Formation of gas discharging from Taketomi submarine hot spring off Ishigaki Island in the southern Ryukyu Islands, Japan

Tomohiro Toki, Daigo Iwata, Urumu Tsunogai, Daisuke D. Komatsu, Yuji Sano, Naoto Takahata, Hiroshi Hamasaki, Jun ichiro Ishibashi

研究成果: Contribution to journalArticle査読

1 被引用数 (Scopus)

抄録

Taketomi submarine hot spring lies off Ishigaki Island in the southern Ryukyu Islands and vents hot spring waters at temperatures up to ~ 50 °C from the seafloor at a depth of 20 m. We investigated the chemical and isotopic composition of gases discharging from Taketomi hot spring. The gases were composed mainly of methane, with secondary nitrogen at higher than atmospheric concentration. Carbon and hydrogen isotope data suggest that the methane in the discharging gases was derived mainly from thermal decomposition of organic matter. Helium isotopes were enriched in 3He relative to the atmosphere, suggesting a supply of mantle-derived helium to the discharging gases. The mantle-derived gases transfer the deep-originated thermal energy to the hot spring and thermogenesis of organic matter. The hydrocarbons in the venting gas could be sourced from sedimentary rocks of the Yaeyama or Shimajiri Groups, or Yaeyama metamorphic rocks, and added to the ascending gases as they pass through those source rocks on their way to the surface. Because the Pleistocene rocks of the Ryukyu Group beneath the hot spring have been altered by the spring activity, the Taketomi hot spring began venting after the Pleistocene.

本文言語英語
ページ(範囲)24-35
ページ数12
ジャーナルJournal of Volcanology and Geothermal Research
330
DOI
出版ステータス出版済み - 1 15 2017

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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