High alkalinity due to sulfate reduction in the CLAM hydrothermal field, Okinawa Trough

Toshitaka Gamo, Hitoshi Sakai, Eun Soo Kim, Kiminori Shitashima, Jun ichiro Ishibashi

研究成果: Contribution to journalArticle査読

58 被引用数 (Scopus)

抄録

High alkalinity ( > 1.8 mmol kg-1), pH (4.7-5.3), and ammonium ( ∼ 5 mmol kg-1) in hydrothermal fluids from the JADE and CLAM sites in the Mid-Okinawa Trough back-arc basin demonstrate organic matter decomposition during high-temperature fluid-sediment interaction. The endmember fluid from the JADE site ( ∼ 320°C black smoker), which is free of Mg and SO4, has similar chemical characteristics as those at the Escanaba Trough, one of the representative sediment-hosted ridge systems in the eastern Pacific. On the other hand, fluid samples from the CLAM site ( ∼ 100°C) show remarkably high alkalinity (10.3 mmol kg-1) comparable to the highest alkalinity of 10.6 mmol kg-1 (Guaymas Basin) yet observed in hydrothermal fluids, and significantly higher δ34S of SO4 ( > 25‰) than ambient seawater (21‰). It is suggested that sulfate reduction plays a dominant role in decomposing organic matter to increase alkalinity in the CLAM site. Variation of the δ34S values of H2S (from -0.2 to +3.0‰) in the CLAM fluids taken from different vents suggests that the CLAM site should consist of multiple local hydrothermal systems in different evolutionary stages with regard to sulfate reduction.

本文言語英語
ページ(範囲)328-338
ページ数11
ジャーナルEarth and Planetary Science Letters
107
2
DOI
出版ステータス出版済み - 11 1991
外部発表はい

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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