Ore Deposits and Mantle Plumes

Transcription

1 Ore Deposits and Mantle Plumes by Franco Pirajno Geological Survey of Western Australia, Perth, Australia KLUWER ACADEMIC PUBLISHERS DORDRECHT / BOSTON / LONDON

2 CONTENTS PREFACE ACKNOWLEDGEMENTS INTRODUCTION XI XIII XVII PART ONE CHAPTER 1 The Earth's Internal Structure and Convection in the Mantle 1. 1 Introduction 1.2 Early planetary evolution 2.3 The Earth's internal structure The crust The mantle The core-mantle boundary (CMB) and D" layer The core 25.4 Convection in the mantle; theories and models Theories and dynamics of convection Physical parameters of mantle convection Whole mantle and two-layers mantle convection models 32.5 Mantle geochemistry 41.6 Mantle evolution through time and implications for Earth's history 46.7 Concluding remarks 53.8 References CHAPTER 2 Mantle Plumes and Superplumes; Continental Breakups, Supercontinent Cycles and Ore Deposits Introduction Hotspots: distribution and relationship to rifting Laboratory modelling, structure and dynamics of mantle plumes Doming of the crust (hotspot swells) and associated topographic and drainage features 71

3 VIII Contents 2.5 Mantle plume-lithosphere interactions and plume-generated melts Crustal stress regimes in response to mantle plumes Superplumes and continental breakup Gondwana and Rodinia breakups, mantle plumes or plate forces? Supercontinent cycles and ore deposits The "other side" of the mantle plume theory Concluding remarks References 105 CHAPTER 3 Oceanic Islands, Large Igneous Provinces, Mafic Dyke Swarms, and Intracontinental Alkaline Magmatism Introduction Oceanic volcanic islands The Hawaiian-Emperor seamounts chain Marquesas Islands Walvis Ridge and Tristan da Cunha Iceland Reunion Island Geochemical and isotopic characteristics of oceanic volcanic island basalts Large igneous provinces (LIP): oceanic plateaux and continental flood basalts (CFB) " Introduction Isotope systematics Oceanic plateaux \ Volcanic-rifted continental margins Continental flood basalts (CFB) Mafic dyke swarms Mafic dyke swarms in the Kaapvaal Craton, South Africa The Mackenzie dyke swarm, Canada Parana-Etendeka dykes Intracontinental alkaline magmatism Tectonic settings, ages and controls of intracontinental alkaline magmatism in Africa The Damaraland alkaline province, Namibia Carbonatites Kimberlites and lamproites Concluding remarks References 202

4 Contents IX CHAPTER 4 Rifting Processes, Volcano-Sedimentary Basins and the Role of Mantle Plumes Introduction Rifting dynamics: passive and active Passive rifting Active rifting Rifting and basic formation related to compression in thickened crust Geophysical signatures of rifts Stratigraphic successions as records of basin evolution The stratigraphic record of intracontinental basins and aulacogens The East African Rift System and the Afar Triangle: examples of modern continental rifting where mantle plume activity is recognised Introduction The East African Rift System (EARS) Examples of ancient continental rifts where mantle plume activity is assumed: Thuli-Sabi-Lebombo hotspot junction; Damara and Irumide hotspot junctions Tuli-Sabi-Lebombo hotspot junction Damara and Irumide hotspot junctions, southwestern Africa Sequence stratigraphy, eustasy and mantle plumes Concluding remarks References 256 CHAPTER 5 The Planetary and Meteorite Impact Context of Mantle Plumes Introduction Moon Mercury Venus Mars Large meteorite impacts and possible correlations with mantle plumes Ore deposits and impact structures Can meteorite mega-impacts trigger continental breakup and the ascent of mantle plumes? Concluding remarks References. 286

5 X Contents PART TWO CHAPTER 6 Intracontinental Magmatism, Anorogenic Metamorphism, Ore Systems and Mantle Plumes Introduction Intracontinental layered igneous intrusions Anorogenic prograde metamorphism and hydrothermal convention in hotspot-related rift systems Anorogenic metamorphism in the Central Zone of the Damara Orogen, Namibia Anorogenic metamorphism in the eastern Pyrenees Anorogenic metamorphism and intraplate magmatism around the Vredefort Dome, South Africa Metamorphism and fluid generation; metamorphogenic hydrothermal systems Concluding remarks References 317 CHAPTER 7 Direct Links; Magmatic Ore Deposits Fundamental Features and Concepts Introduction Definitions and terminology, Geometry of layered intrusions and magmatic processes Magmatic oxide ores Crystallisation of spinels from mafic-ultramafic magmas Magmatic sulphides and platinum group elements (PGE) ores The formation of Ni sulphide ores Platinum group elements (PGE) Concluding remarks References 380 CHAPTER 8 Magmatic Ore Deposits Introduction Large layered igneous complexes The Great Dyke, Zimbabwe The Bushveld Igneous Complex, South Africa Molopo Farms Complex, South Africa and Botswana Magmatic ore deposits in igneous complexes associated with continental flood basalts Duluth Complex, Mid-continent Rift System, USA Noril'sk-Talnakh, Siberian Traps, Russia 428

6 Contents XI The Insizwa Complex, Karoo Igneous Province Skaergaard and Kap Edvard Holm, East Greenland magmatic ores in Proterozoic troctolite-anorthosite complexes Voisey's Bay Ni-Cu-Co Komatiite-related magmatic ore deposits Komatiite volcanology Komatiite mineralogy and whole rock geochemistry Komatiite-hosted Fe-Ni-Cu sulphide ores Hydrothermal Ni-cu and PGE mineralisation in ultraultramafic rocks Concluding remarks References 459 CHAPTER 9 Indirect Links: Hydrothermal Mineral Deposits Introduction Ring complexes and carbonatites Proterozoic Cu-Au-U-REE-Fe deposits Mesothermal ore deposits Carlin-type epithermal ore deposits Ore deposits associated with intracontinental anorogenic magmatism Metallogeny of the Damara and Irumide orogens, Southwestern Africa, and the Mid Continent Rift System, USA Metallogeny of the Damara and Irumide orogens Metallogeny of the Mid-continent Rift System, North America Archaean lode Au deposits Concluding remarks References 504 CHAPTER 10 Indirect Links: Sedimentary Rock-Hosted Ore Deposits. Epilogue Introduction Metallogeny in modern rift settings The East African Rift System The Red Sea brine pools Sedimentary-hydrothermal ore deposits Mississippi Valley-type sulphide deposits Sedimentary exhalative (SEDEX) massive sulphide deposits Stratabound Cu-Ag and Cu-Co ore deposits Metalliferous black shales 531

7 XII Contents Mo-Ni-V-PGE-Au in black shales, southern China Iron-formations and manganese deposits Concluding remarks and epilogue References 540 APPENDIX 547 INDEX 549