BIMODAL VOLCANISM OF THE KAPSIKI PLATEAU (NORTHERNMOST CAMEROON)

The Kapsiki Plateau is the northern most volcanic zone of the Cameroon Line. The Cenozoic volcanism is alkaline and characterized by basalti c lavas associated with fifty trachyte and rhyolite plugs and spines. Some basalts are primitive. Trachytes are leucocratic, biotite-bearing , or peralkaline, with Ti-, Na-, F-rich aegirine-augite, richterite, a rfvedsonite phenocrysts. Rhyolites contain Ti-rich biotite, arfvedsoni te and quartz phenocrysts. Despite a large gap between basalts and fel sic lavas, major and trace element distributions indicate co-magmatism for basaltic and felsic lavas. Feldspar, biotite and apatite fraction ations govern the differentiation process, the fluid role being of min or effect. Probable crustal (selective) contamination affected felsic lavas.