Host: Japan Association of Mineralogical Sciences
Late-Pliocene to Quaternary volcanic rock in Aso area in SW Japan, were determined to reveal temporal changes of the magma characteristics and a mechanism of magmatic system. Isotopic ratios of volcanic products at each stage distributed in 87/86 Sr-143/144 Nd diagram are as follows. 1) early pre-caldera stage: separately distributed in two areas (component A: around (0.7040, 0.51285), component B: around (0.7044, 0.51270), 2) late pre-caldera stage: distributed between component A and B along mantle array, 3) caldera forming stages: distributed in an area surrounded by component A, a point (0.7040, 0.51270) and a point (0.7042, 0.51270), showing that component of low Nd ratio affecting component A, 4) inter-caldera stage: distributed within the area of caldera forming stage (excepting for ratios of Neko-dake), 5) post caldera stage: distributed between component A and B like that of late pre-caldera stage.
