Table of Contents

Preface xi

About the companion website xiii

Chapter 1: Atoms and nuclei: their physics and origins 1

1.1 Introduction 1

1.2 Physics of the Nucleus 2

1.2.1 Early development of atomic and the nuclear theory 2

1.2.2 Some definitions and units 3

1.2.3 Nucleons, nuclei, and nuclear forces 3

1.2.4 Atomic masses and binding energies 4

1.2.5 The liquid-drop model 6

1.2.6 The shell model of the nucleus 7

1.2.7 Collective model 11

1.3 Radioactive Decay 12

1.3.1 Gamma decay 12

1.3.2 Alpha decay 13

1.3.3 Beta decay 13

1.3.4 Electron capture 14

1.3.5 Spontaneous fission 15

1.4 Nucleosynthesis 16

1.4.1 Cosmological nucleosynthesis 18

1.4.2 Stellar nucleosynthesis 18

1.4.3 Explosive nucleosynthesis 25

1.4.4 Nucleosynthesis in interstellar space 27

1.4.5 Summary 28

Notes 29

References 29

Suggestions for Further Reading 30

Problems 30

Chapter 2: Decay systems and geochronology I 32

2.1 Basics of Radioactive Isotope Geochemistry 32

2.1.1 Introduction 32

2.1.2 The basic equations 33

2.1.3 A special case: the U-Th-Pb system 35

2.2 Geochronology 36

2.2.1 Isochron dating 36

2.2.2 Calculating an isochron 37

2.3 The K-Ar-Ca System 39

2.3.1 Diffusion, cooling rates, and closure temperatures 40

2.3.2 40Ar-39Ar dating 43

2.4 The Rb-Sr System 47

2.4.1 Rb-Sr chemistry and geochronology 48

2.4.2 Sr isotope chronostratigraphy 49

2.5 The Sm-Nd System 50

2.5.1 Sm-Nd model ages and crustal residence times 55

2.6 The Lu-Hf System 56

2.7 The Re-Os System 61

2.7.1 The Re-Os decay system 61

2.7.2 Re-Os geochronology 63

2.7.3 The 190Pt-186Os decay 65

Notes 66

References 66

Suggestions for Further Reading 68

Problems 69

Chapter 3: Decay systems and geochronology II: U and Th 72

3.1 Introduction 72

3.1.1 Chemistry of U, Th, and Pb 72

3.1.2 The 238U/235U ratio and uranium decay constants 73

3.2 Pb-Pb Ages and Isochrons 74

3.2.1 Total U-Pb isochrons 76

3.2.2 Th/U ratios 77

3.3 Zircon Dating 77

3.4 U-decay Series Dating 83

3.4.1 Basic principles 84

3.4.2 234U-238U dating 86

3.4.3 230Th-238U dating 88

3.4.4 231Pa-235U dating 91

3.4.5 226Ra dating 93

3.4.6 210Pb dating 93

3.4.7 210Po-210Pb dating 95

Notes 96

References 97

Suggestions for Further Reading 98

Problems 98

Chapter 4: Geochronology III: other dating methods 101

4.1 Cosmogenic Nuclides 101

4.1.1 Cosmic rays in the atmosphere 101

4.1.2 14C dating 102

4.1.3 10Be, 26Al, and 36Cl 106

4.1.4 Cosmogenic and bomb-produced radionuclides in hydrology 108

4.1.5 In-situ produced cosmogenic nuclides 110

4.2 Fission Tracks 114

4.2.1 Analytical procedures 115

4.2.2 Interpreting fission track ages 117

4.2.3 Interpreting track length 119

Notes 121

References 122

Suggestions for Further Reading 123

Problems 123

Chapter 5: Isotope cosmochemistry 125

5.1 Introduction 125

5.2 Cosmochronology 126

5.2.1 Conventional methods 126

5.2.2 Extinct radionuclides 129

5.2.3 Extinct radionuclides in the Earth 136

5.2.4 Origin of short-lived nuclides 145

5.3 Stardust and Isotopic Anomalies in Meteorites 146

5.3.1 Neon alphabet soup and “pre-solar” noble gases in meteorites 146

5.3.2 Isotopic composition of pre-solar grains 148

5.3.3 Other exotic components in meteorites 151

5.4 Oxygen Isotope Variations and Nebular Processes 151

5.5 Exposure Ages of Meteorites 154

Notes 154

References 155

Suggestions for Further Reading 158

Problems 159

Chapter 6: Radiogenic isotope geochemistry of the mantle 161

6.1 Introduction 161

6.1.1 Definitions: time-integrated and time-averaged 162

6.2 Isotope Geochemistry of the Earth’s Mantle 163

6.2.1 The Sr-Nd-Hf picture 163

6.2.2 The Pb picture 166

6.3 Balancing Depleted Mantle and Crust 172

6.4 Mantle Plume Reservoirs 179

6.4.1 Mantle plumes and the mantle zoo 179

6.4.2 The evolution of mantle geochemical reservoirs 180

6.5 Geographic Variations in Mantle Isotopic Composition 187

6.6 The Subcontinental Lithosphere 189

6.7 U-Series Isotopes and Melt Generation 193

6.7.1 Spiegelman and Elliot model of melt transport 194

Notes 198

References 201

Suggestions for Further Reading 203

Problems 204

Chapter 7: Radiogenic isotope geochemistry of the continental crust and the oceans 205

7.1 Introduction 205

7.2 Growth of the Continental Crust Through Time 205

7.2.1 Mechanisms of crustal growth 205

7.2.2 The Hadean eon and the earliest continental crust 206

7.2.3 Subsequent growth of the crust 212

7.2.4 Nd and Hf isotopic approaches to crustal evolution 215

7.3 Isotopic Composition of the Continental Crust 217

7.3.1 Sediments and rivers as samples of the upper crust 218

7.3.2 Isotopic composition of the lower crust 221

7.3.3 Pb isotope ratios and the Th/U ratio of the crust 223

7.4 Other Approaches to Crustal Composition and Evolution 224

7.5 Subduction Zones 226

7.5.1 Geochemistry of two-component mixtures 226

7.5.2 Isotopic compositions of subduction-related magmas 228

7.6 Radiogenic Isotopes in Oceanography 231

7.6.1 Oceanographic circulation and geochemical cycling 232

7.6.2 Nd, Hf, Os, and Pb in the modern ocean 233

7.6.3 Radiogenic isotopes in paleoceanography 236

Notes 240

References 240

Suggestions for Further Reading 244

Problems 244

Chapter 8: Stable isotope geochemistry I: Theory 246

8.1 Introduction 246

8.2 Notation and Definitions 246

8.2.1 The 𝛿 notation 246

8.2.2 The fractionation factor 247

8.3 Theory of Mass Dependent Isotopic Fractionations 247

8.3.1 Equilibrium fractionations 249

8.3.2 Kinetic fractionation 258

8.4 Mass Independent Fractionation 260

8.5 Hydrogen and Oxygen Isotope Ratios in the Hydrologic System 262

8.6 Isotope Fractionation in the Biosphere 265

8.6.1 Carbon isotope fractionation during photosynthesis 265

8.6.2 Nitrogen isotope fractionation in biological processes 269

8.6.3 Oxygen and hydrogen isotope fractionation by plants 271

8.6.4 Carbon and hydrogen isotopic composition of organic matter in sediments 271

8.6.5 Biological fractionation of sulfur isotopes 273

Notes 274

References 274

Suggestions for Further Reading 275

Problems 276

Chapter 9: Stable isotope geochemistry II: High temperature applications 277

9.1 Introduction 277

9.2 Equilibrium Fractionations Among Minerals 277

9.2.1 Compositional and structural dependence of equilibrium fractionations 277

9.2.2 Geothermometry 279

9.3 Stable Isotope Composition of the Mantle 282

9.3.1 Oxygen 283

9.3.2 Carbon 284

9.3.3 Hydrogen 286

9.3.4 Nitrogen 287

9.3.5 Sulfur 288

9.4 Oxygen Isotopes in Magmatic Processes 288

9.4.1 Oxygen isotope changes during crystallization 289

9.4.2 Combined fractional crystallization and assimilation 291

9.4.3 Combining radiogenic and oxygen isotopes 291

9.4.4 Sediment subduction versus assimilation 292

9.4.5 Stable isotopes as indicators of crust-to-mantle recycling 296

9.5 Oxygen Isotopes in Hydrothermal Systems 298

9.5.1 Ridge crest hydrothermal activity and metamorphism of the oceanic crust 298

9.5.2 Meteoric geothermal systems 301

9.5.3 Water-rock reaction: Theory 301

9.5.4 The Skaergaard intrusion 303

9.5.5 Oxygen isotopes and mineral exploration 304

9.6 Sulfur Isotopes and Ores 305

9.6.1 Introduction 305

9.6.2 Sulfur isotope fractionations in magmatic processes 306

9.6.3 Sulfur isotope fractionation in hydrothermal systems 307

9.6.4 Isotopic composition of sulfide ores 309

Notes 312

References 312

Suggestions for Further Reading 314

Problems 315

Chapter 10: Stable isotope geochemistry III: Low temperature applications 316

10.1 Stable Isotopes in Paleontology, Archeology, and the Environment 316

10.1.1 Introduction 316

10.1.2 Isotopes and diet: You are what you eat 316

10.1.3 Carbon isotopes and the evolution of horses and grasslands 318

10.1.4 Isotopes, archeology, and paleodiets 321

10.1.5 Carbon isotopes and the earliest life 323

10.1.6 Tracing methane contamination in drinking water 325

10.2 Stable Isotopes in Paleoclimatology 326

10.2.1 Introduction 326

10.2.2 The record of climate change in deep sea sediments 327

10.2.3 The quaternary δ18O record 327

10.2.4 The cause of quaternary glaciations 329

10.2.5 Carbon isotopes, ocean circulation, and climate 332

10.2.6 The tertiary marine δ18O record 334

10.2.7 Continental isotopic records 336

10.2.8 Vostok and EPICA Antarctic ice cores 337

10.2.9 Ice records from Greenland: GRIP, GISP, and NGRIP 338

10.2.10Speleotherm and related climate records 340

10.2.11Soils and paleosols 341

10.3 The Carbon Cycle, Isotopes, and Climate 342

10.3.1 The short-term carbon cycle and anthropogenic impacts 342

10.3.2 The quaternary carbon isotope record and glacial cycles 347

10.3.3 The long-term carbon cycle 351

Notes 359

References 359

Suggestions for Further Reading 362

Problems 363

Chapter 11: Unconventional isotopes and approaches 364

11.1 Introduction 364

11.2 Applications of Isotopic Clumping 365

11.3 Mass Independent Isotope Fractionations 368

11.3.1 Mass-independent fractionation of oxygen in the atmosphere 368

11.3.2 Mass independent sulfur isotope fractionation and the rise of atmospheric oxygen 369

11.4 Isotopes of Iron and Molybdenum 370

11.4.1 Fe isotopes and the great oxidation event 371

11.4.2 Mo isotopes and oxygenation of the oceans 374

11.5 Isotopes of Copper and Zinc 377

11.5.1 Cu isotopes 377

11.5.2 Zn isotopes 380

11.6 Isotopes of Boron and Lithium 383

11.6.1 Boron isotopes 384

11.6.2 Li isotopes 389

11.7 Isotopes of Magnesium and Calcium 392

11.7.1 Mg isotopes 392

11.7.2 Calcium isotopes 396

11.8 Silicon Isotopes 400

11.9 Chlorine Isotopes 404

Notes 407

References 408

Suggestions for Further Reading 416

Problems 416

Chapter 12: Noble gas isotope geochemistry 418

12.1 Introduction 418

12.1.1 Noble gas chemistry 418

12.1.2 Noble gases in the Solar System 419

12.2 Helium 422

12.2.1 He in the atmosphere, crust, and oceans 422

12.2.2 He in the mantle 424

12.3 Neon 426

12.3.1 Neon in the solid earth 428

12.4 Argon 429

12.5 Krypton 431

12.6 Xenon 432

12.7 Implications of Noble Gas Isotope Ratios for the Origin and Evolution of the Earth 436

12.7.1 Mantle reservoirs of noble gases in the modern Earth 436

12.7.2 Formation of the Earth and evolution of the atmosphere 443

Notes 447

References 448

Suggestions for Further Reading 452

Problems 452

Appendix: Mass spectrometry 453

A.1 Sample Extraction and Preparation 453

A.2 The Mass Spectrometer 453

A.2.1 The ion source 454

A.2.2 The mass analyzer 455

A.2.3 The detector 457

A.3 Accelerator Mass Spectrometry 458

A.4 Analytical Strategies 459

A.4.1 Correcting mass fractionation 459

A.4.2 Deconvolution of results 461

A.4.3 Isotope dilution analysis 461

Notes 462

References 463

Problems 463

Index 465

About the Author

William White teaches geochemistry as a Professor of earth and atmospheric sciences at Cornell University. He received a B.A. in geology from the University of California, Berkeley and a PhD in oceanography from the University of Rhode Island. He is a Fellow of the Geochemical Society/European Association of Geochemistry and the AGU and has been named a highly cited author by ISI. He is the author of Geochemistry, also published by Wiley-Blackwell.