Abstract

This paper addresses the problem of simulating the copper grade and rock type in a Chilean porphyry copper deposit recognized by a set of exploration drill holes. The application of contact analysis tools (cross-to-direct variogram ratios, cross-correlograms, pseudo cross-variograms and lagged scatter plots) reveals the coexistence of hard and soft boundaries between rock type domains. A quadrivariate coregionalization model is developed to fit the spatial correlation structure of the rock type and grade, based on indicator and normal scores direct and cross-variograms. A two-stage approach is first used for simulating the intrusive porphyry and the copper grade in it, while the other two rock type domains and their copper grade are jointly simulated in the space not occupied by porphyry. Such a mixed approach is shown to reproduce the nature of the rock type boundaries and is validated by split-sample validation.