Lanthanide Tetrad Effects in Stream Sediment Rich- Gold of Betare Oya Area (Cameroon Pan-African Fold Belt, Betare Oya Gold District): Implications for REE- Bearing Phase

Abstract

Stream sediment surveys were carried out in Betare Oya area and samples collected were analyzed by ICP-MS technology. The purpose of this research was to investigate the geochemical behavior of lanthanides in stream sediment and their implication for REE-bearing phase. The 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). The covariance between rare earth element (REE) and Mn suggests that all the REE are incompatible, this implies that the REE are significantly fractionated during differentiation. High rare earth element (510.7-3340.2 ppm) and Y contents were recorded from Betare Oya, the Upper Continental Crust normalized REE patterns show light rare earth element enrichment (LaN/SmN: 0.81 – 1.32) relative to heavy rare earth element (GdN/YbN: 2.26 – 15.32), with a negative Eu anomaly (Eu/Eu*: 0.15 – 0.29). The 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 the majority of samples and the second group encompasses few samples indicating the 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. The samples of group 2 have significant tetrad effects (1.88 – 2.28) and sediments indicate non-CHARAC behavior. The enrichment of light rare earth element (LREE) compared to heavy rare earth element (HREE) is due to the presence of monazite. The slight discontinuity in rare earth element (REE) patterns at Nd is the characteristic aspect of tetrad effect for monazite fractionation. The result of this research serves as new evidence for REE dynamics in Cameroon, the contents of REE can be used as background values for further investigations.