Geochemistry of carbonate-clastic strata in NW Douala sub-basin, Cameroon: Implications for provenance, tectonics and source area weathering

The geochemistry of carbonate-clastic strata in part of the northwestern Douala Basin has been studied through major and trace element, including rare earth elements (REEs) in order to understand their provenance, tectonic settings and paleoweathering conditions. Different geochemical discriminants and elemental ratios such as K2O/Na2O vs SiO2 and Th-Sc-Zr/10, Eu/Eu*, La/Sc, Th/Co and Th/Cr, Th/Sc vs. Zr/Sc and Eu/Eu* vs (Gd/Yb)N indicate that the rocks were derivative from felsic igneous source with substantial sediment recycling. Geochemical signatures from plots of K2O/Na2O against SiO2, discriminant functions F4 against F3 after Roser and Korsch (1988) using raw oxides for provenance signatures and Th-Sc-Zr/10 all validate deposition of sandstone and shales in a passive continental margin setting. An A-CN-K (Al2O3-CaO-K2O) ternary diagram and chemical index of alteration (CIA) values suggest that the studied rock experienced moderate to intensive degree of chemical weathering under moderate weathering conditions for an extended period of time, or under humid weathering for shorter periods of time.