Geochemistry of the mafic dykes in parts of the Singhbhum granitoid complex: petrogenesis and tectonic setting

Singhbhum granitoid complex has been intruded by numerous mafic dykes trending in different directions. The studied dykes were originated from subalkaline magma, ranging in composition from basalt through basaltic-andesite to andesite. In the present work, the studied dykes are divided into two groups on the bases of abundance of SiO2, MgO, Al2O3, Ni, and Cr. The first one has higher Mg# than that of group II. These dykes have enriched incompatible trace element patterns. These are particularly enriched in the light rare earth elements and large ion lithophile elements with depleted high field strength elements (Nb, P, Ti). High Ba/Nb and Sr/P ratios of present mafic dykes are the indications of subduction signature. The geochemical characters of the back arc extension basalt tectonic setting is suggested for the studied dykes. Higher PM-normalized Th/Nb, Rb/Nb, and Ba/Nb ratios of studied samples support their non-plume source.