Crust-Mantle Structure And Lithospheric Destruction Of The Oldest Craton In The Indian Shield

The Singhbhum craton is among the five Archean cratons of Peninsular India that preserves some of the oldest continental nuclei. In this work, we present a new and complete Bouguer gravity map of this craton with insights into its deep crust-mantle structure, lithospheric thickness and density variations beneath this craton. The conspicuous presence of high-order residual gravity low anomalies, together with low estimated densities, suggests voluminous presence of Singhbhum granitic batholiths that built the dominant crustal architecture. The isolated residual gravity highs correspond to the mafic and ultramafic volcanic suites like, Dhanjori, Simlipal and Dalma, while the relatively low gravity anomalies observed over the western volcanic suites like Malangtoli, Jagannathpur and Ongarbira, indicate their relatively felsic nature. The estimated lithospheric thickness of about similar to 130 km below the granitic batholithic region, and about 112 km beneath the Precambrian volcanic terranes, together with low effective elastic thickness (T-e,) of only about 31 km, suggest a thin and weak lithosphere. The craton witnessed extensive lithospheric destruction with the removal of nearly 100-150 km of the cratonic root. The decratonization may be linked to subduction during the Paleo-Mesoproterozoic period, together with mantle plumes at different times, suggesting a combined mechanical, thermal and chemical erosion of the cratonic keel.