Abstract:
Cratons are the oldest parts of continents with cold and thick, high velocity, depleted lithosphere, which remained stable for billions of years. However, many of them are susceptible to deformation and erosion under various geological settings, such as near subduction zones and above mantle plumes. The role of mantle plumes in eroding the overlying lithosphere remains elusive, particularly for the fast-moving cratons. In this study, we examine the plume-lithosphere interaction in the Dharwar Craton located in South India by comparing the lithospheric property derived from the diamondiferous kimberlite xenoliths with its present-day shear velocity structure computed from collocated seismological data. The lithosphere-asthenosphere system beneath a 200 km long profile is explored at 13 locations through joint inversion of receiver function and surface wave phase dispersion data. The velocity model suggests 165 ± 15 km thick present-day lithosphere, marginally lower than 180 ± 20 km derived from the kimberlite xenoliths which erupted around 1100 Myr. The velocity increases from the Moho to ∼100 km depth, possibly due to the spinel-garnet peridotite transformation. The cold cratonic lithosphere of Eastern Dharwar craton (EDC) is manifested in very high shear velocities, up to >4.7 km/s indicating harzburgite-dunite composition, correlating well with the composition inferred from analysis of xenolith data. Our result suggests no significant thermal alteration to the lithosphere of the eastern Dharwar Craton despite being affected by three mantle plumes in the last 90 Myr.