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

作　　者：Pauline Wokwenmendam Nguet Benjamin Ntieche Joseph Legrand Tchop Bouba Christian Mana Eddy Ferdinand Mbossi 

机构地区：[1]Research Center for Geophysics and Volcanology,Institute of Geological and Mining Research,PO Box 370 Buea,Cameroon [2]Geology laboratory,Higher Teacher Training College,University of YaoundéI,PO Box 47 Yaoundé,Cameroon [3]Department of Earth Sciences,Faculty of Sciences,University of YaoundéI,PO Box 812 Yaoundé,Cameroon [4]Research Center for Geology and Mining,PO Box 333 Garoua,Cameroon

出　　处：《Journal of Geological Research》2021年第3期28-43,共16页地质研究（英文）

摘　　要：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 iron-titanium 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.

关 键 词：Alkali lavas Fractional crystallization Partial melting Spinel lherzolite Volcanic zone within plate 

分 类 号：P58[天文地球—岩石学]