Geochemistry of meta‐sediments from Neoproterozoic Shimla and Chail Groups of Outer Lesser Himalaya: Implications for provenance, tectonic setting, and paleo‐weathering conditions

Abstract

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. SiO2/Al2O3 <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 arc-derived 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 Archean Aravalli-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.