Development of an internally heated gas apparatus useful for crustal geological problems

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Various geological phenomena (e.g., volcanic activity, metamorphism, earthquakes, etc) take place under crustal environment beneath Japan (a typical island arc). In order to study these geologic phenomena, we developed an internally heated gass apparatus SMC-5000 which are capable to generate pressure for up to 5000 bars and temperature to 1600 degree centigrade. Due to the very severe control under the High-pressure Gas Regulation Law, we oblighed to lower the maximum pressure from 8000 to 5000 and had to abandone the automatic pressure regulating valve. Otherwise the SMC-5000 was built with excellent pressure regulating system, rapid quenching device, precise temperature controlling capability and long durability for holding very long (up to a week long) high pressure experiments.Using the SMC-5000 apparatus, we conducted melting experiments on some lower crustal amphibolites taken from the Hidaka metamorphic belt in Hokkaido and the Ichiomegata crater in Akita prefecture. The melt frctions as well as the composition of melt and residues were determine with EPMA.The results were then compared with petrologic datra on calc-alkaline volcanic rocks. Based on the comparison, we proposed a model for the deep root zone of Japanese volcanoes.