Sequential Indicator Simulation with Locally Varying Anisotropy – Simulating Mineralized Units in a Porphyry Copper Deposit

Resumen

The definition of mineralized units is key to the predictive capacity of a resource model, since these units define homogeneous volumes where spatial estimation or simulation of the relevant grades can be performed. In this paper, we adapt sequential indicator simulation to model mineralization units in a large porphyry copper deposit, accounting for the weathering profile that defines the vertical zoning of these units. A locally varying anisotropy field is created from the geological interpretation of the contact between the mixed mineralized unit, where the rock mineralization transitions from supergene to hypogene sulphides. A sequential indicator simulation routine is modified to account for the local variations of the units, and all distances are computed through these folded surfaces. Sensitivities related to the main parameters of the simulation algorithm that accounts for the locally varying anisotropy are performed to select the optimum parameters. The final result is compared with conventional sequential indicator simulation, against the geological units logged in blast holes, at a much denser grid, showing an increase in the accuracy in predicting the mineralized unit from the drillhole logged data.