The Karnataka Late Cretaceous dykes as products of the Marion hot spot at the Madagascar-India breakup event: evidence from Ar-40-Ar-39 geochronologyand geochemistry

Two late Cretaceous mafic dykes with an ENE strike that is orthogonal to th e west coast of India and located nearly 200 km inland around Huliyardurga, Karnataka state, yield Ar-40-Ar-39 plateau ages of 90.0 +/-1.0 and 87.5 +/ -0.9 Ma. These Fe-Ti-enriched tholeiites are essentially co-eval with at le ast four ether igneous suites widely scattered in southern India, namely, t he south and north Kerala dykes, the Agali-Anaikatti dykes of central Keral a-Tamil Nadu and lavas of St Mary islands off the west coast of India. The Karnataka Cretaceous dykes are also co-eval and compositionally very simila r to the Fe-Ti-enriched tholeiitic lavas and dykes around Mananjary, a majo r phase of Late Cretaceous magmatism along the eastern rifted margin of Mad agascar which are believed to be products of the Marion hot spot that extru ded at similar to 88 Ma, synchronous with the India - Madagascar break up e vent. The age and compositional similarities between these Late Cretaceous magmatic rocks from India and Madagascar constitute a clear evidence for ex tension of the thermal manifestations deep into the Indian peninsula.