Petrological and Geochemical Studies on the Basalts of Mandla Lobe, Eastern Deccan Volcanic Province; Implications on the Shallow Melting of a Spinel Peridotite and Crustal Contamination

The petrological studies and geochemical analysis carried out on the basalts of Mandla Lobe (MB), Madhya Pradesh of eastern Deccan Volcanic Province (EDVP) to evaluate their petrogenetic and tectonic evolution. A variety of lavas such as columnar, vesicular, amygdaloidal, inflated pahoehoe flows and red bole interflow horizons around the study areas Chutka, Mandla and Jabalpur-Niwas sectors of Mandla lobe are found. These basalts are fine to medium grained porphyritic and non-porphyritic composed of calcic plagioclase (An 36 Ab 61 Or 3 to An 74 Ab 25 Or 1 ; labradorite to bytonite), clinopyroxene (Wo 24–42 , En 30–52 , Fs 15–43 ; augite-ferroaugite), altered olivine, chlorophaeite, opaque and glass usually show a variety of intersertal (seriate, ophitic and subophitic), intergranular (porphyritic, glomeroporphyritic, poikilitic) textures indicating variable cooling histories and melt replenishment in a magma chamber. The MB samples exhibit tholeiitic trends evidenced by iron enrichment on AFM diagram. The La/Yb ratios of MB suggest relative enrichment of LREE over HREE without significant Europium anomalies. Low HREE ratios such as (Tb/Yb) N and Dy/Yb suggest the precursor melts derived by low to moderate degree partial melting of a spinel peridotite mantle source. In the geochemical discrimination plots such as TiO2 vs MgO, Ba/Y vs Zr/Nb and Rb/Y vs Nb/Y and discriminant function analysis (DFA) show the MB correspond to the overlapping field between Poladpur and Ambenali Formations of Wai subgroup imply uncontaminated to significant crustal contamination (Nb/La range from 0.18–1.31; Nb/La=1 is the boundary condition) well characterized in Western Ghat sections of WDVP.