Study on high- and ultrahigh- temperature metamorphic rocks and partial melting, with a point of view of quartz occurrence

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Psammitic and pelitic rocks are SiO2 saturated rocks. On the partial melting process, quartz occurrence and silica saturation index are the important factors. However, modal composition of quartz is ignored as an excess component for the equilibrium computation. The purpose of this study is, analysis of timing of metamorphism, partial melting, and granitic melt separation, by the cathodoluminescence (CL) image, with a point of view of quartz occurrence.This project made innovative results. These are, we had found out older stage cores of zircon in the granulite, migmatite, tonalite, are residual material of the sediment. These must be residual grain of sediment. Whereas we also found out that bright rims is the new growth pert by the partial melting. We also revealed the age of the bright rims.Our results changed the tectonic history of the Hidaka Metamorphic Belt.These are:(1) Main thermal event is not 55Ma. That was two times, 37Ma and 19Ma.(2) 37Ma is island-arc type igneous activity.(3) 19Ma is another igneous activity related by back-arc basin opening. This stage is the MORB-type activity and the granulite facies high-temperature metamorphism.Our result was published by "Geology", and also newspapers. The CL detector was indispensable item for the new discovery.