Mesoarchaean mafic–ultramafic Ikauna layered intrusion, Bundelkhand craton, India: geology, U–Th–Pb age (SHRIMP) and correlation

Abstract

ABSTRACT Mafic–ultramafic rocks, occurring as intrusions in the Ikauna area, are a well-differentiated complex comprising dunite (serpentinite), pyroxenite, gabbro, and gabbro-pegmatite in the southern Bundelkhand craton. This complex intruded into Palaeo-Mesoarchaean TTG and was cut by Neoarchaean granites. The age of a late stage in the formation of the layered intrusion is estimated at 2798 ± 17 Ma, based on the U – Th – Pb dating (SHRIMP) of zircons from pegmatitic gabbro. The presence of grains with Palaeo-Mesoarchaean cores among the zircons indicates the contamination of the gabbro with crustal TTG granitoids. Furthermore, zircons, altered hydrothermally in the Palaeoproterozoic, were revealed. Thus, the age dates for the zircons are in good agreement with the relative geological age of the intrusion and the crustal evolution of the Bundelkhand craton. No mafic – ultramafic layered intrusions, similar to the Ikauna layered intrusion, have been reported from other cratons in the Indian Shield, but Keshargaria Swarm dykes of similar age (2800 ± 0.7 Ma) have been described from the Singhbhum craton.