Geochemistry of Volcanic Rocks of Beka, North East of Ngaoundéré (Adamawa Plateau, Cameroon): Petrogenesis and Geodynamic Context

Pauline Wokwenmendam Nguet (Research Center for Geophysics and Volcanology, Institute of Geological and Mining Research, PO Box 370 Buea,Cameroon)
Benjamin Ntieche (Geology laboratory, Higher Teacher Training College, University of Yaoundé I, PO Box 47 Yaoundé, Cameroon)
Joseph Legrand Tchop (Research Center for Geophysics and Volcanology, Institute of Geological and Mining Research, PO Box 370 Buea,Cameroon;Department of Earth Sciences, Faculty of Sciences, University of Yaoundé I, PO Box 812 Yaoundé, Cameroon)
Bouba Christian Mana (Research Center for Geology and Mining, PO Box 333 Garoua, Cameroon)
Eddy Ferdinand Mbossi (Research Center for Geophysics and Volcanology, Institute of Geological and Mining Research, PO Box 370 Buea,Cameroon;Department of Earth Sciences, Faculty of Sciences, University of Yaoundé I, PO Box 812 Yaoundé, Cameroon)


Beka area is situated in the Adamaoua Plateau of Cameroon in central Arica. Lavas in this area has not been studied before the present work.The volcanism of Beka is characterized by basalt, trachyte and phonolite domes and flows. The petrographic study shows that basaltic lavas have porphyritic microlitic textures. The felsic lavas indicate trachytic textures.The rocks are composed of olivine, clinopyroxene, plagioclase and irontitanium oxide minerals for the basalts; clinopyroxene, alkali feldspar (including foids), sphene and titanomagnetite for the felsic lavas. Chemical analyses show that basaltic lavas are basanites. Felsic lavas contain modal feldspathoid (nepheline in phonolites). All these lavas belong to the same series, because the felsic lavas are derived from the differentiation of basaltic lavas by fractional crystallization. They show an alkaline nature according to their geochemistry. Trace elements including Rare Earth Elements characteristics show that rocks emplaced in the Winthin Plate volcanic zone. They derived from an evolved parent magma showing a low degree of partial melting and characteristics closer to a modified and evolved primitive spinel lherzolite.


Alkali lavas;Fractional crystallization;Partial melting;Spinel lherzolite;Volcanic zone within plate

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