沈み込み変成作用の圧力ー温度ー水生成量

概要

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Metamorphic pressure and temperature paths were precisely inferred by chemical zonal structure of garnet from the core to the rim in pelitic systems using the differential thermodynamic method. We obtained P-T paths from the Sambagawa metamorphism such that the pressure and temperature increased gradually during the growth of garnet. The zonal structures of garnet show a continuous change of pressure and temperature but indicate wide variations in the garnet production rate. The molar production rates of garnet during prograde metamorphism, denned by dm/dP were precisely obtained, in which m is the molar production of garnet normalized by the grain volume. The rates commonly show two peaks near the early and late stages. The general trends of molar production rates show a gradual increase with increasing pressure, but there are several peaks and the rates suggest episodic water release from metamorphic rocks in the process of subduction.