オホーツク海および日本海に胚胎する表層型ガスハイドレート鉱床における間隙水のハロゲンと放射性ヨウ素同位体(^<129>I)の地球化学 Geochemistry of Halogen and Iodine Radioisotope (^<129>I) in Pore Waters from Shallow Gas Hydrate Systems in the Okhotsk Sea and Japan Sea

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著者

    • 戸丸 仁 TOMARU Hitoshi
    • 北見工業大学未利用エネルギー研究センター New Energy Resources Research Center, Kitami Institute of Technology
    • 南 尚嗣 MINAMI Hirotsugu
    • 北見工業大学未利用エネルギー研究センター New Energy Resources Research Center, Kitami Institute of Technology
    • 庄子 仁 [他] SHOJI Hitoshi
    • 北見工業大学未利用エネルギー研究センター New Energy Resources Research Center, Kitami Institute of Technology
    • 蛭田 明宏 HIRUTA Akihiro
    • 東京大学大学院理学系研究科地球惑星科学専攻 Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo
    • 松本 良 MATSUMOTO Ryo
    • 東京大学大学院理学系研究科地球惑星科学専攻 Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo
    • 陸 尊礼 LU Zunli
    • オックスフォード大学地球科学科 Department of Earth Sciences, University of Oxford
    • FEHN Udo
    • ロチェスター大学地球環境学科 Department of Earth and Environmental Sciences, University of Rochester
    • JIN Young K.
    • 韓国海洋研究開発研究所韓国極地研究所 Korea Polar Research Institute, Korea Ocean Research and Development Institute
    • OBZHIROV Anatoly
    • ロシア科学アカデミー極東支部V.I.イリチェフ太平洋海洋学研究所 V.I. Il'ichev Oceanological Institute FEB RAS

抄録

 Sulfate, halogen, and radioactive <sup>129</sup>I concentrations were determined in pore waters associated with massive gas hydrate deposits in shallow sediments along the boundary between the Amurian and Okhotsk plates in the Okhotsk Sea and Japan Sea. Because of the strong biophilic behavior of iodine and weaker behavior of bromine, in contrast to conservative chlorine, in the marine system and the presence of a long-lived radioisotope of iodine (<sup>129</sup>I), these analyses are useful for determining the age and nature of source organic materials responsible for hydrocarbons, mostly methane, in gas hydrates. Rapid sulfate decreases with depth reflect active methane migration toward the seafloor, particularly around gas hydrate-bearing sites at both locations. While salt exclusion from gas hydrates during crystallization is likely to have resulted in the downward increase of Cl, and potentially Br and I concentrations, gas hydrate dissociation at depth caused a gentle dilution of pore waters. Biophilic Br and I concentrations rapidly increase with depth, reaching 1500 and 400 μM at the core bottom, respectively, indicating that upwelling fluids are enriched in Br and I derived from marine organic materials degraded in deep sediments. The <sup>129</sup>I/I ratios thus reflect the potential ages of source formations of iodine and associated methane, providing ∼35 Ma northeast off Sakhalin Island in the Okhotsk Sea and ∼30 Ma in the Umitaka Spur-Joetsu Knoll region in the eastern margin of the Japan Sea. These ages correspond well with the initial activities of the Amurian and Okhotsk plates and the subsequent opening of the Japan Sea, which formed the present geological setting of the northeastern margin of the Eurasian continent. Active plate motions led to the rapid accumulation of organic-rich sediments that are responsible for iodine and methane in gas hydrate occurring along the plate boundary.

収録刊行物

  • 地學雜誌

    地學雜誌 118(1), 111-127, 2009-03-25

    公益社団法人 東京地学協会

参考文献:  49件中 1-49件 を表示

被引用文献:  4件中 1-4件 を表示

各種コード

  • NII論文ID(NAID)
    10030364877
  • NII書誌ID(NCID)
    AN00322536
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    0022135X
  • NDL 記事登録ID
    10232645
  • NDL 雑誌分類
    ZM41(科学技術--地球科学)
  • NDL 請求記号
    Z15-169
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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