Experimental Geochemistry of Rock-Forming Minerals

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9310264 Newton This project is to investigate the thermodynamic stabilities of many different major minerals, including silicates, oxides, hydrates and carbonates. The data to be acquired are of crucial importance to the erection of thermodynamic datasets for calculation of the stabilities of natural mineral assemblages. The concentration will be on important mineral species whose thermodynamic properties are still uncertain. Because of the interdependent nature of mineral properties in the self-consistent datasets, insertion of accurately-measured free energies, enthalpies and entropies of key minerals will force changes of the thermodynamic parameters of most of the other minerals of the datasets. Free energy data of solid solution will be measured for several important mineral families. Methods to be used are simple-system phase equilibrium measurements at elevated temperatures and pressures, including experiments in the presence of a single-component or mixed vapor phase and with polyionic oxide melts, and solution calorimetry. Major improvement in the ability to calculate heterogeneous equilibria of earth processes will result from accurate definition of the thermodynamic formation and solid solution properties of key garnets, pyroxenes, feldspars, micas and carbonate minerals.