Metamorphic Processes: Reactions and Microstructure Development

1 Background Discussion.- Scope of Metamorphism.- Temperatures and Pressures of Metamorphism.- Movement of Material in Metamorphism.- Mineral Assemblages ('Pangeneses').- Microstructures of Metamorphic Rocks.- Preferred Orientation in Metamorphic Rocks.- Metamorphic Grade.- Metamorphic Facies.- Tectonic Setting of Metamorphism.- References.- 2 Equilibrium Aspects of Metamorphic Reactions.- Driving Force for Metamorphic Reactions.- Types of Metamorphic Reactions.- Variance of Metamorphic Reactions.- Metamorphic Reactions and Resulting Assemblages.- Sliding Reactions at Isograds.- Effect of One Phase on the Stability of Another.- Criteria of Stable Coexistence of Metamorphic Minerals.- Domains of Local (Mosaic) Equilibrium.- Calculation of the Topology of Metamorphic Phase Diagrams (Schreinemakers' Analysis).- Calculation of Slopes of Reaction Curves.- Experimental Location of Reaction Curves.- Reversal of Experimental Reactions.- Discrepancies Between Calculated and Experimentally Determined Reaction Curves.- Open Systems in Metamorphism.- Fluid Phase in Metamorphism.- Pressure of Fluid Phase.- Effect of Fluid Pressure on Reaction Curves.- Effects of Composition of Fluid Phase (Fugacities of Mixed Volatile Components) on Reaction Curves.- Effect of Oxygen Fugacity.- Coexisting Magnetite and Ilmenite.- Effect of fO2 on Hydrous Silicates Without Cations of Variable Valency.- Distribution of Elements Between Coexisting Minerals.- References.- 3 Kinetics of Metamorphic Reactions.- Diffusion in Metamorphism.- Nucleation and Growth.- Application of Reaction Kinetics to Metamorphism.- Zoning in Metamorphic Minerals.- Problems of Aragonite in Metamorphic Rocks.- Kinetics of the Reaction: Calcite + Quartz ? Wollastonite + CO2.- References.- 4 Reactions in Metamorphic Rocks.- Mechanisms of Metamorphic Reactions.- Reactions in Metapelitic Systems.- Reactions in Mafic and Ultramafic Systems.- How Relevant Are Available Experimental and Theoretical Determinations of P-T-X Equilibria?.- Retrograde Reactions.- Reactions Involving Zoned Minerals.- Reactions Involving Zoned Garnet.- Compositional Changes During Metamorphism ('Metamorphic Differentiation').- References.- 5 Stable Metamorphic Microstructures.- Unstable Grain Arrangements.- Stable Grain Arrangements in Isotropic Single Phase Aggregates.- Anisotropic Single Phase Aggregates.- Aggregates with More than One Phase.- Spatial and Size Distribution of Grains in Metamorphic Rocks.- Environments of Grain Adjustment in the Solid State.- References.- 6 Deformation, Recovery and Recrystallisation Processes.- Brittle Versus Ductile Deformation.- Crystal Plasticity.- Primary Modes of Intragranular Plastic Deformation.- Secondary Modes of Deformation.- Dislocations.- How Do Dislocations Assist Deformation?.- Experimental Detection of Dislocations.- Mobility of Dislocations.- Production of Dislocations.- Dislocations in Relation to Work-Hardening and -Softening.- Partial Dislocations.- Dislocations in Non-Metals.- Surface Imperfections 160 Effect of Grain Boundaries on Deformation (Intergranular Deformation).- Recovery and Recrystallisation 166 Development of Crystallographic Preferred Orientation by Recrystallisation.- Development of Preferred Orientations by Deformation.- Some Generalities.- Appendix: Methods of Detecting Slip Systems.- References.- 7 Deformation, Recovery and Recrystallisation of Some Common Silicates.- Quartz.- Microstructural Features of Deformed Quartz.- Experimental Deformation, Recovery and Recrystallisation of Quartz.- Natural Deformation, Recovery and Recrystallisation of Quartz.- Preferred Orientation.- Variation in Quartz Microfabric with Metamorphic Conditions.- Stress Indicators in Deformed Quartz.- Olivine.- Experimental Deformation, Recovery and Recrystallisation of Olivine.- Natural Deformation, Recovery and Recrystallisation of Olivine.- Preferred Orientation of Olivine.- Layer Silicates.- Deformation of Mica Single Crystals.- Deformation of Fine-Grained Lay