閉鎖系実験における水-岩石相互反応の初期反応速度の温度依存性  [in Japanese] Temperature Dependence of Reaction Rate at the Initial Stage of Water-Rock Interaction in a Closed System Experiment  [in Japanese]

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Author(s)

    • 高屋 康彦 TAKAYA Yasuhiko
    • 筑波大学生命環境科学研究科地球環境科学専攻 Geoenvironmental Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba
    • 八田 珠郎 HATTA Tamao
    • 独立行政法人国際農林水産業研究センター Japan International Research Center for Agricultural Sciences
    • 松倉 公憲 MATSUKURA Yukinori
    • 筑波大学生命環境科学研究科地球環境科学専攻 Geoenvironmental Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba

Abstract

A dissolution experiment was carried out to examine a temperature dependence of reaction rate and characteristics of water-rock interaction using fifteen principal rock-types: four kinds of sedimentary rock (limestone, chert, sandstone, and tuff), five kinds of plutonic rock (dunite, gabbro, diorite, granodiorite, and granite), four kinds of volcanic rock (basalt, andesite, dacite, and rhyolite), and two kinds of metamorphic rock (serpentinite and hornfels). For each rock type, a small block sample (5.0×5.0×40.0 mm^3) was treated with distilled water of 250.0 mL at 5, 50, and 75 ℃. Electric conductivity (EC) of the aqueous solution was measured as an index of total concentration of dissolved materials at several-hour and day interval during 2164 hours (ca. 90 days). The EC of aqueous solution was larger at higher temperature for all rock-types, although there was an exception for sandstone. Change in EC with time was parabolic at an initial stage of experiment. The changing curve was adapted to a parabolic rate law: EC = kt^<1/2>, where k is a rate constant of reaction. The duration in which the curve followed the parabolic rate law, i.e. a period of initial reaction, was shorter, and the k-value was larger at higher temperature in the same rocktype. The k-value in limestone was the highest, and chert and granite had a lower k-value than the other rock-types under all thermal conditions. The temperature dependence of k is represented by the Arrhenius equation: k=A exp (-E_<app>/RT), where E_<app> is the apparent activation energy, R is gas constant and T is absolute temperature. The E_<app> of initial reaction were calculated to be from the lowest value of 11.4 kJ/mol for tuff to the highest value of 27.7 kJ/mol for dunite. These values were lower than the values of mineral dissolution according to the data collected from literature. This indicates that the rate-determining step of the overall reaction at the initial stage of water-rock interaction is mainly a mass transport process.

Journal

  • Transactions,Japanese Geomorphological Union

    Transactions,Japanese Geomorphological Union 27(2), 245-258, 2006-04-25

    日本地形学連合

References:  37

Cited by:  4

Codes

  • NII Article ID (NAID)
    110004686810
  • NII NACSIS-CAT ID (NCID)
    AN00333248
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    03891755
  • NDL Article ID
    7932486
  • NDL Source Classification
    ZM49(科学技術--地球科学--地質)
  • NDL Call No.
    Z15-386
  • Data Source
    CJP  CJPref  NDL  NII-ELS  NDL-Digital 
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