Mesoproterozoic 40Ar/39Ar age and Sr-Nd isotopic geochemistry of calc-alkaline lamprophyre from the Mudigubba area, Eastern Dharwar Craton, India

We report a 40Ar/39Ar Mesoproterozoic radiometric age for a calc-alkaline lamprophyre dyke from the Mudigubba area towards the western margin of the Cuddapah Basin, Eastern Dharwar Craton (EDC), Southern India. Amphibole phenocryst separates from this lamprophyre yielded a plateau age of 1169 +/- 8 Ma (2 sigma), which is almost 50 million years older than the majority of radiometric dates available for the Wajrakarur field kimberlites which are proximal to this dyke. Bulk-rock Sr-Nd isotopic analyses of the Mudigubba lamprophyre dykes (epsilon Nd-(t) between -13.3 and -12.4) reveal their derivation from an old, enriched, continental lithospheric mantle unlike the kimberlites (bulk- rock and perovskite in situ epsilon Nd-(t) between - 0.77 and + 7.93), which originated either from a chondritic or depleted mantle source. This study provides further evidence for emplacement of compositionally distinct, mantle-derived Mesoproterozoic alkaline magmas in the EDC and highlights the extremely heterogeneous character of the lithospheric mantle beneath this craton.