Thermal Modification of the Northwest Indian Shield: As Evidenced by Integrated Geopotential Modelling

The architecture of the continental lithospheric mantle is vital for understanding the wide-ranging processes that govern the creation of Earth's continents. The present investigation delineates the crustal and lithospheric boundaries underneath northwest India, which provides essential constraints as an imprint of tectonomagmatic events under the distinct tectonic setting. This study integrates three data sets (gravity, geoid, and topography data) and thermal parameters in a three-dimensional inversion algorithm to northwest India. Inversion results are constrained by available passive seismic crustal thickness, which we are using as a priori information. Our modelling results show crust down to a depth of 33 to 39 km in the Saurashtra and Kachchh region, which increases gradually to about 40 km beneath the Jaisalmer region. The deepest Moho at about 42-45 km is found under the Aravalli-Delhi fold belt and Indo-Gangetic plain. A comparable crustal thickness of 41-44 km is observed beneath the Bundelkhand craton. The mean crustal density varies laterally between 2850 and 2890 kg/m(-3) in the study area. The lithosphere-asthenosphere boundary (LAB) is 115-145 km deep under Saurashtra and Kachchh regions, which remains comparable under the Barmer-Pokharan region (130-160 km). A moderate LAB depth under the Aravalli-Delhi fold belt (140-180 km) and relatively deeper under the Bundelkhand craton (175 to 185 km) reaches over 200 km below the Indo-Gangetic plain. The thinned lithosphere beneath the Kachchh, Saurashtra, and Barmer-Pokhran regions, crisscrossed by two different rift systems, together with the dominance of the volcanic centres of two major magmatic episodes, and the possible presence of a low-velocity zone in the subcrustal upper mantle region suggest a genetic link between the evolution and the multistage thermal modification of the mantle lithosphere of this region.