著者

伊藤 純一 白木 敬一

出版者

日本地質学会

雑誌

地質學雜誌 (ISSN:00167630)

巻号頁・発行日

vol.105, no.11, pp.810-813, 1999-11-15

被引用文献数

3 8

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Picrite basalts containing MgO up to 16 wt.% were found in the lowest part of the Pliocene Uegusukudake Formation on the north coast of Kumejima island ; in the close proximity northwest of the island lies an active back-arc basin, Okinawa Trough. The high Fo (92.2) of olivine and Cr_2O_3 (56.5%) of spinel in the picrite basalts indicate the existence of a magma with >13% MgO and >0.15% Cr_2O_3. The Kumejima picrite basalts are tholeiitic arc picrites having relatively high SiO_2 and low incompatible element abundances.They may have formed accompanying the opening of the Okinawa Trough.