Grant-in-Aid for Co-operative Research (A).
|Research Institution||Yamaguchi University|
KIMINAMI Kazuo Yamaguchi Univ., Fac.Sci., Assis.Prof., 理学部, 助教授 (20127757)
TAKESHITA Tooru Hiroshima Univ., Fac.Sci., Assis.Prof., 理学部, 助教授 (30216882)
AIHARA Atsuo Kyushu Univ., Fac.Sci., Prof., 理学部, 教授 (80037291)
公文 富士夫 信州大学, 理学部, 助教授 (60161717)
KOMATSU Masayuki Ehime Univ., Fac.Sci., Prof., 理学部, 教授 (00018665)
MIYASITA Sumio Niigata Univ., Fac.Sci., Assis.Prof., 理学部, 助教授 (60200169)
MAEDA Jin-ichiro Hokkaido Univ., Fac.Sci., Assis., 理学部, 助手 (50165643)
|Project Fiscal Year
1992 – 1993
Completed(Fiscal Year 1993)
|Budget Amount *help
¥9,800,000 (Direct Cost : ¥9,800,000)
Fiscal Year 1993 : ¥4,900,000 (Direct Cost : ¥4,900,000)
Fiscal Year 1992 : ¥4,900,000 (Direct Cost : ¥4,900,000)
|Keywords||Ridge collision / Ridge subduction / Shimanto Belt / Sanbagawa metamorphic belt / Ryoke metamorphic belt / Cretaceous / Greenstone / 海嶺衝突 / 海嶺沈みこみ / 四万十帯 / 三波川変成帯 / 領家変成帯 / 白亜紀 / 緑色岩 / 四万十累層群 / 日高累層群 / 領家帯 / 西南日本白亜紀大成岩類 / 原地性緑色岩|
The following summary of the research results obtained.
1. Tere ara three rows of strata containing in in-situ greenstones at least in the Hidaka Belt. Geochemical signatures indicate that at least some of the in-situ greenstones are similar to mafic lava generated at spreading ridges.
2. Geochemical and petrological studies on the igneous rocks from the Hidaka metamorphic belt have revealed that they were emplaced in connection with a ridge subduction.
3. On the basis of geochemical studies, the granitic rocks in the Kitakami Mountains, Northeast Japan, are inferred to have been emplaced in connection with a subduction of a hot oceanic plate.
4. Some melange-like units in the Shimanto Supergroup, such as Naze Formation(Amami-Oshima), Makimine Formation(Kyushu), Okitsu Melange(west Shikoku), Mugi Formation(east Shikoku), Ryujin Formation(Kii Peninsula) and Inui Group(Akaishi Mountains), contain greenstones which were extruded upon and intruded into unconsolidated fine-grained terrigenous clastic sediments.
5. Geochemical signatures indicate that the in-situ greenstones from the Shimanto Supergroup are similar to mafic lavas generated at spresding ridges.
6. Organic metamorphism in the Shimanto and Hidaka Supergroups was studied by means of vitrinite reflectance. The study has revealed thermal history of the both supergroup.
7. The relationship between ridge collision and sedimentation on the trench floor in the Shimanto Belt has been clarified.
8. Ar/Ar isotope ages from the Sanbagawa metamorphic rocks have resulted in the time relationship between the exhumation of the Sanbagawa metamorphic rocks and ridge cillision.
9. Petrological study of xenoliths in the granitic rocks from the Shimanto Belt revealed a thermal event during the Eocene.