Mineral Resources classification of a nickel laterite deposit: Comparison between conditional simulations and specific areas

Abstract

Classification of Mineral Resources as Measured, Indicated, or Inferred depends on the level of confidence the resource geologist has in the estimation of the deposit. This is based on different factors such as the geological or geometrical model, the sampling quality and, from the geostatistical point of view, the distance between drill-holes. However, many methods or criteria used for classification, geometrical ones for instance, are not based on an actual measure of uncertainty. In the present case, which corresponds to a nickel laterite deposit studied in two dimensions, Mineral Resources are classified based on the drilling mesh, and associated probabilities that nominal productions do not deviate from estimations by more than 15%. In this paper we present two methods to assess such probabilities: conditional simulations and the specific areas method. Both methods include the drilling mesh and the spatial variability as principal components for classification and both yield similar results, which allows the validation of one with the other. Benefits and limitations of these two methods are also given. Simulations are time-consuming, but they are the most accurate; specific areas are time-saving and less restrictive for testing several drilling meshes, but the results are more approximate.