Tectono-metamorphic evolution of high-P/T and low-P/T metamorphic rocks in the Tia Complex, southern New England Fold Belt, eastern Australia: Insights from K-Ar chronology

Shiro Fukui, Tatsuki Tsujimori, Teruo Watanabe, Tetsumaru Itaya

    Research output: Contribution to journalArticle

    9 Citations (Scopus)

    Abstract

    The Tia Complex in the southern New England Fold Belt is a poly-metamorphosed Late Paleozoic accretionary complex. It consists mainly of high-P/low-T type pumpellyite-actinolite facies (rare blueschist facies) schists, phyllite and serpentinite (T=300. °C and P=5. kbar), and low-P/high-T type amphibolite facies schist and gneiss (T=600. °C and P<5. kbar) associated with granodioritic plutons (Tia granodiorite). White mica and biotite K-Ar ages distinguish Carboniferous subduction zone metamorphism and Permian granitic intrusions, respectively. The systematic K-Ar age mapping along a N-S traverse of the Tia Complex exhibits a gradual change. The white mica ages become younger from the lowest-grade zone (339. Ma) to the highest-grade zone (259. Ma). In contrast, Si content of muscovite changes drastically only in the highest-grade zone. The regional changes of white mica K-Ar ages and chemical compositions of micas indicate argon depletion from precursor high-P/low-T type phengitic white mica during the thermal overprinting and recrystallization by granitoids intrusions. Our new K-Ar ages and available geological data postulate a model of the eastward rollback of a subduction zone in Early Permian. The eastward shift of a subduction zone system and subsequent magmatic activities of high-Mg andesite and adakite might explain formation of S-type granitoids (Hillgrove suite) and coeval low-P/high-T type metamorphism in the Tia Complex.

    Original languageEnglish
    Pages (from-to)62-69
    Number of pages8
    JournalJournal of Asian Earth Sciences
    Volume59
    DOIs
    Publication statusPublished - Oct 1 2012

    Keywords

    • Accretionary complex
    • Eastern Australia
    • High-P/T schists
    • K-Ar mica ages
    • Mica chemistry
    • New England Fold Belt
    • Pacific-type orogeny
    • Thermal overprinting
    • Tia Complex

    ASJC Scopus subject areas

    • Geology
    • Earth-Surface Processes

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