Develpment of a Laser-Excited System for 16 O, 17 O, and 18 O Analysis of Molecular Oxygen from Small Samples of Silicate and Oxide Minerals

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9708023 Perry This grant provides $65,895 as one-half support of the costs of acquiring necessary components to develop a laser-based oxygen extraction system for direct mass spectrometric analyses of molecular oxygen liberated from oxide and silicate minerals. Direct analysis of molecular oxygen has the advantages of; reducing isotopic fractionation that occurs when oxygen is converted to CO instead of CO2 as in conventional laser fluorination; will allow analysis of all three stable isotopes of oxygen including 17O, which cannot be determined by conventional CO2 mass spectrometric analysis due to isobaric interference; and, will allow analysis of sub-milligram size samples, thereby increasing the spatial resolution achievable in oxygen isotope studies of silicate and oxide minerals. The capabilities of this system should allow study of a number of fundamental Earth science problems that might otherwise be difficult to address such as, elucidation of the oxygen isotope history of seawater as recorded in very small, indentifiably unaltered samples of precipitated marine cherts and carbonates and microfossil tests, and the determination of relative contributions of subducted components (i.e. sediment, altered oceanic crust, fluids, melt) to arc volcanics based on oxygen isotopic analyses of olivine phenocrysts. ***