Physics and Chemistry of the Earth (eBook)

Front Cover 1
Physics and Chemistry of the Earth 4
Copyright Page 5
Table of Contents 6
PREFACE 12
CHAPTER 1. MODEL OF A KIMBERLITE PIPE 16
ABSTRACT 16
INTRODUCTION 16
KIMBERLITE PIPES WHICH HAVE UNDERGONE RELATIVELY LITTLE EROSION 17
THE STRUCTURE AND COMPOSITION OF THE ORAPA PIPE IN BOTSWANA 17
ORIGIN OF THE EPICLASTIC KIMBERLITES 18
DISTRIBUTION OF THE EPICLASTIC KIMBERLITES 19
THE DEPTH OF EROSION IN THE KIMBERLEY AREA 20
ACCIDENTAL INCLUSIONS IN THE PIPES 20
RELEVANT STUDIES OF SILLS AND THEIR DEPTH FORMATION 21
THICKNESS OF THE KARROO SYSTEM AND AGE OF THE KIMBERLITES 22
SLOPE ANGLES OF PIPE WALLS IN VARIOUS ENVIRONMENTS 23
MODEL OF A KIMBERLITE PIPE IN THE KIMBERLEY AREA 28
WALLROCK GEOLOGY 28
THE KIMBERLITE PIPE 29
ACKNOWLEDGEMENTS 31
REFERENCES 31
CHAPTER 2. FORMATION OF PHREATOMAGMATIC MAAR-DIATREME VOLCANOES AND ITS RELEVANCE TO KIMBERLITE DIATREMES 34
ABSTRACT 34
INTRODUCTION 34
MAAR-DIATREME VOLCANOES 34
MODEL OF MAAR-DIATREME FORMATION 37
KIMBERLITE DIATREMES 40
CONCLUDING REMARKS 43
ACKNOWLEDGEMENTS 43
REFERENCES 43
CHAPTER 3. MODELING OF DIATREME EMPLACEMENT BY FLUIDIZATION 46
ABSTRACT 46
INTRODUCTION 46
EXPERIMENTAL PROCEDURE 47
EXPERIMENTAL RESULTS 49
SUMMARY AND CONCLUSIONS 56
ACKNOWLEDGEMENTS 58
REFERENCES 58
CHAPTER 4. STRUCTURAL ASPECTS OF KIMBERLITE DYKE AND SHEET INTRUSION IN SOUTH-WEST GREENLAND 60
ABSTRACT 60
INTRODUCTION 60
FIELD RELATIONSHIPS 60
MECHANISM OF INTRUSION 64
STRUCTURAL CONTROL OF DYKE AND SHEET INTRUSION 66
ACKNOWLEDGEMENTS 66
REFERENCES 67
CHAPTER 5. THE EMPLACEMENT OF SOME DIATREME-FACIES KIMBERLITES 68
ABSTRACT 68
INTRODUCTION 68
PETROGRAPHY 69
SIMILAR ROCKS FROM OTHER SOURCES 72
ORIGIN OF THE CALCITE IN THE ROCKS 72
EMPLACEMENT OF THE KIMBERLITES 73
DISCUSSION 74
ACKNOWLEDGEMENTS 75
REFERENCES 75
CHAPTER 6. MAGNETITE-SERPENTINE-CALCITE DYKES AT PREMIER MINE AND ASPECTS OF THEIR RELATIONSHIP TO KIMBERLITE AND TO CARBONATITE OF ALKALIC CARBONATITE COMPLEXES 78
ABSTRACT 78
INTRODUCTION 78
PREVIOUS INVESTIGATIONS INTO THE CARBONATE-RICH ROCKS 79
THE DYKES STUDIED 80
GEOCHEMISTRY AND MAGMA DERIVATION 85
ACKNOWLEDGEMENTS 87
REFERENCES 87
CHAPTER 7. THE BUSHMANLAND KIMBERLITES AND RELATED ROCKS 88
ABSTRACT 88
INTRODUCTION 88
DESCRIPTION 92
AGE 93
CHEMICAL COMPOSITION 93
CONCLUSIONS 96
ACKNOWLEDGEMENTS 97
REFERENCES 97
CHAPTER 8. KIMBERLITE AND RELATED ROCKS FROM THE NAMA PLATEAU OF SOUTH-WEST AFRICA 98
ABSTRACT 98
INTRODUCTION 98
PREVIOUS WORK 98
REGIONAL GEOLOGY 99
KIMBERLITES 101
RELATED ROCKS 105
CHEMISTRY 107
EVOLUTION OF KIMBERLITE PROVINCES 109
ACKNOWLEDGEMENTS 110
REFERENCES 111
CHAPTER 9. ECLOGITE NODULES FROM KIMBERLITE PIPES OF THE COLORADO PLATEAU—SAMPLES OF SUBDUCTED FRANCISCAN-TYPE OCEANIC LITHOSPHERE 112
ABSTRACT 112
INTRODUCTION 112
ACKNOWLEDGEMENTS 125
REFERENCES 126
CHAPTER 10. A PLATE TECTONICS MODEL INVOLVING NON-LAMINAR ASTHENOSPHERIC FLOW TO ACCOUNT FOR IRREGULAR PATTERNS OF MAGMATISM IN THE SOUTHWESTERN UNITED STATES 130
ABSTRACT 130
INTRODUCTION 130
RECONSTRUCTED HISTORY OF THE PACIFIC MARGIN AND PATTERNS OF CENOZOIC IGNEOUS ACTIVITY IN THE WESTERN UNITED STATES 131
NON-LAMINAR FLOW BELOW THE COLORADO PLATEAU 133
EDDIES RESULTING FROM VISCOUS HEAT PRODUCTION 134
RUNAWAY TEMPERATURES IN VISCOUS FLOW 135
THE INITIATION OF "UNSTEADY EDDIES" IN THE ASTHENOSPHERE 136
SUMMARY 138
ACKNOWLEDGEMENTS 138
REFERENCES 138
CHAPTER 11. MINERALOGY AND PETROLOGY OF THE KIMBERLITE FROM SOMERSET ISLAND, N.W.T, CANADA 140
ABSTRACT 140
INTRODUCTION 140
MINERALOGY 141
EPITAXIAL SEQUENCES AND MANTLING 147
SILICATE-CARBONATE LIQUID IMMISCIBILITY 147
IMMISCIBLE SULPHIDE LIQUID 149
PETROGENESIS 151
ACKNOWLEDGEMENTS 152
REFERENCES 152
CHAPTER 12. KIMBERLITIC-CARBONATITIC DIKES OF THE SAGUENAY RIVER VALLEY, QUEBEC, CANADA 154
ABSTRACT 154
INTRODUCTION AND GENERAL GEOLOGY 154
MINERALOGY 156
PETROGENESIS 161
ACKNOWLEDGEMENTS 164
REFERENCES 165
CHAPTER 13. KIMBERLITIC DIATREMES IN NORTHERN COLORADO AND SOUTHERN WYOMING 166
ABSTRACT 166
INTRODUCTION 166
PETROGRAPHY AND CHEMISTRY 169
KIMBERLITE 169
PETROLOGY OF NODULES 175
SUMMARY 177
ACKNOWLEDGEMENTS 177
REFERENCES 177
CHAPTER 14. THE FEN DAMKJERNITE: PETROLOGY OF A "CENTRAL-COMPLEX KIMBERLITE" 180
ABSTRACT 180
INTRODUCTION 180
PETROGRAPHY 181
ROCK CHEMISTRY 182
MINERAL CHEMISTRY 184
CONDITIONS OF CRYSTALLIZATION 186
CONDITIONS OF GENERATION 187
Sr ISOTOPE GEOCHEMISTRY 188
DISCUSSION 191
ACKNOWLEDGEMENTS 193
REFERENCES 193
CHAPTER 15. MINERALOGY AND PETROLOGY OF KIMBERLITE DYKE AND SHEET INTRUSIONS AND INCLUDED PERIDOTITE XENOLITHS FROM SOUTH-WEST GREENLAND 196
ABSTRACT 196
INTRODUCTION 196
KIMBERLITE PETROGRAPHY AND MINERALOGY 197
KIMBERLITE GEOCHEMISTRY 207
PETROGRAPHY AND MINERALOGY OF PERIDOTITE XENOLITHS 208
KIMBERLITE PETROGENESIS 212
DERIVATION OF PERIDOTITE XENOLITHS 213
ACKNOWLEDGEMENTS 213
REFERENCES 213
CHAPTER 16. THE IGWISI HILLS EXTRUSIVE "KIMBERLITES" 216
ABSTRACT 216
INTRODUCTION 216
PETROGRAPHY 217
MINERAL CHEMISTRY 219
IGWISI MATRIX 228
SOURCE REGION OF THE OLIVINE NODULES 231
SOURCE OF IGWISI MATRIX 232
FORMATION OF THE IGWISI EXTRUSIVES 232
IGWISI HILLS AND KIMBERLITES 233
ACKNOWLEDGEMENTS 234
REFERENCES 234
CHAPTER 17. GROSS BRUKKAROS: A KIMBERLITE-CARBONATITE VOLCANO 236
ABSTRACT 236
INTRODUCTION 236
METHODS USED 237
SATELLITE VENTS 237
PETROGRAPHY 240
CHEMISTRY 243
NATURE OF SOLUTIONS 246
PETROGENESIS 248
ACKNOWLEDGEMENTS 252
REFERENCES 252
CHAPTER 18. THE COMPOSITION OF LATE STAGE KIMBERLITE LIQUIDS AS REVEALED BY NUCLEATED AUTOLITHS 254
ABSTRACT 254
INTRODUCTION 254
PETROGRAPHY AND MINERAL CHEMISTRY 255
KIMBERLITES AND THE CMAS TETRAHEDRON 260
CONCLUSIONS 262
ACKNOWLEDGEMENTS 262
REFERENCES 263
CHAPTER 19. GARNET PERIDOTITE XENOLITHS IN A MONTANA, U.S.A., KIMBERLITE 266
ABSTRACT 266
REFERENCES 274
CHAPTER 20. AL-AUGITE AND CR-DIOPSIDE ULTRAMAFIC XENOLITHS IN BASALTIC ROCKS FROM WESTERN UNITED STATES 276
ABSTRACT 276
CLASSIFICATION 277
STRUCTURAL RELATIONSHIPS 279
TEXTURAL RELATIONSHIPS 282
COMPOSITIONAL TRENDS 284
INTERPRETATION 286
ACKNOWLEDGEMENTS 290
REFERENCES 290
CHAPTER 21. PETROLOGY OF PERIDOTITE NODULES FROM NDONYUO OLNCHORO, SAMBURU DISTRICT, CENTRAL KENYA 292
ABSTRACT 292
GENERAL GEOLOGY 292
PETROGRAPHY AND PETROCHEMISTRY 293
MINERALOGY 299
DISCUSSION 302
ACKNOWLEDGEMENTS 304
REFERENCES 305
CHAPTER 22. "PYROXENE"-ILMENITE XENOLITHS FROM THE STOCKDALE PIPE, KANSAS: CHEMISTRY, CRYSTALLOGRAPHY, AND ORIGIN 306
ABSTRACT 306
INTRODUCTION 306
PETROGRAPHY 307
CHEMISTRY 307
CRYSTALLOGRAPHY 309
DISCUSSION 311
ACKNOWLEDGEMENTS 312
REFERENCES 312
CHAPTER 23. THE CHEMISTRY AND GENESIS OF OPAQUE MINERALS IN KIMBERLITES 314
ABSTRACT 314
INTRODUCTION 314
SPINEL GROUP 315
ILMENITE 321
RARE AND ACCESSORY MINERALS 324
ACKNOWLEDGEMENTS 325
REFERENCES 325
CHAPTER 24. CHEMISTRY OF TI-POOR SPINELS, ILMENITES AND RUTILES FROM PERIDOTITE AND ECLOGITE XENOLITHS 328
ABSTRACT 328
INTRODUCTION 328
TI-POOR SPINEL 329
ILMENITE AND MAGNETITE 335
RUTILE 336
CONCLUSION 339
ACKNOWLEDGEMENTS 339
REFERENCES 340
CHAPTER 25. PENTLANDITE-MAGNETITE INTERGROWTH IN DE BEERS SPINEL LHERZOLITE: REVIEW OF SULPHIDES IN NODULES 342
ABSTRACT 342
INTRODUCTION 342
OBSERVATIONS 343
SILICATES 349
GENERAL DISCUSSION OF SULPHIDE GLOBULES 349
SULPHIDES IN NATURAL BASIC MELTS 350
EXPERIMENTAL DATA 350
SULPHIDES IN NODULES 353
DISCUSSION OF DE BEERS INTERGROWTH 355
FINAL REMARKS 355
ACKNOWLEDGEMENTS 355
REFERENCES 356
CHAPTER 26. CHROMITE-SILICATE INTERGROWTHS IN UPPER-MANTLE PERIDOTITES 358
ABSTRACT 358
INTRODUCTION 358
DESCRIPTION OF THE INTERGROWTHS 359
CHEMISTRY OF THE INTERGROWTH PHASES 363
ORIGIN OF THE INTERGROWTHS 366
INTERGROWTH IN LASHAINE PERIDOTITE 368
ACKNOWLEDGEMENTS 369
REFERENCES 369
CHAPTER 27. TWO ROBERTS VICTOR CUMULATE ECLOGITES AND THEIR RE-EQUILIBRATION 370
ABSTRACT 370
INTRODUCTION 370
MINERAL CHEMISTRY 374
GARNETS 374
CLINOPYROXENES 377
BULK COMPOSITIONS 378
CONDITIONS OF EQUILIBRATION 379
PROCESSES PRIOR TO SUBSOLIDUS EQUILIBRATION 381
ACKNOWLEDGEMENTS 383
REFERENCES 384
CHAPTER 28. EVOLUTION OF CLINOPYROXENE AND GARNET IN AN ECLOGITE NODULE FROM THE ROBERTS VICTOR KIMBERLITE PIPE, SOUTH AFRICA 386
ABSTRACT 386
INTRODUCTION 386
PETROGRAPHY 387
CHEMICAL ANALYSES 390
RELATIONS IN ACF PROJECTION 398
DISTRIBUTION OF IRON AND MAGNESIUM 400
EXPERIMENTAL DATA 402
SUMMARY AND CONCLUSIONS 405
ACKNOWLEDGEMENTS 406
REFERENCES 406
CHAPTER 29. LIGHT ELEMENT METASOMATISM OF THE CONTINENTAL MANTLE: THE EVIDENCE AND THE CONSEQUENCES 408
ABSTRACT 408
INTRODUCTION 408
THE WEST EIFEL AND CENTRAL SOUTH WEST UGANDAN PROVINCES 409
MINERAL ASSEMBLAGES OF THE NODULES 410
PARAGENESIS OF THE NODULE PHASES 420
ORIGIN OF THE NODULES AND THEIR RELATIONSHIP TO THE LAVAS 423
PROPOSED MODEL 426
SUMMARY 430
APPENDIX. CALCULATIONS OF UPLIFT DUE TO MANTLE METASOMATISM 430
ACKNOWLEDGEMENTS 432
REFERENCES 432
CHAPTER 30. PRIMARY AND SECONDARY PHLOGOPITES AND CLINOPYROXENES IN GARNET LHERZOLITE XENOLITHS 436
ABSTRACT 436
INTRODUCTION 436
PETROGRAPHY 437
MINERAL CHEMISTRY 439
DISCUSSION 444
ACKNOWLEDGEMENTS 447
REFERENCES 447
CHAPTER 31. ORIGINS OF THE ULTRAMAFIC NODULES FROM SOME KIMBERLITES OF NORTHERN LESOTHO AND THE MONASTERY MINE, SOUTH AFRICA 450
ABSTRACT 450
INTRODUCTION 450
THE GEOTHERM 451
THE LHERZOLITES 454
ORIGIN OF THE INFLECTION 460
THE HARZBURGITES AND THE CHROMITE PROBLEM 460
THE DUNITES 462
THE ILMENITE ASSOCIATION 462
THE DISCRETE NODULE ASSOCIATION 464
PHLOGOPITE RELATIONS 469
DISCUSSION 471
REFERENCES 472
CHAPTER 32. PETROLOGIC AND THERMAL STRUCTURE OF THE UPPER MANTLE BENEATH SOUTH AFRICA IN THE CRETACEOUS 474
ABSTRACT 474
INTRODUCTION 474
DESCRIPTION OF SAMPLES 475
MINERAL CHEMISTRY 477
DISCUSSION 480
ACKNOWLEDGEMENTS 484
REFERENCES 485
CHAPTER 33. CLASSIFICATION OF TEXTURES AND FABRICS OF PERIDOTITE XENOLITHS FROM SOUTH AFRICAN KIMBERLITES 486
ABSTRACT 486
INTRODUCTION 486
MAIN TEXTURES 487
COMPARISON WITH PERIDOTITES FROM BASALTIC XENOLITHS AND MASSIFS 493
INTERPRETATION OF THE TEXTURES AND FABRICS 493
DISCUSSION OF THE RECENT MODELS OF THE UPPER MANTLE BELOW SOUTH AFRICA 495
ACKNOWLEDGEMENTS 496
REFERENCES 496
CHAPTER 34. PETROGRAPHY AND GEOLOGICAL HISTORY OF UPPER MANTLE XENOLITHS FROM THE MATSOKU KIMBERLITE PIPE 498
ABSTRACT 498
INTRODUCTION 498
COARSE-GRAINED XENOLITHS 500
FLASER XENOLITHS 505
EVEN-TEXTURED XENOLITHS 507
DISCUSSION OF PRINCIPAL TEXTURES 511
METASOMATISM 516
BANDING 522
CONCLUSIONS 525
ACKNOWLEDGEMENTS 526
REFERENCES 526
CHAPTER 35. MANTLE XENOLITHS IN THE MATSOKU KIMBERLITE PIPE 528
ABSTRACT 528
INTRODUCTION 528
MINERAL COMPOSITIONS 529
THE ORTHOPYROXENES AND OLIVINES 533
DISCUSSION 534
BULK COMPOSITIONS 538
DISCUSSION 540
ACKNOWLEDGEMENTS 545
REFERENCES 545
CHAPTER 36. MINERAL CHEMISTRY OF PERIDOTITE XENOLITHS FROM THE LASHAINE VOLCANO, TANZANIA 548
ABSTRACT 548
INTRODUCTION 548
MINERAL ASSEMBLAGES 549
MINERAL CHEMISTRY 550
SAMPLE 825 559
SECONDARY PROCESSES 561
SOURCE REGION FOR THE GARNET PERIDOTITES 561
SOURCE REGION FOR THE GARNET-FREE PERIDOTITES 563
PHLOGOPITE AND PARTIAL MELTING 564
NATURE OF THE GARNET PERIDOTITES IN THE MANTLE BENEATH THE LASHAINE VOLCANO 565
ACKNOWLEDGEMENTS 566
REFERENCES 566
CHAPTER 37. MAJOR AND TRACE ELEMENT CHEMISTRY OF PERIDOTITE INCLUSIONS FROM THE LASHAINE VOLCANO, TANZANIA 568
ABSTRACT 568
INTRODUCTION 568
ANALYTICAL METHODS 569
CHEMISTRY OF THE PERIDOTITE XENOLITHS 570
CONTAMINATION OF THE XENOLITHS 574
XENOLITH-ANKARAMITE RELATIONSHIPS 575
THE NATURE OF THE MANTLE SAMPLED BY THE LASHAINE VOLCANO 577
ACKNOWLEDGEMENTS 579
REFERENCES 579
CHAPTER 38. LITHOPHILE TRACE ELEMENT DATA BEARING ON THE ORIGIN OF PERIDOTITE XENOLITHS, ANKARAMITE AND CARBONATITE FROM LASHAINE VOLCANO, N. TANZANIA 582
ABSTRACT 582
INTRODUCTION 582
ANALYTICAL METHODS 583
RESULTS 583
DISCUSSION 586
ACKNOWLEDGEMENTS 591
REFERENCES 592
CHAPTER 39. GARNET-PERIDOTITE, PRIMARY ULTRABASIC MAGMA AND ECLOGITE INTERPRETATION OF UPPER MANTLE PROCESSES IN KIMBERLITE
ABSTRACT 594
1. INTRODUCTION 594
2. PARTIAL MELTING AND CRYSTALLIZATION IN THE MANTLE 595
3. MINERALOGY AND ORIGIN OF GARNET-PERIDOTITE AND ECLOGITE 602
4. CHEMISTRY OF SELECTED ULTRAMAFIC AND ECLOGITE NODULES FROM KIMBERLITE 606
5. TRUE PRIMARY MAGMA IN THE MANTLE 608
6. UPPER MANTLE COMPOSITION MODELS COMPARED 610
7. ECLOGITE AND OLIVINE FRACTIONATION 618
REFERENCES 624
APPENDIX. DATA REPRESENTATION 626
CHAPTER 40. RB-SR AGE DETERMINATIONS ON SOUTH AFRICAN KIMBERLITE PIPES 628
ABSTRACT 628
INTRODUCTION 628
ANALYTICAL PROCEDURE AND RESULTS 629
DISCUSSION 630
APPENDIX l. SAMPLE DESCRIPTIONS 637
APPENDIX 2. Rb, Sr AND Sr87/Sr86 DATA FOR ALL SAMPLES 637
ACKNOWLEDGEMENTS 639
REFERENCES 639
CHAPTER 41. COMPLEMENTARY PETROGRAPHIC AND STRONTIUM-ISOTOPE RATIO STUDIES OF SOUTH AFRICAN KIMBERLITE 642
ABSTRACT 642
INTRODUCTION 642
ANALYTICAL PROCEDURE 643
CRITERIA OF FRESHNESS (BASED ON PETROGRAPHY) 643
RESULTS AND DISCUSSION 649
HIGHER STRONTIUM RATIOS IN THE MICACEOUS AND IN TYPICAL KIMBERLITE 649
SIGNIFICANCE OF LOW RATIOS 655
CONCLUSION 655
ACKNOWLEDGEMENTS 656
APPENDIX 1 656
APPENDIX 2 657
REFERENCES 657
CHAPTER 42. THE GENESIS OF KIMBERLITES AND ASSOCIATED ROCKS: STRONTIUM ISOTOPIC EVIDENCE 660
ABSTRACT 660
INTRODUCTION 660
RESULTS AND DISCUSSION 664
APPENDIX 1. ASSESSMENT OF SAMPLES 671
APPENDIX 2. SAMPLE LOCATIONS AND NOMONICS 674
ACKNOWLEDGEMENTS 674
REFERENCES 675
CHAPTER 43. GEOCHEMISTRY OF ULTRAMAFIC INCLUSIONS FROM SALT LAKE CRATER, HAWAII, AND FROM SOUTHERN AFRICAN KIMBERLITES 678
ABSTRACT 678
INTRODUCTION 678
INCLUSIONS FROM SALT LAKE CRATER, HAWAII 679
INCLUSIONS FROM SOUTHERN AFRICAN KIMBERLITES 686
ACKNOWLEDGEMENTS 690
REFERENCES 691
CHAPTER 44. RARE EARTH ELEMENT GEOCHEMISTRY OF KIMBERLITE 694
ABSTRACT 694
INTRODUCTION 694
EXPERIMENTAL 695
RESULTS 695
COMPARISON WITH PREVIOUS STUDIES 698
DISTRIBUTION OF REE IN KIMBERLITE 699
REFRACTORY TRACE ELEMENTS 699
RELATION TO MELELITITES 700
PARTIAL MELTING 701
ECLOGITE CRYSTALLIZATION 703
FRACTIONAL CRYSTALLIZATION OR PARTIAL MELTING? 705
RELATION OF KIMBERLITES TO BASALTIC VOLCANISM AND CONTINENTAL MAGMATIC CYCLES 707
ACKNOWLEDGEMENTS 708
REFERENCES 708
CHAPTER 45. ASPECTS OF THE GEOCHEMISTRY OF KIMBERLITES FROM THE PREMIER MINE, AND OTHER SELECTED SOUTH AFRICAN OCCURRENCES WITH PARTICULAR REFERENCE TO THE RARE EARTH ELEMENTS 710
ABSTRACT 710
INTRODUCTION 710
GENERAL GEOLOGY OF THE KIMBERLITES STUDIED 711
SAMPLING, SAMPLE PREPARATION AND ANALYTICAL METHODS 712
RESULTS 715
MINOR AND TRACE ELEMENT GEOCHEMISTRY 717
MOBILE ELEMENTS 719
ACKNOWLEDGEMENTS 727
REFERENCES 728
CHAPTER 46. THE SIGNIFICANCE OF THE INTER-ELEMENT RELATIONSHIPS OF SOME MINOR AND TRACE ELEMENTS IN SOUTH AFRICAN KIMBERLITES 732
ABSTRACT 732
INTRODUCTION 732
SAMPLE LOCALITIES AND DESCRIPTION 733
SAMPLE PREPARATION 733
ANALYTICAL METHODS 733
RESULTS 733
DISCUSSION 735
ACKNOWLEDGEMENTS 755
REFERENCES 755
CHAPTER 47. ISOTOPE GEOCHEMISTRY AND PETROLOGY OF AFRICAN CARBONATITES 758
ABSTRACT 758
INTRODUCTION 758
EXPERIMENTAL TECHNIQUES AND NOTATION 759
PRECAMBRIAN PALABORA CARBONATITE 759
PRECAMBRIAN SPITSKOP CARBONATITE 760
PRECAMBRIAN PREMIER MINE CARBONATITE 761
MESOZOIC MBEYA CARBONATITE 762
TERTIARY HOMA MOUNTAIN CARBONATITE 763
RECENT OLDOINYO LENGAI VOLCANO ERUPTION 764
CONCLUSION 766
ACKNOWLEDGEMENTS 767
REFERENCES 767
CHAPTER 48. HYDROGEN, CARBON AND OXYGEN ISOTOPE STUDIES OF MEGACRYST AND MATRIX MINERALS FROM LESOTHAN AND SOUTH AFRICAN KIMBERLITES 770
ABSTRACT 770
INTRODUCTION 770
EXPERIMENTAL 771
SAMPLE LOCALITIES AND ISOTOPIC RESULTS 772
DISCUSSION 772
CONCLUSIONS 783
ACKNOWLEDGEMENTS 784
REFERENCES 785
CHAPTER 49. A CLASSIFICATION SCHEME FOR DIAMOND AND A COMPARATIVE STUDY OF SOUTH AFRICAN DIAMOND CHARACTERISTICS 788
ABSTRACT 788
INTRODUCTION 788
THE CLASSIFICATION SCHEME 789
CLASSIFICATION PROCEDURE 793
DISCUSSION 802
FINAL REMARKS 806
ACKNOWLEDGEMENTS 807
REFERENCES 807
CHAPTER 50. MINERAL INCLUSIONS IN BRAZILIAN DIAMONDS 810
ABSTRACT 810
INTRODUCTION 810
GEOLOGIC OCCURRENCE 810
SAMPLE DESCRIPTION AND TECHNIQUES 811
MINERALOGY 812
DISCUSSION 817
ACKNOWLEDGEMENTS 819
REFERENCES 819
CHAPTER 51. INCLUSIONS IN DIAMONDS: GARNET LHERZOLITE AND ECLOGITE ASSEMBLAGES 822
ABSTRACT 822
INTRODUCTION 822
METHODS OF STUDY 823
RESULTS 824
DISCUSSION AND CONCLUSIONS 837
ACKNOWLEDGEMENTS 839
REFERENCES 839
CHAPTER 52. A COMPARATIVE TRACE ELEMENT STUDY OF DIAMONDS FROM PREMIER, FINSCH AND JAGERSFONTEIN MINES, SOUTH AFRICA 842
ABSTRACT 842
INTRODUCTION 842
SELECTION AND ANALYSIS OF DIAMONDS 843
RESULTS AND DISCUSSION 844
SUMMARY 858
ACKNOWLEDGEMENTS 859
REFERENCES 859
CHAPTER 53. VERIFICATION OF THE STABILITY OF MODIFIED SPINEL STRUCTURE BY MEANS OF HIGH-PRESSURE AND HIGH-TEMPERATURE X-RAY ANALYSIS 862
ABSTRACT 862
INTRODUCTION 862
EXPERIMENTAL 863
RESULTS AND DISCUSSION 864
ACKNOWLEDGEMENTS 868
REFERENCES 868
CHAPTER 54. PARTIAL MELTING OF PHLOGOPITE-BEARING SYNTHETIC SPINEL- AND GARNET-LHERZOLITES 870
ABSTRACT 870
INTRODUCTION 870
COMPARISONS WITH OTHER WORK 876
APPENDIX 878
REFERENCES 878
CHAPTER 55. MELTING IN THE MANTLE: PHASE RELATIONSHIPS IN NATURAL AND SYNTHETIC PERIDOTITE-H2O AND PERIDOTITE-H20-C02 SYSTEMS AT HIGH PRESSURES 880
ABSTRACT 880
INTRODUCTION 880
SCOPE AND PROCEDURE 881
RESULTS 883
CONCLUSIONS 889
ACKNOWLEDGEMENTS 890
REFERENCES 891
CHAPTER 56. C02 AS A VOLATILE COMPONENT OF THE MANTLE: THE SYSTEM Mg2SiO4-SiO2-H2O-CO2 894
ABSTRACT 894
INTRODUCTION 894
PHASE RELATIONS 895
DISCUSSION 901
SUMMARY 904
REFERENCES 905
CHAPTER 57. RELATIONSHIP OF MELILITE-BEARING ROCKS TO KIMBERLITE: A PRELIMINARY REPORT ON THE SYSTEM AKERMAN1TE-CO2 908
ABSTRACT 908
INTRODUCTION 908
AKERMANITE-CO2 909
RELATIONSHIP OF MELILITE-BEARING ROCKS AND MAGMAS TO KIMBERLITE 914
ASSOCIATED CARBONATITE 915
METAMORPHISM OF A SILICEOUS DOLOMITE 918
ACKNOWLEDGEMENTS 918
REFERENCES 918
CHAPTER 58. CRYSTALLIZATION OF SOME NATURAL ECLOGITES AND GARNETIFEROUS ULTRABASIC ROCKS AT HIGH PRESSURE AND TEMPERATURE 920
ABSTRACT 920
INTRODUCTION 920
RESULTS FOR GARNET-OLIVINE-WEBSTERITE AND GARNET-LHERZOLITE 925
REFERENCES 927
CHAPTER 59. THEORETICAL ASPECTS OF GASEOUS AND ISOTOPIC EQUILIBRIA IN THE SYSTEM C-H-O-S WITH APPLICATION TO KIMBERLITE 928
ABSTRACT 928
INTRODUCTION 928
GAS EQUILIBRIA 929
TEMPERATURES AND PRESSURES 929
OXYGEN FUGACITES 930
SULPHUR FUGACITY 931
GAS COMPOSITIONS IN THE SYSTEM C-H-O-S 932
COMPARISON WITH AGPAITIC ROCKS 936
CARBON ISOTOPIC FRACTIONATION-GRAPHITE AND DIAMOND 936
ACKNOWLEDGEMENTS 939
REFERENCES 939
AUTHOR INDEX 942
SUBJECT INDEX 952