Two stage growth of microdiamond in UHP dolomite marble from Kokchetav Massif, Kazakhstan

H. Ishida, Yoshihide Ogasawara, K. Ohsumi, A. Saito

    Research output: Contribution to journalArticle

    31 Citations (Scopus)

    Abstract

    The abundance and morphology of microdiamond in dolomite marble from Kumdy-kol in the Kokchetav Massif, are unusual; a previous study estimated the maximum content of diamonds in dolomite marble to be about 2700 carat ton-1. Microdiamond is included primarily in garnet, and occasionally in diopside and phlogopite pseudomorphs after garnet. They are classified into three types on the basis of their morphology: (1) S-type: star-shaped diamond consisting of translucent cores and transparent subhedral to euhedral very fine-grained outer parts; (2) R-type: translucent crystals with rugged surfaces; and (3) T-type: transparent, very fine-grained crystals. The S-type is the most abundant. Micro-Laue diffraction using a 1.6-μm X-ray beam-size demonstrated that the cores of the starshaped microdiamond represent single crystals. In contrast, the most fine-grained outer parts usually have different orientations compared to the core. Laser-Raman studies indicate that the FWHM (Full Width at Half Maximum) of the Raman band of the core of the S-type diamond is slightly larger than that for the outer parts. Differences in morphology, crystal orientations, and in the FWHM of the Raman band between the core and the fine-grained outer-parts of S-type microdiamond suggest that the star-shaped microdiamond was formed discontinuously in two distinct stages.

    Original languageEnglish
    Pages (from-to)515-522
    Number of pages8
    JournalJournal of Metamorphic Geology
    Volume21
    Issue number6
    DOIs
    Publication statusPublished - 2003 Aug

    Keywords

    • Dolomite marble
    • Kokchetav Massif
    • Micro-Laue diffraction
    • Microdiamond
    • Ultrahigh-pressure metamorphism

    ASJC Scopus subject areas

    • Geology

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