Petrogenesis of lavas from Mokolo-Kosséhone region, northernmost segment of the Cameroon Volcanic Line: constraints from major/trace elements and Sr-Nd-Pb isotopic data

This study presents major and trace elements, and Sr-Nd-Pb isotope data of the Mokolo-Kosséhone volcanic rock (basanite, trachybasalt, trachyte, and rhyolite) from the northernmost segment of the Cameroon Volcanic Line (CVL). The basanite sample exhibits primitive character (MgO: 12–14 wt%; Mg#: 69–72; Ni: 327–427 ppm; Cr: 524–599 ppm; Co: 57–60 ppm). Trace element and isotopic signatures of the mafic lavas are similar to those of OIB. The trends observed in the major oxides and compatible trace elements against SiO2 from basanite to rhyolite are attributed to the fractionation of different mineral phases such as Fe-Ti oxides, olivine, clinopyroxene, feldspar, and quartz. The enrichment in LREEs and depletion in HREEs associated with (La/Yb)N > 5 (12.39–32.65), (Tb/Yb)N > 1.7 (1.71–2.89), and Dy/Yb > 2 (2.16–3.63), suggest the presence of a garnet phase in a mantle source. The lavas were produced at varying depths by low degrees of partial melting (< 4%) of a source containing less than 5% of garnet peridotite. The 206Pb/204Pb values of basanite (19.69630–19.79122) are similar to those of FOZO (206Pb/204Pb > 19.5). The trachybasalt samples with 206Pb/204Pb values of 19.25 and 19.37 suggest the probable enrichment of magma with a high-μ (HIMU) signature (206Pb/204Pb < 19.5) by a crustal component. Trace elements and isotopic compositions (87Sr/86Sr: 0.70308–0.70378, 143Nd/144Nd: 0.51287–0.51296, 206Pb/204Pb: 19.24652–19.79122) of the Mokolo-Kosséhone lavas are consistent with a mixture of different source material from the sub-continental lithospheric mantle (SCLM) and the asthenosphere with minor crustal contamination. The composition of the source is analogous to those described in the northern portion of the CVL and other volcanic massifs along the CVL.