Mantle Plumes and Their Record in Earth History

Preface page xi
1 Introduction 1
General Features of Mantle Plumes 1
Plume Nomenclature 2
Internal Structure of the Mantle 3
An Overview 3
The Lithosphere 5
The Low-Velocity Zone 5
The 410-km Discontinuity 7
The 660-km Discontinuity 8
The Lower Mantle 9
General Features 9
The D" Layer 9
Plumes and Convection in the Mantle 11
Organizational Strategy 12
2 Hotspots and Mantle Upwellings 14
Introduction 14
Hotspot Characteristics 14
Hotspot Tracks 16
Hawaiian–Emperor Volcanic Chain 16
Louisville Volcanic Chain 19
Easter Volcanic Chain 19
Austral–Cook and Society Volcanic Chains 20
Continental Hotspot Tracks 20
Yellowstone 23
Seamount Arrays 24
Hotspot Swells 25
Hotspot Volcanoes 27
Hotspot Magma Composition 28
Seismicity and Tectonics of Hotspots 30
Hawaii 30
Yellowstone 32
Plume–Hotspot Relationships 33
Plume–Ridge Interactions 37
The Hotspot Reference Frame 39
True Polar Wander 42
Hotspot Origin 42
Venusian Hotspots 43
Mantle Upwellings 44
Introduction 44
Superswells 45
Geoid Anomalies 46
Seismic-Wave and Density Anomalies 48
The Pacific Upwelling 50
The African Upwelling 50
Descending Slabs and Mantle Upwellings 51
Geotectonic Bipolarity 51
Plumes in Perspective 52
3 Large Igneous Provinces 54
Introduction 54
Characteristics of Flood Basalts 57
LIP Eruption Rates 59
Crustal Structure of Oceanic Plateaus 59
Seismic Structure 59
Composition of the Deep Crust 62
Lithospheric Roots 63
Examples of Large Igneous Provinces 64
Columbia River Basalts 64
North Atlantic Igneous Province 67
Ontong Java and Hikurangi Plateaus 69
General Features 69
Tectonic History 70
The Ontong–Australian Plate Collision 72
Hikurangi Plateau 72
Siberian Traps 75
Paran´a–Etendeka Flood Basalts 76
Deccan Traps 78
Kerguelen Plateau 79
Karoo–Ferrar Province 82
Ethiopian and East African Plateaus 85
Plumes and Sediments 87
LIPS on Mars and Venus 88
Martian LIPS 89
Venusian LIPS 92
Giant Dyke Swarms 95
Introduction 95
Relationship of Dyke Swarms to Plumes 97
Dyke Swarms on Venus and Mars 100
Large Layered Intrusions 103
The Muskox Intrusion 104
The Bushveld Complex 104
General Features 104
Crystallization 105
A Plume Origin 106
Kimberlites, Diamonds, and Mantle Plumes 106
LIP Magma Composition 107
LIP Mineral Deposits 111
LIPS in Perspective 112
4 Mantle Plume Generation and Melting 115
Introduction 115
Plume Characteristics 115
Experimental Models 115
Numerical Models 118
Uplift, Deformation, and Subsidence 118
General Features 118
Laboratory Models 119
Field and Dating Evidence 119
Wrinkle Ridges 121
How Fast Do Plumes Rise? 122
How Long Do Plumes Survive? 122
Entrainment in Plumes 123
Plume Roots 125
Seismic Evidence 125
Osmium Isotope Evidence 127
Plume Families and Head–Tail Detachments 127
Plume Temperatures 128
Phase Transitions and Plumes 129
Hard Turbulence and Plumes 131
Effect of Planetary Rotation on Plume Distribution 132
Melting in Mantle Plumes 133
Introduction 133
Rift-Related Melting 134
Melting in a Mantle Plume 136
Plumes with Eclogite 137
Lithosphere–Plume Interactions 138
Plume Erosion of the Lithosphere 138
Dehydration Melting of the Lithosphere 139
Depth of Melting 140
Magma Composition and Plume Melting 141
Do We Need More Plume Modeling? 143
5 Plumes as Tracers of Mantle Processes 145
Introduction 145
Identifying Oceanic Mantle Components with Isotopic Tracers 146
An Overview 146
Depleted Mantle 147
HIMU Mantle 148
Enriched Mantle 148
Helium Isotopes 149
The Dupal Anomaly 150
Summary 152
Lithosphere and Crustal Contributions to Plumes 152
Introduction 152
Trace Elements 152
Overview 152
Nb/U Ratios in the Mantle 154
Th/Ta and La/Yb Ratios 156
Nd and Sr Isotopes 159
High- and Low-Ti Basalts 162
Oxygen Isotopes 163
Osmium Isotopes 163
Summary 164
Mixing in the Mantle 165
New Ideas on Mantle Convection 167
6 Mantle Plumes and Continental Growth 170
Introduction 170
Accreted Oceanic Plateaus 171
Caribbean Oceanic Plateau 171
Tectonic Overview 171
Mantle Sources 172
Tectonic History of the Caribbean Plateau 174
Accreted Oceanic Plateaus in the American Cordillera 175
Wrangellia Terrane 175
Angayucham Terrane 177
Bridge River Terrane 178
Siletz Terrane 179
Accreted Oceanic Plateaus in Japan 179
How Do Continents Grow? 182
Plume-Related Underplating during Supercontinent Breakup 183
Accretion of Plume Heads to the Lithosphere 185
Oceanic Plateaus and Continental Growth 186
Oceanic Plateaus as Lower Continental Crust 186
Making Continental Crust from Oceanic Plateaus 190
Discussion of Oceanic Plateau Accretion 191
What the Future Holds 193
7 Mantle Plumes in the Archean 195
Introduction 195
Tracking Plumes into the Archean with Greenstones 195
Overview 195
Greenstone Lithologic Associations 196
Greenstone Geochemistry 198
Komatiites 202
Overview 202
Heads It’s Basalts, Tails It’s Komatiites 202
Geochemistry 203
Archean Flood Basalts 206
Plume-Head Underplating of the Lithosphere 208
Secular Changes in the Mantle 208
The Appearance of Enriched Mantle 208
Komatiites as Geothermometers 210
How Hot Was the Archean Mantle? 211
Was the Archean Mantle Iron-Rich? 212
Were Mantle Plumes More Widespread in the Archean? 214
A Final Word 215
8 Superplume Events 216
Plumes and Supercontinents 216
Introduction 216
Mantle Plumes and Supercontinent Breakup 216
Large Plates and Mantle Upwelling 220
The Supercontinent Cycle 222
Episodic Crustal Growth 223
The Mid-Cretaceous Superplume Event 227
What Is a Superplume Event? 229
Precambrian Superplume Events 229
Kimberlites and Superplumes 230
Initiation of Superplume Events 231
Slab Avalanches 231
Core Rotational Dynamics 231
A Superplume Event Model 232
Superplume Events and Supercontinents 235
The First Supercontinent 237
The Grenville Event at 1 Ga 238
Superchrons and Superplumes 240
Perspective 241
9 Mantle Plumes and Earth Systems 242
Introduction 242
Superplumes, Supercontinents, and the Carbon Cycle 243
Introduction 243
Supercontinent Formation 243
Supercontinent Breakup 246
Superplume Events 246
Sea Level 247
Global Warming 249
The Biosphere 250
Sedimentary Systems 251
Strontium Isotopes in Marine Carbonates 251
Banded Iron Formation 252
Sedimentary Phosphates 253
Geological Consequences of Superplume Events and Supercontinents 253
Mid-Cretaceous Event 253
Permo–Carboniferous Event 255
Ordovician Event 257
The 1.9-Ga Event 257
Sea Level 257
Black Shales 258
Paleoclimate 261
Banded Iron Formation 262
Sedimentary Phosphates 262
Strontium Isotopes in Seawater 263
Stromatolites 263
Massive Sulfate Evaporites 264
Carbon and Sulfur Isotopes 265
The Case for a 1.9-Ga Superplume Event 267
The 2.7-Ga Event 268
2.0- and 0.6-Ga Events 269
Mass Extinctions 270
Conclusion 272
References 273
Index 303