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      https://www.ias.ac.in/article/fulltext/jess/119/03/0365-0381

    • Keywords

       

      South Andaman; serpentinite; geothermobarometry; zoned plagioclase; idealized ophiolite.

    • Abstract

       

      Field studies supplemented by petrographic analyses clearly reveal complete preservation of ophiolite suite from Port Blair (11° 39′ N: 92° 45′E) to Chiriyatapu (11° 30′ 24′′N: 92° 42′ 30′′E) stretch of South Andaman. The ophiolite suite reveals serpentinite at the base which is overlain unconformably by cumulate ultramafic–mafic members with discernible cumulus texture and igneous layering. Basaltic dykes are found to cut across the cumulate ultramafic–mafic members. The succession is capped by well exposed pillow basalts interlayered with arkosic sediments. Olivine from the basal serpentinite unit are highly magnesian (Fo80.1–86.2). All clinopyroxene analyses from cumulate pyroxenite, cumulate gabbro and basaltic dyke are discriminated to be ‘Quad’ and are uniformly restricted to the diopside field. Composition of plagioclase in different lithomembers is systematically varying from calcic to sodic endmembers progressively from cumulate pyroxenite to pillow basalt through cumulate gabbro and basaltic dyke. Plagioclase phenocrysts from basaltic dyke are found to be distinctly zoned (An60.7$–$An35.5) whereas groundmass plagioclase are relatively sodic (An33$–$An23.5). Deduced thermobarometric data from different lithomembers clearly correspond to the observed preservation of complete ophiolite suite.

    • Author Affiliations

       

      Abhishek Saha1 Avik Dhang1 Jyotisankar Ray1 Suvankar Chakraborty2 David Moecher2

      1. Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata 700 019, India.
      2. Department of Earth and Enviornmental Sciences, University of Kentucky, Lexington, Kentucky 40506, USA.
    • Dates

       
  • Journal of Earth System Science | News

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