Water content and lithium isotope fractionation in subduction-zone mantle olivine

• Project/Area Number: 24540513
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Petrology/Mineralogy/Science of ore deposit
• Research Institution: Okayama University
• Principal Investigator: OTA Tsutomu 岡山大学, 地球物質科学研究センター, 助手 (80379817)
• Research Collaborator: MALFAIT WIM J. スイス連邦工科大学, 地球化学研究所, 上級研究員
• Project Period (FY): 2012-04-01 – 2015-03-31
• Project Status: Completed (Fiscal Year 2014)
• Budget Amount: ¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000); Fiscal Year 2014: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2013: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2012: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
• Keywords: リチウム / 同位体分別 / カンラン石 / 水流体 / 沈み込み帯 / 高温高圧実験 / 二次イオン質量分析計 / 流体 / 二次イオン質量分析装置

Outline of Final Research Achievements

In terms of lithium (Li) isotope fractionation between mantle olivine and aqueous fluid, we examined an interaction between mantle and surficial material, which has strongly affected the earth’s chemical evolution.
Combining an experimental study in a simple system with Li-isotope analysis of natural mantle olivine revealed that the mantle olivine yielded Li isotopic abundances that fractionated by an interaction with aqueous fluid is relatively enriched in hydrogen, compared with the less fractionated ones.
This result indicates that mantle materials that interacted with surficial materials have maintained their chemical characteristics including Li isotopic abundance, even under high temperature conditions in mantle on a geologic timescale. The mantle materials, interacted with surficial materials, have been transported back to the mantle by lithospheric plate subduction; such cycling has chemically differentiated the mantle and the surface, that is, the earth’s chemical evolution.

Research Products

• [Journal Article] Supervolcano eruptions driven by melt buoyancy in large silicic magma chambers (2014)
  • Author(s): Malfait, J. W., Seifert, R., Petitgirard, S., Perrillat, J., Mezouar, M., Ota, T., Nakamura, E., Philippe, L., Sanchez-Valle, C.
  • Journal Title: Nature Geoscience Volume: 7 Issue: 2 Pages: 122-125
  • DOI: 10.1038/ngeo2042
  • Peer Reviewed
• [Journal Article] Ion microprobe U-Th-Pb geochronology and study of micro-inclusions in zircon from the Himalayan high- and ultrahigh-pressure eclogites, Kaghan Valley of Pakistan (2013)
  • Author(s): Hafiz Ur Rehman, Katsura Kobayashi, Tatsuki Tsujimori, Tsutomu Ota, Hiroshi Yamamoto, Eizo Nakamura, Yoshiyuki Kaneko, Tahseenullah Khan , MasaruTerabayashi, Kenta Yoshida, Takao Hirajima
  • Journal Title: Journal of Asian Earth Sciences Volume: 63 Pages: 179-196
  • DOI: 10.1016/j.jseaes.2012.04.025
  • Peer Reviewed
• [Remarks] 岡山大学地球物質科学研究センター
  • URL: http://www.misasa.okayama-u.ac.jp/