Orthopyroxene + sillimanite predating sapphirine + quartz

A rare case of ultrahigh-temperature metamorphism from the central zone, limpopo complex, South Africa

Georgy A. Belyanin, H. M. Rajesh, Krishnan Sajeev, Dirk D. Van Reenen

    Research output: Contribution to journalArticle

    3 Citations (Scopus)

    Abstract

    Sapphirine + quartz and orthopyroxene + sillimanite occur in garnet from an Mg-Al granulite from the Central Zone of the Limpopo Complex in South Africa. Textural evidence and a chemical gradient in garnet between the zones preserving the inclusions argue for the formation of sapphirine + quartz after orthopyroxene + sillimanite. Petrological observations, pressure-temperature phase diagrams, and compositional and model proportion results on isopleths indicate the sapphirine + quartz + garnet + orthopyroxene (high-Al) assemblage as the peak metamorphic assemblage (~1050 °C at ~8.5 kbars), whereas orthopyroxene (low-Al) + sillimanite represents the prograde stage (at ca. 900 °C at ~8.5 kbars). Our report of these two diagnostic ultrahigh-temperature mineral assemblages in garnet from an Mg-Al granulite is unique, given the rare occurrence of sapphirine + quartz postdating orthopyroxene + sillimanite assemblage in granulites.

    Original languageEnglish
    Pages (from-to)1153-1163
    Number of pages11
    JournalCanadian Mineralogist
    Volume50
    Issue number5
    DOIs
    Publication statusPublished - Oct 2012

    Fingerprint

    ultrahigh temperature metamorphism
    sapphirine
    Quartz
    Garnets
    sillimanite
    orthopyroxene
    quartz
    garnet
    granulite
    Temperature
    Phase diagrams
    Minerals
    temperature
    diagram
    Africa
    mineral

    All Science Journal Classification (ASJC) codes

    • Geochemistry and Petrology

    Cite this

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    abstract = "Sapphirine + quartz and orthopyroxene + sillimanite occur in garnet from an Mg-Al granulite from the Central Zone of the Limpopo Complex in South Africa. Textural evidence and a chemical gradient in garnet between the zones preserving the inclusions argue for the formation of sapphirine + quartz after orthopyroxene + sillimanite. Petrological observations, pressure-temperature phase diagrams, and compositional and model proportion results on isopleths indicate the sapphirine + quartz + garnet + orthopyroxene (high-Al) assemblage as the peak metamorphic assemblage (~1050 °C at ~8.5 kbars), whereas orthopyroxene (low-Al) + sillimanite represents the prograde stage (at ca. 900 °C at ~8.5 kbars). Our report of these two diagnostic ultrahigh-temperature mineral assemblages in garnet from an Mg-Al granulite is unique, given the rare occurrence of sapphirine + quartz postdating orthopyroxene + sillimanite assemblage in granulites.",
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    Orthopyroxene + sillimanite predating sapphirine + quartz : A rare case of ultrahigh-temperature metamorphism from the central zone, limpopo complex, South Africa. / Belyanin, Georgy A.; Rajesh, H. M.; Sajeev, Krishnan; Van Reenen, Dirk D.

    In: Canadian Mineralogist, Vol. 50, No. 5, 10.2012, p. 1153-1163.

    Research output: Contribution to journalArticle

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    AU - Sajeev, Krishnan

    AU - Van Reenen, Dirk D.

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    N2 - Sapphirine + quartz and orthopyroxene + sillimanite occur in garnet from an Mg-Al granulite from the Central Zone of the Limpopo Complex in South Africa. Textural evidence and a chemical gradient in garnet between the zones preserving the inclusions argue for the formation of sapphirine + quartz after orthopyroxene + sillimanite. Petrological observations, pressure-temperature phase diagrams, and compositional and model proportion results on isopleths indicate the sapphirine + quartz + garnet + orthopyroxene (high-Al) assemblage as the peak metamorphic assemblage (~1050 °C at ~8.5 kbars), whereas orthopyroxene (low-Al) + sillimanite represents the prograde stage (at ca. 900 °C at ~8.5 kbars). Our report of these two diagnostic ultrahigh-temperature mineral assemblages in garnet from an Mg-Al granulite is unique, given the rare occurrence of sapphirine + quartz postdating orthopyroxene + sillimanite assemblage in granulites.

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