Abstract The 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.

Abstract The Bhatwari Gneiss of Bhagirathi Valley in the Garhwal Himalaya is a Paleoproterozoic crystalline rock from the Inner Lesser Himalayan Sequence. On the basis of field and petrographic analyses, we have classified the Bhatwari Gneiss into two parts: the Lower Bhatwari Gneiss (LBG) and the Upper Bhatwari Gneiss (UBG). The geochemical signatures of these rocks suggest a monzonitic protolith for the LBG and a granitic protolith for the UBG. The UBG has a calc-alkaline S-type granitoid protolith, whereas the LBG has an alkaline I-type granitoid protolith; the UBG is more fractionated. The trace element concentrations suggest a volcanic arc setting for the LBG and a within-plate setting for the UBG. The U–Pb geochronology of one sample from the LBG gives an upper intercept age of 1988 ± 12 Ma (n = 10, MSWD = 2.5). One sample from the UBG gives an upper intercept age of 1895 ± 22 Ma (n = 15, MSWD = 0.82), whereas another sample does not give any upper intercept age, but indicates magmatism from c. 1940 to 1840 Ma. Based on these ages, we infer that the Bhatwari Gneiss has evolved due to arc magmatism and related back-arc rifting over a time period of c. 100 Ma during the Proterozoic. This arc magmatism is related to the formation of the Columbia supercontinent.