Geochemical constraints for unravelling the conditions of sedimentation, Paleoclimate variations, and provenance and metallogenic implication of the Cretaceous sequence deposits along the Mayo Louti, Babouri-Figuil Basin (North Cameroon, Africa)

Abstract

The sediments from the Babouri-Figuil intracontinental Basin were investigated by major and trace elements geochemistry and paleontological analysis to infer their Paleoenvironment and paleoclimate evolution and metallogenic implication of an approximately 120-m thick sequence along the Mayo Louti River in this basin. The geochemical compositions revealed that the studied materials are mainly composed of Shales associated with Fe-sands, Wacke and Litharenite. These sediments show high ΣLREE/ΣHREE ratios (Σlight rare earth elements/Σheavy rare elements ratios: 5.16 to 10.49); weak negative and positive Eu anomaly (Eu/Eu* = 0.84 to 1.28) and Ce anomaly (Ce/Ce* = 0.93 to 1.10); Al₂O₃/TiO₂ ratios (17.02–28.16); Th/Co ratios (0.23–1.36). These features, together with the Ce vs La/Yb, Zr vs TiO2 and La/Sc vs Th/Co plots, indicate that the sediments are derived mainly from felsic rocks associated with intermediate composition rocks. The CIA and CIX (Chemical Index of Alteration: respectively 48.02 to 60.97 and 62.69 to 71.42) suggest that the source rocks have experienced low to moderate recycling and sorting and weathering. The SiO₂ vs. Al₂O₃ + K₂O + Na₂O, C-values, Sr/Ba, and Rb/Sr plots, and palynological content dominated by Gymnosperm pollens such as Classopollis sp. and Araucariacites sp., associated with single spores such as Cicatricosisporites sp indicate mainly semi-arid/humid to arid climate during the period of deposition, fluctuating from the bottom to the top of the sequence. The Sr/Ba values ranging from 0.78 to 12.23, suggest a fluctuating and sometimes high salinity (Hypersaline milieu). The presence of numerous tetrads to dyads and wood trunks indicates a lacustrine or swampy environment surrounded by vegetation, and the Ni/Co (1.75 to 4.14) and U/Th (0.10 to 0.64) ratios are consistent with oxic conditions. The discriminant function-based multidimensional tectonic diagrams show an arc-collisional setting, which is consistent with the Precambrian geological history of the study area, and indicate the unreworked and unsorted character of these sediments. The Al/Si ratio shows positive correlation with CIA (R² = 0.59), Th (R² = 0.37), Zr (R² = 0.47), Hf (R² = 0.51), Na (R² = 0.39), K (R² = 0.73) and negative correlation with Ca (R² = 0.32) and Mg (R² = 0.30). The positive correlation with K, Hf, Na, Zr, and Th from detrital origin and negative correlation with Ca and Mg from chemical origin could suggest the geochemical composition control of grain size as in the Amazonian floodplain deposits. The studied samples are essentially terrigenous and very weakly metalliferous.