Co-simulating Total and Soluble Copper Grades in an Oxide Ore Deposit

Abstract

In oxide copper deposits, the acid soluble copper represents the fraction of total copper recoverable by heap leaching. Two difficulties often complicate the joint modeling and simulation of total and soluble copper grades: the inequality constraint linking both grade variables and the sampling design for soluble copper grade, which may be preferential and cause biases in sample statistics. A methodology is presented in order to accurately estimate the total and soluble copper grade bivariate distribution, based on an explicit modeling of the conditional distributions of soluble copper grade. Co-simulation is then realized by converting the copper grades into Gaussian random fields, through stepwise conditional transformation, and by fitting a coregionalization model while accounting for the preferential sampling design. The proposed approach is illustrated through an application to an ore deposit located in northern Chile.