COLLABORATIVE RESEARCH: 10 Be and 9 Be in Volcanic Arc Lavas: Investigation of Sediment Recycling

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Recent measurements of Be-10 in ~250 volcanic rocks from various geologic settings indicate that that young, near-surface oceanic sediments are subducted and incorporated in arc magmas in the Kurile, Aleutian, Central America, Peru-Chile and New Britain arcs. Integration of Be-10 data with geophysical and structural studies of convergent margins suggests that sedfiments may be subducted in grabens in the subducting plate, as Be-10 concentrations an arc lavas are highest where the pelagic sediment thickness approximately equals vertical displacement of the down- dropped basins. Recent improvements in the University of Pennsylvania accelerator permit smaller samples to be analyzed more precisely, and the recent acqusition of an I.C.P. spectrometer at Carnegie permits measurement of Be-9. This project is to measure Be-10/Be-9 ratios and Sr, Nd and Pb isotopic compositions for mineral seperates, new volcanic arc lavas, and a subset of the existing sample collection. Wherever possible results will be combined with other geochemical studies and evaluated in the context of geophysical studies in order to arrive at an integrated model of sediment subduction and recycling at volcanic arcs.