The Kobe CK carbonaceous chondrite : petrography, mineralogy and metamorphism

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Author(s)

    • TOMEOKA Kazushige
    • Department of Earth and Planetary Sciences, Faculty of Science, Kobe University
    • KOJIMA Tomoko
    • Department of Environmental Science, Faculty of Science, Kumamoto University
    • OHNISHI Ichiro
    • Department of Earth and Planetary Sciences, Faculty of Science, Kobe University
    • ISHII Yoshitaka
    • Department of Earth and Planetary Sciences, Faculty of Science, Kobe University
    • NAKAMURA Noboru
    • Department of Earth and Planetary Sciences, Faculty of Science, Kobe University

Abstract

A petrographic and mineralogical study of Kobe indicates that it can be classified as a CK4 carbonaceous chondrite. CK chondrites differ from other groups of carbonaceous chondrites, because all normal CK chondrites have been thermally metamorphosed. Olivine and plagioclase are the two most abundant minerals in Kobe. Olivine is very homogeneous in composition, which is consistent with the metamorphic feature of Kobe. However, plagioclase shows large grain to grain compositional variations. The matrix and chondrule mesostases exhibit pronounced silicate darkening. They contain unusual olivine that contains numerous small vesicles (< 0.1-3 μm in diameter) and inclusions (< 0.1-10 μm) of magnetite, pentlandite and minor plagioclase, pyroxene and chlorapatite. The vesicular olivine is particularly abundant in regions that exhibit a high degree of darkening. The vesicular olivine is clearly the principal cause of the silicate darkening. Plagioclase in matrix and chondrule mesostases also contains numerous small vesicles and inclusions of magnetite, pyroxene and minor pentlandite and olivine. The texture and mineralogy of the vesicular olivine and plagioclase suggest that they recrystallized from melts that were produced from olivine and plagioclase in the matrix by shock. We suggest that the shock event occurred at a relatively mild pressure and a high temperature, probably at the state where the meteorite underwent thermal metamorphism.

Journal

  • Journal of Mineralogical and Petrological Sciences

    Journal of Mineralogical and Petrological Sciences 100(3), 116-125, 2005-06-01

    Japan Association of Mineralogical Sciences

References:  19

Cited by:  1

Codes

  • NII Article ID (NAID)
    10014351021
  • NII NACSIS-CAT ID (NCID)
    AA11460926
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    13456296
  • Data Source
    CJP  CJPref  J-STAGE 
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