9406177 Grove The proposed research involves experimental, field and theoretical studies aimed at understanding the processes and conditions that lead to the formation and chemical evolution of subduction zone magmas. The proposed experimental studies consist of (1) a series of elevated (1 to 3 GPa) experiments that would investigate the effects of variable amounts of H2O (between 2 and 6 wt. %) on the compositions of primary magmas produced from partial melting of peridotite bulk compositions, and (2) a series of H2O bearing experiments under crustal pressure conditions (100 to 300 MPa) on natural basalts, andesites, and on basalt- analog compositions. A complementary program of field studies would be carried out in the Southern Cascade Range of the U.S.A. The study will provide fundamental data to develop models of arc magma generation, to elucidate conditions in crustal magma reservoirs, and to understand processes that lead to explosive volcanic eruptions.