Phase Equilibria and Crystal-Chemistry of Some Calcic Amphiboles ,

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The project will investigate several chemical reactions that will shed light on important chemical processes in calcic amphiboles. It will address the following processes: (1) The pressure and temperature dependence of Al solubility in amphibole (2) The upper thermal stability of natural tremolite will be compared with that of synthetic tremolite in the pressure range of 1-10 kbar. (3) A study of the solubility of Ti in pargasite will be made to see if the Ti content of amphiboles is a good indicator of temperature, as field studies suggest. (4) the kinetics of F- and Cl-OH exchange in tremolite will be investigated to determine how rapidly halide metasomatism can occur. (5) A unique method of forming H2O-CO2 fluid inclusions in spontaneously nucleated crystals of clinopyroxene and forsterite, resulting from incongruent dissolution of tremolite, will be employed to test how accurately fluid inclusions represent the composition of a fluid during prograde metamorphism. The study has strong basic application to the determination of conditions during regional metamorphism.