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Case histories |
Mineral Resource Evaluation Research Unit, Department of Geology, University of Wales College of Cardiff, PO Box 914, Cardiff CF1 3YE, UK
The Nsuta manganese deposit is located about 6.5 km south of Tarkwa in the southwestern region of Ghana. It is associated with a carbonate horizon within a thick series of interbedded grey tuffs and thin argillaceous horizons of Precambrian, Upper Birimian age. The manganese oxide mineralization, produced by supergene enrichment of the stratiform carbonate horizon, occurs as massive, patchy or bedded accumulations of psilomelane, with numerous veinlets and cavity fillings of pyrolusite. Due to the impact of folding and faulting and past mining activity (open-pit), the remaining resources have a complex spatial distribution. The study described is based on a portion of this deposit referred to as Hill D (South Crest). Initial statistical studies revealed the existence of two assay populations which appear to correspond to two geologically identifiable ore types that cannot be differentiated at the present scale of mining. Two geostatistical methods (ordinary kriging and indicator kriging) were used to evaluate the resource and the estimates so produced were then compared. A wireframe model was used to constrain the three dimensional geostatistical block model.
