TITLE:
Magmatism of the Beka Volcanic Massifs (Cameroon Volcanic Line, West-Central Africa): New Petrographical and Mineralogical Data
AUTHORS:
Jacques Dili-Rake, Sahabo Aboubakar Abdoulaye, Joseph Legrand Tchop, Merlin Isidore Teitchou, Christian Mana Bouba, Oumarou Faarouk Nkouandou, Daouda Dawaï, Eddy Ferdinand Mbossi
KEYWORDS:
Cameroon Volcanic Line, Adamawa Plateau, Beka Volcanic Massif, Fractional Crystallization, OIB-Type Mantle
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.10 No.7,
July
26,
2022
ABSTRACT: The Beka volcanic massifs are located northeast of Ngaoundere region,
within the Adamawa plateau. It consists mainly of basanites, trachytes and
phonolites. The petrographic study shows that all the basanite lavas have
porphyritic microlitic textures with a more pronounced magmatic fluidity than
the felsic lavas displaying trachytic textures. The lavas are composed of
phenocrysts, microlites and microphenocrysts of olivine, clinopyroxene,
plagioclase and iron-titanium oxides for the basanites and of greenish
clinopyroxene, alkali feldspar, and titanomagnetite for the felsic lavas.
Chemical microprobe analysis indicates that
the olivine crystals are magnesian (Fo73-78). Clinopyroxene crystals
have a composition of diopside (Wo47-) in the basaltic lavas and
diopside near the hedenbergite pole in the trachytes phonoliths and
titanomagnetite (TiO2: 21.13% - 22.36% and FeO: 68% - 68%). Chemical
analyses on whole rocks show that all the lavas belong to the same series and
the felsic lavas come from the differentiation of basanite lavas by fractional
crystallization of the minerals therein. The basanites originate from a low
rate of partial melting of an OIB-type mantle. Contamination and mixing
processes are suspected. Lavas of similar composition are found in other volcanic centres of the Adamawa plateau and the
continental and oceanic sectors of the Cameroon Volcanic Line, in particular the
Kapsiki plateau, Mounts Cameroon and Bamenda.