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 l4C 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 eosmochemistry ............................. 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 8 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 Hydrologie
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 6180 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 6l80 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, G1SP, and
NGRIP ............................................. 338
10.2.10 Speleotherm and related climate records .......... 340
10.2.11 Soils 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.l 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
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