF (1972a) distinguished residual and sedimentary deposits. His further
subdivisions of both groups are based on tectonic position distinguishing platform and
géosynclinal zones. Within these main groups, he distinguished a total of 14 subgroups
on the basis of deposit and bedrock morphology. However, even his primary criterion
of classification involves an ambiguity as in addition to pure autochthonous and pure
allochthonous deposits there are mixed (allo-autochthonous) ones, the position of
which cannot be decided unequivocally in his system. In his tectonically-based
subgrouping, all the contradictions inherent in Peive's classification emerge again.
With a view to getting rid of these difficulties, KirpaF (1977), leaving aside the issue of
tectonic position, proposed a new classification in terms of the following four groups
and 16 subgroups.
(1) Lateric bauxite (residual) deposits.
(1.1) Deposits of linear form.
(1.2) Deposits of lenticular form.
(1.3) Deposits of bowal type.
(2) Polygenetic bauxite deposits (with local reworking).
(2.1) Lenticular karst deposits.
(2.2) Lenticular deposits.
(2.3) Stratiform deposits.
(3) Sedimentary bauxite deposits in terrigenous sequences.
(3.1) Valley-floor deposits.
(3.2) Stratiform deposits.
(3.3) Karst deposits.
2*