Occurrence and field relationships of ultrahigh-pressure metagranitoid and coesite eclogite in the Su-Lu terrane, eastern China

S. R. Wallis, Akira Ishiwatari, T. Hirajima, K. Ye, J. Guo, D. Nakamura, T. Kato, M. Zhai, M. Enami, B. Cong, S. Banno

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    92 Citations (Scopus)

    Abstract

    Coesite eclogite is associated with metagranitoid in a 50 × 100 m2 outcrop within the regionally developed amphibolite-facies Su-Lu orthogneiss. Primary intrusive relationships between the metagranitoid and basic rocks and bulk-chemistry analyses show that together they represent a composite igneous body that has subsequently been strongly deformed and metamorphosed. The presence of rutile, sodic pyroxene, corona garnet, and possible pseudomorphs after coesite all suggest very high pressures of metamorphism in the metagranitoid. This is the first documented occurrence of ultrahigh-pressure (UHP) metagranitoid outside of the European Alps. The existence of UHP metagranitoid shows that low density of rocks does not necessarily prevent subduction to mantle depths. Even at peak metamorphic conditions the UHP composite igneous body reported here would have a bulk density less than the mantle. Buoyancy forces may, therefore, have been important in the early exhumation of this unit. Other outcrops of coesite eclogite in the Su-Lu region may also have been originally metamorphosed along with low-density granitoid rocks.

    Original languageEnglish
    Pages (from-to)45-54
    Number of pages10
    JournalJournal of the Geological Society
    Volume154
    Issue number1
    DOIs
    Publication statusPublished - 1997 Jan 1

    Keywords

    • China
    • Coesite
    • Eclogite
    • High pressure
    • Metagranite

    ASJC Scopus subject areas

    • Geology

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    Wallis, S. R., Ishiwatari, A., Hirajima, T., Ye, K., Guo, J., Nakamura, D., Kato, T., Zhai, M., Enami, M., Cong, B., & Banno, S. (1997). Occurrence and field relationships of ultrahigh-pressure metagranitoid and coesite eclogite in the Su-Lu terrane, eastern China. Journal of the Geological Society, 154(1), 45-54. https://doi.org/10.1144/gsjgs.154.1.0045