Comprehensive Study of the Platinum-Group Elements (PGE) in Normal and Hotspot Affected Mid Ocean Ridge Basalts

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A comprehensive documentation and study of a selected group of highly siderophile and chalcophile elements in mid-ocean ridge basalt (MORB) glasses from the URI dredge rock collection will be conducted, with emphasis on relative fractionations and systematic geographical variations. The URI dredged rock collection has focused on unusually elevated mid-ocean ridge affected by nearby hotspots and underlying mantle plumes. So far, PGE contents in MORB reported in the literature have been very limited and not very systematic, primarily due to their very low abundances and resulting analytical difficulties. The use of high resolution, high sensitivity, inductive plasma-mass spectrometry (HR-ICP-MS) is providing new analytical opportunities. An isotopic dilution / HR-ICP-MS method of analysis for Ir, Ru, Pt , Pd, Re, Ag, Cd, and Te will be developed and tested initially, and followed by analyses of a large number of MORB glasses. The same glasses will also be analyzed for S (with the electron microprobe) and Se (by radiochemical neutron activation analysis). The focus will be on delineating the full range of siderophile/chalcophile element variations of MORBs, their relative fractionation and seek possible correlations, or decoupling, between these elements and the Pb, Sr, Nd, and He isotope systems, S, Se and Te, and other geochemical parameters previously established on the very same basalt glasses. The purpose is to gain new and greater insights in our understanding of the PGE content of the oceanic crust and underlying mantle, length-scales of mantle heterogeneities in PGE, melting conditions, sources of mantle plumes and mantle dynamics.