Paleoclimate characteristics of source area weathering and metallogenic implication of cretaceous black shales in the Mamfe basin, (SW Cameroon): Evidence from lithogeochemistry

Abstract

Black shales are highly enriched in essential elements containing critical information on metallic richness and paleoclimatic imprints during deposition. The Cretaceous period marks the age of Basin formation from which the Mamfe Basin was formed from the Albian to Cenomanian. The purpose of this study is to investigate the geochemical behaviour of the shales in the Mamfe Basin and their paleoclimatic and metallogenic significance. Twenty-five representative shale samples were collected from seven sites outcrops in the Mamfe Basin. The major and trace elements composition in the shale samples were analysed using Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In comparison with standard values for metalliferous shales, the shales from the Mamfe Basin are enriched in Boron (B), with only few samples enriched in Li, Rb, Cu, Pb and Zn. The Aluminium module (Alm) and ternary diagram plotted from Al–Fe–Mn shows that all the shales are considered as terrigenous sediments with only 02 samples (08%) falling within the zone of metalliferous sediments. The paleoclimatic characteristics that were inferred from the C-values (0.3–3.1), Sr/Cu (0.6–8.9), Sr/Ba (0.1–2.8), Rb/Sr (0.3–0.9), Fe/Mn (1.8–180), Al/Mg (0.31–31) and Mg/Ca (0.05–16.4) data of the shales in the Mamfe Basin indicate that the climate that existed during source area weathering ranged from a sub humid to a more humid climate with few samples ≤5% displaying arid climate.