Petrochemical Studies on the Cretaceous Granite of Inner Belt of Southwest Japan in the East Side to Fossa Magna

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Summary of research results; The objects of this project are as follows; (1) The granite area of the Inner Belt of Southwest Japan is divided into three zones, that is, the Ryoke zone, the San-yo- Naegi zone and the San-in - Shirakawa zone. In this case, how are these zones extended on the east side of Fossa Magna?, (2) The chemical composition of granite in each zone is compared and discussed.About the first theme, the followings have been made clear; (1)Three zones are extended on the east side of Fossa Magna. (2)The Ryoke zone is situated on the northern margin of the Kanto Mountains to the southern end of Mt. Tsukuba, but granite, except a small part, is belonging to the extension of the San-yo -Naegi zone. Gneissose granite of Mt. Tsukuba, which has been considered to be the older Ryoke granite, has no hornblende and has generally muscovite. Such a granite is not detectable in the Ryoke zone. (3) The boundary between the Ryoke and the San- yo - Naegi zones is roughly located on the southern side of the Ashio Mountains.In this zone, the tangusten mineralization is seen in Itani of Tochigi Pref. and Takatori of Ibaraki Pref. Also in this zone, there is common the Mannari type of granite, which shows reddish color by much pink potash feldspar. (4) The boundary of the San-yo - Naegi zone to the San-in - Shirakawa zone is roughly located near the Okutadami Dam. In this zone, some bodies of granite belong to the magnetite series and to the Paleogene granite. Moreover, the molibdenum mineralization is known in Tagokura of Fukushima Pref., in Nippo of the Iide Mountains and in Nishitagawa of Yamagata Pref.