Insights into the evolution of the Dharwar craton, South India through three dimensional P-wave velocity imaging of upper mantle

The Dharwar craton in South India has a geological history of approximately 3.4 billion years with geological units varying in ages from mid-Archean to late Proterozoic. Post cratonization, three important geological events influenced the Dharwar craton: kimberlite eruption at 1100 Ma, India-Antarctica separation at - 120 Ma and separation of India from Madagascar at - 85 Ma. We investigate the deep structure and evolution of the Dharwar craton, and effect of the subsequent tectonic events on the lithospheric mantle through inversion of 8435 teleseismic travel times residuals from 63 broadband seismic stations. Teleseismic P- wave travel time residuals vary azimuthally from -0.4 s to 0.5 s indicating significant seismic velocity variation at depth. Inversion of these time residuals show higher upper mantle velocity up to at least 200 km depth in most part of the craton, locally extending to 300 km beneath south and south- west part of the western Dharwar craton. The thick high velocity lithosphere (-300 km) in the south and south- west part of the mid-Archean western Dharwar craton has been preserved for long geological time due to its unique chemical composition and remained largely unaffected by subsequent geodynamic events. Whereas, the - 200 km thick cratonic root beneath the late Archean eastern Dharwar craton might be a modified cratonic root by magmatic, volcanic and thermal activity in this part of the Dharwar craton.