Tectono-metamorphic evolution of Mafic Granulite from South Delhi Terrane, Aravalli Delhi Mobile Belt, Northwestern India: Constraints from Pseudosection Modelling and Geochemical Study

The granulite facies rocks of the Balaram area within the South Delhi Terrane of the Aravalli Delhi Mobile Belt (ADMB) provide valuable insights into the deeper levels of Earth's crust. These mafic granulite exhibit a mineral assemblage of orthopyroxene, clinopyroxene, and plagioclase, with accessory ilmenite, magnetite, and rutile. Petrological investigations reveal symplectite and corona textures, reflecting a range of P-T conditions during metamorphism. Using Perple_X software for pseudosection modeling within the NCKFMASHTO system, the peak P-T conditions for mafic granulite formation were determined to be 7.6kbar and 770°C, respectively, following a clockwise metamorphic path. The Balaram mafic granulite show high concentrations of rare earth elements (REE), ranging from 86.26 to 314.90ppm. Assuming an isochemical metamorphic process likely driven by a hybrid mechanism involving mantle-derived and sialic magmas, the precursor materials are inferred to be low-clay ancient basement rocks, rich in clinopyroxene, such as basalt or gabbro. Geodynamic reconstructions suggest a shift from extensional to compressional regimes, with lithospheric extension facilitating partial melting of mantle material. The granulites likely formed through hybridization of mantle-derived and sialic magmas, with crustal rock assimilation during magma ascent. Tectonic settings inferred from Ti/Zr and (Zr/Y)/Y ratios indicate a combination of volcanic arc basalt and mid-ocean ridge basalt origins. This study provides significant insights into the petrogenesis and geodynamic evolution of the Balaram granulites within the ADMB. The mafic granulite suite indicates continental arc magmatism within the Delhi Supergroup, suggesting that the Aravalli mountain range evolved through continental collision and subduction during the upper Proterozoic era.