Archean sedimentation on Dharwar Craton, India and its implications

Abstract

The Dharwar Craton is the largest Archean cratonic nuclei of India and is made up of western and eastern blocks separated by the 2.5 Ga Closepet granite batholith. The Western Dharwar Craton consists mostly of 3.3–3.0 Ga TTG (the Peninsular Gneissic Complex), older Mesoarchean greenstone (Sargur type) and younger Neorchean greenstone (the Dharwar Supergroup, comprising of lower Bababudan and upper Chitradurga Groups). In contrast, the Eastern Dharwar Craton is mostly made of granitoid gneisses and felsic volcanics with some Neorchean supracrustal enclaves (Sandur, Ramgiri, Kolar-Kadri Schist belts). Recently it has been suggested that the Dharwar cratonic block is formed by assembly of western, central and eastern micro-blocks separated by shear zones (Jayananda et al., 2018). The greenstone successions are present in all three Dharwar micro-blocks. However, the proportion of greenstones is much higher and the quality of preservation is much better in the western micro-block.The Mesoarchean Sargur Group hosts barite deposit and consists of fuchsite quartzites, carbonates, metapelites, banded iron formations and metamorphosed basalts and komatiites. Researchers have postulated a platformal (orthoquartzite-carbonate-pelite) association for the Sargur Group; some researchers examined the barite deposits of the Sargur Group and inferred a subaerial volcanism during the Sargur sedimentation. The Neoarchean Bababudan Group comprises largely terrestrial to shallow marine sedimentary successions, glacial deposits, BIF, volcanic and volcaniclastics rocks. In contrast, the overlying Chitradurga Group comprises conglomerates, greywackes, phyllites, carbonates BIFs, cherts, shales, associated with a variety of volcanic rocks ranging from pillowed basalts to rhyolites and indicates relatively deep water sedimentation in a subsiding basin in an active continental margin setting. Stromatolites are abundant in the Chitradurga Group as also in other Neoarchean supracrustal successions of the Dharwar craton. In this review we have critically synthesized published sedimentological data from both older as well as younger greenstone successions of the Dharwar craton and have presented the Archean sedimentation history of the Dharwar craton. We have highlighted the research gaps that researchers may find helpful.