The long-term objective of this research program, which has remained the same over the years, is to develop a systemically collected body of phase equilibrium data that imposes progressively tighter constraints on the origin of basalt and the formation of the earth's crust from the mantle. In order to generalize results and to develop a more comprehensive body of data in an important pressure range, it is proposed to determine, using a piston-cylinder apparatus, the phase relationships at 15, 25, and 30 kbar and the effect of Na2O on melting relationships. The data would provide new constraints on (1) the origin of primary mid-ocean ridge basalts, (2) the composition, depth of generation, and percent melting of primary tholeiitic magmas in the Hawaiian Islands, and (3) the origin of high-alumina basalts in subduction zones. In addition, it is proposed to study melting relations in the system Mg2SiO4-SiO2 up to pressures of 250 kbar using an MA-8 apparatus at the University of Alberta. This study would bear on very high pressure magmatic processes in the early history of the earth.
