Hydrogeochemical study of the fractured/weathered basement of the Oban Massif, southeastern Nigeria has been carried out. Results indicated that concentrations of major cations and anions exhibited the following order of abundance: Ca>Na>Mg>K and HCO3>SO4>Cl, respectively, with minor variations across sampling seasons. Ca-Na-Cl-SO4 and Ca-Mg-HCO3 water types have been identified as major facies, resultant from congruent influences of weathering (mainly silicates), ion exchange processes, and water mixing.
groundwater; cation; anion; weathering; ion exchange; Oban massif; Nigeria