Rhenium-Osmium geochemistry for the mantle plume and the Kuroko ore deposits formed at the time of the opening of the Japan Sea

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In this study, the mass-spectrometer used was reconstructed and arranged to measure negative ion beams and to improve the stability. Re and Os concentrations and Os isotopic compositions were measured for several rocks and minerals. These data as well as the blank values indicate that at present some rocks and minerals which has relatively high concentrations of these elements can provide usable data for geological discussion, but some rocks and minerals do not contain enough amounts of these elements for analyzes. Much efforts should be necessary for lowering the blank values. Despite such incomplete attainment for analytical methods, some useful information can be drawn from relatively high concentration materials. In the present study, the initial Os isotopic ratio for the Kuroko ore deposits were found to be around the values of the seawater, suggesting that the Kuroko minerals had been precipitated from the seawater. Moreover, some other geological standard rocks and magnetites separated from the granitiv rocks were measured.