It has long been realized that the mineral assemblages of igneous and metamorphic rocks may reflect the approach of a rock to chemical eCluilibrium during its formation. However progress in the application of chemical thermodynamics to geological systems has been hindered since the time of Bowen and the other early physical-chemical petrologists by the recurring Cluandary of the experimental geologist. His systems are complex and are experimentally intractable, but if they were not so refractory they would not be there to study at all. It is only recently that accurate measurements of the thermodynamic properties of pure, or at least well-defined minerals, melts and volatile fluid phases, combined with experimental and theoretical studies of their mixing properties, have made it possible to calculate the eCluilibrium conditions for particular rock systems. Much work is now in progress to extend the ranges of com position and conditions for which sufficient data exist to enable such calculations to be made. Moreover the routine availability of the electron microprobe will ensure that the demand for such information will continue to increase. The thermodynamic techniClues reCluired to apply these data to geological problems are intrinsically simple and merely involve the combination of appropriate standard state data together with corrections for the effects of solution in natural minerals, melts or volatile fluids.

Klappentext

Proceedings of the NATO Advanced Study Institute, Oxford, England, September 17-27, 1976

Inhalt

1. Geological Applications of High Temperature Reaction Calorimetry.- 1.1 Introduction.- 1.2 Calorimetric solvents and oxide melts.- 1.3 Applications of high temperature calorimetry to mineral thermodynamics.- 1.4 Calorimetry of geothermal fluids and water containing systems at pressures up to 2 kbar.- Study Problems.- 2. Experimental Determination of the Mixing Properties of Solid Solutions with Particular Reference to Garnet and Clinopyroxene Solutions.- 2.1 Introduction.- 2.2 NaA1Si308-KA1Si308 feldspar solutions.- 2.3 MgSi0.502-FeSi0.502 olivine solutions.- 2.4 Aluminosilicate garnet solid solutions.- 2.5 Clinopyroxenes containing CaA12Si06 component.- 2.6 Conclusions.- 3. Thermochemistry of garnets and aluminous pyroxenes in the CMAS system.- 3.1 Importance of the CMAS system.- 3.2 Experimental difficulties.- 3.3 The role of thermochemistry.- 3.4 CaMgSi206-CaA12Si06 clinopyroxene.- 3.5 Mg3A12Si3012-Ca3A12Si3012 garnet.- 3.6 Application to the garnet peridotite problem.- Study Problems.- Solutions to Problems.- 4. Activity-Composition Relationships for Crystalline Solutions.- 4.1 Introduction.- 4.2 Mole fractions.- 4.3 Activity coefficients.- 4.4 Conclusions.- 5. Chemical Mixing in Multicomponent Solutions: An Introduction to the Use of Margules and Other Thermodynamic Excess Functions to Represent Non-Ideal Behaviour.- 5.1 Introduction.- 5.2 The solution properties of a binary mixture.- 5.3 Ternary and higher order chemical mixtures.- 5.4 Representation of the excess Gibbs free energy of mixing.- 5.5 The Margules equations.- 5.6 An annotated list of geological publications utilizing the Margules equations or their equivalents.- Study Problems.- 6. Determination of Atomic Occupancies.- 6.1 Introduction.- 6.2 The diffraction method.- 6.3 Mössbauer spectroscopy.- 6.4Infra-red methods.- 6.5 The meaning of occupancy.- Study Problem.- Solution to Problem.- 7. The Accuracy and Precision Of Calculated Mineral Dehydration Equilibria.- 7.1 Introduction.- 7.2 Definitions.- 7.3 Accuracy of calculated equilibria.- 7.4 Precision of calculated equilibria.- 7.5 Thermochemical data from P-T brackets.- 7.6 Discussion and conclusions.- Study Problems.- 8. Thermodynamics of Dehydration Equilibria.- 8.1 Introduction.- 8.2 Theoretical background.- 8.3 Retrieval of thermodynamic data.- 8.4 Calculation of phase diagrams.- 8.5 Dehydration equilibria involving crystalline solutions.- Study Problems.- Solutions to Problems.- 9. Fugacity and Activity of Molecular Species in Supercritical Fluids.- 9.1 Introduction.- 9.2 Scope and definitions.- 9.3 Review of available experimental data.- 9.4 Molecular dynamics.- 9.5 The Redlich-Kwong equation of state.- 9.6 Conclusions.- Study Problems.- 10. Compositions and Thermodynamics of Metamorphic Solutions.- 10.1 Introduction.- 10.2 O-H gases.- 10.3 C-O gases.- 10.4 C-O-H gases.- 10.5 C-O-H-S gases.- 10.6 H-O-F and H-O-N gases.- 10.7 Acids and bases.- 10.8 Measurement of the activity of H20.- 10.9 Summary and conclusions.- Study Problems.- 11. The Significance of Fluid Inclusions in Metamorphic Rocks.- 11.1 Introduction.- 11.2 Observation by conventional techniques (petrographic microscopy).- 11.3 Microthermometry: Tf and Th.- 11.4 Other analytical methods.- 11.5 Conclusion.- Study Problems.- Solutions to Problems.- 12. The Stability of Phlogopite in the Presence of Quartz and Diopside.- 12.1 Introduction.- 12.2 Experimental methods.- 12.3 Stability of phlogopite and quartz.- 12.4 Stability of phlogopite quartz and diopside.- 12.5 Thermodynamic considerations.- 12.6 Geological applications.- Study Problems.- 13. Opaque Minerals as Sensitive Oxygen Barometers and Geothermometers in Lunar Basalts.- 13.1 Introduction.- 13.2 Spinel solid solution series.- 13.3 Armalcolite series.- 13.4 Subsolidus reduction reactions.- 14. Thermodynamic Properties of Molten Salt Solutions.- 14.1. Introduction.- 14.2 Systems of the type AX-BX.- 14.3 Systems of the type AX-AY.- 14.4 Charge unsymmetrical mixtures which contain a common anion.- 14.5 Mixtures containing two cations and two anions.- 15. Thermodynamic Properties of Silicate Melts.- 15.1 Introduction.- 15.2 Nature of silicate melts.- 15.3 Acids and bases.- 15.4 Binary silicate melts.- 15.5 Application of mixing models.- 15.6 Standard states of oxide components.- 15.7 Effects of melt structure on liquidus boundaries.- 16. The Activities of Components in Natural Silicate Melts.- 16.1 Introduction.- 16.2 Thermodynamic characterization of silicate melts.- 16.3 Estimation of pressures and temperatures of equilibration.- 16.4 Example and discussion.- Appendix: Program for solving equations for P and T.- Study problem.- 17. The Thermodynamics of Trace Element Distribution.- 17.1 Introduction.- 17.2 Henry's Law.- 17.3 Formulation of distribution coefficients.- 17.4 Relationship between distribution coefficients and equilibrium constants.- 17.5 Geothermometry and geobarometry.- 17.6 Trace elements in gas-solid reactions.- 17.7 Concluding Remarks.- 18. The Solubility of Calcite in Sea Water.- 18.1 Introduction.- 18.2 In situ saturometry.- 18.3 Laboratory kinetic measurements.- 18.4 Possible explanations for the differences between the Berner and Ingle et al. solubility results.- 18.5 Conclusions.- 19. Nonequilibrium Thermodynamics in Metamorphism.- 19.1 Introduction.- 19.2 Fundamental relations.- 19.3 Models for diffusion-controlled, steady-stateprocesses.- 19.4 The transformation to practical reference frames.- 19.5 Application to the Vastervik segregations.- 19.6 Conclusion.- Study Problems.- Solutions to Problems.