Risk quantification in grade-tonnage curves and resource categorization in a lateritic nickel deposit using geologically constrained joint conditional simulation

The risk quantification in grade-tonnage curves is critical for capital investment in mining projects. Geostatistical simulations for orebodies can be used to obtain grade-tonnage curves, and determine uncertainty and risk assessments. Applying these in multi-element deposits can be a difficult practice, as the related attributes using the traditional co-simulation approaches require intensive computational work and may be impractical for use in the mineral industry. This paper presents the risk assessment for integrating grade-tonnage curves and resources categorization for lateritic nickel deposits in the central region of Brazil, by joint simulation of multiple correlated variables of interest: Ni, MgO and SiO2. The joint simulation of these variables is based on Minimum/Maximum Autocorrelation Factors (MAF). Based on this approach, the resources are categorized honoring Ni joint simulated results by applying the 15 % rule, where it is considered there will be a statistical error < 15 %, with 90 % of a confidence interval per production period. © 2011 Pleiades Publishing, Ltd.