The Karnataka late cretaceous dykes as products of the Marion hot spot at the Madagascar ‐ India breakup event: evidence from⁴⁰Ar‐³⁹Ar geochronology and geochemistry

Abstract

Two late Cretaceous mafic dykes with an ENE strike that is orthogonal to the west coast of India and located nearly 200 km inland around Huliyardurga, Karnataka state, yield ⁴⁰Ar‐³⁹Ar plateau ages of 90.0±1.0 and 87.5±0.9 Ma. These Fe‐Ti‐enriched tholeiites are essentially co‐eval with at least four other igneous suites widely scattered in southern India, namely; the south and north Kerala dykes, the Agali‐Anaikatti dykes of central Kerala‐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 similar to the Fe‐Ti‐enriched tholeiitic lavas and dykes around Mananjary, a major phase of Late Cretaceous magmatism along the eastern rifted margin of Madagascar which are believed to be products of the Marion hot spot that extruded at ∼88 Ma, synchronous with the India‐Madagascar break up event. The age and compositional similarities between these Late Cretaceous magmatic rocks from India and Madagascar constitute a clear evidence for extension of the thermal manifestations deep into the Indian peninsula.