Episodes 2020; 43(1): 346-357
Published online March 1, 2020
Copyright © International Union of Geological Sciences.
A.K. Jain1*, P.K. Mukherjee2 and Saurabh Singhal2
*1 CSIR-Central Building Research Institute, Roorkee-247667 (India)
#2 Wadia Institute of Himalayan Geology, Dehradun-248 001 (India)
*3 IUAC-National Geochron Facility, New Delhi 110067 (India)
Correspondence to:E-mail: firstname.lastname@example.org
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In the Himalaya, distinct terranes are juxtaposed across the Main Central Thrust Zone (MCTZ) where subthrust Inner Lesser Himalaya (iLH) sedimentary belt yielded nearly unimodal U-Pb detrital zircon (DZ) between 2.05 and 1.80 Ga. Within this thrust zone, orthomylonite and other lithologies represent the Proterozoic magmatic arc with zircon having U-Pb ~1.95 to 1.89 Ga crystallization ages; together, these represent the Columbian Supercontinent assembly. In contrast, first appearance of the Neoproterozoic 1.05-0.85 Ga zircon characterizes the overthrust Great Himalayan Sequence (GHS–Vaikrita Group) along the Main Central Thrust (MCT), while early Paleozoic detrital zirconhas first appearance in tectonically overlying Tethyan Himalayan Sequence (THS).
The iLH sediments were possibly derived both from a northernly ~1.9 Ga magmatic arc and the Archean- Proterozoic Aravalli-Bundelkhand nuclei of the Indian craton. Source rocks for Neoproterozoic zircon in the GHS—a distinct terrane in the Himalaya—may possibly be the Neoproterozoic magmatic bodies within the GHS and ‘In-board’ Aravalli-Delhi Fold Belt (ADMB)– Central Indian Tectonic Zone (CITZ), though northern ‘Off-board’ sources cannot be ruled out, altogether.