This proposal is for support of theoretical studies aimed at retrieving thermodynamic data for F- and Cl- endmember micas, amphiboles and other phases for use in deciphering the behavior of F and Cl in reacting hydrothermal systems. These studies will enable constraints to be placed on the speciation and total halide contents of hydrothermal fluids based on known compositions of silicate minerals. In addition, it will be possible to predict how F and Cl partitioned between minerals and aqueous fluids during water-rock interactions and whether this partitioning is important in the generation of F-rich ore deposits. The most important aspects of this work are the retrieval of the thermodynamic properties of fluoride and chloride end-member minerals from published experimental studies, and the application of these results to geologic problems. The scope of the research will be limited to these aspects.
