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Entire magmatic evolution of the Kikai caldera revealed by zircon triple (U-Pb, Th-Pb, U-Th) dating and its chemistry

Hisatoshi Ito

  • Affiliations: Geology and Geotechnical Engineering Division, Central Research Institute of Electric Power Industry, Abiko, Japan

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 266

  • Programme No: 1.3.13

  • Theme 1 > Session 3

Abstract

Elucidating the volcanic history of the Kikai caldera, an active large volcano that erupted a volume of ~160 km3 at 7.3 ka off the southern coast of Kyushu Island, southwest Japan, is critically important to assess future volcanic hazards on a regional and/or global scale. Nevertheless, revealing its volcanic history before the 7.3 ka eruption has been challenging partly because it is a mostly submerged caldera. Here, we show that the Kikai caldera experienced a geochemically unique silicic lava eruption at ~250 ka by using zircon triple (U-Pb, Th-Pb, U-Th) dating and its chemistry. The 7.3 ka eruption contained 1.5--1.0 Ma zircons, indicating that zircon crystallizing magmatism initiated at this time at the Kikai caldera. We further infer that enigmatic large eruptions at 0.7--0.6 Ma are reasonable and therefore the Kikai caldera may have experienced at least 5 large eruptions during its 1.5--1.0-million-year magmatic history.