ストロンチウム同位体の挙動から見た岩石の化学風化 : 釜石鉱山の地下水による水–岩石反応の研究  [in Japanese] Chemical weathering of rocks in the view of Sr isotopic ratio: Study of groundwater at Kamaishi mine  [in Japanese]

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Author(s)

    • 高木 真理 TAKAGI Mari
    • 名古屋大学大学院理学研究科地球惑星理学専攻 Department of Earth and Planetary Sciences, Graduate School of Science, Nagoya University
    • 田中 剛 TANAKA Tsuyoshi
    • 名古屋大学大学院理学研究科地球惑星理学専攻 Department of Earth and Planetary Sciences, Graduate School of Science, Nagoya University
    • 天野 健治 AMANO Kenji
    • 核燃料サイクル開発機構東農地科学センター Japan Nuclear Cycle Development Institute, Tono Geoscience Center

Abstract

<sup>87</sup>Sr/<sup>86</sup>Sr ratio as well as dissolved major elements in rainwater, surface water and groundwater around the Kamaishi mine were examined to understand <i>in-situ</i> water-rock interaction. Clay minerals exist in the soil covering the surface. However, they have little effect on the groundwater chemical composition. The groundwater does not change its Na/Ca, Rb/Sr and <sup>87</sup>Sr/<sup>86</sup>Sr ratios in the depths shallower than 300 meters. It is considered that groundwater has been at steady state reaction condition with plagioclase in the surrounding granodiorite. Na/Ca, Rb/Sr and <sup>87</sup>Sr/<sup>86</sup>Sr ratios increase with depth in the deeper aquifers than 300 meters, suggesting that the dissolution of K-feldspar and/or biotite rich in alkaline and high <sup>87</sup>Sr/<sup>86</sup>Sr ratio is prompted. The concentration of Sr is lower in the deeper groundwater probably due to mineral precipitation and/or ion exchange reaction. Rb/Sr ratio of groundwater in the borehole, drilled 10 years ago, on the contrary, decreases with depth and becomes close to the value of bedrock at the deepest. It can be interpreted in two ways. One is a contribution of the deep groundwater and another is the influence of mineral dissolution at an early stage of water-rock interaction. Though the interpretations are seriously different, plagioclase must play an important role at the early stage of chemical weathering process.

Journal

  • Chikyukagaku

    Chikyukagaku 35(2), 61-72, 2001

    The Geochemical Society of Japan

References:  24

Cited by:  1

Codes

  • NII Article ID (NAID)
    110008680017
  • NII NACSIS-CAT ID (NCID)
    AN00141280
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    0386-4073
  • NDL Article ID
    5812262
  • NDL Source Classification
    ZM41(科学技術--地球科学)
  • NDL Call No.
    Z15-645
  • Data Source
    CJP  CJPref  NDL  NII-ELS  J-STAGE 
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