Geological and Petrological Study of the Cenozoic Volcanic Rocks in the Southwest Japan

1987-1988年的最新研究结果表明：1)九州、琉球群岛、Setouchi和Sanin地区、冲绳和小川群岛的火山地层清楚；2)日本西南部新生代地质因火山岩系列而变得非常复杂，如中新世的绿凝灰岩和Setouchi系列，晚中新世至全新世的太日岛系列，上新世至早更新世的Hohi和Hisatsu系列，中更新世的Buzen系列，晚更新世至全新世的三宁和琉球系列。3)碱性岩被识别为太日岛和Hohi火山岩系列的一部分。拉斑玄武岩产于绿凝灰岩、太日岩、和日岩、久津岩系和琉球岩系的一部分。4)高镁安山岩产于钙碱性岩系的色头池系列，拉斑玄武岩产于绿凝灰岩系列的伊里莫特-吉马、琉球群岛。5)从地幔岩石的差异、P-T条件和熔融程度、岩浆结晶的P-T条件、岩浆不混溶、岩浆混合、同化和混染等条件解释了各火山岩的成因。

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.