The methods of experimental petrology an geochemistry will be applied to oceanic volcanic rocks to understand their compositional variations, their relation to coeval plutonic geochemical characterization, phase equilibrium, and experimental characterized suites of rocks from the East Pacific Rise at 21 N will be undertaken in an effort to resolve the apparent conflict between geology and geochemistry about the merits of a shallow magma reservoir and the scale of magma supply variations. In addition, high pressure research on perousicite fractionation and loivine floatation and its implications as a source region for mid-ocean ridge basalts will be initiated. Finally, continued work on boundary layer fractionation models will be carried out. %%% Understanding magmatic diversity among mid-ocean ridge basalts is a first order problem in ocean crust petrology. The experiments to be carried out in this project will help unravel some of the complicated processes that may give rise to compositional variations among mid-ocean ridge basalts.