Provenance and Heavy Metals Concentrations in the Bedrocks and Sediments of Okemesi/Ijero District, Southwestern Nigeria

An assessment was conducted on the bedrocks and sediments of Okemesi/Ijero area using geochemical approach in order to establish the concentration of heavy metals; determine the level of enrichment and develop their geo-accumulation index. Field studies of the bedrocks were carried out, and provenance of the sediments was determined. Thirty-five bedrocks and sediment samples were collected for this study in a grid-controlled sampling method. The samples were dissolved using Lithium Tetraborate fusion method followed by HCl and HF acid digestion. Field studies revealed that the sediments were derived from the weathering of the bedrocks such as quartz-biotite-schists, banded gneisses, granite gneisses, biotite gneisses, calc gneisses, porphyritic granites, charnockites, massive/schistose quartzites and mica schists which are the dominant lithologic units in the study area while intermediate rock is attributed as the probable source of sediments. The concentration of Cu, Pb, Zn and Ti were found to be higher in both bedrocks and sediments more than the background. Positive correlation occurred between Pb, Cu and Zn indicating a common lithogenic source in the sediments and bedrocks but Fe and Ti were discovered to be anthropogenically and extremely enriched in the sediments. The enrichment factors of the heavy metals showed moderate to significant enrichment (EF- 5-20) for Pb (28.95%), Cu (73.68) and Zn (2.63%) in bedrocks and Cu (45.7%), Pb (82.86%) and Nb (54.29%) in sediments. However, gold mineralization potentials in the study area is very high based on moderate to significant enrichment of its pathfinder elements in the bedrocks and sediments of the studied areas.