4.7 Article

PGE and isotopic characteristics of Shergol and Suru Valley Ophiolites, Western Ladakh: Implications for supra-subduction tectonics along Indus Suture Zone

Journal

GEOSCIENCE FRONTIERS
Volume 12, Issue 3, Pages -

Publisher

CHINA UNIV GEOSCIENCES, BEIJING
DOI: 10.1016/j.gsf.2020.11.014

Keywords

PGE; Nd-isotope; Mantle peridotites; Ophiolites; Ladakh; Neo-Tethys Ocean

Funding

  1. Council of Scientific and Industrial Research (CSIR), New Delhi
  2. DST-SERB, New Delhi

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The study of PGE geochemistry of mantle peridotites and Nd-isotope geochemistry of arc-related mafic rocks in the Indus Suture Zone (ISZ) in western Ladakh shows distinct characteristics indicating interaction between subduction zone tectonic settings and arc environments.
Present study reports the PGE-geochemistry of mantle peridotites and Nd-isotope geochemistry of arc related mafic rocks from the Indus Suture Zone (ISZ), western Ladakh. The total PGE concentration of the Shergol and Suru Valley peridotites (Sigma PGE = 96-180 ppb) is much higher than that of the primitive mantle and global ophiolitic mantle peridotites. The studied peridotites show concave upward PGE-distribution patterns with higher palladium-group PGE/Iridium-group PGE ratios (i.e., 0.8-2.9) suggesting that the partial melting is not the sole factor responsible for the evolution of these peridotites. The observed PGE-distribution patterns are distinct from residual/refractory mantle peridotites, which have concave downward or flat PGE-distribution patterns. Relative enrichment of palladium-group PGE as well as other whole-rock incompatible elements (e.g., LILE and LREE) and higher Pd/Ir ratio (1.1-5.9) reflects that these peridotites have experienced fluid/melt interaction in a supra-subduction zone (SSZ) tectonic setting. Also, the Shergol mafic intrusives and Dras mafic volcanics, associated with the studied peridotites, have high Nd-143/Nd-144 ratios (i.e., 0.512908-0.513078 and 0.512901-0.512977, respectively) and positive epsilon(Nd(t)) (calculated for t = 140 Ma) values (i. e., +5.3 to +8.6 and + 5.1 to +6.6, respectively), indicating derivation from depleted mantle sources within an intra-oceanic arc setting, similar to Spongtang and Nidar ophiolites from other parts of Ladakh Himalaya. The transition from SSZ-type Shergol and Suru Valley peridotites to Early Cretaceous tholeiitic Shergol mafic intrusives followed by tholeiitic to calc-alkaline Drasmafic volcanics within the Neo-Tethys Ocean exhibit characteristics of subduction initiation mechanism analogous to the Izu-Bonin-Mariana arc system within western Pacific. (c) 2021 ChinaUniversity of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.

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