| Co-Investigator(Kenkyū-buntansha) |
NAGAO Takashi Yamaguchi University, Faculty of Science, Assistant Prof., 理学部, 助教授 (40136164)
SHIRAKI Keiichi Yamaguchi University, Faculty of Science, Assistant Prof., 理学部, 助教授 (60144911)
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| Research Abstract |
Results of the recent study in 1987-1988 arrived at the following conclusions.
1) The volcanostratigraphy of Kyushu, Ryukyu Islands, Setouchi and sanin regions, Oki and Ogasawara Islands are well defined.
2) The cenozoic geology in southwest Japan was so complicated by the volcanic series, such as, the Green Tuff and Setouchi series in the Miocene, Tairiku series from the late Miocene to Holocene, Hohi and Hisatsu series from the Pliocene to early Pleisto-cene, Buzen series in the middle Pleistocene, Sanin and Ryukyu series from the late Pleistocene to Holocene.
3) The alkali rocks are recognized in a part of the Tairiku and Hohi volcanic series. The tholeiitic rocks are observed in a part of the Green Tuff, Tairiku, Hohi, Hisatsu and Ryukyu series. Other volcanic rocks are belonged the calc-alkali rock series.
4) The high magnesian andesites are occured in the Setouchi series of calc-alkali rock series, and the tholeiitic rock from Iriomote-jima, Ryukyu islands of the Green Tuff series. the latter are explained by the crystallization of high temparature.
5) The petrogenesis of each volcanic rocks are explained by some condition, such as, the difference of mantle rocks, P-T condition and degree of melting, P-T condition of crystallization in magma, immiscibility in magam, magma mixing, assimilation and contamination.
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