Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

S (Solid Earth Sciences) » S-VC Volcanology

[S-VC43] Volcanic and igneous activities, and these long-term forecasting

Sun. May 20, 2018 10:45 AM - 12:15 PM A05 (Tokyo Bay Makuhari Hall)

convener:Teruki Oikawa(GSJ, National Institute of Advanced Industrial Science and Technology), Takeshi Hasegawa(Department of Earth Sciences, College of Science, Ibaraki University), Daisuke MIURA(一般財団法人 電力中央研究所 地球工学研究所 地圏科学領域, 共同), Nobuo Geshi(Geological Survey of Japan, The National Institute of Advanced Industrial Science and Technology), Chairperson:Hasegawa Takeshi(Department of Earth Sciences, College of Science, Ibaraki University), Maeno Fukashi

11:45 AM - 12:00 PM

[SVC43-09] Gigantic eruption history of the Kikai Caldera inferred from zircon U-Pb dating and elemental analysis

*Hisatoshi Ito1, Simpei Uesawa1 (1.Central Research Institute of Electric Power Industry)

Keywords:Kikai Caldera, U-Pb dating, elemental analysis

The Kikai Caldera, situated ~50 km south of the Kyushu Island, experienced a gigantic eruption at ~7300 years ago (or 7.3 ka). In order to understand the next gigantic eruption it is now under an intensive investigation using a research vessel (Tatsumi et al., 2018), receiving a great deal of attention from researchers and the public. Meanwhile, we performed zircon U-Pb dating of three widespread tephras (Anbo, Ksd, K-Tz) from the Yakushima Island, ~30 km south of the Kikai Caldera, and found ~0.7 Ma and ~0.6 Ma zircons in the ~0.1 Ma K-Tz tephra of the Kikai Caldera origin. Therefore we speculated that the Kikai Caldera may have experienced at least 3 gigantic eruptions before the 7.3 ka eruption (Ito et al., 2017). In order to verify this hypothesis, we collected volcanic products from the Tanegashima Island and the Kikai Caldera (Satsuma-Iwojima and Takeshima Islands), and performed zircon U-Pb dating and elemental analysis of zircon and volcanic glass. So far, zircon U-Pb dating ascertained that the Ksd is also distributed in the Tanegashima Island and revealed that the age of the Akazaki lava in the Takeshima Island is ~0.2 Ma. Through these investigations, we propose a new history of gigantic eruptions in the Kikai Caldera.

Reference

Ito, H., Uesawa, S., Nanayama, F., and Nakagawa, S., 2017. Zircon U–Pb dating using LA-ICP-MS: Quaternary tephras in Yakushima Island, Japan. J. Volcanol. Geotherm. Res., 338, 92–100.

Tatsumi, Y. et al., 2018. Giant rhyolite lava dome formation after 7.3 ka supereruption at Kikai caldera, SW Japan. Sci. Rep. 8, 2753; DOI:10.1038/s41598-018-21066-w.