SHRIMP U-Pb c. 1860 Ma anorogenic magmatic signatures from the NW Himalaya: implications for Palaeoproterozoic assembly of the Columbia Supercontinent

Abstract

AbstractThe basal parts of the Higher Himalayan Crystallines (HHC), Lesser Himalayan sedimentary sequences and mylonite zone at the base of Main Central Thrust (MCT) within the NW Himalaya clearly demonstrate anorogenic magmatic signatures at around 1860 Ma, as indicated by SHRIMP U–Pb zircon ages from Bandal granitoids, Kulu–Bajura mylonite and Wangtu granitoids along the Sutlej Valley, Himachal Pradesh. Some of the zircon crystals contain older cores mostly extending back to 2600 Ma. We report for the first time a 3000 Ma old zircon core from Wangtu granitoids, which indicates reworking of ensialic Archaean crust during the assembly of the Columbia Supercontinent between 2.1 and 1.8 Ga. During the Himalayan collisional tectonics, the reworked Archaean and Palaeoproterozoic crust was imbricated and placed adjacent to each other in the Higher Himalayan Crystallines, the Inner Lesser Himalayan window zone and the Kulu–Bajura Nappe.