Carbon isotope heterogeneity in metamorphic diamond from the Kokchetav UHP dolomite marble, northern Kazakhstan

Kyoko Imamura, Yoshihide Ogasawara*, Hisayoshi Yurimoto, Minoru Kusakabe

*この研究の対応する著者

    研究成果: Article査読

    7 被引用数 (Scopus)

    抄録

    We analysed isotopic compositions of metamorphic microdiamond secondary ion mass spectrometry. Typical microdiamonds in this dolomite marble show star-shaped morphologies (S-type) consisting of single-crystal cores and polycrystalline rims. Four S-type microdiamonds and two R-type microdiamonds (single crystals with rugged surfaces) were analysed using a 5 μm diameter ion beam. S-type microdiamonds have heterogeneous carbon isotopic compositions even in a single grain. Analysis of a typical S-type microdiamond (no. xx01-1-13) revealed clear difference in δ13C between core and rim. The rim shows lighter isotopic compositions ranging from -17.2% to -26.9%, whereas the core is much heavier, with δ13C ranging from -9.3% to -13.0%. The δ13C values of R-type microdiamonds fall into narrow ranges from -8.3% to -14.9% for no. xx01-1-10 and from -8.3% to -15.3% for no. xx01-1-16. These δ13C values are similar to those of the S-type microdiamond cores. The R-type probably formed at the same stage as the core of the S-type, whereas rim growth at a second stage did not occur or occurred very weakly in R-type microdiamonds. These carbon isotopic data support the two-stage growth of microdiamonds in the Kokchetav ultrahigh-pressure host rock. To explain the second stage growth of S-type microdiamonds, we postulate a simple fluid infiltration of light carbon from neighbouring gneisses into the dolomite marble.

    本文言語English
    ページ(範囲)453-467
    ページ数15
    ジャーナルInternational Geology Review
    55
    4
    DOI
    出版ステータスPublished - 2013 3月 1

    ASJC Scopus subject areas

    • 地質学

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