India’s Fast Mesozoic Drift Linked to Continental Mantle Lithosphere Delamination: New Insights From (U-Th)/He Thermochronology of Dharwar Craton Kimberlites

English Abstract:

Periods of significant continental uplift and erosion are believed to be caused by processes that operate within Earth’s mantle. Among these processes are strong thermochemical upwelling and convective erosion of mantle lithosphere. Peninsular India is comprised of a collage of Archean cratonic blocks bounded by Proterozoic mobile belts. The basement blocks are overlain by remnants of thick sedimentary successions of Proterozoic basins ranging from 1.9 to possibly 0.7 Ga. Basin formation was accompanied by pronounced kimberlite magmatic activity across Peninsular India between 1.4-1.0 Ga. However, the tectonic setting of the Proterozoic basins and associated kimberlites remains poorly understood. In particular, the relationship to the coeval mobile belts, for which subduction processes have been invoked, is enigmatic. We are studying the (U-Th)/He systematics of a variety of kimberlite-derived minerals from across the Dharwar craton in an attempt to understand the burial and unroofing history of these small diamond-bearing magmatic bodies. Whereas previous studies suggested that basin inversion occurred during the Late Proterozoic, our novel perovskite (U-Th)/He thermochronology results suggest that the Dharwar craton crust was affected by nearby tectonothermal events during the Early Paleozoic assembly of Gondwana. Our apatite (U-Th)/He results indicate that diatreme root-zones of the once-buried 1.1 Ga Dharwar craton kimberlites were unroofed to within ~1 km of the Earth’s surface during the Mesozoic, most likely during the Early Cretaceous. This timing corresponds to the break-up of Gondwana after which the Indian plate drifted for several hundred kilometers with record speed toward its current position. India’s fast drift during the Mesozoic has been explained by significant plume-related delamination of its cratonic mantle lithosphere, which also appears to be the root-cause for km-scale uplift and erosion across Peninsular India during the Mesozoic.