Boron Isotopes (eBook)

Contents 6
1 Boron Isotopes in the Earth and Planetary Sciences—A Short History and Introduction 7
Abstract 7
1.1 Introduction 7
1.2 A Short History of Boron Isotope Analyses 8
1.2.1 The Discovery of Boron Stable Isotopes 8
1.2.2 Natural Abundances and Variations 8
1.2.3 TIMS and the Establishment of Standards 9
1.2.4 Plasma Mass Spectrometry and Interlaboratory Comparison 10
1.2.5 The Development of in Situ Techniques 11
1.2.6 Theoretical and Experimental Boron Isotope Fractionation 11
1.3 The Fifth Element 12
Acknowledgements 14
References 14
2 Boron Isotope Analysis of Geological Materials 18
Abstract 18
2.1 Introduction 19
2.2 Digestion and Purification Methods for Boron Isotope Analysis of Geologic Materials 19
2.2.1 Sample Digestion 19
2.2.2 Ion Exchange 25
2.2.3 Purification by Non Exchange Resin Methodologies 26
2.3 Analytical Methods for Boron Isotope Analysis of Geological Materials 26
2.3.1 The Isotopic Analysis of Boron in Solution Mode 26
2.3.1.1 Positive Ion Thermal Ionization Mass Spectrometry 26
2.3.1.2 Negative Ion Thermal Ionization Mass Spectrometry 27
2.3.1.3 Inductively Coupled Plasma Mass Spectrometry 28
2.3.2 The Isotopic Analysis of Boron in Situ 29
2.3.2.1 Secondary Ion Mass Spectrometry (SIMS) 29
2.3.2.2 Laser Ablation Inductively Coupled Mass Spectrometry 32
2.4 Summary and Outlook 33
Acknowledgements 33
References 33
3 Boron Isotope Fractionation Among Vapor–Liquids–Solids–Melts: Experiments and Atomistic Modeling 37
Abstract 37
3.1 Introduction 37
3.2 Notations 38
3.3 Controls of B-Isotopic Fractionation 39
3.4 B-Speciation in Liquids, Vapor, and Melts 40
3.4.1 B-Speciation in Aqueous Fluids 40
3.4.2 Boron Speciation in Vapor 40
3.4.3 Boron Speciation in Melt 42
3.5 Experimental Determination of B-Isotope Fractionation 43
3.5.1 Vapor–Liquid–Melt Boron Isotope Fractionation 43
3.5.1.1 Vapor–Liquid Boron Isotope Fractionation 43
3.5.1.2 Aqueous Fluid–Melt B-Isotope Fractionation 45
3.5.2 Solid–Fluid B-Isotope Fractionation 46
3.5.2.1 Low-Temperature Solid–Aqueous Fluid B-Isotope Fractionation 46
Carbonate–Fluid B-Isotope Fractionation 46
Clay Mineral–Fluid B-Isotope Fractionation 48
Boron-Isotope Fractionation in Other Low-Temperature Solid–Fluid Systems 49
3.5.2.2 High-Temperature Solid–Aqueous Fluid B-Isotope Fractionation 50
Mica–Fluid B-Isotope Fractionation 50
Tourmaline—Fluid B-Isotope Fractionation 53
3.6 Ab Intio Prediction of B-Isotope Fractionation 56
3.6.1 Computational Approach 57
3.6.1.1 The “Single Atom Approximation” Following Bigeleisen and Mayer (1947) 57
3.6.1.2 Computational Technique 58
3.6.1.3 Error Estimation Technique 59
3.6.2 Computation of Fractionation Factors 59
3.6.2.1 Vapor 59
3.6.2.2 Aqueous Fluid 59
3.6.2.3 Pressure Dependence of the Fractionation Factor in Aqueous Fluids 61
3.6.3 Computationally Determined Mineral–Fluid B-Isotope Fractionation 61
3.6.3.1 Tourmaline–Neutral Fluid B-Isotope Fractionation 61
3.6.3.2 Boromuscovite–Strongly Basic Fluid B-Isotope Fractionation 64
3.6.3.3 Boromuscovite–Neutral Fluid B-Isotope Fractionation 64
3.6.4 B-Isotope Fractionation Among Minerals 65
3.7 Conclusions 66
References 68
4 Boron Incorporation into Marine CaCO3 74
Abstract 74
4.1 Introduction 75
4.2 Marine Calcium Carbonate Minerals 78
4.2.1 Carbonate Mineral Formation 78
4.2.1.1 Terrace-Ledge-Kink (TLK) Growth 79
4.2.1.2 Non-classical Crystal Growth 81
4.2.2 Impurity Incorporation in Carbonates 81
4.2.2.1 Reaction-Limited Impurity Incorporation 84
4.2.2.2 Diffusion-Limited Surface Environments 86
4.2.2.3 Impurity Incorporation in Non-classical Growth 87
4.3 Boron Incorporation in Calcium Carbonates 87
4.3.1 Aqueous Boron Chemistry 87
4.3.2 Boron in Synthetic Carbonates 88
4.3.2.1 Synthetic Aragonite 89
4.3.2.2 Synthetic Calcite 90
4.3.2.3 Differences Between Calcite and Aragonite 92
4.3.2.4 The Variability of B in Calcite: Possible Causes 93
4.3.2.5 The Variability of B in Calcite: A Surface Kinetic Explanation? 94
4.4 Boron in Carbonate Biominerals 101
Acknowledgements 103
References 103
5 Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction 109
Abstract 109
5.1 Introduction 110
5.1.1 Aqueous Boron Isotope Systematics 110
5.1.2 The Carbonate ?11B-pH Proxy 112
5.2 Methods of Boron Isotope Analysis in Foraminifera 114
5.2.1 Samples 114
5.2.1.1 Sample Size and Preparation 114
5.2.1.2 Preservation and Diagenesis 114
5.2.2 Cleaning of Foraminiferal Samples 114
5.2.3 Chemical Purification 115
5.2.3.1 Column Chromatography 115
5.2.3.2 Microsubliation 115
5.2.4 Mass Spectrometry 116
5.2.4.1 NTIMS 116
5.2.4.2 MC-ICPMS 116
5.2.4.3 In Situ Analysis 116
5.3 Boron Isotope Systematics in Modern Foraminifera 116
5.3.1 Results of Boron Isotope Calibration Studies on Modern Foraminifera 117
5.3.1.1 Deep Sea Benthic Foraminifera—A Model System? 117
5.3.1.2 Planktic Foraminifera—Key Proxy Carriers 118
5.3.1.3 Other Benthic Foraminifera—Enigmatic Signals in High-Mg Calcite and Aragonite 121
5.3.2 Discussion of Boron Isotope Calibration on Modern Foraminifera 121
5.3.2.1 Boron Incorporation in Foraminifera 121
5.3.2.2 Boron Isotope Fractionation in Foraminifera 122
5.3.2.3 Boron Isotope Constraints on Biomineralisation 125
5.4 ?11B-Derived pH and CO2 128
5.4.1 pH from ?11B 129
5.4.1.1 ?11B of Borate and pH 129
5.4.1.2 KB 130
5.4.1.3 ?11B of Seawater 130
5.4.2 CO2 from pH 133
5.5 Proxy Application: Examples 137
5.5.1 Glacial-Interglacial CO2 137
5.5.2 pH and CO2 Beyond the Ice Cores 138
5.6 Summary and Outlook 139
Acknowledgements 139
References 140
6 Boron Isotopic Systematics in Scleractinian Corals and the Role of pH Up-regulation 146
Abstract 146
6.1 Introduction 147
6.2 Calcification in Scleractinian Corals 148
6.3 Boron Isotopic Systematics 149
6.4 Boron Isotopic Compositions of Scleractinian Corals 151
6.5 Experimental Constraints on the Relationship Between Calcifying Fluid pH and Seawater pH 151
6.6 Cold-Water Corals 154
6.7 pH Up-Regulation in the Natural Environment 155
6.7.1 Corals Under Free Ocean Carbon Enrichment (FOCE) Conditions 155
6.7.2 Corals Under Natural Conditions of Seasonal Forcing 157
6.8 Summary and Conclusions 159
Acknowledgements 161
References 161
7 Boron in the Weathering Environment 164
Abstract 164
7.1 The Main Fractionating Mechanisms of Boron on Terrestrial Surfaces 165
7.1.1 The Crystallochemistry of Boron 165
7.1.2 Interaction of Dissolved Boron with Mineral Surfaces 166
7.1.3 Coprecipitation of Boron into Solids 168
7.1.4 Behavior of Boron During Evaporation and Condensation Processes 170
7.1.5 Behavior of Boron in Biological Processes 171
7.2 Biogeochemistry of Boron in the Critical Zone 172
7.2.1 Boron Isotopes in Precipitation 172
7.2.2 Boron Isotopes in Soil Profiles 173
7.2.3 Boron Isotopes at the Catchment Scale 174
7.2.4 Boron Isotopes in Groundwaters 176
7.2.5 Boron Isotopes in River Systems 178
7.2.6 Partitioning of Boron Isotopes Between Water and Modern Day River Sediments 180
7.2.7 Boron Isotopes in Lakes 181
7.3 The Riverine Input of Boron to the Ocean and Secular Evolution of the Ocean 182
7.3.1 The Riverine Input of Boron to the Ocean 182
7.3.2 Boron as an Integrated Tracer of Global Weathering and Erosion 183
7.3.3 The Secular Evolution of Boron Isotopes in the Ocean 184
7.4 Conclusion 185
Acknowledgements 185
References 185
8 Boron Isotopes in the Ocean Floor Realm and the Mantle 190
Abstract 190
8.1 Introduction 190
8.2 The Oceanic Crust 191
8.3 Mid-Ocean Ridge Basalts 192
8.4 Ocean Island Basalts 194
8.5 The Mantle 197
8.6 Hydrothermal Alteration and Weathering 198
8.6.1 Alteration of the Igneous Crust 199
8.6.2 Serpentinization 203
8.6.3 Hydrothermal Vent Fluids 204
8.6.4 Subaerial Hydrothermal Alteration 205
8.7 Oceanic Sediments 205
8.8 Paleo-Ocean Chemistry of Boron 207
8.9 Summary and Outlook 210
Acknowledgements 211
References 211
9 Boron Isotopes as a Tracer of Subduction Zone Processes 217
Abstract 217
9.1 Introduction 217
9.2 Metamorphic Processes in the Subducting Slab 218
9.2.1 Physical and Thermal Geometry of Subduction Zones 219
9.2.2 Subduction Metamorphism: Sediments Including Their Pore Waters 220
9.2.3 Subduction Metamorphism: Altered Oceanic Crust 223
9.2.4 Serpentinized Oceanic Floor and Mantle 224
9.3 Mantle Wedge Processes and the Subduction Interface 227
9.3.1 Boron Isotope Composition of Mantle Wedge Serpentinites 227
9.3.2 Role of the Subduction Interface in B Recycling 227
9.4 Modelling of B Isotope Fractionation During Subduction 228
9.5 Boron Isotope Signature of Volcanic Arcs 230
9.5.1 Global Boron Isotopic Database from Volcanic Arcs 231
9.5.2 Variations of Boron Isotope Signatures with Subducting Slab Parameters 232
9.5.3 Variations of Boron Isotope Signatures with Geochemical Proxies 234
9.6 Deep B Recycling 238
9.7 Outstanding Issues and Future Work Needed 239
Acknowledgements 241
References 241
10 Boron Isotopes in the Continental Crust: Granites, Pegmatites, Felsic Volcanic Rocks, and Related Ore Deposits 248
Abstract 248
10.1 Introduction 249
10.2 Boron in the Continental Crust 249
10.3 B-Isotope Systematics in Crustal Processes 251
10.3.1 Metamorphism and Partial Melting 252
10.3.2 Boron in Granitic Magmas 256
10.3.2.1 Boron in I-Type Magmas 258
10.3.2.2 Processes Affecting B-Isotope Composition in I-Type Magmas: Differentiation, Assimilation, Degassing 258
10.3.2.3 Boron in S-Type Magmas 259
10.3.2.4 Implications for B-Isotope Composition of the Continental Crust 260
10.3.3 Late-Stage Granites and Pegmatites: The Magmatic-Hydrothermal Transition 260
10.3.3.1 B-Isotope Variations in Early- to Late-Magmatic Tourmaline 261
10.3.4 Boron Isotopes in Magmatic-Hydrothermal Ore Deposits 263
10.3.4.1 Ore Deposits with I-Type Association 264
10.3.4.2 Ore Deposits with S-Type Association 264
10.4 Summary 265
Acknowledgements 266
References 266
11 The Cosmochemistry of Boron Isotopes 272
Abstract 272
11.1 Basics of Boron Isotopes 272
11.1.1 Boron Nucleosynthesis 272
11.1.2 Cosmochemistry of Boron 275
11.2 Boron Isotopes in the Galaxy 277
11.2.1 Boron Abundances in Stars 277
11.2.2 Boron in the Interstellar Medium 278
11.3 Boron Isotopes in the Early Solar System 279
11.3.1 Mass Spectrometry for B Isotope Measurements 279
11.3.2 B Isotopes in Chondritic Meteorites 280
11.3.3 B Isotopes in CAIs and Implications for Early Solar System Irradiation 281
11.3.4 B Isotopes in Chondrules 284
11.4 Concluding Remarks 285
Acknowledgements 285
References 285