Major/trace elements and Sr–Nd–Pb isotope systematics of lavas from lakes Barombi Mbo and Barombi Koto in the Kumba graben, Cameroon volcanic line: Constraints on petrogenesis

Abstract This study presents major elements, trace elements and Sr–Nd–Pb isotope data for fifteen (15) representative volcanic rock samples from volcanic edifices of Lakes Barombi Mbo (n = 9) and Barombi Koto (n = 6), located in the Kumba graben along the Cameroon Volcanic Line (CVL). The samples are dominantly basalts and trachy-basalts with MgO ranging from 7 to 9 wt.%. The lavas from the edifice of Lake Barombi Mbo are slightly richer in TiO2 (mean 3.3 wt%) and lower in CaO (mean 9.2 wt%) relative to those from the edifice of Lake Barombi Koto (2.9 wt% and 10.3 wt%, respectively). Trace element characteristics of the lavas suggest an enrichment of the source by carbonatitic metasomatism and melting of a heterogeneous source at varying depth in the garnet-spinel transition zone. Trace elements and isotopic composition of the lavas suggest insignificant crustal contamination. Modelling of the degree of partial melting suggest that the magmas were formed at varying depth (60–80 km) and by ∼2% partial melting of a source containing less than 4% garnet. Samples from Lake Barombi Mbo formed at a higher degree of partial melting (2%–0.5%) and at a shallower depth relative to those from the volcanic edifice of Lake Barombi Koto (mostly