Table Of ContentORE DEPOSITS AND MANTLE PLUMES
Ore Deposits and
Mantle Plumes
by
Franeo Pirajno
Geological Survey ofWestern Australia, Perth, Australia
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
Library of Congress Cataloging-in-Publication Data
ISBN 978-90-481-4026-8 ISBN 978-94-017-2502-6 (eBook)
DOI 10.1007/978-94-017-2502-6
Cover illustration:
The image on the cover is a modified version of that shown in Figure 5.7B in
the text and represents a computer simulation of mantie processes; hot
regions are red and cold regions are blue and green. The hot mantie material
rises and uplifts the surface of the planet. The rising hot mantie simulates a
mantie plume. This convection simulation model was created by Walter Kiefer
Lunar and Planetary Institute, Houston, USA) and Louise Kellogg (University
of California, Davis, USA) for the planet Mars, but is not specific to Mars,
and is applicable to mantie plumes that occur on Earth. The element symbols
represent those that may be directiy or indirectly linked to mantie plume
activities on Earth, resulting in anomalous concentrations of these elements
in the crust where they form ore deposits. The image is used by
permission of the authors.
Printed on acid-free paper
Ali Rights Reserved
© 2000 F. Pirajno
Originally published by Kluwer Academic Publishers in 2000
No part of the material protected by this copyright notice may be reproduced
or utilized in any form or by any means, electronic or mechanical,
including photocopying, recording or by any information storage and
retrieval system, without written permission from the copyright owner.
To Mariateresa, my wife
CONTENTS
PREFACE XI
ACKNOWLEDGEMENTS XIII
INTRODUCTION XVII
PARTONE
CHAPTER 1 The Earth's Interna! Structure and Convection in the
Mantle 1
1.1 Introduction 1
1.2 Early planetary evolution 2
1.3 The Earth's interna1 structure 5
1.3.1. The crust 7
1.3.2. The mantle 11
1.3.3. The core-mantle boundary (CMB) and D" 1ayer 20
1.3.4. The core 25
1.4 Convection in the mantle; theories and models 27
1.4.1. Theories and dynamics of convection 29
1.4.2. Physical parameters ofmantle convection 31
1.4.3. Whole mantle and two-layers mantle convection models 32
1.5 Mantle geochemistry 41
1.6 Mantle evolution through time and implications for Earth's
%
h~~cy
1. 7 Concluding remarks 53
1.8 References
CHAPTER 2 Mantle Plumes and Superplumes; Contineotal
Breakups, Supercontinent Cycles and Ore Deposits 59
2.1 Introduction 59
2.2 Hotspots: distribution and relationship to rifting 61
2.3 Labaratory modelling, structure and dynamics of mantle plumes 65
2.4 Doming ofthe crust (hotspot swells) and associated
topographic and drainage features 71
VIII Contents
2.5 Mantle plume-lithosphere interactions and plume-generated
melts 77
2.5.1. Crustal stress regimes in response to mantle plumes 85
2.6 Superplumes and continental breakup 86
2.6.1. Gondwana and Rodinia breakups, mantle plumes or plate
forces? 90
2.6.2. Supercontinent cycles and ore deposits 94
2.7 The "other side" ofthe mantle plume theory 100
2.8 Concluding remarks 104
2.9 References 105
CHAPTER 3 Oceanic Islands, Large lgneous Provinces, Mafic Dyke
Swarms, and Intracontinental Alkaline Magmatism 111
3.1 Introduction 111
3.2 Oceanic volcanic islands 112
3.2.1. The Hawaiian-Emperor seamounts chain 116
3.2.2. Marquesas Islands 119
3.2.3. Walvis Ridge and Tristan da Cunha 119
3.2.4. leeland 124
3.2.5. Reunion Island 127
3.2.6. Geochemical and isotopic characteristics of oceanic volcanic
island basalts 128
3.3 Large igneous provinces (LIP): oceanic p1ateaux and continenta1
flood basalts (CFB) 135
3.3.1. lntroduction 135
3.3.2. Isotope systematics 139
3.3.3. Oceanic plateaux 140
3.3.4. Volcanic-rifted continental margins 149
3.3.5. Continental flood basalts (CFB) 151
3.4 Mafic dyke swarms 183
3.4.1. Mafic dyke swarms in the Kaapvaal Craton, South Africa 189
3.4.2. The Mackenzie dyke swarm, Canada 190
3.4.3. Parami-Etendeka dykes 192
3.5 Intracontinental alkaline magmatism 193
3.5.1. Teetonic settings, ages and controls of intracontinental
alkaline magmatism in Africa 194
3.5.2. The Damaraland alkaline province, Namibia 198
3.5.3. Carbonatites 199
3.5.4. Kimberlites and lamproites 200
3.6 Concluding remarks 201
3.7 References 202
CHAPTER 4 Rifting Proeesses, Volcano-Sedimentary Basins and
the Role ofMantle Plumes 215
4.1 Introduetion 215
4.2 Rifting dynamies: passive and aetive 220
4.2.1. Passive rifting 221
4.2.2. Aetive rifting 222
4.3 Rifting and basie formation related to eompression in
thiekened erust 223
4.4 Geophysieal signatures of rifts 227
4.5 Stratigraphie sueeessions as reeords ofbasin evolution 230
4.5.1. The Stratigraphie reeord ofintraeontinental basins and
aulaeogens 230
4.6 The East Afriean Rift System and the Afar Triangle: examples
of modern eontinental rifting where mantle plume aetivity is
reeognised 239
4.6.1. Introduetion 239
4.6.2. The East Afriean Rift System (EARS) 240
4. 7 Examples of aneient eontinental rifts where mantle plume
aetivity is assumed: Thuli-Sabi-Lebombo hotspotjunetion;
Damara and Irumide hotspot junetions 244
4.7.1. Tuli-Sabi-Lebombo hotspotjunetion 244
4. 7. 2. Damara and Irumide hotspot junetions, southwestern Afriea 248
4.8 Sequenee stratigraphy, eustasy and mantle plumes 252
4.9 Concluding remarks 254
4.10 Referenees 256
CHAPTER 5 The P1anetary and Meteorite Impact Context of
Mantle P1umes 261
5.1 Introduction 261
5.2 Moon 263
5.3 Mercury 265
5.4 Venus 265
5.5 Mars 269
5.6 Large meteorite impaets and possible eorrelations with mantle
plumes 274
5.6.1. Ore deposits and impaet structures 277
5.6.2. Can meteorite mega-impaets trigger eontinental breakup and
the ascent of mantle plumes? 279
5.7 Concluding remarks 285
5.8 Referenees 286
X Contents
PARTTWO
CHAPTER 6 Intracontinental Magmatism, Anorogenic
Metamorphism, Ore Systems and Mantle Plumes 291
6.1 Introduction 291
6.2 Intracontinenta1layered igneous intrusions 291
6.3 Anorogenic prograde metamorphism and hydrothermal
convention in hotspot-related rift systems 299
6.3.1. Anorogenic metamorphism in the Central Zone ofthe
Damara Orogen, Namibia 301
6.3.2. Anorogenic metamorphism in the eastern Pyrenees 302
6.3.3. Anorogenic metamorphism and intraplate magmatism
around the Vr edefort Dome, South Africa 303
6.3.4. Metamorphism and fluid generation; metamorphogenic
hydrothermal systems 306
6.4 Concluding remarks 317
6. 5 References 317
CHAPTER 7 Direct Links; Magmatic Ore Deposits-
Fundamental Features and Concepts 323
7.1 Introduction 323
7. 1.1. Definitions and terminology 323
7. 1.2. Geometry of layered intrusions and magmatic processes 331
7.2 Magmatic oxide ores 342
7. 2.1. Crystallisation of spine1s from mafic-ultramafic magmas 344
7.3 Magmatic sulphides and platinum group elements (PGE) ores 347
7.3.1. The formation ofNi sulphide ores 347
7.3.2. Platinum group elements (PGE) 355
7.4 Concluding remarks 378
7.5 References 380
CHAPTER 8 Magmatic Ore Deposits 387
8.1 lntroduction 387
8.2 Large layered igneous complexes 388
8.2.1. The Great Dyke, Zimbabwe 389
8.2.2. The Bushveld lgneous Complex, South Africa 401
8.2.3. Molopo Farms Complex, South Africa and Botswana 425
8.3 Magmatic ore deposits in igneous complexes associated with
continental flood basalts 426
8.3.1. Duluth Complex, Mid-continent Rift System, USA 426
8.3.2. Noril'sk-Talnakh, Siberian Traps, Russia 428
8.3.3. The Insizwa Complex, Karoo lgneous Province 433
8.3.4. Skaergaard and Kap Edvard Holm, East Greenland 438
8.4 magmatic ores in Proterozoic troctolite-anorthosite complexes 441
8.4.1. Voisey's Bay Ni-Cu-Co 442
8.5 Komatiite-related magmatic ore deposits 445
8.5.1. Komatiite volcanology 446
8.5.2. Komatiite mineralogy and whole rock geochemistry 447
8.5.3. Komatiite-hosted Fe-Ni-Cu sulphide ores 449
8.6 Hydrothermal Ni-cu and PGE mineralisation in ultra-
ultramafic rocks 453
8. 7 Concluding remarks 458
8.8 References 459
CHAPTER 9 Indirect Links: Hydrothermal Mineral Deposits 469
9.1 Introduction 469
9.2.1. Ring complexes and carbonatites 471
9.2.2. Proterozoic Cu-Au-U-REE-Fe deposits 473
9.2.3. Mesothermal ore deposits 480
9.2.4. Carlin-type epithermal ore deposits 483
9.2 Ore deposits associated with intracontinental anorogenic
magmatism 471
9.3 Metallogeny ofthe Damara and Irumide orogens, Soutb-
western Africa, and the Mid Continent Rift System, USA 491
9.3.1. Metallogeny ofthe Damara and Irumide orogens 491
9.3.2. Metallogeny ofthe Mid-continent Rift System,
N orth America 497
9.4 Archaean 1ode Au deposits 498
9.5 Concluding remarks 502
9.6 References 504
CHAPTER 10 Indirect Links: Sedimentary Rock-Hosted Ore
Deposits. Epilogue 509
10.1 Introduction 509
10.2 Metallogeny in modern rift settings 511
10.2.1. The East African Rift System 511
10.2.2. The Red Sea brine pools 516
10.3 Sedimentary-hydrothermal ore deposits 520
10.3.1. Mississippi Valley-type sulphide deposits 520
10.3.2. Sedimentary exhalative (SEDEX) massive sulphide deposits 523
10.3.3. Stratabound Cu-Ag and Cu-Co ore deposits 528
10.4 Metalliferous black shales 531
