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      Permanent link:
      https://www.ias.ac.in/article/fulltext/jess/123/08/1839-1855

    • Keywords

       

      Sylhet Traps; Shillong Plateau; Kerguelen; mantle plume.

    • Abstract

       

      In this study, mineralogical, geochemical, and isotopic data are presented for the Sylhet Trap at the southern flank of the eastern Shillong Plateau, northeastern India, to determine the magma genesis in relation to the Kerguelen plume mantle source. Sylhet Trap rocks are porphyritic tholeiite and have diverse chemical compositions from picro-basalt, basalt, andesite to dacite, but mostly are within the subalkaline field. Major and trace element data were used to identify two distinct magma fractionation trends, a low and medium K series, characterized by relatively flat MORB-like (analogous to Rajmahal Traps (II)) and enriched OIB chondrite-normalized Rare Earth Element (REE) patterns. Initial 87Sr/86Sr, 143Nd/144Nd$, and 206Pb/204Pb isotope compositions were widely varied, ranging from 0.70435–0.71357, 0.51196–0.51266, and 17.92–19.72, respectively, when compared with basalts from the West Bengal, the Rajmahal Traps and the Kerguelen plume. Correlations among isotopic and trace element ratios of the Sylhet Traps provide evidence for the involvement of (1) HIMU-like mantle component, (2) the Kerguelen plume-like component, and (3) EMII-like crustal component. Magma from the Sylhet Traps was originated from a melting that derived directly from the heterogeneous Kerguelen mantle plume (components 1 and 2), which strongly suggests the presence of the Kerguelen plume-head in the Bengal basin.

    • Author Affiliations

       

      Md Shofiqul Islam1 2 Daniel Meshesha1 3 Ryuichi Shinjo1

      1. Department of Physics and Earth Sciences, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan.
      2. Department of Petroleum and Mining Engineering, Shahjalal University of Science and Technology, Sylhet 3114, Bangladesh.
      3. EL MINING PLC, Addis Ababa, Ethiopia.

    • Dates

       
      Published
      December 2014
      Manuscript received
      26 August 2013
      Manuscript revised
      7 April 2014
      Accepted
      2 July 2014

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