Hydroxyl in clinopyroxene and titanite in a UHP diamond-free garnet-clinopyroxene rock from the Kokchetav Massif, northern Kazakhstan

Kunihiko Sakamaki, Yoshihide Ogasawara

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    4 Citations (Scopus)

    Abstract

    Hydroxyls in clinopyroxene and supersilicic titantite in diamond-free garnet-clinopyroxene rock from the Kumdy-Kol area of the Kokchetav Massif were characterized using micro-FT-IR spectroscopy. The presence of supersilicic titanite is evidence of ultra-high pressure (UHP) metamorphic conditions of at least 6 GPa. Significant amounts of hydroxyls were detected suggesting that supersilicic titanite crystallized in an H2O-rich environment at a depth of >200 km. Clinopyroxenes coexisting with supersilicic titanite contain exsolved K-feldspar and phengite lamellae and were classified into three types on the basis of exsolved lamellae texture. Hydroxyl was identified in types A and B, but was not present in type C. The variety of reintegrated hydroxyl contents in clinopyroxenes reflected the differences of H2O activities when they crystallized: type C formed at extremely low H2O activities; type B crystallized at high H2O activities; and type A formed under a range of conditions from high (pyroxene cores) to low (pyroxene mantles) H2O activities. Clinopyroxenes recorded local heterogeneity of H2O activity on the scale of individual grains during UHP metamorphism and represent the best indicator of H2O activity. The fluid environment is an important factor attending petrogenesis during UHP metamorphism. Variations in abundance of hydroxyl in UHP clinopyroxene can be used to clarify fluid environments at great depths.

    Original languageEnglish
    Pages (from-to)133-149
    Number of pages17
    JournalInternational Geology Review
    Volume56
    Issue number2
    DOIs
    Publication statusPublished - 2014 Jan 25

    Fingerprint

    titanite
    diamond
    clinopyroxene
    ultrahigh pressure metamorphism
    garnet
    pyroxene
    rock
    phengite
    fluid
    petrogenesis
    feldspar
    texture
    spectroscopy
    mantle

    Keywords

    • HO activity
    • Hydroxyl
    • Kokchetav Massif
    • Micro-FT-IR
    • Nominally anhydrous minerals
    • Northern Kazakhstan
    • Supersilicic titanite
    • UHP metamorphism

    ASJC Scopus subject areas

    • Geology

    Cite this

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    title = "Hydroxyl in clinopyroxene and titanite in a UHP diamond-free garnet-clinopyroxene rock from the Kokchetav Massif, northern Kazakhstan",
    abstract = "Hydroxyls in clinopyroxene and supersilicic titantite in diamond-free garnet-clinopyroxene rock from the Kumdy-Kol area of the Kokchetav Massif were characterized using micro-FT-IR spectroscopy. The presence of supersilicic titanite is evidence of ultra-high pressure (UHP) metamorphic conditions of at least 6 GPa. Significant amounts of hydroxyls were detected suggesting that supersilicic titanite crystallized in an H2O-rich environment at a depth of >200 km. Clinopyroxenes coexisting with supersilicic titanite contain exsolved K-feldspar and phengite lamellae and were classified into three types on the basis of exsolved lamellae texture. Hydroxyl was identified in types A and B, but was not present in type C. The variety of reintegrated hydroxyl contents in clinopyroxenes reflected the differences of H2O activities when they crystallized: type C formed at extremely low H2O activities; type B crystallized at high H2O activities; and type A formed under a range of conditions from high (pyroxene cores) to low (pyroxene mantles) H2O activities. Clinopyroxenes recorded local heterogeneity of H2O activity on the scale of individual grains during UHP metamorphism and represent the best indicator of H2O activity. The fluid environment is an important factor attending petrogenesis during UHP metamorphism. Variations in abundance of hydroxyl in UHP clinopyroxene can be used to clarify fluid environments at great depths.",
    keywords = "HO activity, Hydroxyl, Kokchetav Massif, Micro-FT-IR, Nominally anhydrous minerals, Northern Kazakhstan, Supersilicic titanite, UHP metamorphism",
    author = "Kunihiko Sakamaki and Yoshihide Ogasawara",
    year = "2014",
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    doi = "10.1080/00206814.2013.819965",
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    TY - JOUR

    T1 - Hydroxyl in clinopyroxene and titanite in a UHP diamond-free garnet-clinopyroxene rock from the Kokchetav Massif, northern Kazakhstan

    AU - Sakamaki, Kunihiko

    AU - Ogasawara, Yoshihide

    PY - 2014/1/25

    Y1 - 2014/1/25

    N2 - Hydroxyls in clinopyroxene and supersilicic titantite in diamond-free garnet-clinopyroxene rock from the Kumdy-Kol area of the Kokchetav Massif were characterized using micro-FT-IR spectroscopy. The presence of supersilicic titanite is evidence of ultra-high pressure (UHP) metamorphic conditions of at least 6 GPa. Significant amounts of hydroxyls were detected suggesting that supersilicic titanite crystallized in an H2O-rich environment at a depth of >200 km. Clinopyroxenes coexisting with supersilicic titanite contain exsolved K-feldspar and phengite lamellae and were classified into three types on the basis of exsolved lamellae texture. Hydroxyl was identified in types A and B, but was not present in type C. The variety of reintegrated hydroxyl contents in clinopyroxenes reflected the differences of H2O activities when they crystallized: type C formed at extremely low H2O activities; type B crystallized at high H2O activities; and type A formed under a range of conditions from high (pyroxene cores) to low (pyroxene mantles) H2O activities. Clinopyroxenes recorded local heterogeneity of H2O activity on the scale of individual grains during UHP metamorphism and represent the best indicator of H2O activity. The fluid environment is an important factor attending petrogenesis during UHP metamorphism. Variations in abundance of hydroxyl in UHP clinopyroxene can be used to clarify fluid environments at great depths.

    AB - Hydroxyls in clinopyroxene and supersilicic titantite in diamond-free garnet-clinopyroxene rock from the Kumdy-Kol area of the Kokchetav Massif were characterized using micro-FT-IR spectroscopy. The presence of supersilicic titanite is evidence of ultra-high pressure (UHP) metamorphic conditions of at least 6 GPa. Significant amounts of hydroxyls were detected suggesting that supersilicic titanite crystallized in an H2O-rich environment at a depth of >200 km. Clinopyroxenes coexisting with supersilicic titanite contain exsolved K-feldspar and phengite lamellae and were classified into three types on the basis of exsolved lamellae texture. Hydroxyl was identified in types A and B, but was not present in type C. The variety of reintegrated hydroxyl contents in clinopyroxenes reflected the differences of H2O activities when they crystallized: type C formed at extremely low H2O activities; type B crystallized at high H2O activities; and type A formed under a range of conditions from high (pyroxene cores) to low (pyroxene mantles) H2O activities. Clinopyroxenes recorded local heterogeneity of H2O activity on the scale of individual grains during UHP metamorphism and represent the best indicator of H2O activity. The fluid environment is an important factor attending petrogenesis during UHP metamorphism. Variations in abundance of hydroxyl in UHP clinopyroxene can be used to clarify fluid environments at great depths.

    KW - HO activity

    KW - Hydroxyl

    KW - Kokchetav Massif

    KW - Micro-FT-IR

    KW - Nominally anhydrous minerals

    KW - Northern Kazakhstan

    KW - Supersilicic titanite

    KW - UHP metamorphism

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    EP - 149

    JO - International Geology Review

    JF - International Geology Review

    SN - 0020-6814

    IS - 2

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