The Nature and Origin of Granite

401 Pages·1997·23.513 MB·English

by  Wallace Spencer Pitcher (auth.)

The Nature and
Origin of Granite
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The Nature and
Origin of Granite
Second edition
Wallace Spencer Pitcher
Emeritus Professor of Geology
University of Liverpool
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SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
First edition 1993
Reprinted 1995
Second edition 1997
© 1997 Springer Science+Business Media Dordrecht
Originally published by Chapman & Hall in 1997
Softcovcr rcprint of the hardcovcr 2nd cdition 1997
Typeset on 10/12 Palatino by Best-Set Typesetters Ud., Hong Kong
ISBN 978-94-010-6464-4 ISBN 978-94-011-5832-9 (eBook)
DOI 10.1007/978-94-011-5832-9
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Library of Congress Catalog Card Number: 97-65818
@i Printed on permanent acid-free text paper, manufactured in accord
ance with ANSI/NISO Z39.48-1992 and ANSI/NISO Z39.48-1984 (Perma
nence of Paper).
'Granite is not a rock which was simple in its origin but
might be produced in more ways than one'. Joseph Beete
Jukes in 1863, as Director of the Irish Geological Survey,
attempting to arbitrate in a vigorous debate on the origin
of granite in the mid-19th century.
Contents
Preface xv
1 The historical perspective: an ever changing emphasis 1
The beginning 1
The influence of Lyell 3
The French tradition 4
Sederholm to Read: a proposition sustained 5
A universal debate 9
Rosenbusch to Bowen: the alternative 9
Daly to Cloos: considerations of space 13
The shift from the great debate 15
References and further reading 17
2 The categories of granitic rocks: the search for a
genetic typology 19
The granitic rocks 19
Is categorization possible? 20
Categorization by mode 21
Categorization by rock series 23
Categorization by source rock 25
Categorization by tectonic setting 29
Selected references 31
3 Granite as a chemical system: the experimental impact 32
The possible and the impossible 32
Granite systems 33
Role of water 34
On the contribution of mineral chemistry 38
Further roles for the volatiles 40
On partial melting: a preliminary statement 43
Selected references 46
viii Contents
4 The physical nature of granitic magmas: a case of
missing information 48
The nature of the granite mush 48
Suspensions, mushes and Bingham bodies 49
Flow in granitic magmas: a first statement of a prejudice 53
Flow in the mush: a preliminary comment on magma
deformation 53
Evidence from the sinking of stoped blocks 57
A source control of mushine~s: per magma ad migma 58
Schlieren and banding: evidence of magma fluidity? 59
Schlieren: the omnibus term 59
Those mysterious orbs 63
On banding due to deformation 65
Per magma ad migma usque ad textus 66
Selected references 67
5 The evolution of the granitic texture: a continuum of
crystal growth 68
Introduction 68
On granitic texture in the magmatic context 68
Textural geometry 68
A fresh stereological approach: stereology 70
A measure of porosity as revealed by textural studies 73
The backcloth of theory and experiment 74
A comment on nucleation and growth 76
Paragenetic sequences 78
Individual case histories of minerals as a guide to
processes 79
The accessory minerals: a source of vital information 79
A footnote on epidote 80
Mafic minerals and the fugacity of oxygen and water 81
The problem with muscovite 82
A comment on the significance of zoning 82
On big crystals of potassium feldspar 84
More on myrmekite 87
Rims and swapped rims 88
Some special features of microgranites 89
Microgranitic textures 89
Importance of petrography 90
Selected references 91
6 Differentiation in granitic magmas: zoning as an example
of multifactorial processes at work 92
Aspects of differentiation in granitic magmas:
a multifactorial process 92
Contents ix
Separating out of crystals from liquid or liquid from
crystals 94
Convective motion and mineral orientation 97
Co-lateral processes: the recharge model 98
Co-lateral processes: assimilation 98
Late stages in the differentiation processes 99
Genetic significance of zoning in plutons 100
Pattern of zoning 101
A specific example of sidewall boundary layer
differentiation 102
Some of the complexities of zonation 103
Some more examples of zoned plutons 105
Isotope ratios and zonation 109
Selected references 113
7 The volcano-plutonic interface: not Read's hiatus 115
Introduction 115
Nature of the interface 115
Evolution of silicic magma in subvolcanic magma
chambers 119
Examples from western North America 119
Rhyolites and granites: are they the same? 122
Selected references 124
8 The evidence for restite: unmixing as an
alternative hypothesis 125
A statement in favour 125
The debates 128
An outcrop example of reality 129
The Lachlan experience: suites and supersuites:
granite types and their source rocks 130
Possible S-types in the European Hercynian:
Italy in particular 138
S-type magmas 142
Selected references 143
9 The mingling and mixing of granite with basalt:
a third term in a multiple hypothesis 144
Preamble: mixing and mingling 144
Gabbro against granite 146
Precursor appinite and diorite against granite 148
Synplutonic pipes, net veins and magma pillows 148
Synplutonic dykes 150
Some possible alternatives: pseudo-dykes and relict dykes 153
Crystal transfer: les dents de cheval 154
x Contents
The mafic enclaves themselves 156
The processes of mingling, mixing and hybridization 161
The science of mixing 163
Bulk mixing at depth 164
The enigmatic mixing zone revealed 165
Selected references 167
10 Appinites, diatremes and granodiorites: the interaction
of 'wet' basalt with granite 168
Introduction 168
Crystallization from a water-saturated magma 170
The lamprophyre connection 173
A chemically distinctive series 173
Explosion breccias and diatremes 175
Magma-rock interaction: a multiple source for
the volatiles 177
A model for appinite petrogenesis 179
A role for immiscibility? 179
Appinites galore 181
Selected references 182
11 Controls of upwelling and emplacement: the response
of the envelope: balloons, pistons and reality 183
Preamble 183
Fabric as a guide to flow or to deformation? 184
The foliation in outcrop 187
Effect of lithology 191
A mere footnote on the effects of contact metamorphism 192
Ductile shear belts, heat flux and granite intrusions 192
Concordant plutons: diapirism or ballooning? 193
A modem debate on bursting the bubble 195
A return to multiple prejudices? 197
The special case of magma blisters 198
The sucking-in of magma: cavity-fill emplacement into
extensional shear zones 199
Zone-melting and granitization: a declared prejudice 201
Discordant plutons: fracture propagation and control
of intrusion 201
The importance of giant dykes and sheets 206
Interrelations and connections 209
Plutons in three dimensions: different crustal environments 210
The global tectonic frame and the mechanisms of
emplacement 212
Selected references 214
Contents xi
12 On the rates of emplacement, crystallization and cooling 215
Introduction 215
Measuring the cooling times 215
Rates of ascent of magma 219
Times of generation and the accumulation of magmas 221
Episodicity and periodicity of emplacement 222
Differing rates in response to tectonic environment 224
Selected reference 225
13 Plagiogranite and ferrogranophyre: extreme
differentiation in contrasted situations 226
(a) Oceanic plagiogranite: granite in the ocean floor 226
(b) Ferrogranophyres: granite in the tops of continental
giant sills and ultramafic complexes 229
An extreme form of differentiation 229
The granophyre life cycle 230
Selected references 230
14 Cordilleran-type batholiths: magmatism and crust
formation at a plate edge 231
Introduction 231
Batholiths and marginal basins 232
The example of the Huarmey-Caftete Basin 234
Basin and batholith coincidence 236
The precursor gabbros 236
Anatomy of a batholith: a multiple intrusion 238
Suites, supersuites and pulses 242
Evolution of the magmas 243
Origin of the magmas: a two-stage model 246
The Cordillera Blanca Batholith: from the abyss without
change 250
Cordilleran batholiths in South and North America 251
The Peninsular Ranges Batholith 251
The Sierra Nevada Batholith 254
An interim conclusion 255
Selected references 257
15 Intraplate, rift-related magmatism: mainly the A-type,
alkali feldspar granites 258
The nature of intracratonic magmatism in general 258
Is there a unique A-type? 259
Geochemical characteristics 260
Mineralogical characteristics 262
Texture: the result of subsolidus reactions 263