Precise ⁴⁰Ar/³⁹Ar age determination of the Kotakonda kimberlite and Chelima lamproite, India: implication for the timing of mafic dyke swarm emplacement in the eastern Dharwar craton

Abstract

We report a ⁴⁰Ar/³⁹Ar whole rock age of 491±11 Ma for the hypabyssal facies, diamondiferous, Kodomali diatreme from the Mainpur kimberlite field (MKF) located 135 km SE of Raipur city, within the Bastar craton, Central India. This age is well supported by the available stratigraphic evidence and also by the recently published Nd isotopic data of the pipe. This study provides the first radiometric evidence for Palaeozoic kimberlite activity of Pan-African age in the Indian shield and recognizes a new and important diamondiferous kimberlite emplacement epoch in this part of the Gondwanaland. Our results also highlight the fact that kimberlite and lamproite emplacement in various Indian cratons occurred over a large time interval and was not essentially contemporaneous during Mesoproterozoic (~1090Ma) as suggested by some earlier workers. If the Pan African age of the Kodomali kimberlite corresponds to a collision with the craton, then the amalgamation of the Indian craton into the Indo-Antarctic supercontinent indeed took place considerably much later than previously assumed.