Volcanology and geochemical study of the volcanic rocks of the Bafmeng area (Mount Oku, Cameroon Volcanic Line)

Abstract

Detailed volcanological and petrographic descriptions, and petrogenetic studies of lavas from Bafmeng were performed, with the aim to establish their origin, magmatic evolution, and the tectonic environment. Bafmeng area is located on the NW flank of Mount Oku, an important volcanic massif along the Cameroon Volcanic Line in Central Africa. Four types of eruptive dynamisms are successively manifested; (1) an effusive dynamism (basaltic flows); (2), an extrusive dynamism (rhyolitic and trachytic domes); (3) a basaltic explosive dynamism (Strombolian cones) and (4) hydromagmatic eruption (maar). The lavas form a sodic alkaline series with three distinctive types: ultra-basic type (basanite), an intermediate type (benmoreite and trachyte), and an acid type (rhyolite). The mineralogical composition is made up of olivine, augite, plagioclase and opaque minerals for basic lavas. Acidic lavas are made up of sanidine, quartz, clinopyroxene, opaque minerals, and aegyrine. The peridotite has as minerals; plagioclases, spinel, olivine, and pyroxene The lavas show enrichment in LREE as compared to HREE with negative anomalies in Ba, Eu, Sr in trachyte and rhyolite and a positive anomalies in Nb, La, Zr, Dy. The major process responsible for the emplacement of the Bafmeng felsic lavas is partial melting of spinel-garnet rich peridotite, followed by contamination and assimilation. Mafic lavas are derived from the partial melting of the asthenospheric mantle. The tectonic context based on geochemistry indicates that, the regional development is related to within plate setting.

Keywords: Cameroon Volcanic Line, Mount Oku, Bafmeng, Peridotite, Eruptive dynamism.