論文

査読有り
2016年10月

Lithium isotopic systematics of submarine vent fluids from arc and back-arc hydrothermal systems in the western Pacific

GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
  • Daisuke Araoka
  • ,
  • Yoshiro Nishio
  • ,
  • Toshitaka Gamo
  • ,
  • Kyoko Yamaoka
  • ,
  • Hodaka Kawahata

17
10
開始ページ
3835
終了ページ
3853
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1002/2016GC006355
出版者・発行元
AMER GEOPHYSICAL UNION

The Li concentration and isotopic composition (delta Li-7) in submarine vent fluids are important for oceanic Li budget and potentially useful for investigating hydrothermal systems deep under the seafloor because hydrothermal vent fluids are highly enriched in Li relative to seawater. Although Li isotopic geochemistry has been studied at mid-ocean-ridge (MOR) hydrothermal sites, in arc and back-arc settings Li isotopic composition has not been systematically investigated. Here we determined the delta Li-7 and Sr-87/Sr-86 values of 11 end-member fluids from 5 arc and back-arc hydrothermal systems in the western Pacific and examined Li behavior during high-temperature water-rock interactions in different geological settings. In sediment-starved hydrothermal systems (Manus Basin, Izu-Bonin Arc, Mariana Trough, and North Fiji Basin), the Li concentrations (0.23-1.30 mmol/kg) and delta Li-7 values (+4.3 parts per thousand to 17.2 parts per thousand) of the end-member fluids are explained mainly by dissolution-precipitation model during high-temperature seawater-rock interactions at steady state. Low Li concentrations are attributable to temperature-related apportioning of Li in rock into the fluid phase and phase separation process. Small variation in Li among MOR sites is probably caused by low-temperature alteration process by diffusive hydrothermal fluids under the seafloor. In contrast, the highest Li concentrations (3.40-5.98 mmol/kg) and lowest delta Li-7 values (11.6 parts per thousand to 12.4 parts per thousand) of end-member fluids from the Okinawa Trough demonstrate that the Li is predominantly derived from marine sediments. The variation of Li in sediment-hosted sites can be explained by the differences in degree of hydrothermal fluid-sediment interactions associated with the thickness of the marine sediment overlying these hydrothermal sites.

Web of Science ® 被引用回数 : 7

リンク情報
DOI
https://doi.org/10.1002/2016GC006355
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000388694600001&DestApp=WOS_CPL
URL
http://www.scopus.com/inward/record.url?eid=2-s2.0-84990225657&partnerID=MN8TOARS
URL
http://orcid.org/0000-0001-5249-4995

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