| 研究課題/領域番号 |
21K03739
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| 研究機関 | 東京大学 |
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研究代表者 |
Snyder Glen 東京大学, 大気海洋研究所, 特任研究員 (90751777)
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| 研究分担者 |
柿崎 喜宏 東京大学, 大学院理学系研究科(理学部), 特任研究員 (20570633) [辞退]
白石 史人 広島大学, 先進理工系科学研究科(理), 准教授 (30626908)
松本 良 明治大学, 研究・知財戦略機構(生田), 研究推進員(客員研究員) (40011762)
戸丸 仁 千葉大学, 大学院理学研究院, 准教授 (80588244)
高畑 直人 東京大学, 大気海洋研究所, 助教 (90345059)
伊地知 雄太 東京大学, 大学院理学系研究科(理学部), 特任研究員 (10911258)
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| 研究期間 (年度) |
2021-04-01 – 2024-03-31
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| キーワード | authigenic carbonate / noble gas / helium isotopes / protodolomite / EPS / microbial methane / thermogenic methane |
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| 研究実績の概要 |
During this year, we have completed analysis of noble gas inclusions in methane derived authigenic carbonates from samples recovered in shallow sediments in both Joetsu Basin, Sea of Japan, and from offshore Sakhalin Island, in Tatar Strait and Brejo du Espinho, Brazil (Snyder and Takahata, AORI, Univ. Tokyo). These samples show different amounts of mantle-derived helium as well as helium derived in the crust, providing some information as to the origin of gases that produced the carbonates, as well as where they were formed. In addition, Shiraishi (Hiroshima Univ.) prepared microdolomite sections using focused ion beam (FIB), followed by observation using scanning transmission X-ray microscopy (STXM) and a transmission electron microscopy (TEM). These sections reveal inclusions of extracellular polymeric substances (EPS), as well as protodolomite inclusions. Two field excursions were taken this year to the Mobara gas field area in Chiba Prefecture (Snyder, AORI; Matsumoto, Meiji U.; and Tomaru, Chiba U.) to collect gas samples as well as sediment and water near the seep sites that may potentially yield microbial carbonates. Sample analysis is still ongoing, although we have determined the stable carbon isotope signature of carbon dioxide present in the gases, which we will later compare with the stable isotopic composition of the associated microbial carbonates
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
COVID-related restrictions delayed our initial sampling plan in Niigata Prefecture. In addition, Co-PI Yoshihiro Kakizaki from U.Tokyo left the university to take another job. Fortunately, Yuta Ijichi at U.Tokyo was able to take over the portion of the project originally assigned to Kakizaki-san and will proceed with the planned analyses. Despite these delays, we have been able to carry out analyses with the Chiba samples and archived samples which we had on hand.
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| 今後の研究の推進方策 |
During the last week of May, we will present two talks with results from the research in this grant at the annual JpGU conference later this month: [BGM02-01] “Characteristics of microdolomite associated with gas hydrate” (to be presented by Fumito Shiraishi, Hiroshima U.), and [SGC35-07] “Hydrocarbon seep dynamics revealed by noble gas and stable isotope analysis of gas inclusions of authigenic carbonates: A comparison of samples from Tatar Strait, Russia; Joetsu Basin, Japan; and Brejo do Espinho, Brazil” (To be presented by Glen Snyder, AORI, Tokyo U.).
This Summer/Fall we will carry out gas and sediment sampling in Niigata Prefecture. Sediment sample splits will go to Hiroshima U. for analysis of EPS and proto-dolomnite, to U. Tokyo for XRD and stable carbon isotopic analysis, to Gakushuin U. for Mg-isotopic analysis. Gas samples will be analyzed to AORI for stable carbon and noble gas isotopic analysis. Water samples will be analyzed at Chiba U. for major cation and anion analysis.
We also hope to have journal manuscripts submitted on the research which we have currently completed by the end of the year.
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| 次年度使用額が生じた理由 |
The funding for next year will include expenses for field sampling in Niigata, Analytical costs, conference fees, and manuscript publication fees.
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