摘要：The Mbondo-Ngazi Tina area belongs to the Adamawa-Yade domain within the Pan-African Central Africa Fold Belt in Cameroon (CAFB). The basement of this area is dominated by metasedimentary rocks composed of sericite schist, chlorite schist and muscovite schist. Whole-rock geochemical compositions of these rocks were investigated in order to determine their provenance and tectonic setting. The studied metasedimentary rocks have SiO2 and Al2O3 contents comparable to the average composition of the Neoproterozoic upper continental crust (UCC). These rocks are strongly depleted in CaO, MgO, and enriched in K2O, Ba and Rb with respect to UCC, reflecting K addition during diagenesis. The CIA, CIW, PIA and the SiO2/Al2O3 and Th/U ratios indicated that these rocks had suffered varying degrees of weathering as the source rocks underwent mild to moderate chemical weathering. The PAAS-normalized REE patterns are almost flat with slightly LREE depletion with respect to HREE and null to weakly positive Eu anomalies. Their chondrite-normalized REE patterns are parallel to sub-parallel, LREE-enriched, and display distinct negative Eu anomalies and weakly fractionated HREE segments. Overall, they are geochemically mature and have suffered sedimentary recycling. They derived mainy from felsic to intermediate rocks with minor contamination of mafic rocks. The Mbondo-Ngazi Tina metasedimentary rocks show REE and trace element compositions similar to those of Archean sediments, suggesting that the continental crust of the study area during the early Proterozoic had chemical compositions similar to those of the Archean crust and were probably deposited in active to passive continental margin settings.
关键词：Metasediments; UCC; chemical weathering; Archean crust; Adamawa-Yade
