Mineralogical and geochemical signatures of surface stream sediments from Dibamba River basin, SW Cameroon: Implications for provenance, weathering, and tectonic setting

Abstract

The Dibamba River (DR) basin is one of the major fluvial basins of the Cameroon coastal area. The current work presents the very first systematic study of elemental geochemical characteristics, including REE, of surface sediments collected from the river bed at different parts of the river courses to determine the intensity of weathering, provenance, and tectonic settings, and evaluate the features that most faithfully mirror the nature of the source terrane. The sediments are dominantly fine and coarse sands. The framework components mainly consist of quartz. The clay minerals comprise kaolinite and illite. Opaque minerals, associated with kyanite, zircon, sillimanite, garnet, and hypersthene, are present as common accessory minerals. The DR sediments are classified geochemically as Fe-shale and Fe-sand. The CIA (72.04 ± 7.1), PIA (66.1–89.2), CIW, and the A–CN–K and (A-K)-C-N plots indicate moderate to high intensity of chemical weathering in the source areas. The SiO2/Al2O3, Al2O3/Na2O, K2O/Na2O ratios, and ICV indicate that the samples were predominantly texturally and compositionally mature. The ZTR index and the ternary Al2O3–TiO2–Zr and binary Th/Sc versus Zr/Sc diagrams suggest recycling and sorting of almost all the sediments. The REE patterns and the size of Eu, and various ternary and bivariate plots such as Zr versus TiO2, Th/Co versus La/Sc, and Cr/V versus Y/Ni indicate the contribution of sediments from intermediate and felsic source rocks. The tectonic discriminant-function-based diagrams revealed a rift or a passive margin setting for the source region. This is consistent with the tectonic history of the Pan-African domain and the Douala Cretaceous sub-basin, which are the probable source terranes of the studied stream sediments.