Metamorphic history of the lower crust, in the east end of the SW Japan Arc

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Plutonic and volcanic rocks of Cretaceous to Paleogene age are widely distributed in the Uetsu area, northern Japan. These plutonic suites have been emplaced into the Ashio Belt, a pre-Cretaceous accretionary complex. The correlation between the Uetsu area and the SW Japan is still in discussion. The purpose of this study is to make clear the metamorphic history of this area.The main results are as follows.Metamorphic grade of the Sumikawa xenoliths is from amphibolite facies to granulite facies. The metamorphic P-T-t path is clockwise.Awataki metamorphics can be subdivide to peraluminous granite origin and pelitic-psammitic rock origin. Two stages metamorphism can be recognized, the first stage is regional metamorphism and the second is contact metamorphism. Both of these are amphibolite facies.Metamorphic grade of the Iide metamorphics is amphibolite facies.The Sumikawa xenoliths and Awataki meramorphics are the source rocks of the Cretaceous granite. The lower most crust of the Uetsu area reached to the ultrahigh-temperature metamorphism. The metamorphic rocks and Cretaceous plutonic rocks of the Uetsu area are thought to be the Ryoke-Belt. On the other hand Paleogene igneous rocks are correlated to the Sanin-Belt.