Preface ........................................................ ix
Acknowledgements ............................................... xi
List of abbreviations and symbols ............................. xii
Part I. 'How': isotopes and how they are measured ............... 1
1 Isotopes and geochemistry .................................... 3
1.1 Introduction ............................................ 3
1.2 Elements and isotopes ................................... 5
2 Processes .................................................... 9
2.1 Fractionation: chemical vs isotopic ..................... 9
2.2 Isotopic fractionation ................................. 10
3 Mass spectrometry ........................................... 17
3.1 Principles of mass spectrometry ........................ 17
3.2 TIMS vs ICP-MS (PIMS) vs GS IRMS ....................... 22
3.3 In situ mass spectrometry .............................. 25
3.4 Noble gas mass spectrometry and irradiation for Ar
analysis ............................................... 26
3.5 Measurement of concentrations by mass spectrometry:
isotope dilution ....................................... 27
4 Stable isotopes ............................................. 32
4.1 Nomenclature ........................................... 33
4.2 Major element stable isotopes .......................... 36
4.3 Minor and trace element stable isotopes ................ 37
5 Radioactivity, radioactive decay and isotope systems
applied in the geosciences .................................. 40
5.1 Half life and decay constant ........................... 41
5.2 Equations .............................................. 42
5.3 Geologically useful decay schemes ...................... 43
5.4 Closure temperature (Tc) ............................... 52
Part II 'When': geological time, ages and rates of geological
phenomena ...................................................... 57
6 Underpinnings of geochronology: background and principles ... 59
6.1 Accuracy and precision in geochronology ................ 60
6.2 Statistical treatment of geochronological data ......... 61
7 Isochron geochronology ...................................... 79
7.1 Principles of isochrons ................................ 79
7.2 Metamorphism and resetting of isochrons ................ 86
8 U-Pb, Pb-Pb and Re-Os sulphide geochronology ................ 89
8.1 Principles of U-Pb geochronology ....................... 91
8.2 U-series isotopes ..................................... 104
8.3 EPMA and CHIME dating ................................. 106
8.4 Thermochronology: fission tracks and (U + Th)/He ...... 108
8.5 Re-Os geochronology of molybdenite and LLHR (low-
level highly radiogenic) sulphides .................... 111
9 Argon geochronology ........................................ 115
9.1 K-Ar .................................................. 115
9.2 Ar-Ar ................................................. 117
Part III 'Where': tracking the course of material through
the earth ..................................................... 125
10 Isotopes as tracers: general principles .................... 127
10.1 Generic model ages .................................... 128
10.2 Mixing ................................................ 135
10.3 AFC (assimilation-fractionation-crystallisation) ...... 140
11 Applications of radiogenic tracers ......................... 145
11.1 Differentiation within the crust and crustal growth ... 145
11.2 Isotopic characteristics of the mantle ................ 162
11.3 Tracing petroleum migration and sources ............... 172
12 New developments in radiogenic isotopes .................... 177
12.1 Looking forward: the next generation of tools and
techniques ............................................ 177
Appendix 1 Conversion between wt% oxide and ppm ............... 181
Appendix 2 Isotopic abundances ................................ 183
Glossary ...................................................... 186
Further reading ............................................... 189
Index ......................................................... 194
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