GEOLOGICAL MAPPING AND HYDROGEOCHEMICAL CHARACTERIZATION OF OGAMINANA AND ITS ENVIRON PART OF KABBA SHEET 246SW

ABSTRACT This study integrates geological mapping and hydrogeochemical assessment to examine the relationship between bedrock geology and groundwater quality in Ogaminana and its environs, part of the Kabba Sheet 246SW, Kogi State, Nigeria. Detailed field mapping identified granite gneiss, alkaline granite gneiss, alkaline gneiss, and minor pegmatite and quartz veins as dominant lithology. These medium- to coarse-grained crystalline rocks exhibit well-developed flirtations, joints, and fracturplagioclase es, which enhance secondary porosity and influence groundwater storage and movement.Fifteen groundwater samples from hand-dug wells and boreholes were analyzed for physical, chemical, and biological parameters. Results show pH values between 6.83 and 7.98 (neutral to slightly alkaline), Total Dissolved Solids of 84.32–478.56 mg/L, and a dominant calcium–bicarbonate water type. Hydrogeochemical processes are mainly controlled by silicate weathering and carbonate dissolution. Most major ion concentrations comply with WHO (2022) standards; however, cadmium, iron, copper, and arsenic exceed permissible limits, indicating geogenic and possible anthropogenic influences. Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) values are elevated, suggesting localized organic contamination.Piper, Durov, and Schoeller diagram interpretations confirm Ca–HCO₃ facies for most samples, with minor mixed facies reflecting mineralized water mixing and local contamination. The study concludes that groundwater quality is largely influenced by lithology and structural controls, and recommends regular monitoring, contamination source control, and sustainable resource management to ensure safe and reliable water supply