This book provides a comprehensive introduction to the field of geochemistry. The book first lays out the ‘geochemical toolbox’: the basic principles and techniques of modern geochemistry, beginning with a review of thermodynamics and kinetics as they apply to the Earth and its environs. These basic concepts are then applied to understanding processes in aqueous systems and the behavior of trace elements in magmatic systems. Subsequent chapters introduce radiogenic and stable isotope geochemistry and illustrate their application to such diverse topics as determining geologic time, ancient climates, and the diets of prehistoric peoples. The focus then broadens to the formation of the solar system, the Earth, and the elements themselves. Then the composition of the Earth itself becomes the topic, examining the composition of the core, the mantle, and the crust and exploring how this structure originated. A final chapter covers organic chemistry, including the origin of fossil fuels and the carbon cycle’s role in controlling Earth’s climate, both in the geologic past and the rapidly changing present.

Geochemistry is essential reading for all earth science students, as well as for researchers and applied scientists who require an introduction to the essential theory of geochemistry, and a survey of its applications in the earth and environmental sciences.

About the companion website viii

Chapter 1: Introduction 1

1.1 Geochemistry 1

1.2 This book 2

1.3 The philosophy of science 4

1.4 Elements, atoms, and chemical bonds: some chemical fundamentals 6

1.5 A brief look at the Earth 15

References and suggestions for further reading 19

Chapter 2: Energy, entropy and fundamental thermodynamic concepts 20

2.1 The thermodynamic perspective 20

2.2 Thermodynamic systems and equilibrium 21

2.3 Equations of state 24

2.4 Temperature, absolute zero, and the zeroth law of thermodynamics 26

2.5 Energy and the fi rst law of thermodynamics 27

2.6 The second law and entropy 30

2.7 Enthalpy 38

2.8 Heat capacity 39

2.9 The third law and absolute entropy 47

2.10 Calculating enthalpy and entropy changes 48

2.11 Free energy 51

2.12 The maxwell relations 58

References and suggestions for further reading 58

Problems 59

Chapter 3: Solutions and thermodynamics of multicomponent systems 61

3.1 Introduction 61

3.2 Phase equilibria 62

3.3 Solutions 67

3.4 Chemical potential 68

3.5 Ideal solutions 71

3.6 Real solutions 73

3.7 Electrolyte solutions 80

3.8 Ideal solutions in crystalline solids and their activities 88

3.9 Equilibrium constants 89

3.10 Practical approach to electrolyte equilibrium 96

3.11 Oxidation and reduction 100

References and suggestions for further reading 110

Problems 111

Chapter 4: Applications of thermodynamics to the Earth 116

4.1 Introduction 116

4.2 Activities in non-ideal solid solutions 116

4.3 Exsolution phenomena 120

4.4 Thermodynamics and phase diagrams 122

4.5 Geothermometry and geobarometry 128

4.6 Thermodynamic models of magmas 137

4.7 Reprise: thermodynamics of electrolyte solutions 145

References and suggestions for further reading 154

Problems 156

Chapter 5: Kinetics: the pace of things 160

5.1 Introduction 160

5.2 Reaction kinetics 161

5.3 Relationships between kinetics and thermodynamics 172

5.4 Diffusion 179

5.5 Surfaces, interfaces, and interface processes 191

5.6 Kinetics of dissolution and leaching 201

5.7 Diagenesis 207

References and suggestions for further reading 211

Problems 213

Chapter 6: Aquatic chemistry 217

6.1 Introduction 217

6.2 Acid–base reactions 217

6.3 Complexation 231

6.4 Dissolution and precipitation reactions 239

6.5 Clays and their properties 249

6.6 Mineral surfaces and their interaction with solutions 253

References and suggestions for further reading 265

Problems 265

Chapter 7: Trace elements in igneous processes 268

7.1 Introduction 268

7.2 Behavior of the elements 270

7.3 Distribution of trace elements between coexisting phases 281

7.4 Factors governing the value of partition coefficients 283

7.5 Crystal-fi eld effects 294

7.6 Trace element distribution during partial melting 299

7.7 Trace element distribution during crystallization 310

7.8 Summary of trace element variations during melting and crystallization 315

References and suggestions for further reading 316

Problems 318

Chapter 8: Radiogenic isotope geochemistry 321

8.1 Introduction 321

8.2 Physics of the nucleus and the structure of nuclei 322

8.3 Basics of radiogenic isotope geochemistry 330

8.4 Decay systems and their applications 334

8.5 Cosmogenic and fossil isotopes 360

References and suggestions for further reading 365

Problems 367

Chapter 9: Stable isotope geochemistry 371

9.1 Introduction 371

9.2 Theoretical considerations 373

9.3 Isotope geothermometry 384

9.4 Isotopic fractionation in the hydrologic system 387

9.5 Isotopic fractionation in biological systems 388

9.6 Paleoclimatology 396

9.7 Hydrothermal systems and ore deposits 404

9.8 Stable isotopes in the mantle and magmatic systems 409

9.9 Isotopes of boron and lithium 417

References and suggestions for further reading 424

Problems 428

Chapter 10: The big picture: cosmochemistry 430

10.1 Introduction 430

10.2 In the beginning . . . nucleosynthesis 431

10.3 Meteorites: essential clues to the beginning 442

10.4 Time and the isotopic composition of the solar system 456

10.5 Astronomical and theoretical constraints on

solar system formation 467

10.6 Building a habitable solar system 478

References and suggestions for further reading 489

Problems 492

Chapter 11: Geochemistry of the solid earth 493

11.1 Introduction 493

11.2 The Earth’s mantle 493

11.3 Estimating mantle and bulk earth composition 502

11.4 The Earth’s core and its composition 510

11.5 Mantle geochemical reservoirs 516

11.6 The crust 529

References and suggestions for further reading 557

Problems 561

Chapter 12: Organic geochemistry, the carbon cycle, and climate 563

12.1 Introduction 563

12.2 A brief biological background 564

12.3 Organic compounds and their nomenclature 565

12.4 The chemistry of life: important biochemical processes 575

12.5 Organic matter in natural waters and soils 580

12.6 Chemical properties of organic molecules 589

12.7 Sedimentary organic matter and coal and oil formation 599

12.8 Isotope composition of hydrocarbons 614

12.9 The carbon cycle and climate 617

References and suggestions for further reading 629

Problems 633

Appendix 635

Index 637