Paleoarchean surface processes and volcanism: Insights from the eastern Iron Ore Group, Singhbhum craton, India

The Singhbhum craton of eastern India contains an almost continuous depositional record from the Paleoarchean to the Neoproterozoic. Although researchers have examined the Mesoarchean to Neoproterozoic geological history in the last decade, the Paleoarchean sedimentological inventory is poor and the crust-mantle interaction is poorly constrained. Here we present new sedimentological data from the Paleoarchean-early Mesoarchean eastern Iron Ore Group (EIOG) from the Singhbhum craton, India and critically synthesize the earlier published data to constrain the depositional setting of the EIOG succession. Two distinct facies associations characterize the EIOG succession: while the lower facies association is marine and indicates initial shallowing and subsequent deepening of the sea level, the upper facies association is terrestrial (alluvial fan-fluvial) with an unconformable lower contact. The upper facies association formed because of continental emersion at around 3300 Ma. The ultramafic (komatiite)-mafic (minor felsic) volcanic rocks indicate mantle plume activity and crustal contamination. Carbon isotopic analysis of the carbonaceous matter (CM) preserved within the lower facies association reveals that these are syngenetic with the host rock without any evidence of migration of bitumen and modern organic contamination. A peak metamorphic temperature around 450 ± 50 °C is inferred from Raman spectroscopic analysis of the CM. Intensive paleobiological research is of paramount interest to decode the co-evolution of life and environment and the mysteries of early Earth.