Lanthanide tetrad effects in stream sediment rich- gold of Betare Oya area (Cameroon Pan-African fold belt, Betare Oya gold district): implication for REE- bearing phases fractionation

Abstract

Stream sediment geochemical surveys were carried out in Betare Oya in the Cameroon Pan-African Fold Belt. Samples collected were analyzed by ICP-MS for major, trace and rare earth element contents. The purpose of this research was to investigate the geochemical behavior of lanthanides in sediments and their implication for REE-bearing phase formation. Sediments exhibit higher content in Fe2O3 (3.96–21.30%), Au (133->10000 ppb), Hg (4000->10000 ppb), Mn (868–2950), Pb (20.96–2950 ppm). High REE (510.7-3340.2 ppm) and Y contents were delivered from Betare Oya, the UCC- normalized REE patterns show LREE enrichment (LaN/SmN: 0.81–1.32) relative to HREE (GdN/YbN: 2.26–15.32), with a negative Eu anomaly (Eu/Eu*: 0.15–0.29). REE patterns exhibit tetrad effects showing W- and M- types. The plots of the sizes of tetrad effects with some geochemical parameters allow to characterize two distinct groups of population: the first group involved majority of samples and the second group encompasses few samples indicating samples were less affected by terrigenous source materials. The two groups are related to tetrad effect, they can serve as geochemical indicator to determine the environmental conditions. Samples of group 2 have significant tetrad effects (1.88–2.28) and sediments indicate the non-CHARAC behavior. The enrichment of LREE compared to HREE is due to the presence of monazite. The result of this research serves as new evidence for REE dynamics in Cameroon, the values of REE can be used as background values for further investigation.