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We reassess the geodynamic context close to the Congo craton during the pre-collisional period of the Pan-African orogeny from whole-rock major and trace element compositions and isotopic data obtained in the westward extension of the Yaounde series (Boumnyebel area, Cameroon). The series consists of metasediments (micaschists, minor calc-silicate rocks and marbles) and meta-igneous rocks (hornblende gneisses, amphibolites, metagabbros, pyroxenites and talcschists) recrystallized under high-pressure conditions.

Chemically, the micaschists correspond to shales and greywackes similar to the Yaounde high-grade gneisses. ⁸⁷Sr/⁸⁶Sr initial ratios (0.7084–0.7134), moderately negative ε_Nd(620 Ma) values (−5.75 to −7.81), Nd model ages (1.66 < T_DM < 1.74 Ga) and radiometric ages point to the conclusion that the Yaounde basin was filled with siliciclastic sediments derived from both reworked older …