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S U M M A R YA detailed 2-D modelling of the seismic structure and other geological and geophysical signatures across the Cuddapah basin of the southern Indian shield suggests upwarping of highvelocity and high-density layers, which are observed close to the surface below the southwestern part of the basin. This anomalous feature is constrained by (i) a strong gravity high anomaly of about 55 mGal, (ii) a 100 km wide high conductivity anomaly (resistivity < 100 -m) extending from surface to a minimum depth of 50 km in the mantle lithosphere and (iii) large scale massive intrusive activity. These features are interpreted to be an expression of a thermal anomaly, which may have acted like a plume during the Proterozoic and could well correspond to a 1.1 Ga kimberlitic activity. Below this region, the thin granitic-gneissic crust is underlain by well-differentiated, high-velocity layers, possibly due to underplating and densification of much of the crust by extruded magma.

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