Discovery of coesite from Indus Suture Zone (ISZ), Ladakh, India: Evidence for deep subduction

Himanshu K. Sachani, Barun K. Mukherjee, Yoshihide Ogasawara, Shigenori Maruyama, Haruhito Ishida, Atsumi Muko, Nobuhiro Yoshioka

    Research output: Contribution to journalArticle

    69 Citations (Scopus)

    Abstract

    Coesite, the high-pressure polymorph of quartz has been identified for the first time in the Tso-Morari Crystalline Complex, Ladakh (India) in the Himalayan belt. The preservation of coesite grains as inclusions in garnet within eclogite boudins indicates the existence of UHP metamorphism in this continental collision setting. The coesite was identified optically and its presence confirmed by its characteristic Raman bands. Both coesite and polycrystalline quartz inclusions exhibit prominent radial fractures in their host garnet. The silica inclusions (monomineralic coesite, monomineralic quartz and bimineralic quartz+coesite) are associated with various textural features and well-developed chemical zonation within the garnet, which show the prograde nature of the UHP metamorphism. Preliminary P-T estimates suggest that the coesite growth took place at pressure > 28 kbar (> 90 km depth) and temperatures > 640°C. Significantly, the coesite inclusions are interpreted as having suffered decompression during exhumation without changing to quartz, most likely due to the rapid uplift. This finding also indicates deep subduction of the Indian plate beneath the Asian continent, The occurrence of coesite and subduction of the Indian plate was essentially governed by a low geothermal gradient which occurred prior to rapid exhumation. This was vital for generating the coherent picture of metamorphism and exposure of UHP rocks.

    Original languageEnglish
    Pages (from-to)235-240
    Number of pages6
    JournalEuropean Journal of Mineralogy
    Volume16
    Issue number2
    DOIs
    Publication statusPublished - 2004 Mar

    Keywords

    • Coesite
    • Garnet
    • Raman spectroscopy
    • Tso-Morari
    • UHP eclogite
    • Western Himalaya

    ASJC Scopus subject areas

    • Geochemistry and Petrology

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  • Cite this

    Sachani, H. K., Mukherjee, B. K., Ogasawara, Y., Maruyama, S., Ishida, H., Muko, A., & Yoshioka, N. (2004). Discovery of coesite from Indus Suture Zone (ISZ), Ladakh, India: Evidence for deep subduction. European Journal of Mineralogy, 16(2), 235-240. https://doi.org/10.1127/0935-1221/2004/0016-0235