CONTENTS

Preface to the Second Edition

ONE   INTRODUCING CONCEPTS IN GEOCHEMICAL SYSTEMS

Overview

What Is Geochemistry?

Historical Overview

Beginning Your Study of Geochemistry

Geochemical Variables

Geochemical Systems

Thermodynamics and Kinetics

An Example: Comparing Thermodynamic and Kinetic Approaches

Notes on Problem Solving

Suggested Readings

Problems

TWO   HOW ELEMENTS BEHAVE

Overview

Elements, Atoms, and the Structure of Matter

Elements and the Periodic Table

The Atomic Nucleus and Isotopes

The Basis for Chemical Bonds: The Electron Cloud

Size, Charge, and Stability

Elemental Associations

Bonding

Perspectives on Bonding

Structural Implications of Bonding

Retrospective on Bonding

Summary

Suggested Readings

Problems

THREE   A FIRST LOOK AT THERMODYNAMIC EQUILIBRIUM

Overview

Temperature and Equations of State

Work

The First Law of Thermodynamics

Entropy and the Second Law of Thermodynamics

Entropy and Disorder

Reprise: The Internal Energy Function Made Useful

Auxiliary Functions of State

Enthalpy

The Helmholtz Function

Gibbs Free Energy

Cleaning Up the Act: Conventions for E, H, F, G, and S

Composition as a Variable

Components

Changes in E, H, F, and G Due to Composition

Conditions for Heterogeneous Equilibrium

The Gibbs-Duhem Equation

Summary

Suggested Readings

Problems

FOUR   HOW TO HANDLE SOLUTIONS

Overview

What Is a Solution?

Crystalline Solid Solutions

Amorphous Solid Solutions

Melt Solutions

Electrolyte Solutions

Gas Mixtures

Solutions That Behave Ideally

Solutions That Behave Nonideally

Activity in Electrolyte Solutions

The Mean Salt Method

The Debye-Hückel Method

Solubility

The Ionic Strength Effect

The Common Ion Effect

Complex Species

Summary

Suggested Readings

Problems

FIVE   DIAGENESIS: A STUDY IN KINETICS

Overview

What Is Diagenesis?

Kinetic Factors in Diagenesis

Diffusion

Advection

Kinetics of Mineral Dissolution and Precipitation

The Diagenetic Equation

Summary

Suggested Readings

Problems

SIX   ORGANIC MATTER AND BIOMARKERS: A DIFFERENT PERSPECTIVE

Overview

Organic Matter in the Global Carbon Cycle

Organic Matter Production and Cycling in the Oceans

Fate of Primary Production: Degradation and Diagenesis

Factors Controlling Accumulation and Preservation

Preservation by Sorption

Degradation in Oxic Environments

Diagenetic Alteration

Chemical Composition of Biologic Precursors

Carbohydrates

Proteins

Lipids

Lignin

Biomarkers

Application of Biomarkers to Paleoenvironmental Reconstructions

Alkenone Temperature Records

Amino Acid Racemization

Summary

Suggested Readings

Problems

SEVEN   CHEMICAL WEATHERING: DISSOLUTION AND REDOX PROCESSES

Overview

Fundamental Solubility Equilibria

Silica Solubility

Solubility of Magnesian Silicates

Solubility of Gibbsite

Solubility of Aluminosilicate Minerals

Rivers as Weathering Indicators

Agents of Weathering

Carbon Dioxide

Organic Acids

Oxidation-Reduction Processes

Thermodynamic Conventions for Redox Systems

Eh-pH Diagrams

Redox Systems Containing Carbon Dioxide

Activity-Activity Relationships: The Broader View

Summary

Suggested Readings

Problems

EIGHT   THE OCEANS AND ATMOSPHERE AS A GEOCHEMICAL SYSTEM

Overview

Composition of the Oceans

A Classification of Dissolved Constituents

Chemical Variations with Depth

Composition of the Atmosphere

Carbonate and the Great Marine Balancing Act

Some First Principles

Calcium Carbonate Solubility

Chemical Modeling of Seawater: A Summary

Global Mass Balance and Steady State in the Oceans

Examining the Steady State

How Does the Steady State Evolve?

Box Models

Continuum Models

A Summary of Ocean-Atmosphere Models

Gradual Change: The History of Seawater and Air

Early Outgassing and the Primitive Atmosphere

The Rise of Oxygen

Summary

Suggested Readings

Problems

NINE   TEMPERATURE AND PRESSURE CHANGES: THERMODYNAMICS AGAIN

Overview

What Does Equilibrium Really Mean?

Determining When a System Is in Equilibrium

The Phase Rule

Open versus Closed Systems

Changing Temperature and Pressure

Temperature Changes and Heat Capacity

Pressure Changes and Compressibility

Temperature and Pressure Changes Combined

A Graphical Look at Changing Conditions: The Clapeyron Equation

Reactions Involving Fluids

Raoult’s and Henry’s Laws: Mixing of Several Components

Standard States and Activity Coefficients

Solution Models: Activities of Complex Mixtures

Thermobarometry: Applying What We Have Learned

Summary

Suggested Readings

Problems

TEN   PICTURING EQUILIBRIA: PHASE DIAGRAMS

Overview

-X2 Diagrams

Derivation of T-X2 and P-X2 Diagrams

T-X2 Diagrams for Real Geochemical Systems

Simple Crystallization in a Binary System: CaMgSi2O6-CaAl2Si2O8

Formation of a Chemical Compound in a Binary System: KAlSi2O6-SiO2

Solid Solution in a Binary System: NaAlSi3O8-CaAl2Si2O8

Unmixing in a Binary System: NaAlSi3O8-KAlSi3O8

Thermodynamic Calculation of Phase Diagrams

Binary Phase Diagrams Involving Fluids

P-T Diagrams

Systems with Three Components

Summary

Suggested Readings

Problems

ELEVEN   KINETICS AND CRYSTALLIZATION

Overview

Effect of Temperature on Kinetic Processes

Diffusion

Nucleation

Nucleation in Melts

Nucleation in Solids

Growth

Interface-Controlled Growth

Diffusion-Controlled Growth

Some Applications of Kinetics

Aragonite Calcite: Growth as the Rate-Limiting Step

Iron Meteorites: Diffusion as the Rate-Limiting Step

Bypassing Theory: Controlled Cooling Rate Experiments

Bypassing Theory Again: Crystal Size Distributions

Summary

Suggested Readings

Problems

TWELVE   THE SOLID EARTH AS A GEOCHEMICAL SYSTEM

Overview

Reservoirs in the Solid Earth

Composition of the Crust

Composition of the Mantle

Composition of the Core

Fluxes in the Solid Earth

Cycling between Crust and Mantle

Heat Exchange between Mantle and Core

Fluids and the Irreversible Formation of Continental Crust

Melting in the Mantle

Thermodynamic Effects of Melting

Types of Melting Behavior

Causes of Melting

Differentiation in Melt-Crystal Systems

Fractional Crystallization

Chemical Variation Diagrams

Liquid Immiscibility

The Behavior of Trace Elements

Trace Element Fractionation during Melting and Crystallization

Compatible and Incompatible Elements

Volatile Elements

Crust and Mantle Fluid Compositions

Mantle and Crust Reservoirs for Fluids

Cycling of Fluids between Crust and Mantle

Summary

Suggested Readings

Problems

THIRTEEN   USING STABLE ISOTOPES

Overview

Historical Perspective

What Makes Stable Isotopes Useful?

Mass Fractionation and Bond Strength

Geologic Interpretations Based on Isotopic Fractionation

Thermometry

Isotopic Evolution of the Oceans

Fractionation in the Hydrologic Cycle

Fractionation in Geothermal and Hydrothermal Systems

Fractionation in Sedimentary Basins

Fractionation among Biogenic Compounds

Isotopic Fractionation around Marine Oil and Gas Seeps

Summary

Suggested Readings

Problems

FOURTEEN   USING RADIOACTIVE ISOTOPES

Overview

Principles of Radioactivity

Nuclide Stability

Decay Mechanisms

Rate of Radioactive Decay

Decay Series and Secular Equilibrium

Geochronology

Potassium-Argon System

Rubidium-Strontium System

Samarium-Neodymium System

Uranium-Thorium-Lead System

Extinct Radionuclides

Fission Tracks

Geochemical Applications of Induced Radioactivity

Neutron Activation Analysis

40Argon-39 Argon Geochronology

Cosmic-Ray Exposure

Radionuclides as Tracers of Geochemical Processes

Heterogeneity of the Earth’s Mantle

Magmatic Assimilation

Subduction of Sediments

Isotopic Composition of the Oceans

Degassing of the Earth’s Interior to Form the Atmosphere

Summary

Suggested Readings

Problems

FIFTEEN   STRETCHING OUR HORIZONS: COSMOCHEMISTRY

Overview

Why Study Cosmochemistry?

Origin and Abundance of the Elements

Nucleosynthesis in Stars

Cosmic Abundance Patterns

Chondrites as Sources of Cosmochemical Data

Cosmochemical Behavior of Elements

Controls on Cosmochemical Behavior

Chemical Fractionations Observed in Chondrites

Condensation of the Elements

How Equilibrium Condensation Works

The Condensation Sequence

Evidence for Condensation in Chondrites

Infusion of Matter from Outside the Solar System

Isotopic Diversity in Meteorites

A Supernova Trigger?

The Discovery of Stardust in Chondrites

The Most Volatile Materials: Organic Compounds and Ices

Extraterrestrial Organic Compounds

Ices—The Only Thing Left

A Time Scale for Creation

Estimating the Bulk Compositions of Planets

Some Constraints on Cosmochemical Models

The Equilibrium Condensation Model

The Heterogeneous Accretion Model

The Chondrite Mixing Model

Planetary Models: Cores and Mantles

Summary

Suggested Readings

Problems

 

Appendix A: Mathematical Methods

Appendix B: Finding and Evaluating Geochemical Data

Appendix C: Numerical Values of Geochemical Interest

Glossary

Index