Geochemistry and U–Pb zircon age of the Paleoproterozoic metasedimentary rocks from the Bidou I, Nyong Series, Cameroon: Implications for provenance and tectonic setting

The Bidou I polymetallic prospect, located in the Nyong series, belongs to the northwestern edge of the Congo craton and consists of metasedimentary rocks. Combination of geochemistry with U–Pb zircon dating of these metamorphic formations was used to constrain the source and the tectonic setting of their protolith. Samples are highly enriched in SiO 2 (54.4–88.06%) and Al 2 O 3 (5.81–19.66%), depleted in CaO with a very high K 2 O/Na 2 O ratio > 1, which are characteristics of metasedimentary rocks. The studied samples are garnet gneisses and garnet micaschists having arkoses and greywackes as inferred protoliths, respectively. The felsic/intermediate nature of those protoliths is related to intracrustal differentiation of sedimentary recycling, marked by the accumulation of zircon. The metasediments undergone weak chemical alteration, range from immature to slightly mature and were derived from a moderately altered sedimentary source in an active tectonic setting. The protoliths of the Bidou I metasedimentary rocks are from the upper continental crust and were deposited in an active or passive continental margin. The duality of the tectonic setting highlights the progressive change in the geometry of the basin and the development of a continental island arc. U–Pb zircon dating yields ages of 2065 ± 25 Ma for garnet gneisses and 2405 ± 24 Ma for garnet micaschists. These new ages are consistent with the data presented by previous works at the NW border of the Congo craton in Cameroon.