Geochemistry and Petrogenesis of Jasrapura Granitoid, North Khetri Copper Belt, Rajasthan: Evidence for Island Arc Magmatism

The Jasrapura granitoid intrudes the rocks of Proterozoic Delhi Supergroup in the northern part of the Khetri Copper Belt (KCB), Rajasthan. It forms a lenticular sheet like body, exposed in the core of an NNE-SSW ) trending anticline formed by the Alwar feldspathic quartzite. Quartz, microcline, microcline-perthite, plagioclase and biotite are the main mineral constituents while titanite, magnetite, allanite and epidote occur as accessory minerals. The Jasrapura granitoid has been characterised as peraluminous, I-type, calc-alkaline granite with subordinate granodioritic component. Various petrological and geochemical parameters collectively indicate its fractionation-related petrogenesis from magma generated in the mantle wedge overlying the subduction zone. The calc-alkaline trend of evolution, high K₂O/Na₂O ratios, enriched incompatible trace elements (Rb, Ba, Th, U, etc), flat HREE profiles, low (La/Yb)_N, ratios and high Yb_N values of Jasrapura granitoid compare favourably with the post-Archaean arc granitoids. The trace element tectonic discrimination diagrams and spidergrams suggest an island arc tectonic regime for the Jasrapura granitoid.