Rhenium-Osmium Isotope and Platinum Group Element Systematics of Lower Oceanic Crust

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

Kelemen EAR-0337677 Formation, alteration and subduction of oceanic crust are fundamental processes of Earth's ongoing chemical differentiation. The chemical transformations of oceanic crust from igneous accretion to subduction are of fundamental importance to constraining the chemical evolution of the Earth. While the chemical composition of upper oceanic crust has been studied using multiple shallow drill holes, our knowledge of middle and lower oceanic crust is limited to ophiolite sections and few drill holes into deeper oceanic crust. This project is aimed at investigating refractory cumulate gabbros and complementary lavas from well studied sections in the southernmost massifs in the Oman ophiolite, that overlap compositionally with the depleted end of the mid-ocean-ridge compositional spectrum. Two important hypothesis will be tested: 1) The lower oceanic crust is the main reservoir of platinum group elements (PGE) in the oceanic crust, and 2) The average rhenium/osmium in lavas is higher than that in corresponding cumulates. The project also aims at identifying important PGE carrier phases to better understand magmatic fractionation of these elements, and investigating the effects of hydrothermal alteration on the PGE budget of the oceanic crust. Complementary isotope, major and trace element, as well as petrographic and mineral analyses will be carried out to place the Re/Os/PGE data in a broader geochemical context. Results from this study will significantly improve our understanding of chemical interaction between the oceans, crust and mantle.