In the Mikawa district, Central Japan,the so-called Ryoke granites are widely distributed. They are classified into six granitic bodies according to their field occurrences and characteristic features of accessory zircon. The name of these bodies and their order of intrusion are as follows; Miya, Kiyosaki, Mitsuhashi, Sumikawa, Busetsu and Naegi granites, from older to younger. The granitic bodies are divided into two groups according to their distribution, the features of metamorphic rocks associated with them and geologic relations to Cretaceous Nohi rhyolite. Namely, the first group, consisting of Miya, Kiyosaki and Mitsuhashi granites, are distributed in the southeastern part of the Ryoke metamorphic belt and associated with metamorphic rocks of only higher metamorphic grade. While, the second group, consisting of Sumikawa, Busetsu and Naegi granites, are distributed in the northwestern part of this belt, associated with both the higher grade metamorphic rocks and the lower ones, and evidently younger than the Nohi rhyolite.
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