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2004 Fiscal Year Final Research Report Summary

Dissolution of Fe-bearing silicate minerals and weathering processes and rates in the Precambrian

Research Project

Project/Area Number 14340159
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Petrology/Mineralogy/Science of ore deposit
Research InstitutionThe University of Tokyo

Principal Investigator

MURAKAMI Takashi  The University of Tokyo, Graduate School of Science, Professor, 大学院・理学系研究科, 教授 (00253295)

Co-Investigator(Kenkyū-buntansha) KOGURE Toshihiro  The University of Tokyo, Graduate School of Science, Associate Professor, 大学院・理学系研究科, 助教授 (50282728)
Project Period (FY) 2002 – 2004
KeywordsPrecombrian / Atmospheric evolution / Paleosol / Weathering / Mineral-water-atmosphere interaction / Dissolution rate
Research Abstract

Atmospheric oxygen concentration in the Precambrian has been intensively studied for the past decade mainly because it is closely related to the environment of the Earth's surface, especially life evolution. Paleosols, soils fowled by ancient weathering, retain the information on atmospheric oxygen at the time of weathering. Paleosols, however, were affected by later geologic events such as diagenesis and metainoiphism, and are actually metamorphic rocks. Weathering processes in the Precambrian are not well understood, and atmospheric oxygen suggested by the paleosols is not unambiguous. We carried out dissolution experiments of minerals under Precambrian atmospheric conditions, compared the results to those obtained from paleosols, and tried to clarify the mineral-water-atmosphere interactions in the Precambrian.
Dissolution experiments of Fe-rich biotite were carried out in a glove box at 1 atm of carbon dioxide partial pressure and < 3x10(-5) atm of oxygen partial pressure (anoxia experiments). For comparison, similar experiments were done under modern atmospheric conditions (oxic experiments). Fe(II) is instantaneously oxidized to form Fe(III) oxides and little Fe(II) is present in the solution in the oxic experiments. In contrast, Fe(II) is present considerably and Fe(II)-bearing vermiculite is formed in the anoxia experiments. The variations of Fe(II) and Fe(III) distributions and of Fe/Mg ratio in chlorite with depth for a 2.5 Ga paleosol are well explained by the present experimental results. Other anoxia experiments of flow-through dissolution revealed that mineral dissolution rates are faster by 3 to 4 times under anoxic conditions than oxic ones and are not affected by the presence of Fe(II) in the solution.

  • Research Products

    (12 results)

All 2005 2004 2003 2002

All Journal Article (12 results)

  • [Journal Article] Emerging views on the Precambrian atmospheric oxygen evolution2005

    • Author(s)
      Sreenivas, B.
    • Journal Title

      Journal of Mineralogical and Petrological Sciences (in press)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Emerging views on the Precambrian atmospheric oxygen evolution2005

    • Author(s)
      Sreenivas, B., Murakami, T.
    • Journal Title

      Journal of Mineralogical and Petrological Sciences (in press)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Anoxic dissolution processes of biotite : implications for Fe behavior during Archean weathering2004

    • Author(s)
      Murakami, T.
    • Journal Title

      Earth and Planetary Science Letters 224

      Pages: 117-129

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] The formation of uranium mineral within leached layer of dissolving apatite : Incorporation mechanism of uranium by apatite2004

    • Author(s)
      Ohnuki, T.
    • Journal Title

      Chemical Geology 211

      Pages: 1-14

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Anoxia dissolution processes of biotite : implications for Fe behavior during Archean weathering2004

    • Author(s)
      Murakami, T., Ito, J., Utsunomiya, S., Kasama, T., Kozai, N., Ohnuki, T.
    • Journal Title

      Earth and Planetary Science Letters 224

      Pages: 117-129

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] The formation of uranium mineral within leached layer of dissolving apatite : Incorporation mechanism of uranium by apatite2004

    • Author(s)
      Ohnuki, T., Kozai, N., Samadfam, M., Yasuda, Y., Yamamoto, S., Narumi, K., Naramoto, H., Murakami, T.
    • Journal Title

      Chemical Geology 211

      Pages: 1-14

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Biotite dissolution processes and mechanisms in the laboratory and in nature : Early stage weathering environment and vermiculitization2003

    • Author(s)
      Murakami, T.
    • Journal Title

      American Mineralogist 88

      Pages: 377-386

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Iron oxidation state of a 2.45 b.y.-old paleosol developed on mafic volcanics2003

    • Author(s)
      Utsunomiya, S.
    • Journal Title

      Geochimica et Cosmochimica Acta, 67 67

      Pages: 213-221

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Biotite dissolution processes and mechanisms in the laboratory and in nature : Early stage weathering environment and vermiculitization2003

    • Author(s)
      Murakami, T., Utsunomiya, S., Yokoyama, T., Kasama, T.
    • Journal Title

      American Mineralogist 88

      Pages: 377-386

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Iron oxidation state of a 2.45 by-old paleosol developed on mafic volcanics2003

    • Author(s)
      Utsunomiya, S., Murakami, T., Nakada, M., Kasama, T.
    • Journal Title

      Geochimica et Cosmochimica Acta 67

      Pages: 213-221

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Biotitization of vermiculite under hydrothermal condition2002

    • Author(s)
      Murakami, T.
    • Journal Title

      Journal of Mineralogical and Petrological Sciences 97

      Pages: 263-268

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Biotitization of vermiculite under hydrothermal condition2002

    • Author(s)
      Murakami, T., Kasama, T., Sato, M.
    • Journal Title

      Journal of Mineralogical and Petrological Sciences 97

      Pages: 263-268

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 2006-07-11  

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