Current Science

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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 (2σ ), 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 (εNd(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 εNd(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.

Keywords

Alkaline Magma, Lamprophyre Dyke, Lithospheric Mantle, Kimberlites, Radiometric Age.
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