RUI: Crystallization and Differentiation in a Sheet-like Magma Chamber: An Integrated Study of the Graveyard Point Sill, Eastern Oregon

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9304102 White This is a collaborative project between Cornell and Brown Universities. We propose to study magma genesis and evolution in St. Lucia, St. Vincent, and Grenada through a multi-disciplinary approach that will include field work, petrographic study, major element, trace element, Sr, Nd, Pb and O isotope determination, and K-Ar dating. Petrographic study will include both micro probe and laser-ablation- inductively-coupled-plasma-mass-spectrometry studies. The immediate objectives of this study are to: (1) determine the contribution of arc crust to the evolution of mantle- derived magmas in Grenada and St. Lucia, (2) use the most magnesian of these magmas, some of which are only slightly evolved since production in the mantle wedge, to investigate degree of melting and source enrichment, and (3) determine how magma composition has changed through time on these islands. Achieving these objectives allows us to address several broader objectives. These are: enhanced understanding of (1) magma generation and evolution processes in island arcs, (2) tectonic evolution of the Caribbean region, (3) the conditions necessary for crustal assimilation to occur or not to occur, (4) mass transport from the subducting slab to island arc magmas, and (5) mass fluxes of incompatible elements to the deep mantle from subduction zones. By focusing on a few localities with an improved experimental knowledge base, and having a wide range of data, we believe we can substantially improve earlier models. ***