The role of fluid for diamond-free UHP dolomitic marble from the Kokchetav Massif

Yoshihide Ogasawara, Kazumasa Aoki

    Research output: Contribution to journalArticle

    14 Citations (Scopus)

    Abstract

    A diamond-free, dolomite-bearing UHP marble showing a banded structure occurs at Kumdy-kol in the Kokchetav Massif, northern Kazakhstan. Three centimeter-scale zones occur in this marble (sample no. Y665): zone A = Ti-elinohumite-bearing dolomitic marble; zone B = dolomite marble; and zone C = dolomitic marble lacking Ti-clinohumite and forsterite. The occurrence of phlogopite and garnet lamellae in diopside in zone C suggests UHP metamorphism. Large-area chemical mapping covering about two-thirds of the sample surface was conducted. Ti-Kα X-ray images clearly indicate that TiO2 is concentrated in zone A. Ca-Kα and Mg-Kα images showed that zones A and C have similar modal compositions of carbonates, but they have strong contrasts in TiO2 contents and mineral paragenesis. Mineral assemblages in each zone were analyzed in terms of the CaO-(MgO, FeO)-TiO2-SiO2 compositional tetrahedron. In zone A, the aragonite-Ti-elinohumite tieline was stable under UHP conditions, whereas it was unstable in zones B and C. This indicates that XCO2 in zone A was lower than that in zones B and C. Infiltration of TiO2-bearing aqueous fluid is implied on the basis of paragenetic relations, distribution of Ti-bearing phases and chemical zonation in Ti-clinohumite in zone A. The lack of microdiamond in this dolomite-bearing carbonate rock suggests extremely low-XCO2 conditions, and implies the infiltration of an aqueous fluid during UHP metamorphism.

    Original languageEnglish
    Pages (from-to)1178-1193
    Number of pages16
    JournalInternational Geology Review
    Volume47
    Issue number11
    Publication statusPublished - 2005 Nov

    Fingerprint

    marble
    diamond
    fluid
    clinohumite
    dolomite
    metamorphism
    infiltration
    forsterite
    phlogopite
    diopside
    mineral
    paragenesis
    aragonite
    carbonate rock
    zonation
    garnet

    ASJC Scopus subject areas

    • Geology

    Cite this

    The role of fluid for diamond-free UHP dolomitic marble from the Kokchetav Massif. / Ogasawara, Yoshihide; Aoki, Kazumasa.

    In: International Geology Review, Vol. 47, No. 11, 11.2005, p. 1178-1193.

    Research output: Contribution to journalArticle

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    abstract = "A diamond-free, dolomite-bearing UHP marble showing a banded structure occurs at Kumdy-kol in the Kokchetav Massif, northern Kazakhstan. Three centimeter-scale zones occur in this marble (sample no. Y665): zone A = Ti-elinohumite-bearing dolomitic marble; zone B = dolomite marble; and zone C = dolomitic marble lacking Ti-clinohumite and forsterite. The occurrence of phlogopite and garnet lamellae in diopside in zone C suggests UHP metamorphism. Large-area chemical mapping covering about two-thirds of the sample surface was conducted. Ti-Kα X-ray images clearly indicate that TiO2 is concentrated in zone A. Ca-Kα and Mg-Kα images showed that zones A and C have similar modal compositions of carbonates, but they have strong contrasts in TiO2 contents and mineral paragenesis. Mineral assemblages in each zone were analyzed in terms of the CaO-(MgO, FeO)-TiO2-SiO2 compositional tetrahedron. In zone A, the aragonite-Ti-elinohumite tieline was stable under UHP conditions, whereas it was unstable in zones B and C. This indicates that XCO2 in zone A was lower than that in zones B and C. Infiltration of TiO2-bearing aqueous fluid is implied on the basis of paragenetic relations, distribution of Ti-bearing phases and chemical zonation in Ti-clinohumite in zone A. The lack of microdiamond in this dolomite-bearing carbonate rock suggests extremely low-XCO2 conditions, and implies the infiltration of an aqueous fluid during UHP metamorphism.",
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