10th U6+ Consortium of African Universities International Conference

Phosphate rock and shale samples were collected from five mine sites (P1–P5) in the Sokoto Basin, northwestern Nigeria, to characterize their mineralogical composition, quantify naturally occurring radioactive element concentrations, and evaluate associated radiological hazards to mine workers. Ten samples from each lithology were analyzed by X-Ray Diffraction (XRD) for mineral identification, while Uranium (U), Thorium (Th) and Potassium (K) concentrations were determined using ICP-MS. Phosphate deposits occurred as nodules intercalated within shale at depths of 0.25–7 m. Dominant phosphate minerals included fluoroapatite (1.33–79.28%), calcite (42.22–97.89%) and smectite (2.39–13.13%), while shales were characterized by smectite (23.01–64.78%), quartz (1.92–64.08%) and calcite (0–67.75%). P₂O₅ concentrations of 0.29–22.29% indicate low-to-medium grade ore. Uranium and Thorium were preferentially enriched in phosphate and shale respectively, consistent with apatite lattice substitution and clay-mineral affinity. Radiological hazard parameters for all shale samples remained within internationally recommended safety limits, indicating no significant health risk from shale exposure. However, phosphate samples at several sites exceeded safe thresholds: radium equivalent activity and external hazard index were exceeded at P2 and P5; the internal hazard index surpassed 1.0 at P1, P2, P4 and P5; and gamma index and annual effective dose exceeded acceptable levels at P1, P2 and P5. These results indicate that prolonged, unprotected exposure to phosphate material, particularly at sites P1, P2 and P5, poses a measurable long-term radiological health risk to mine workers.