Thermodynamics of Aluminous Amphiboles

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9628203 Evans This proposal is to continue work on the thermodynamic properties of quadrilateral amphiboles and includes three tasks. (1) Complete the research and manuscript on the dependence of the optical properties of the ferromagnesian amphiboles on the composition and ordering states of natural and heat-treated samples. (2) Conduct single crystal XRD refinements on room temperature and heat-treated natural gedrites to determine the effects of temperature, Fe/Mg, and tschermaks and edenite exchanges on long-range ordering. (3) Initial heat-treatment and single-crystal study of natural hornblendes from amphibolites. The goal of this project is to calibrate the thermodynamic properties of aluminous, calcic and ferromagnesian amphiboles with compositions typical of those found in metamorphic and igneous assemblages. These properties will allow the PI's to calculate the theoretical phase diagrams involving amphiboles and other minerals for which they have previously developed internally consistent thermodynamic models. The PI's tend to incorporate the models developed in the course of this proposal into the software package MELTS, thereby allowing the modeling of amphibole crystallization in magmatic and subsolidus systems.