Lithosphere–asthenosphere interaction and carbonatite metasomatism in the genesis of Mesoproterozoic shoshonitic lamprophyres at Korakkodu, Wajrakarur kimberlite field, Eastern Dharwar Craton, southern India

Abstract

The spatial and temporal association between lamprophyres and kimberlites provides unique opportunities to explore their genetic relationships. This paper explores such a relationship by detailing mineralogical and geochemical aspects of Korakkodu lamprophyre dykes located within the well‐known Mesoproterozoic diamondiferous Wajrakarur Kimberlite field (WKF), towards the south‐western margin of Paleo–Mesoproterozoic Cuddapah Basin, Eastern Dharwar Craton, southern India. Mineralogy reveals that these dykes belong to calc‐alkaline variety of lamprophyres, but their geochemistry display mixed signals of both alkaline and calc‐alkaline lamprophyres. These lamprophyres are highly potassic, and their high Al2O3 and low‐TiO2 content implies a shoshonitic character. Low Mg#, Ni, and Cr concentration highlight their evolved nature. High (La/Yb)N and (Gd/Yb)N content is consistent with their derivation from low degrees of partial melting, whereas highly fractionated nature suggests the presence of garnet in their source. Absence of prominent Nb‐Ta anomaly implies to the dilution of lithospheric mantle source by melts rich in HFSEs and low La/Nb ratio compared to those of the calc‐alkaline island arc volcanics and suggests an asthenospheric overprint on lithospheric mantle source. Carbonatite metasomatism in the source region of these lamprophyres is apparent from conspicuously high‐Zr/Hf ratio, and the HFSE budget of these lamprophyres are principally controlled by the presence of phlogopite veins in their lithospheric source. An extremely heterogeneous and layered lithospheric mantle beneath Eastern Dharwar Craton has been inferred from the divergent genetic history of Mesoproterozoic lamprophyres and kimberlites in the Wajrakarur field.