A novel geostatistical index of uncertainty for short-term mining plan

Abstract

ABSTRACT The uncertainty associated with geostatistical estimates is as important in a model as the estimated value itself. This uncertainty is commonly assessed through different scenarios obtained by geostatistical simulation methods. Although the applications of geostatistical simulation methods have grown significantly in recent decades in long-term modeling, the same improvement has not occurred in medium- and short-term modeling. This study presents the “geological-operational risk indicator,” which comprises: (1) the uncertainty of geological contacts, determined by the variance of the sequential indicator simulation; and (2) the continuity of grades, obtained by sequential Gaussian simulation for variability of grades in relation to the economic or operational limit of that variable. The proposed index is applied to five grade variables of a short-term model of the Capitão do Mato iron mine in Brazil. The results are satisfactory and advance the concept of a geological risk indicator that is appropriate for medium- and short-term operations. This novel indicator helps to predict and manage in advance the uncertainties associated with mining plans.