Existence de dykes doléritiques anciens à composition de tholéiites continentales au sein de la province alcaline de la ligne du Cameroun. Implication sur le contexte géodynamique

n the Adamawa Plateau (Northern Cameroon), doleritic dykes belong to a magmatic activity which predated the Cenozoic alkaline volcanism of the Cameroon Line. They have the chemical composition of continental tholeiites with Nb-Ta- and Ti-negative anomalies. This magmatism is interpreted as being derived from a sub-continental lithospheric source, which may have been contaminated during a former subduction event, linked to the Pan-African convergence. It is related to an early stage of continental break-up, which was contemporaneous or predated the Cretaceous tholeiitic magmatism of predominantly asthenospheric origin, which indicates a lithospheric thinning

Evaluation of the impact of gold mining activities on the waters and sediments of Lom River, Wakaso, Cameroon and the restorative effect of Moringa Oleifera seeds

Abstract The impact of gold mining activities on the Lom River in Wakaso (Adamawa Cameroon) and the potential of Moringa Oleifera seeds for the removal of pollutants from wastewater is evaluated on this paper. Water samples were collected for physicochemical (hydrogen potential, electrical conductivity, turbidity and suspended solids) and chemical (major ions and heavy metals) analyses. To evaluate the effect of mining activities on waters and sediments, a combination of multivariate statistical analysis (MSA) and methods to assess the sediment quality was used. The restorative effect of Moringa oleifera seeds was studied with the determination of the maximum removal efficiencies and the maximum adsorption capacities. The results of the physicochemical characterization of waters showed that these waters were slightly acidic to slightly basic (6.12–8.12), weakly conductive (185.8–584.1 μS cm−1), turbid (345–801NTU) and had high content of suspended solids (167–700 mg L−1). The average concentrations of studied heavy metals (Ni, Cd, Fe, Mn, As and Hg) in waters exceeded the limits recommended by the World Health Organization (WHO) standards. Physicochemical characterization of sediments revealed that they were acidic to neutral (5.95–6.80) and organic matter (OM) content ranged from 11.11 to 15.78%. The concentrations of studied trace metals (Ni, Cd, Fe, Hg, Mn and As) in sediments were below the limits recommended by the WHO except for Cd and Hg. The study of the capacity of Moringa oleifera seeds to remove pollutants in waters showed that 54% of the electrical conductivity, 80% of turbidity and 94% of suspended solids were reduced. The maximum removal efficiency of 91.66, 92.30 and 24.48 and the maximum adsorption capacity of 2.4, 2.6 and 16.6 mg g−1were observed for Cd (II), Hg (II) and Fe (II), respectively. Thus, the Moringa oleifera seeds which are locally available natural bio-adsorbent exhibit attractive property to treat wastewater