Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-VC Volcanology

[S-VC36] Volcanic and igneous activities, and these long-term forecasting

Sun. May 26, 2019 9:00 AM - 10:30 AM A07 (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(Department of Physical Science, Graduate School of Science, Osaka Prefecture University), Nobuo Geshi(Geological Survey of Japan, The National Institute of Advanced Industrial Science and Technology), Chairperson:Daisuke Miura, Nobuo Geshi(GSJ/AIST)

9:00 AM - 9:15 AM

[SVC36-01] The entire magmatic history of the Toba Caldera Complex that influenced human evolution, northern Sumatra, inferred from zircon U-Pb geochronology

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

Keywords:super-eruption, Toba Caldera, U-Pb dating

The entire magmatic history of the Toba Caldera Complex (TCC), which involves the climactic Youngest Toba Tuff (YTT) super-eruption at ~74 ka, was investigated using zircons from the Oldest Toba Tuff, a post-caldera lava dome and detrital zircons from Toba lake sediments (whitish tuffaceous fine sand) deposited after the YTT activity. It was reconfirmed by U-Pb method that magmatic activity of the TCC started at ~1.3 Ma and it was newly found that the zircon-forming magmatic activity of TCC culminated at ~0.3 Ma, well before the ~0.07 Ma YTT eruption. Therefore, the climatic YTT eruption was not triggered by intensive/rapid magma supply at the time of eruption. The trigger should have been a small magmatic input or some other mechanisms (such as mechanical roof failure and roof subsidence into the magma reservoir). The TCC magma was stored incrementally over 1 million years as cold storage and finally it vented voluminous tephras at ~0.07 Ma. The remarkable accordance of zircon U-Pb age distribution between YTT and a post YTT lava dome (Tuk Tuk lava dome) indicates that post-caldera magmatic activity/resurgence occurred using essentially the same magma with YTT.