Petrology, geochemistry and geochronology of granites and granite gneisses in the SE Karakoram, India: Record of subduct
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ORIGINAL PAPER
Petrology, geochemistry and geochronology of granites and granite gneisses in the SE Karakoram, India: Record of subduction-related and pre- to syn-kinematic magmatism in the Karakoram Fault Zone Shailendra Pundir 1 & Vikas Adlakha 1
&
Santosh Kumar 2 & Saurabh Singhal 3 & Koushik Sen 1
Received: 10 December 2019 / Revised: 12 March 2020 / Accepted: 24 March 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The granites and granite gneisses from a tectono-metamorphic complex exposed along the Shyok Valley in the Karakoram region, India, forms the southern margin of Asian plate in the India-Asia collision zone. These rocks have been subjected to mineralogical, geochemical, and U-Pb zircon geochronological investigations to constrain the petrogenetic and geodynamic evolution of the Karakoram terrane. Outcrop-scale observations reveal the presence of pre- and syn-kinematic leucogranite bodies intruded within the granites and granite gneisses. The foliation-parallel deformed leucogranite sill shows the dextral shear sense in an extensive metamorphic complex that is in concordance with the Karakoram Fault (KF) in the Ladakh region, NW India. Whole-rock elemental and biotite chemistry equivocally suggest subduction-related metaluminous (I-type) calc-alkaline nature for most of the host granites and gneisses, and generation of syn-collisional peraluminous (S-type) leucogranites through crustal anatexis of pre-existing rocks. The obtained U-Pb zircon ages for the granites, granite gneisses, deformed and undeformed leucogranites vary widely from ca. 160 Ma to 15 Ma and reveal: (a) the initiation of subduction of the Neo-Tethyan oceanic crust beneath the southern Asian Plate at least ~160 Ma ago, and (b) existence of continuous or intermittent deformation along ~1000 km long lithospheric scale dextral KF during ~27−15 Ma. Keywords Magmatism . Tectonism . Geochronology . Karakoram . India
Introduction The granites (sensu lato) from the accretionary orogens preserve the temporal records of magmatic events that may have been formed during subduction (e.g., Kumar et al. 2017 and references therein), continent-continent collision (e.g., Zhu Editorial handling: Q. Li Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00710-020-00706-y) contains supplementary material, which is available to authorized users. * Vikas Adlakha [email protected] 1
Structure and Tectonics Group, Wadia Institute of Himalayan Geology, 33 GMS Road, Dehradun, Uttarakhand 248001, India
2
Centre of Advanced Study, Department of Geology, Kumaun University, 263001 Nainital, Uttarakhand, India
3
Petrology and Geochemistry Group, Wadia Institute of Himalayan Geology, 33 GMS Road, Dehradun, Uttarakhand 248001, India
et al. 2015; Sen et al. 2017), and even post-collision shearing events (e.g., Phillips and Searle 2007; Boutonnet et al. 2012; Sen et al. 2014). Combined geochemical, structural, and geochronological investigations of deformed and undeformed granites allo
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