Provenance Characterisation and Tectonic Setting of Mesoproterozoic Alwar and Ajabgarh Quartzites in the Alwar-Jaipur Sub-basin, NW India

ABSTRACT The present study focuses on the characterisation of quartzites of Alwar-Jaipur sub-basin, one of the three subbasins of Proterozoic North Delhi Fold Belt in NW India, besides Bayana-Lalsot and Khetri sub-basins. The study aims to identify the provenance of the Alwar and Ajabgarh Group quartzites and to decipher their tectonic environment of deposition, using major, trace, and REE geochemistry. The Chemical Index of Alteration (CIA) values of 65.63, 72.13, 67.12, and 75.11 for the Rajgarh, Kankwarhi, Pratapgarh (Alwar Group), and Bharkol (Ajabgarh Group) formations, respectively, suggest a moderately weathered source for them. High Th and La contents, and high Th/Sc, Th/Co, and La/Sc ratios indicate derivation from felsic rocks, wherein LREE enrichment and pronounced negative Eu anomalies point to a feldspar-bearing granite-granodiorite provenance. The poorly sorted Rajgarh, Kankwarhi, and Pratapgarh quartzites were sourced from the nearby Archaean-Palaeoproterozoic granitoids, while the well-sorted, texturally mature Bharkol quartzites were derived from a more distal felsic source region with minor mafic input. Geochemical proxies suggest an active continental margin setting for the Pratapgarh Formation. The Rajgarh Formation quartzites show minor interlayers of mafic flows; however, geochemical characteristics suggest a passive margin setting. Proximal granitic rocks occurring at Ajitgarh, Barodiya, Viratnagar (Bairath), Harsora and Dadikar are interpreted as the most probable sources for the sedimentary detritus.