Structural fabric of the Southern Indian shield as defined by gravity trends |
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| Authors: | Niraj Kumar AP Singh Bijendra Singh |
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| Institution: | 1. CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad 500007, India;2. Départment des Sciences de la Terre, UMR 8148 GEOPS, Université Paris-Sud, CNRS, Orsay, France;1. CSIR—National Geophysical Research Institute, Hyderabad 500007, India;2. Earth and Climate Science Program, Indian Institute of Science Education & Research—Pune, Homi Bhabha Road, Pune 411008, India;3. Indian Institute of Science Education & Research—Kolkata, Mohanpur 741246, West Bengal, India |
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| Abstract: | Southern Indian shield represents a mosaic comprised of several smaller structural domains separated by discrete shear zones. Here we present a horizontal Bouguer gravity gradient map of the Indian shield, south of 14 °N, to define a continental mosaic of gravity trends domains akin to structural domains. The gravity gradient image is based on 7862 newly collected observations merged with 6359 old gravity data. This combined dataset delineates structural boundaries of the five gravity domains related to the Eastern Dharwar Craton, the Eastern Ghats Mobile Belt, the extended Eastern Ghats Mobile Belt, the Southern Granulite Terrain, and the Western Dharwar Craton. Other belts of significant gravity gradients are found associated with the Eastern and the Western coasts. The loci of Closepet granite and Kolar schist belts do not manifest themselves as boundary zones between two distinct gravity domains of the Eastern Dharwar Craton. Lack of a gravity gradient across Karur–Oddanchatram–Kodaikanal and Karur–Kambam–Painavu–Trichur Shear Zones may be attributed to a lack of gravity measurements caused by difficulties in collecting data in topographically difficult terrain. The subdued gravity gradient across the Palghat–Cauvery Shear Zone and a weak gradient across the Achankovil Shear Zone indicates a lithological and/or morphological boundary rather than a terrane boundary. Alternatively, structural domains encompassing Palghat–Cauvery and Achankovil Shear Zones may have been in a neighbouring position during the Gondwana assembly, when Pan-African thermal perturbation reactivated the structures and reworked partly or totally obliterating earlier crustal fabric. |
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