Geochemistry of Mesoproterozoic mafic volcanics of Bayana basin, north Delhi fold belt: Constraints on mantle source and magmatic evolution

Mesoproterozoic volcanism in Bayana basin in the northeastern part of Arava lli-Delhi fold belt consists of mafic lava flows with quartzite-conglomerat e intercalations. The volcanics are tholeiites, characterized by enrichment of large ion lithophile elements (LILE) and light rare earth elements (LRE E) and depletion of Nb, P and Sr. The values of TiO2 (1.06 to 2.31 %), Zr ( 50 to 182 ppm), Ti/Y (286 to 521), and Zr/Y (2.63 to 5.70) are low, which i llustrate their close similarity with low-Ti continental flood basalts. The Bayana volcanics may have been derived from an enriched mantle source with no significant crustal contamination. The parental magma appears to have b een derived from a subcontinental lithospheric mantle source with Fe/Mg rat io exceeding that of model pyrolite. It is suggested that the mantle source of these volcanics was enriched through metasomatism by progressive transp ort of mantle fluids and /or melts from deeper mantle. Olivine and clinopyr oxene dominated the fractional crystallization and played a major role in t he evolution of magma, following its derivation from shallow mantle source( s) where clinopyroxene occurred as a residual phase.