Petrochemistry, Petrogenesis and Geodynamic Implications of Mantle Plume Generated Dhanjori Volcanics, Singhbhum Craton (Eastern India)

Abstract

New geological and geochemical data have been presented in this paper to improve the understanding of the petrogenesis and regional geodynamic evolution of the 2.8–2.5 Ga Dhanjori volcanics. These volcanics exhibit porphyritic texture and classified as picritic basalt. The Dhanjori volcanics are MgO-rich (9.97–15.81 wt%) with moderate SiO₂ (51.62–53.82 wt%), FeO_T (9.97–12.57 wt%) and TiO₂ (0.73–1.21 wt%) but relatively higher Ni (123.56–545.35 ppm) and Cr (241.87–1158.41). The rare earth element (REE) patterns and their ratios indicate their derivation from the garnet to spinel stability field due to decompressive melting of a mantle plume head near the crust-mantle boundary, which is supported by the presence of high positive gravity anomaly over the Dhanjori lavas. The thermobarometric studies indicate that the primary magma had an initial mantle potential temperature between 1350 and 1500°C in a pressure range of 1 to 1.8 GPa, thus conforming with the mantle origin, which is further endorsed by supplementary geophysical studies.