Base Metal Mineralization in the Precambrian Rocks of Okemesi-Ijero Area, Southwestern Nigeria

The evaluation of base metals in the bedrocks of Okemesi / Ijero area, southwestern Nigeria has been carried out to assess their potentials, level of accumulation and enrichment. The methodology included systematic geological and geochemical mapping of the rocks using grid-controlled sampling method at a sampling density of one sample per 500m. Ten rock samples were collected at different locations of the study area. The results obtained showed that the major oxides such as SiO2, Al2O3, TiO2, Fe2O3, MnO, MgO, CaO, Na2O, K2O and P2O5 were detected in variable proportions. While SiO2 variedbetween 70.59% and 98.70%, Al2O3 ranged between 15.73% and 0.61%. There is abundanceof barium (Ba), silver (Ag) and gold (Au) with concentration values of 1.6-9.8, 1.24-7.1 and 0.05-10.00 ppm respectively. Base metals such as Cu, Zn, Pb, Bi and Cr enrichment factors and their geo-accumulation index indicates moderately significance to very high enrichment of Cu (10 – 70%) , Pb (20 – 40%) and Bi (10 – 40%). The geo-accumulation indices suggest geogenic concentration of the base metals in the host rocks rather than anthropogenic inputs. The PCA elements loaded Au, As, Ag, Pt and Os on the same factor and they are pathfinder elements of Gold. Correlation coefficients indicate strong positive correlations between the elements. This implies that they are strongly related and therefore of the same source, also suggesting geogenic sources.