This study attemptsthe evaluationofthe geogenic release metalsdue to weathering of basement rock on the shallow groundwater system around Ilesha and environs.The study involves collection of twelve (12) soil samples over four (4) soils profiles and analyzed for major oxides and trace metals using ICP-AES. In addition, atotal of nineteen (19) groundwater samples were obtained from shallow dug wells <25m in areas surrounding the sampled soil profiles. Geochemical analysis revealed the presence of SiO2, Al2O3, MgO, CaO, Na2O, K2O, MnO, P2O5 and Cr2O3 as the major oxides. Ruxton Ratio depicts weathering intensity decreasing from Muscovite schist (MS)> Amphibolite (AS)> Talc schist (TS)> Quartzite quartz schist (QS). Physico-Chemical results of the water samples revealed a slightly acidic to basic water with electric conductivity values of 443μS/cm, 94μS/cm and 267μS/cm for the AM, QS and MS respectively. Hydro-geochemical analysis of the groundwater samplesindicatethe presence of major cations and trace elements and further analysis revealed the order of mean cations abundance for the mafic unit to be Ca2+>Mg2+>Na+ >K+, and Ca2+>Na+>K+>Mg2+ for the felsic. The Gibb's diagram of the study area, plot in the weathering zone. Groundwater around the mafic bedrocks shows high concentration of the major cations, except for Potassium (K), thereby revealing a relationship that correspond to the mineralogy of the bedrock and weathered profile.
Metasediment, Amphibolites, Hydrogeochemical, Groundwater, Basement rock
