Application of geographic information system in reserves estimation of Oyo-lwa marble deposit, Lokoja Area, Central Nigeria

Ore reserves estimation was carried out using GIS modelling on the Oyo-lwa marble deposit in the basement complex of west central Nigeria. Based on topographic, geological, geophysical, and geochemical appraisal, exploratory boreholes and geophysical parameters, distributed on 400m grid pattern were applied. The GIS modelling and delineation using TIN-surface interpolation of the iso-resistivity maps gave approximately 77 million tonnes of marble, while calculations from borehole logs using TIN-surface model, cut and fill method gave approximately 80 million tonnes for a depth recovery of 20m. Using rectangular block method and assuming a recoverable total thickness of 15-20m of the marble, an estimated volume of 24-30 million tonnes is considered to be available for exploitation. With marble bulk density of 2.67t/m3 using rectangular block pattern of estimation, a conservative reserve estimate of 60-80million tonnes of marble is expected to be available for exploitation within the area of investigation.