Ndema Mbongue J. L.^{1, 2}, Ngnotue T.³, Ngo Nlend C. D.⁴, Nzenti J. P.^1,, Cheo Suh E.²

The Nyong series at Edéa and Eseka area is located in the western edge of the Congo Craton and comprise three distinguish rock units namely: metasedimentary rocks unit (schists, garnet-rich micaschist); meta-igneous rocks unit (pyroxene-rich gneiss, garnet-rich charnockitic gneiss, charnockitic gneiss, biotite-rich gneiss, amphibole and biotite-rich gneiss, garnet and amphibole-rich gneiss, amphibolite, pyribolite, pyrigarnite, garnet-rich amphibolite) and a unit of the rocks resulting from the melt (migmatite, TTG) displaying quartzo-feldspathic segregation arising from either in situ partial melting or injection along dykes or ductile shear zones. The meta-igneous rocks derived from (i) intermediate to basic tholeiitic rocks with high TiO₂ (0.6-3.47%) contents compatible with the extensive orogenic domain and (ii) calc-alkaline protolith display high FeO*/MgO (1.5-3.31) ratios which is in accordance with the typical domain of collisional orogeny. The chemical patterns of metasedimentary rocks are those of shale. The average Nb/Y (0.004) ratio and the fractioned REE patterns suggest that the contribution of alkaline vulcanite and a continental environment can be envisaged for these metasedimentary rocks.

nyong series, extensive orogenic domain, domain of collisional orogeny, shale, continental environment