Table Of ContentLecture Notes Earth Sciences
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John Cobbing
The Geology and
Mapping of Granite
Batholiths
With 40 Figures
Springer
Author
Dr. John Cobbing
25, Main Road
NGI 2 2BE Radcliffe on Trent
Great Britain
"For all Lecture Notes in Earth Sciences published till now please see final pages
of the book"
ISSN 0930-03 17
ISBN 3-540-67684-8 Springer-Verlag Berlin Heidelberg New York
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Cobbing, John: The geology and mapping of granite batholiths 1 John Cobbing.
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Springer 2000 (Lecture notes in earth sciences; 96)
ISBN 3-540-67684-8
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Preface
This book is mainly about the field geology of granites at all scales from that of a
single outcrop to plutons and batholiths. All field geologists work initially at the
scale of the outcrop, consequently most of the phenomena treated herein are those
which are visible at outcrop scale. However, granites typically occur as plutons and
batholiths, some of which are so large as to apparently defy any effort at systematic
treatment. Having had the opportunity of mapping two very large and very different
batholiths, namely the Coastal Batholith of Peru and the tin granites of Southeast
Asia, I have found that it is possible to map large batholiths within a relatively short
time, so that the geology of the batholith as a whole can be appreciated. Moreover
batholiths are one of the most common modes of granite occurrence, so it makes
sense to study them at their natural scale.
During my working life I have worked with many geologists from underdevel-
oped countries and this book is mainly to help them in unravelling the geology of
their native batholiths.
I have been lucky with my friends and colleagues of many nationalities, and I
particularly thank Wallace Pitcher, who took me on as an untried apprentice in Peru,
and who, by his kindness and example, showed me how to look at granites properly.
Some geologists may consider that too much of this book is devoted to stating
the obvious. It is written mainly for those many third world geologists engaged in
mapping granites in inaccessible terrains, with inadequate logistic support and an
inadequate time frame in which to complete their task.
The structure of the book has been devised with these requirements in mind and
is based on workshops given in Malaysia, Indonesia, China and Norway. It is con-
cerned principally with the practicalities of field mapping but the first four chapters
are of a more academic turn, and are meant to provide an outline of the current state
of theoretical knowledge of granite geology as the background to field work. The
bulk of the remainder is concerned with the purely practical aspects of the regional
mapping of granitic terrains, and the final chapters provide guidelines for the
requirements to be borne in mind when preparing geological maps of these terrains,
and the presentation of the data in written form.
I have tried to make the descriptive sections on granite geology as comprehensive
and intelligible as possible. Most of the phenomena described are not now contro-
versial, but in those which still are, I have endeavoured to indicate where the areas
of controversy lie, and to state my own opinion if I have one. I have not attempted
to provide a fully comprehensive account of every aspect of granite geology, but
have tried to cover most of the features which are likely to be met with by field geol-
ogists. Paradoxically regional studies of granites are best served by the very careful
VI Preface
observation of the details of granite geology at the scale of the outcrop. I have
endeavoured to focus on these details and show how they may be systematically
identified and recorded. This will ensure that the regional interpretation is solidly
based on an accurate and comprehensive record of the field geology. All granites
result from the interaction of different processes during their generation, crystallisa-
tion and emplacement, and many of these processes leave a permanent imprint on
the rock which can, with care, be identified in the field. One of the objectives of this
book is to indicate how the details of the field geology provide information relating
to these processes.
Many granites are deceptively simple in their appearance and there are many
examples of granites which have been studied carefully and in great detail, but
which have continued to yield additional, and sometimes quite contradictory infor-
mation to later investigators. The history of granite geology is full of instances of
such reversals of interpretation. With this background it is unlikely that any study
will not be subject to reinterpretation at some stage. This should not however dis-
courage future work, for there are still many granite terrains of which we remain
wholly ignorant, and which need to be mapped in order to provide the basis for
comparison and further work. The people who do the regional work form that
section of the profession to which this book is directed, and although they are par-
ticularly vulnerable in this respect, since the reconnaissance nature of their task
renders their conclusions subject to later revision, they should take heart and
persist. Their work provides the basis for all subsequent investigations.
Finally I thank all my friends and colleagues and especially Peter Pitfield, Don
Mallick, Fiona Darbyshire, Michael Schwartz, Bernd Lehmann, Bob Beckinsale,
Willy Taylor, Michael Atherton, Andrew Bussell, Paul Bateman, Gordon Gastil,
Cesar Vidal, Julio Caldas, Julio Garayar, Wilfredo Sanchez, Bill Mc Court, Michael
Crow, John Aspden, Martin Clarke, Teoh Lay Hock, Charles Hutchison, Hong
Dawei, Somboon Khositanont, Somchai Nakapadungrat, Oystein Nordgulen, Brian
Sturt, Larissa Dobrezhinetskaya, Valery Vitrin, Carmen Galindo and Cesar
Casquet. I would also like to pay a tribute to the late Chamrat Mahawat who was
my good friend, and who made it possible for me to work in Thailand.
ACKNOWLEGEMENTS
I thank Dr Reedman of the International Division of BGS for his encouragement
and help towards the production of this book.
Table of Figures VII
Table of Figures
QAP diagram of Streckeisen for granite classification and
utilised by Lameyre & Bowden (1982) for the identification of
granite lineage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Calc-alkali diagram of Peacock (1931) . . . . . . . . . . . . . . . . . . . .
Alkali disciminant diagram of Kuno (19 69) . . . . . . . . . . . . . . . . .
K20 vs Si02 Diagram of Pecerillo & Taylor (1976) . . . . . . . . . . .
Source rock-tectonic setting diagram, after Barbarin (1990) . . . . . .
Trace element discriminant plots of Pearce et a1 (1984) . . . . . . . . .
R1-R2 tectonic discriminant plot of Batchelor & Bowden (19 85) . .
The Main Range Batholith of Peninsular Malaysia . . . . . . . . . . . .
Part of the Lima Segment of the Coastal Batholith of Peru . . . . . . .
Hypidiomorphic texture, Santa Rosa Tonalite, Rio Lurin, Peru . . . .
Specimens of granite with a, allotriomorphic texture b,
two-phase texture c, of microgranite with sparse megacrysts,
Tanjong Pandang Pluton, Indonesia . . . . . . . . . . . . . . . . . . . . . .
Thin sections of a, allotriomorphic texture b, of two-phase
texture, c, of advanced two-phase texture with microgranite
base, d, of microgranite with sparse megacrysts, Tanjong
Pandang Pluton, Indonesia . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Two-phase texture, Rio Gorgor, a tributary of the Rio Pativilca,
Peru. The texture is dominated by plagioclase megacrysts some
of which are in anhedral contact with quartz grains indicating an
earlier touching fabric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tuffisite, Cruz de Laya, Rio Lurin, Peru . . . . . . . . . . . . . . . . . . .
Porphyry stock, Acos Upper, Rio Chancay, Peru. Two-phase
texture dominated by relic plagioclase . . . . . . . . . . . . . . . . . . . .
Schlieren with enclaves, Mt Givens granodiorite, Sierra Nevada . . .
Schlieren with enclaves, whirlpool structure, Mt Givens
granodiorite, Sierra Nevada . . . . . . . . . . . . . . . . . . . . . . . . . . .
Complex Schlieren, Mt Givens granodiorite, Sierra Nevada . . . . . .
Layering, Dindings pluton Malaysia . . . . . . . . . . . . . . . . . . . . .
Detail of layering, Dindings pluton Malaysia . . . . . . . . . . . . . . . .
'Dropstone' of San Jeronimo granite bending the xenolithic
facies of the Puscao granite. Qda Quintay, Rio Huaura, Coastal
Batholith, Peru . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gross layering in a pluton of the Puscao granite. The upper part
consists of sheeted pegmatites, leucogranites and aplites. Rio
Supe Peru . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Granite veining gabbro with the production of quartz ocelli,
Lisa Aragabo Pluton, Kola Peninsula, Russia . . . . . . . . . . . . . . . .
Mafic enclaves with dark margins, Jerong Pluton Eastern
Province Malaysia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VIII Table of Figures
Mafic enclaves in granite, Brittany ......................
Granite veining norite with the formation of pillows, Tregastel,
Ploumanac'h Plutono, Brittany .........................
Dyke of mobilised hybrid with K-feldspar megacrysts cutting
norite with quartz ocelli, Tregastel, Ploumanc'h Pluton,
Brittany ........................................
Granite veining gabbro with development of quartz ocelli, Bosov,
Moldanubian Batholith ..............................
Mafic synplutonic dykes, Santa Rosa Pluton, Peru ............
Pluton geometry controlled by fractures and stoping, Coastal
Batholith, Peru ...................................
Trails of steeply dipping mafic enclaves, Sayan Pluton, Peru .....
The structural controls of granite emplacement, Donegal,
Ireland .........................................
Synplutonic deformation of granite with sillimanite schist, Stong
Complex, Peninsular Malaysia .........................
Leucotonalite orthogneisses in intimate association with
hornblende schists. Ban Nong Yai Thailand. This Complex is of
Cretaceous age ...................................
................................
Kinematic indicators
In situ melting of garnet granites from granulite facies cordierite
gneisses, Toledo, Spain ..............................
Deformed anatexitic S-type granite with folded relic of
metasedimentary rock. St Cast Plage, Brittany ...............
Foliated anatexitic S-type granite with quartz lumps, probably
derived from metasedimentary source rock. St Cast, Plage,
Brittany ........................................
Relatively undeformed S-type granite with enclaves of
predominantly pelitic material. Beach 2 km west of St Cast,
Brittany ........................................
Granite descrivtion sheet .............................
Contents
Preface
1 Introduction .................................... 1
2 Systems of Classification ......................... 5
2.1 Empirical Classification ......................... 6
2.1.1 Lithological ............................ 6
2.1.2 Major Element Geochemistry ................. 8
2.1.3 Mineralogical ........................... 9
2.1.3.1 The Magnetite-Ilmenite Series ................ 9
2.1.3.2Zircon ................................ 10
2.2 Typological Systems ............................ 10
2.3 Geochemical-Tectonic .......................... 12
2.4 Comments on the Question of Source Related Nomenclatures . 14
2.5 Additional Nomenclatural Terms .................... 15
2.5.1 Tectonic ............................... 15
2.5.2 Orogenic ............................... 15
2.5.3 Structural .............................. 15
.................................
3 Granite Geology 17
3.1 The Nomenclature of Plutons and Batholiths ............ 17
3.2 The Anatomy of Batholiths ....................... 17
.........................
3.3 The Structure of Plutons 19
3.4 Granite Units. Super-units and Suites ................ 19
3.5 Granite Belts and Provinces ....................... 20
3.6 Contacts .................................... 20
.............................
3.7 Magmatic Textures 21
......................
3.7.1 Equilibrium Textures 21
3.7.2 Disequilibrium Textures .................... 23
..........................
3.8 Layering and Schlieren 28
...............................
3.9 Residual Fluids 32
3.10 Aplites. Pegmatites and Granite Veins ................ 33
3.11 Enclaves in Granites ............................ 34
