Optimising multi-element cut-off grades for a strategic production plan under geological uncertainty

Abstract

Mines operate in uncertain heterogenous environments, in which the most profitable material must be delineated from lower value-material. Traditionally, single-element cut-off grades provide this delineation and methods for optimising date back to the 1960s. Recent advancements have included geological uncertainty, multiple elements, and production scheduling; however, no method combines all three improvements. Two multi-element cut-off grade definitions are proposed herein, along with a reinforcement learning framework for optimising long-term multi-element cut-off grades under geological uncertainty for an optimal production plan. The method is applied to a gold-copper mining complex, and the performance of both cut-off grade definitions is compared.