Sharp, Zachary

Principles of Stable Isotope Geochemistry

Preface xi About the Author xiii Introduction 1(14) Historical Background 1(3) Scope of the Discipline 4(3) What Are Stable Isotopes? 5(2) Which Elements and Why? 7(1) Abundances of the Rare Isotopes of Light Elements 7(1) Characteristics of Elements That Undergo Significant Isotopic Fractionation 7(2) Applications in the Earth Sciences 9(1) Isotope Effects 10(5) Kinetic Isotope Effects 10(1) Equilibrium Isotope Effects 11(2) References 13(2) Terminology, Standards, and Mass Spectrometry 15(25) Overview 15(1) Isotopologues, Isotopomers, and Mass Isotopomers 15(2) The Delta Value 17(3) Isotope Exchange Reactions 20(1) The Fractionation Factor 21(1) 103 In α, Δ, and the ε Value 22(2) Reference Standards 24(6) Hydrogen 25(3) Carbon 28(1) Nitrogen 28(1) Oxygen 29(1) Sulfur 30(1) Isotope Ratio Mass Spectrometry 30(10) The First Isotope Ratio Mass Spectrometers 30(1) Modern Conventional Mass Spectrometers 31(2) Gas Chromatograph Isotope Ratio Mass Spectrometry (GC-IRMS) 33(1) Gases Measured in Isotope Ratio Mass Spectrometry 33(2) Relations between Measured and Desired Isotopic Ratios 35(1) Ion Microprobe Analyses of Stable Isotope Ratios 36(3) References 39(1) Equilibrium Isotopic Fractionation 40(24) Introduction 40(1) Theoretical Determination of Stable Isotope Fractionation Factors 41(6) Free Energy of Reaction 41(1) The Internal Energy of a Molecule 42(1) Vibrational Partition Function 43(2) Translational and Rotational Partition Function 45(1) The Complete Partition Function Ratio 46(1) Extension to More Complex Molecules 46(1) Relationship to Temperature 46(1) ``Empirical'' Theoretical Methods 47(1) Experimental Determination of Fractionation Factors 47(5) Introduction 47(2) Mineral-Water Exchange Reactions 49(2) Mineral-Calcite Exchange Reactions 51(1) Mineral-CO2 Exchange Reactions 51(1) The Three-Phase Approach 52(1) Empirical Determination of Fractionation Factors 52(1) Other Potential Factors Controlling Isotope Partitioning 53(3) Pressure Effect 53(1) Composition and Structure 54(2) So Which Fractionation Factors Are Correct? 56(8) An Example from Quartz-Calcite Fractionation 56(4) References 60(4) The Hydrosphere 64(39) Overview 64(1) Natural Abundances of the Isotopologues of Water 65(2) Meteoric Water 67(1) The Meteoric Water Line 68(3) General Features of the GMWL 69(1) Variations in Slopes and Intercepts of Local MWLs 69(1) Meteoric Waters in Arid and Semiarid Environments 70(1) The Deuterium Excess Parameter 71(3) Evaporation and Condensation 74(6) Evaporation 74(1) Condensation: Closed-System (Batch) Isotopic Fractionation 75(3) Condensation: Open-System (Rayleigh) Isotopic Fractionation 78(2) Factors Controlling the Isotopic Composition of Precipitation 80(6) Temperature 80(2) Distance or Continentality Effect 82(1) Latitude Effect 83(1) Altitude Effect 83(1) Amount Effect 84(2) Seasonal Effects 86(1) Groundwater 86(2) Geothermal Systems 88(1) Basinal Brines and Formation Waters 89(2) Glacial Ice 91(12) Underlying Bases for Glacial Paleoclimatology 92(1) Determining the Age of Glacial Ice 93(1) Thinning of Ice Layers 94(1) The Example of Camp Century, North Greenland 94(3) Example of the GRIP Summit Core: Flickering Climates 97(3) References 100(3) The Oceans 103(17) Overview 103(1) Oxygen Isotope Variations in Modern Oceans 104(4) Salinity--δ18O Relations in Shallow Marine Waters 104(1) Salinity--δ18O Relations in Deep Ocean Waters 105(3) Depth Profiles in Modern Oceans: δ18O(O2)aq and δ13C(ΣCO2) 108(1) Isotopic Compositions of Ancient Oceans 109(3) Primitive Oceans 109(2) Secular Changes in δ18O of Marine Sediments 111(1) Seawater--Basalt Interactions: Buffering the δ18O Value of the Ocean 112(4) Low-Temperature Alteration 112(1) High-Temperature Alteration 113(1) Evidence from Drill Core Material 114(1) Evidence from Obducted Material 114(2) Buffering the 18O/16O Ratio of Ocean Water 116(4) Summing the Processes Affecting the 18O/16O Ratio of Seawater 116(1) Model Calculations 116(1) Unresolved Controversy 117(1) References 118(2) Biogenic Carbonates: Oxygen 120(29) Introduction 120(1) The Phosphoric Acid Method 121(4) A Major Breakthrough 121(2) Acid Fractionation Factors 123(1) Applicability 124(1) The Oxygen Isotope Paleotemperature Scale 125(4) Factors Affecting Oxygen Isotope Paleotemperatures 129(10) Variations in δ18O of Ocean Water in Space and Time 130(1) Vital Effects 131(2) Diagenesis 133(5) Ecology of the Organism 138(1) Applications of Oxygen Isotope Paleothermometry 139(2) The Quaternary 139(1) The Paleogene and Neogene (Cenozoic) 140(1) Older Samples 140(1) Application to Continental Carbonates 141(8) References 145(4) Carbon in the Low-Temperature Environment 149(30) Introduction 149(1) The Carbon Cycle 150(3) Carbon Isotope Budget of the Earth 153(1) Carbon Reservoirs 153(8) Mantle 153(1) Plants 153(4) Organic Carbon in Sediments 157(2) Methane 159(1) Atmospheric CO2 160(1) δ13C Values of Carbonates 161(10) Introduction 161(1) General Characterization of Carbonates 162(1) The Vital Effect 162(3) Carbonate Speciation Effects 165(1) Controls on the δ13C Value of Marine Carbonates over Long Timescales 165(4) Variations in the δ13C Value of Marine Carbonates at Short Timescales 169(2) δ13C Studies of Terrestrial Carbonates 171(8) References 174(5) Low-Temperature Minerals, Exclusive of Carbonates 179(27) Introduction 179(1) Phosphates 179(10) Analytical Techniques 180(1) Applications to Marine Paleothermometry 181(2) Application to Mammals: Theory 183(3) Sample Applications 186(3) Cherts 189(6) Application to Precambrian Chert Deposits 189(1) Application to Phanerozoic Cherts 190(1) Diagenesis 191(2) Application to Recent Sediments 193(1) Other Silica Applications 194(1) Clay Minerals 195(4) Early ``Bulk'' Sample Studies 195(1) Grain-Size Considerations 196(3) Iron Oxides 199(7) References 201(5) Nitrogen 206(16) Introduction 206(1) The Nitrogen Cycle 207(1) Nitrogen Isotope Fractionation 208(3) Nitrogen Fixation 209(1) Mineralization 209(1) Assimilation 210(1) Nitrification 210(1) Denitrification 210(1) The Characteristic δ15N Values of Various Materials 211(5) Plants and Soil 212(1) Other Terrestrial Reservoirs 212(1) Nitrogen in the Oceans 213(3) Nitrogen Isotope Ratios in Animals 216(6) References 219(3) Sulfur 222(20) Introduction 222(1) Analytical Techniques 223(2) Equilibrium Fractionations and Geothermometry 225(3) Sulfate and Sulfide Formation at Low Temperatures: The Sedimentary Sulfur Cycle 228(3) Secular Variations in Sulfur 231(7) Long-Term Variations 231(1) Alternative Approaches: Barite and Trace Carbonates 232(1) Time Boundaries 233(1) Archean Sulfates: Clues to the Early Atmosphere 234(1) Sulfur Isotope Anomalies: Mass-Independent Fractionation 235(3) Sulfur Isotope Ratios in the Terrestrial Environment 238 Oxygen Isotope Variations in Sulfates 236(6) References 239(3) Igneous Petrology 242(30) Introduction 242(1) The Mantle 243(12) Oxygen 243(4) Carbon 247(4) Nitrogen 251(1) Hydrogen 252(2) Sulfur 254(1) Emplacement of Plutonic Rocks: Interactions with the Crust and Hydrosphere 255(4) Normal Igneous Rocks 256(1) Shallow-Level Hydrothermal Alteration by Meteoric Water: Low δ18O Plutonic Rocks 256(2) High-δ18O Igneous Rocks 258(1) Calculating Fluid/Rock Ratios 259(2) Other Processes: Degassing, Assimilation, and Fractional Crystallization 261(11) Magmatic Volatiles 261(2) Assimilation-Fractional Crystallization (AFC) Processes 263(3) References 266(6) Metamorphic Geology 272(37) Introduction 272(1) Stable Isotopes as Geochemical Tracers 273(7) Closed System: Protolith Identification and Alteration 273(1) Open Systems: Volatilization and Fluid Infiltration Processes 274(6) Fluid Sources and Fluid--Rock Interaction 280(4) Oxygen and Hydrogen 280(2) Carbon 282(1) Sulfur 283(1) Scales of Equilibration During Metamorphism 284(2) Regional-Scale Exchange 284(1) Localized Exchange 285(1) Quantifying Fluid--Rock Ratios and Fluid Fluxes 286(5) Simple Mixing Models: Zero-Dimensional Water-Rock Interaction Models 286(1) One-Dimensional (Directional) Water--Rock Interaction Models 287(4) Thermometry 291(5) Introduction 291(2) Oxygen Isotope Thermometry in Metamorphic Rocks: Testing for Equilibrium 293(2) Applications of Stable Isotope Thermometry 295(1) Retrograde Exchange: ``Geospeedometry'' 296(4) State of the Art 300(9) References 302(7) Extraterrestrial Materials 309(20) Introduction 309(1) Classification of Meteorites 310(1) Oxygen Isotope Variations in Meteorites 310(8) Introduction 310(2) Discovery of an 17O Anomaly 312(1) Possible Explanations: Mixing of Two Distinct Reservoirs 313(3) Mass-Independent Fractionation 316(2) Hydrogen 318(2) Introduction 318(1) Meteorites 319(1) Carbon 320(2) Nitrogen 322(7) References 325(4) Appendix A Standard Reference Materials for Stable Isotopes 329(3) Appendix B Sample Calculation of the Correction Procedure for Adjusting Measured Isotope Data to Accepted IAEA Reference Scales 332(2) Index 334