Petrogenesis of metavolcanics and detrital zircon geochronology of the Mesoarchean western Iron Ore Group supracrustals, Singhbhum Craton (India): Evidence for an intracontinental extension setting

Abstract

The Singhbhum Craton of eastern India, consisting of well-preserved Paleo- to Mesoarchean granitoids, volcanic and sedimentary rocks, is an excellent archive of early earth processes. In this contribution, we investigated the geological evolution of the Noamundi-Jamda-Koira IOG Basin (WIOG) using detrital zircon U-Pb ages, whole rock geochemical and Nd isotopic data on metavolcanic rocks from this belt including the Jagannathpur volcanics. The metavolcanics of the WIOG and Jagannathpur are compositionally basaltic andesites with enriched LREE and negative anomalies of Nb-Ta and Ti. The ratios of crustal contamination sensitive elements such as La/Sm, Sm/Nd, Nb/La, Th/Yb and Nb/Yb are close to that of bulk continental crust. The Nd isotopic composition of these basaltic andesites are broadly chondritic (εNdt = +0.93 to −1.20). The geochemical and isotopic signatures are consistent with significant assimilation of Paleoarchean granitoids of the Singhbhum Craton. The overlapping geochemical and isotopic compositions support the view that Jagannathpur volcanics is an eastward extension of the ∼3.04 Ga WIOG metavolcanics and shouldn’t be considered as a separate stratigraphic unit. The presence of pillowed structures, vesicularity, absence of volcanic breccia, and their association with clastic sediments clearly indicate a subaqueous and shallow marine eruption for the WIOG basaltic andesites. The deposition of clastic sediments before basaltic magmatism points towards lithospheric thinning and basin opening. The detrital zircon ages from the WIOG ranges from 3.51 to 2.96 Ga and the detritus was mainly sourced from the adjacent Singhbhum granite and Bonai granite. The petrogenesis of the WIOG metavolcanics can be attributed to assimilation-fractional crystallisation of a depleted mantle derived tholeiitic mafic-ultramafic magma in an intracontinental extension setting.