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Geochronology and Thermochronology

Geochronology and Thermochronology

Peter W. Reiners , Richard W. Carlson , Paul R. Renne , Kari M. Cooper , Darryl E. Granger , Noah M. McLean , Blair Schoene

ISBN: 978-1-118-45590-6

Nov 2017, American Geophysical Union

480 pages

$80.99

Description

This book is a welcome introduction and reference for users and innovators in geochronology. It provides modern perspectives on the current state-of-the art in most of the principal areas of geochronology and thermochronology, while recognizing that they are changing at a fast pace. It emphasizes fundamentals and systematics, historical perspective, analytical methods, data interpretation, and some applications chosen from the literature. This book complements existing coverage by expanding on those parts of isotope geochemistry that are concerned with dates and rates and insights into Earth and planetary science that come from temporal perspectives. 

Geochronology and Thermochronology offers chapters covering: Foundations of Radioisotopic Dating; Analytical Methods; Interpretational Approaches: Making Sense of Data; Diffusion and Thermochronologic Interpretations; Rb-Sr, Sm-Nd, Lu-Hf; Re-Os and Pt-Os; U-Th-Pb Geochronology and Thermochronology; The K-Ar and 40Ar/39Ar Systems; Radiation-damage Methods of Geo- and Thermochronology; The (U-Th)/He System; Uranium-series Geochronology; Cosmogenic Nuclides; and Extinct Radionuclide Chronology. 

  • Offers a foundation for understanding each of the methods and for illuminating directions that will be important in the near future
  • Presents the fundamentals, perspectives, and opportunities in modern geochronology in a way that inspires further innovation, creative technique development, and applications
  • Provides references to rapidly evolving topics that will enable readers to pursue future developments

Geochronology and Thermochronology is designed for graduate and upper-level undergraduate students with a solid background in mathematics, geochemistry, and geology.

Read an interview with the editors to find out more:
https://eos.org/editors-vox/the-science-of-dates-and-rates

Preface, ix

1 Introduction, 1

1.1 Geo and chronologies, 1

1.2 The ages of the age of the earth, 2

1.3 Radioactivity, 7

1.4 The objectives and significance of geochronology, 13

1.5 References, 15

2 Foundations of radioisotopic dating, 17

2.1 Introduction, 17

2.2 The delineation of nuclear structure, 17

2.3 Nuclear stability, 19

2.3.1 Nuclear binding energy and the mass defect, 19

2.3.2 The liquid drop model for the nucleus, 20

2.3.3 The nuclear shell model, 22

2.3.4 Chart of the nuclides, 23

2.4 Radioactive decay, 23

2.4.1 Fission, 23

2.4.2 Alpha-decay, 24

2.4.3 Beta-decay, 25

2.4.4 Electron capture, 25

2.4.5 Branching decay, 25

2.4.6 The energy of decay, 25

2.4.7 The equations of radioactive decay, 27

2.5 Nucleosynthesis and element abundances in the solar system, 30

2.5.1 Stellar nucleosynthesis, 30

2.5.2 Making elements heavier than iron: s-, r-, p-process nucleosynthesis, 31

2.5.3 Element abundances in the solar system, 32

2.6 Origin of radioactive isotopes, 33

2.6.1 Stellar contributions of naturally occurring radioactive isotopes, 33

2.6.2 Decay chains, 33

2.6.3 Cosmogenic nuclides, 33

2.6.4 Nucleogenic isotopes, 35

2.6.5 Man-made radioactive isotopes, 36

2.7 Conclusions, 36

2.8 References, 36

3 Analytical methods, 39

3.1 Introduction, 39

3.2 Sample preparation, 39

3.3 Extraction of the element to be analyzed, 40

3.4 Isotope dilution elemental quantification, 42

3.5 Ion exchange chromatography, 43

3.6 Mass spectrometry, 44

3.6.1 Ionization, 46

3.6.2 Extraction and focusing of ions, 49

3.6.3 Mass fractionation, 50

3.6.4 Mass analyzer, 52

3.6.5 Detectors, 57

3.6.6 Vacuum systems, 60

3.7 Conclusions, 62

3.8 References, 63

4 Interpretational approaches: making sense of data, 65

4.1 Introduction, 65

4.2 Terminology and basics, 65

4.2.1 Accuracy, precision, and trueness, 65

4.2.2 Random versus systematic, uncertainties versus errors, 66

4.2.3 Probability density functions, 67

4.2.4 Univariate (one-variable) distributions, 68

4.2.5 Multivariate normal distributions, 68

4.3 Estimating a mean and its uncertainty, 69

4.3.1 Average values: the sample mean, sample variance, and sample standard deviation, 70

4.3.2 Average values: the standard error of the mean, 70

4.3.3 Application: accurate standard errors for mass spectrometry, 71

4.3.4 Correlation, covariance, and the covariance matrix, 73

4.3.5 Degrees of freedom, part 1: the variance, 73

4.3.6 Degrees of freedom, part 2: Student’s t distribution, 73

4.3.7 The weighted mean, 75

4.4 Regressing a line, 76

4.4.1 Ordinary least-squares linear regression, 76

4.4.2 Weighted least-squares regression, 77

4.4.3 Linear regression with uncertainties in two or more variables (York regression), 77

4.5 Interpreting measured data using the mean square weighted deviation, 79

4.5.1 Testing a weighted mean’s assumptions using its MSWD, 79

4.5.2 Testing a linear regression’s assumptions using its MSWD, 80

4.5.3 My data set has a high MSWD—what now?, 81

4.5.4 My data set has a really low MSWD—what now?, 81

4.6 Conclusions, 82

4.7 Bibliography and suggested readings, 82

5 Diffusion and thermochronologic interpretations, 83

5.1 Fundamentals of heat and chemical diffusion, 83

5.1.1 Thermochronologic context, 83

5.1.2 Heat and chemical diffusion equation, 83

5.1.3 Temperature dependence of diffusion, 85

5.1.4 Some analytical solutions, 86

5.1.5 Anisotropic diffusion, 86

5.1.6 Initial infinite concentration (spike), 86

5.1.7 Characteristic length and time scales, 86

5.1.8 Semi-infinite media, 87

5.1.9 Plane sheet, cylinder, and sphere, 88

5.2 Fractional loss, 88

5.3 Analytical methods for measuring diffusion, 89

5.3.1 Step-heating fractional loss experiments, 89

5.3.2 Multidomain diffusion, 92

5.3.3 Profile characterization, 93

5.4 Interpreting thermal histories from thermochronologic data, 94

5.4.1 “End-members” of thermochronometric date interpretations, 94

5.4.2 Equilibrium dates, 95

5.4.3 Partial retention zone, 95

5.4.4 Resetting dates, 96

5.4.5 Closure, 97

5.5 From thermal to geologic histories in low-temperature thermochronology: diffusion and advection of heat in the earth’s crust, 105

5.5.1 Simple solutions for one- and two-dimensional crustal thermal fields, 107

5.5.2 Erosional exhumation, 108

5.5.3 Interpreting spatial patterns of erosion rates, 109

5.5.4 Interpreting temporal patterns of erosion rates, 113

5.5.5 Interpreting paleotopography, 113

5.6 Detrital thermochronology approaches for understanding landscape evolution and tectonics, 116

5.7 Conclusions, 121

5.8 References, 123

6 Rb–Sr, Sm–Nd, and Lu–Hf, 127

6.1 Introduction, 127

6.2 History, 127

6.3 Theory, fundamentals, and systematics, 128

6.3.1 Decay modes and isotopic abundances, 128

6.3.2 Decay constants, 128

6.3.3 Data representation, 129

6.3.4 Geochemistry, 131

6.4 Isochron systematics, 133

6.4.1 Distinguishing mixing lines from isochrons, 136

6.5 Diverse chronological applications, 137

6.5.1 Dating diagenetic minerals in clay-rich sediments, 137

6.5.2 Direct dating of ore minerals, 138

6.5.3 Dating of mineral growth in magma chambers, 140

6.5.4 Garnet Sm–Nd and Lu–Hf dating, 141

6.6 Model ages, 143

6.6.1 Model ages for volatile depletion, 144

6.6.2 Model ages for multistage source evolution, 146

6.7 Conclusion and future directions, 148

6.8 References, 148

7 Re–Os and Pt–Os, 151

7.1 Introduction, 151

7.2 Radioactive systematics and basic equations, 151

7.3 Geochemical properties and abundance in natural materials, 154

7.4 Analytical challenges, 154

7.5 Geochronologic applications, 156

7.5.1 Meteorites, 156

7.5.2 Molybdenite, 158

7.5.3 Other sulfides, ores, and diamonds, 159

7.5.4 Organic-rich sediments, 161

7.5.5 Komatiites, 161

7.5.6 Basalts, 163

7.5.7 Dating melt extraction from the mantle—Re–Os model ages, 164

7.6 Conclusions, 167

7.7 References, 167

8 U–Th–Pb geochronology and thermochronology, 171

8.1 Introduction and background, 171

8.1.1 Decay of U and Th to Pb, 171

8.1.2 Dating equations, 173

8.1.3 Decay constants, 173

8.1.4 Isotopic composition of U, 174

8.2 Chemistry of U, Th, and Pb, 176

8.3 Data visualization, isochrons, and concordia plots, 176

8.3.1 Isochron diagrams, 176

8.3.2 Concordia diagrams, 177

8.4 Causes of discordance in the U–Th–Pb system, 178

8.4.1 Mixing of different age domains, 180

8.4.2 Pb loss, 180

8.4.3 Intermediate daughter product disequilibrium, 182

8.4.4 Correction for initial Pb, 183

8.5 Analytical approaches to U–Th–Pb geochronology, 184

8.5.1 Thermal ionization mass spectrometry, 185

8.5.2 Secondary ion mass spectrometry, 187

8.5.3 Laser ablation inductively coupled plasma mass spectrometry, 188

8.5.4 Elemental U–Th–Pb geochronology by EMP, 188

8.6 Applications and approaches, 188

8.6.1 The age of meteorites and of Earth, 188

8.6.2 The Hadean, 192

8.6.3 P–T–t paths of metamorphic belts, 194

8.6.4 Rates of crustal magmatism from U–Pb

geochronology, 197

8.6.5 U–Pb geochronology and the stratigraphic record, 200

8.6.6 Detrital zircon geochronology, 202

8.6.7 U–Pb thermochronology, 204

8.6.8 Carbonate geochronology by the U–Pb method, 209

8.6.9 U–Pb geochronology of baddeleyite and paleogeographic reconstructions, 211

8.7 Concluding remarks, 212

8.8 References, 212

9 The K–Ar and 40Ar/39Ar systems, 231

9.1 Introduction and fundamentals, 231

9.2 Historical perspective, 232

9.3 K–Ar dating, 233

9.3.1 Determining 40Ar∗, 233

9.3.2 Determining 40K, 234

9.4 40Ar/39Ar dating, 234

9.4.1 Neutron activation, 234

9.4.2 Collateral effects of neutron irradiation, 237

9.4.3 Appropriate materials, 240

9.5 Experimental approaches and geochronologic applications, 242

9.5.1 Single crystal fusion, 242

9.5.2 Intragrain age gradients, 243

9.5.3 Incremental heating, 243

9.6 Calibration and accuracy, 248

9.6.1 40K decay constants, 248

9.6.2 Standards, 249

9.6.3 So which is the best calibration?, 250

9.6.4 Interlaboratory issues, 252

9.7 Concluding remarks, 252

9.7.1 Remaining challenges, 252

9.8 References, 253

10 Radiation-damage methods of geochronology and thermochronology, 259

10.1 Introduction, 259

10.2 Thermal and optically stimulated luminescence, 259

10.2.1 Theory, fundamentals, and systematics, 259

10.2.2 Analysis, 260

10.2.3 Fundamental assumptions and considerations for interpretations, 264

10.2.4 Applications, 265

10.3 Electron spin resonance, 266

10.3.1 Theory, fundamentals, and systematics, 266

10.3.2 Analysis, 267

10.3.3 Fundamental assumptions and considerations for interpretations, 268

10.3.4 Applications, 269

10.4 Alpha decay, alpha-particle haloes, and alpha-recoil tracks, 270

10.4.1 Theory, fundamentals, and systematics, 270

10.5 Fission tracks, 273

10.5.1 History, 273

10.5.2 Theory, fundamentals, and systematics, 273

10.5.3 Analyses, 274

10.5.4 Fission-track age equations, 276

10.5.5 Fission-track annealing, 278

10.5.6 Track-length analysis, 280

10.5.7 Applications, 281

10.6 Conclusions, 284

10.7 References, 285

11 The (U–Th)/He system, 291

11.1 Introduction, 291

11.2 History, 291

11.3 Theory, fundamentals, and systematics, 292

11.4 Analysis, 294

11.4.1 “Conventional” analyses, 294

11.4.2 Other analytical approaches, 306

11.4.3 Uncertainty and reproducibility in (U–Th)/He dating, 307

11.5 Helium diffusion, 310

11.5.1 Introduction, 310

11.5.2 Apatite, 311

11.5.3 Zircon, 322

11.5.4 Other minerals, 332

11.5.5 A compilation of He diffusion kinetics, 334

11.6 4He/3He thermochronometry, 342

11.6.1 Method requirements and assumptions, 346

11.7 Applications and case studies, 348

11.7.1 Tectonic exhumation of normal fault footwalls, 348

11.7.2 Paleotopography, 349

11.7.3 Orogen-scale trends in thermochronologic dates, 350

11.7.4 Detrital double-dating and sediment provenance, 353

11.7.5 Volcanic double-dating, precise eruption dates, and magmatic residence times, 353

11.7.6 Radiation-damage-and-annealing model applied to apatite, 355

11.8 Conclusions, 355

11.9 References, 356

12 Uranium-series geochronology, 365

12.1 Introduction, 365

12.2 Theory and fundamentals, 367

12.2.1 The mathematics of decay chains, 367

12.2.2 Mechanisms of producing disequilibrium, 369

12.3 Methods and analytical techniques, 369

12.3.1 Analytical techniques, 369

12.4 Applications, 372

12.4.1 U-series dating of carbonates, 372

12.4.2 U-series dating in silicate rocks, 378

12.5 Summary, 389

12.6 References, 390

13 Cosmogenic nuclides, 395

13.1 Introduction, 395

13.2 History, 395

13.3 Theory, fundamentals, and systematics, 396

13.3.1 Cosmic rays, 396

13.3.2 Distribution of cosmic rays on Earth, 396

13.3.3 What makes a cosmogenic nuclide detectable and useful?, 397

13.3.4 Types of cosmic-ray reactions, 398

13.3.5 Cosmic-ray attenuation, 399

13.3.6 Calibrating cosmogenic nuclide-production rates in rocks, 400

13.4 Applications, 401

13.4.1 Types of cosmogenic nuclide applications, 401

13.4.2 Extraterrestrial cosmogenic nuclides, 401

13.4.3 Meteoric cosmogenic nuclides, 402

13.5 Conclusion, 415

13.6 References, 416

14 Extinct radionuclide chronology, 421

14.1 Introduction, 421

14.2 History, 422

14.3 Systematics and applications, 423

14.3.1 26Al–26Mg, 423

14.3.2 53Mn–53Cr chronometry, 425

14.3.3 107Pd–107Ag, 428

14.3.4 182Hf–182W, 430

14.3.5 I–Pu–Xe, 433

14.3.6 146Sm–142Nd, 436

14.4 Conclusions, 441

14.5 References, 441

Index, 445