Detection of slab-derived fluid in coastal area of Seto Inland Sea, Japan, based on <sup>129</sup>I/<sup>127</sup>I ratios and halogen composition

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  • Togo Yoko S.
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Kazahaya Kohei
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Tosaki Yuki
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Takahashi Masaaki
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Morikawa Noritoshi
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Takahashi Hiroshi A.
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Nakamura Yuri
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Inamura Akihiko
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Shimizu Hinako
    Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)
  • Matsuzaki Hiroyuki
    The University Museum, The University of Tokyo

Bibliographic Information

Other Title
  • ヨウ素同位体比とハロゲン元素比を用いた瀬戸内海沿岸域におけるスラブ起源流体の検出
  • ヨウソ ドウイタイヒ ト ハロゲン ゲンソヒ オ モチイタ セトナイカイ エンガンイキ ニ オケル スラブ キゲン リュウタイ ノ ケンシュツ

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Description

<p>We collected 14 saline groundwater samples from coastal land areas of Hiroshima and Hyogo Prefectures, and Shodoshima of Kagawa Prefecture. Data on δD, δ18O, Li/Cl, Br/Cl, I/Cl, and 129I/127I for the samples reveal that the groundwater collected from Hiroshima Pref. are mainly derived from relatively young seawater, whereas samples from Hyogo Pref. and Shodoshima clearly contain slab-derived fluid characterized by>0.001 Li/Cl weight ratios, and show 1) <1.25×10–3 Br/Cl mole ratios, 2) >50×10–6 I/Cl mole ratios, and 3) low 129I/127I ratios (i.e., old iodine age).In addition, the latter sampling sites were characterized by shallow cutoff depth (D90: the depth above which 90% of earthquakes occur), suggesting that D90 becomes shallow where slab-derived fluids ascend to shallow depths. Halogen composition and 129I/127I ratio are concluded to be good indicators of slab-derived fluid contained in saline groundwater.</p>

Journal

  • Chikyukagaku

    Chikyukagaku 54 (4), 189-200, 2020-12-25

    The Geochemical Society of Japan

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