The depositional history of the Himalayas has been overprinted by the tectonic activities during the Himalayan Orogeny. A detailed investigation of the sedimentary units can provide crucial information regarding their depositional history and provenance.This study aims at constraining the weathering history, tectonic setting, and provenance of meta-sediments from the Shimla and Chail Groups of Outer Lesser Himalaya. With similar major element chemistry, these meta-sediments comprise a low-silica group (avg. SiO 2 /Al 2 O 3 <3.29). Weathering intensity parameters chemical index of alteration (CIA), plagioclase index of alteration (PIA) and index of chemical variability (ICV) range from 62 to 78 (avg. = 69.41), 70 to 96 (avg. = 85.34), and 0.45 to 1.45 (avg. = 1.01), respectively indicating moderate to severe degrees of weathering. Transition element ratios [Cr/V (1.68-5.18), Ni/Co (1.47-30.99), and V/Ni (0.87-4.61)], and trace element bivariate plots suggest a recycled, felsic to intermediate provenance that has primarily been derived from Post-Archean sources with minor inputs from Archean units. A passive margin depositional setting with arcderived sources is suggested for the Chail and Shimla meta-sediments. Rare-earth element patterns reveal similarities between the studied metasediments with TTG gneisses and sanukitoids from the Aravalli and Bundelkhand Cratons, as well as Chaur and Jutogh granitoids. Therefore, Neoproterozoic Himalayan granitoids and ArcheanAravalli-Bundelkhand granitoids (TTGs and high-K granitoids) could be potential sources of these meta-sediments, as also suggested by the detrital zircon age distribution from the Beas-Satluj-Pabbar valleys and Shimla Group.
The present study reports the geochemical composition of Sewariya two-mica granites (SG) and Govindgarh granites (GG) intruding rocks of Delhi Supergroup along the western margin of South Delhi Fold Belt in Rajasthan, India. Both granite varieties are highly evolved possessing high SiO 2 , Al 2 O 3 , low MgO, CaO, Fe 2 O 3 , Ni, Cr and V and are calc-alkaline in nature. In chondrite normalized REE diagrams, SG are characterized by highly fractionated REE patterns (avg La N / Yb N = 21.45) and sharp negative Eu anomaly (Eu/ Eu* = 0.25), whereas GG do not show significant REE fractionated patterns (avg La N /Yb N = 3.31) and have variable Eu anomalies. From primitive mantle normalized multi-element diagrams, crustal signatures (low Nb, Ti and high Pb, U, Th) can be inferred for both the granitoid varieties. Also, strong peraluminous nature, high A/CNK, normative corundum and abundant mica content point towards a (meta)sedimentary protolith for them. An arc setting is indicated by their calc-alkaline nature; volcanic arc or syncollisional affinities in tectonic discriminant diagrams (Nb versus Y; Rb versus Nb + Y). They are peraluminous leucogranites derived from crustal melts with little mantle contribution as is evident from their mineralogy and geochemical characteristics. The anatectic conditions prevalent during the formation of these granites differed with SG being formed under dehydration conditions, while the formation of GG involved fluid-present melting reactions.
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