Regional gravity field distribution over cratonic domains of the Indian shield: Implications for lithospheric evolution and destruction

Abstract

• Detailed analysis of regional gravity field over Indian cratons. • Extremely low Bouguer gravity of −120 mGal associated with Dharwar Craton. • Gravity field is largely positive over the north Indian cratonic segments. • Cratons with positive gravity have thinner lithosphere and higher heat flow. The nature of crust and lithospheric mantle evolution of the Archean shields and their subsequent destruction through intraplate tectonic processes are important in understanding continental dynamics and resources. The Indian shield, which has remained dynamic throughout the past for more than three billion years of geological history, is unique in terms of its lithospheric architecture compared to other Archean terranes on the globe. It consists of five major cratons, the Dharwar, Singhbhum, Bundelkhand, Bastar and Aravalli, which are separated by active rift valleys, mega lineaments and sutures zones. Here, we present a detailed analysis of gravity field over these areas, and their possible relationship with lithospheric thickness variations. Our results show a large variation in residual gravity field among the different cratons. A highly negative anomaly of around -70 mGal occurs over the western part of the Dharwar Craton, beneath which the lithosphere is about 160–200 km thick. In comparison, the anomalies are conspicuously positive, reaching around (i) +10 mGal over Central Dharwar Craton, Eastern Ghats Belt and the eastern part of Singhbhum Craton, (ii) +35 mGal over the Nellore Schist and Aravalli-Delhi Fold Belts, and (iii) +60 to +70 mGal over eastern part of SGT. In these regions, the lithosphere is markedly thinner between 70 and 135 km. Such areas have been associated with episodic magmatism, moderately high heat flow and elevated Moho temperatures, indicating a large-scale upwarping of isotherms leading to lithospheric destruction to the tune of 100–150 km, caused by mechanical, thermal and chemical erosion. Our study confirms that many of the Archean cratons on the globe, like the Indian shield, have undergone substantial erosion of their roots through subsequent geotectonic processes.