日本地球惑星科学連合2018年大会

講演情報

[EE] Eveningポスター発表

セッション記号 S (固体地球科学) » S-IT 地球内部科学・地球惑星テクトニクス

[S-IT21] マントルプルームは存在するか?

2018年5月20日(日) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:眞島 英壽(明治大学黒耀石研究センター)、Gillian R Foulger (Durham University)、趙 大鵬(東北大学大学院理学研究科附属地震・噴火予知研究観測センター)

[SIT21-P04] Evidence for the low-pressure and -temperature origin of the Minami-Shimabara basalts in northwest Kyushu, southwest Japan

*田島 俊彦眞島 英壽1 (1.明治大学)

Hot spot-type basalts erupted from 4.6 to 0.6 Ma are distributed in the Minami-Shimabara area, at the southern foot of the Unzen volcano in northwest Kyushu, southwest Japan. Compositional similarities between the Minami-Shimabara basalts and the host lava of mantle xenoliths from northwest Kyushu indicate that most of the Minami-Shimabara basalts would have originally been primitive or less-fractionated magmas. Their normative olivine–quartz–[Jd + CaTs] compositions demonstrate that the Minami-Shimabara magmas would have been segregated from the heterogeneous source mantle at pressures ranging from 1.5 to 0.5 GPa. Their normative olivine–quartz–[Jd + CaTs] compositions also indicate that the source mantle would have had a relatively low potential temperature, such as 1300 °C. Upwelling of the mantle with such low temperature would have been caused by shallow mantle processes, such as plate tectonics. Potential tectonic activity causing mantle upwelling would be the subsidence of the Amakusa-nada Graben simultaneous with the Minami-Shimabara volcanism.