The proposal requested support for the continuation of a multi- faceted project addressing the role of accessory minerals in the geochemistry of the earth. Over the past 5-1/2 years, efforts have focused principally on the magmatic behavior of these minerals in the continental crust. A principal goal has been to develop, through strategic high pressure-temperature experimentation, predictive models of accessory phase solubilities in crustal melts. The focus now will shift largely away from magmatic behavior of accessory minerals to their behavior under subsolidus or metamorphic conditions, and will include the upper mantle as well as the crust. The overall goal is to provide (and later apply) constraints on the role of accessory minerals in trace element geochemistry, geochronology and heat production in the lithosphere.
