Petrogenesis and tectonic significance of Kawardha lamproite dykes from the Western Bastar Craton, central India

Abstract We present the mineralogy and whole rock geochemistry of the lamproites dykes from the Kawardha area of the Western Bastar Craton. These dykes are characterized by phenocrysts and microphenocrysts of olivine, phlogopite, ulvo-spinel, Cr-spinel and magnetite within the chlorite and carbonate-rich groundmass with rutile and apatite as accessory phases. Mineral chemistry indicates that the lamproites in Kawardha are similar to olivine-phlogopite lamproites and are geochemically similar to other lamproites in the eastern Bastar craton. The Kawardha lamproites are characterized by higher concentrations of MgO (12–20.29 wt%), V (193–502 ppm), Ni (206–823 ppm), Cr (146–1130 ppm), Nb (101–260 ppm), Zr (301–635 ppm), Hf (6–13 ppm) and LREEs. Positive Nb-Ta anomalies and Th, Hf and Zr variations are comparable to other intra-cratonic rift-related lamproites. The geochemical variations (such as REE, HFSE and LILE) are consistent with an asthenospheric mantle source similar to the other lamproites in Bastar craton. Trace element modelling implies a low-degree partial melting (0.1–2%) of phlogopite-bearing garnet-lherzolite and/or phlogopite-bearing spinel-lherzolite mantle source. The widespread Proterozoic rifting events in the Bastar craton likely led to the melting and upwelling of the asthenospheric mantle and which further interacted with the metasomatized lithospheric mantle to form the parental melts of the lamproite dykes of the Kawardha area.