Data for: Major/trace elements and Sr-Nd-Pb isotope systematic of lavas from Lakes Barombi Mbo and Barombi Koto in the Kumba graben, Cameroon Volcanic Line: Constraints on petrogenesis
Description
This study presents major elements, trace elements and Sr–Nd–Pb isotope data for fifteen (15) representative volcanic rock samples from the surroundings 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 basalts and trachy-basalts with MgO ranging from 7–9 wt.%. The lavas from Barombi Mbo are slightly richer in TiO2 (mean 3.3 wt.%) and lower in CaO (mean 9.2 wt.%) relative to those from 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. Model-calculated results for AFC using the equation of Depaolo (1981) suggest an insignificant role of the assimilation of a crustal component in during fractional crystallization. Modelling of the degree of partial melting suggest that the magmas were formed at varying depth (indicate the depths) 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% to 0.5%) and at a shallower depth relative to those from Barombi Koto (mostly <0.5%) and Mt. Cameroon. Interestingly, the relationship of Zr/Hf and 206Pb/204Pb suggests that the magma was affected by carbonatitic metasomatism whose effect decreased from Mt. Cameroon to Lake Barombi Mbo. Our results suggest that Lakes Barombi Mbo and Barombi Koto lavas are typical of lavas with HIMU-like signature and involved contributions from a dominantly sublithospheric mantle and minor contributions from the sub-continental lithospheric mantle. The isotopic composition falls within the range of FOZO, which is consistent with a dominantly SLM origin (e.g., 206Pb/204Pb >19).