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New 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, Fe2O3, TiO2, CaO) with increasing SiO2 contents results from fractionation of olivine, clinopyroxene and Fe-Ti-oxides in the parental basaltic magma. Similarly, for felsic magma, decrease in Al2O3, Na2O and K2O contents depends upon feldspar fractionation and decrease in P2O5 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.
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Keywords: Major and trace elements, fractional crystallization, partial melting, modeling, Ngaoundéré volcanism, Adamawa plateau