This project involves detailed experimental studies of crystal- fluid-melt equilibria for natural melt compositions in equilibrium with C-O-H fluids. Specific objectives of the project include the determination of mineral-melt-vapor relationships for a Mt St Helens andesite and for the Fish Canyon (Colorado) tuff and the development of these and other phase equilibrium data for use as geothermometers, geobarometers, and geohydrometers. The results of these studies will enhance our understanding of the evolution and behavior of volatile-rich calc-alkaline magmas. These data are essential to our understanding of eruptive cycles of explosive volcanos such as Mt St Helens.
