Petrogenesis modeling of the alkaline volcanism of Ngaoundéré (Adamawa plateau, Cameroon, Central Africa)

Abstract

ACKNOWLEDGMENTS Warm thank to 'Agence Universitaire de la Francophonie (AUF)' through 'Projet de soutien aux équipes de recherche n° 51110SU201' for supplement analyses. ABSTRACTNew insights on geochemistry of the alkaline volcanism of Ngaoundéré in Adamawa plateau enable the petrogenesis modelling of Ngaoundéré Miocene lava series. Mass-balance crystal fractionation, closed-system Assimilation, Fractional Crystallization (AFC) and partial melting rate modeling attempted for Ngaoundéré volcanism are re-examined. Inductively Couple Plasma-Mass Spectrometry (ICP-MS) and Inductively Couple Plasma Atomic Emission Spectroscopy (ICP-AES) analyses show that lavas are microlitic porphyritic textures. Decrease of major element (MgO, Fe 2 O 3 , TiO 2 , CaO) with increasing SiO 2 contents results from fractionation of olivine, clinopyroxene and Fe-Ti-oxides in the parental basaltic magma. Similarly, for felsic magma, decrease in Al 2 O 3 , Na 2 O and K 2 O contents depends upon feldspar fractionation and decrease in P 2 O 5 from apatite fractionation, thus underline a typical feature of alkaline basaltic lavas of Ngaoundéré volcanism. The results evidence the differentiation by fractional crystallization process. Parental magmas of Ngaoundéré volcanism have undergone a low partial melting rate (2 to 3 %) of the heterogeneous mantle source.