Contents
DECLARATION
ABSTRACT
ACKNOWLEDGEMENTS
GLOSSARY
CONTENTS
Chapter 1 Introduction
Section 1.1 Philosophy of Study
Section 1.2 São Luiz alluvial diamond deposit
Section 1.3 The diamond deposits of Guinea
Section 1.4 Diamond from a social perspective
Section 1.4.1 Historical interest in diamond
Section 1.4.2 General diamond characteristics
Section 1.5 Diamond studies
Section 1.5.1 Physical characteristics
Section 1.5.2 Compositional characteristics
Section 1.5.2.1 Carbon isotopic content of diamond
Section 1.5.2.2 Nitrogen in diamond
Section 1.5.2.2.1 Aggregation of N in diamond and Infra Red absorption characteristics
Section 1.5.2.2.2 Nitrogen Isotopic content of diamond
Section 1.5.2.3 Additional Impurities
Section 1.5.3 Interrelation of compositional and physical characteristics
Section 1.5.4 Formation of diamond
Section 1.6 Inclusions in diamond
Section 1.6.1 Peridotitic parageneses
Section 1.6.2 Eclogitic paragenesis
Section 1.6.3 Sulphide inclusions
Section 1.6.4 Occurrence and significance of inclusion type
Section 2.1 Inclusion break-out
Section 2.2 Major and minor element analyses of São Luiz and Guinean inclusions determined by electron microprobe
Section 2.2.1 Inclusion type analysis
Section 2.2.1.1 Inclusions of olivine composition
Section 2.2.1.2 Silica inclusions
Section 2.2.1.3 Inclusions with garnet-like compositions
Section 2.2.1.3.1 Grosspaldite garnets
Section 2.2.1.3.2 Majoritic garnets
Section 2.2.1.3.3 TAPP grains
Section 2.2.1.4 fPer inclusions
Section 2.2.1.5 Inclusions with pyroxene-like compositions
Section 2.2.1.6 CaSiO3 composition inclusions (CaSi-Pvk)
Section 2.2.1.7 Alumina inclusions
Section 2.2.1.8 Inclusions of native iron
Section 2.2.1.9 Additional phases
Section 2.2.2 Compositional studies of composite grains
Section 2.2.2.1 EPMA mapping of composite grains
Section 2.2.2.2 EPMA transects across composite grains
Section 2.3 Coexisting phases and mineral associations
Section 2.4 Trace element analyses of São Luiz inclusions by ion microprobe
Section 2.4.1 Trace element characteristics of olivine inclusions
Section 2.4.2 Trace element characteristics of Alumina inclusions
Section 2.4.3 Trace element analyses of inclusions of broadly garnet composition
Section 2.4.3.1 Trace element characteristics of majoritic garnets
Section 2.4.3.2 Trace element characteristics of inclusions with TAPP composition
Section 2.4.4 Trace element characteristics of fPer inclusions
Section 2.4.5 Trace element analyses of inclusions of pyroxene composition
Section 2.4.5.1 Trace element characteristics of upper mantle pyroxene
Section 2.4.5.2 Trace element characteristics of Type I, Type II and Type III pyroxenes
Section 2.4.6 Trace element characteristics of CaSiO3 composition inclusions (CaSi-Pvk)
Section 2.4.7 Discussion of trace element characteristics of inclusions from São Luiz
Section 2.5 Mössbauer Study of inclusions
Section 2.5.1 Mössbauer study of garnet composition inclusions
Section 2.5.1.1 Mössbauer study of majoritic garnet
Section 2.5.1.2 Mössbauer analyses of TAPP
Section 2.5.2 Mössbauer analyses of fPer inclusions
Section 2.5.3 Mössbauer analyses of pyroxene inclusions
Section 2.5.4 Summary of Mössbauer data
Section 2.6 SEM and TEM analyses of fPer inclusions
Section 2.6.1 Observation of blebs in fPer inclusions
Section 2.6.2 Additional visual characteristics of fPer inclusions
Section 2.6.3 Genesis of high BS-intensity features in fPer inclusions
Section 3.1 Techniques adopted for structural analyses
Section 3.2 Subjects of structural analysis
Section 3.3 Results of structural analysis
Section 3.3.1 Investigation of the structure of the tetragonal-pyrope almandine phase (TAPP)
Section 3.3.1.1 Gandolfi camera X-Ray diffraction of TAPP
Section 3.3.1.2 ESPRC X-Ray Diffraction of TAPP, BZ244B
Section 3.3.1.3 Micro-X-Ray diffraction of TAPP, BZ265A at Brookhaven
Section 3.3.1.4 TAPP as a unique phase
Section 3.3.2 Investigation of the structure of alumina inclusion BZ227A
Section 3.3.2.1 ESPRC X-Ray diffraction of alumina, BZ227A
Section 3.3.3 Investigation of the structure of fPer inclusions
Section 3.3.3.1 Gandolfi camera X-Ray diffraction of fPer grains
Section 3.3.3.2 Micro-X-Ray diffraction of fPer at Brookhaven
Section 3.3.3.3 X-Ray diffraction of fPer, BZ257A1 at Edinburgh
Section 3.3.4 ESPRC X-Ray diffraction of olivine inclusion, BZ243C
Section 3.3.5 Structural investigation of pyroxene composition phases
Section 3.3.5.1 X-Ray diffraction of pyroxenes at UCL
Section 3.3.5.2 ESPRC X-Ray diffraction of pyroxenes, BZ241B2 and BZ242B
Section 3.3.5.3 Micro-X-Ray diffraction of pyroxenes at Brookhaven
Section 3.3.6 Additional observations on structural investigations
Section 3.4 Summary of structural determinations
Chapter 4 The nature of mantle regions as seen through study of São Luiz and Guinean inclusionsSection 4.1 Bulk compositions of the mantle
Section 4.2 Mantle Geotherms
Section 4.3 Mantle convection
Section 4.4 Phase relations in mantle systems and the source of São Luiz and Guinean diamonds
Section 4.4.1 Phase relations in the earths transition zone and lower mantle
Section 4.4.1.1 The system MgO - FeO - SiO2
Section 4.4.1.2 The role of Al and Ca on mantle phase relations
Section 4.4.1.3 The role of Na on mantle phase relations
Section 4.4.1.4 Additional components
Section 4.4.1.5 The role of fluid
Section 4.4.1.6 Phase relations involving complex systems
Section 4.4.1.7 Melting relations
Section 4.4.2 The source of São Luiz and Guinean diamonds
Section 4.4.2.1 The UM association
Section 4.4.2.2 Source of majoritic garnet association inclusions (TZ association)
Section 4.4.2.3 Source of the UM/LM association; BZ243
Section 4.4.2.4 The LM I association
Section 4.4.2.5 Source of the LM II association
Section 4.4.2.6 Source of the LM III association
Section 4.4.2.7 Deep mantle inclusions; phase relations over the upper mantle / lower mantle boundary and mantle convection
Section 4.5 Equilibration of São Luiz and FEG inclusions and element partitioning
Section 4.5.1 Partitioning studies
Section 4.5.1.1 Fe / Mg partitioning between fPer and olivine composition
Section 4.5.1.2 fPer - MgSi-Pvk partitioning and thermal state of the upper mantle / lower mantle boundary
Section 4.5.1.3 Deep mantle phases / Liquid
Section 4.5.1.4 Trace element partitioning
Section 4.5.2 Equilibration in composite inclusions
Section 4.6 Liquids in equilibrium with São Luiz associations
Section 4.7 Mantle oxidation through studies of São Luiz inclusions
Chapter 5 Diamond characteristicsSection 5.1 Morphology
Section 5.2 Colour
Section 5.3 Deformation features
Section 5.3.1 Observations of brittle deformation in diamond
5.3.1.1 Visual observation of fracture systems
Section 5.3.1.2 Observation of diamond fracture systems at high resolution
Section 5.3.2 Plastic deformation
Section 5.4 Chemistry of diamond fragments and unbroken stones
Section 5.4.1 Bulk d 13C detemination of broken stones
Section 5.4.2 Nitrogen characteristics of broken and bulk stones
Section 5.4.2.1 FTIR analysis of broken and bulk stones
Section 5.4.2.2 Nitrogen composition by bulk analysis
Section 5.4.3 Additional atomic species within São Luiz diamonds
Section 5.5 Chemistry of polished diamond flats
Section 5.5.1 Determination of d13C
Section 5.5.2 Nitrogen analyses of polished plates
Section 5.5.2.1 FTIR analysis for Nitrogen in polished plates
Section 5.5.2.2 Determination of nitrogen content by ion microprobe
Section 5.6 Cathodoluminescence
Section 5.6.1 Cathodoluminescence characteristics of São Luiz diamonds
Section 5.6.2 Interpretation of cathodoluminescence characteristics of São Luiz diamonds
Section 5.7 Summary of diamond characteristics
Chapter 6 The nature of mantle regions as seen through study of São Luiz diamondsSection 6.1 Mechanisms of diamond formation
Section 6.1.1 Diamond Stability in terms of fluid species
Section 6.1.2 The atomistic growth of diamond and the presence of N and H in São Luiz diamonds
Section 6.2 Formation reactions of deep mantle diamonds and mantle carbon and nitrogen content: inferences from São Luiz stones and deep mantle diamonds from other localities
Section 6.3 Formation environment of São Luiz diamonds
Section 6.3.1 Processes affecting nitrogen content and stable isotope ratios
Section 6.3.2 Formation environment of São Luiz diamonds
Section 6.3.3 Interpretation of additional features of São Luiz diamonds
Section 7.1 Internal pressure
Section 7.1.1 Thermoelastic poperties of minerals
Section 7.1.2 Calculation of elevated internal pressures
Section 7.1.3 Previous indications of elevated internal pressures of diamond inclusions
Section 7.1.4 Internal pressures imposed on fPer inclusions
Section 7.2 Integrity of diamond system through exhumation
Section 7.3 Processes of exhumation
Section 7.3.1 Mantle Plumes and plume-instigated kimberlite magmatism
Section 7.3.2 Entrainment into mantle convection and kimberlite magmatism
Section 7.3.3 Superkimberlites
Section 7.3.4 Rate of exhumation
Chapter 9 Suggestions for further work
References
Appendices
Appendix 1 Inclusion breakout
Appendix 1.1 Apparatus and Methodology
Appendix 1.2 Summary of visual observations on diamonds BZ215 - BZ272, JH7 - JH17 and GU4 with details of breakage where applicable
Appendix 2 Summary of EPMA study and inclusion release from São Luiz diamonds for the present study including Guinean inclusions and unbroken stones assigned BZ- numbers
Appendix 3 Major and minor element compositions of inclusions
Appendix 3.1 Single point electron microprobe analyses
Appendix 3.2 Averaged electron microprobe analyses including cation concentrations
Appendix 4 Trace element compositions of inclusions
Appendix 4.1 Ion Microprobe analyses
Appendix 4.2 Averaged Chondrite Normalised Ion Microprobe Analyses
Appendix 6 Fourier Transform Infra Red (FTIR) analyses of São Luiz and Guinean diamond
Appendix 6.1 One phonon region of FTIR spectra
Appendix 6.2 Tabulation of results of deconvolution of FTIR spectra
Appendix 7 Compositional analyses of bulk diamond
Appendix 8 Electron probe principles and calculations
Appendix 9 Ion microprobe operating conditions and calculations
Appendix 9.1 Analysis of diamond inclusions for trace elements
Appendix 9.2 Analysis of diamond flats for d 13C and N
Appendix 10 X-Ray theory and operating conditions employed
Appendix 11 Gas extraction and the determination of bulk d 13C and d 15N composition of diamond
Appendix 12 Database of experiments aimed at elucidating the state of the deep mantle
Appendix 13 Thermoelastic properties of mantle mineral phases
Appendix 14 Seismologically based models of the mantle and PREM
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