Simulation-based control of cyanide consumption for narrow vein Au-Ag mining incorporating geostatistical simulations into stochastic dynamic mass balance

Narrow vein Au-Ag deposits have practical and academic relevance for mining operations research and geometallurgy. The restricted two-dimensional vein geometry is subject to inflexibility in the mining sequence and thus forces any feed imbalances into the metallurgical plant to be resolved through stockpiling and blending. The geometrical inflexibility simplifies the dynamic simulation of the mining system, allowing a decoupling of (1) the geospatial simulation of critical ore attributes from (2) the downstream operational decisions that govern the metallurgical process. Whereas sequential Gaussian simulation (SGS) is the most common geostatistical technique for conditional simulation of spatially distributed attributes, discrete rate simulation (DRS) is arguably the most basic approach to dynamic mass balance, capable of representing departures from stable metallurgical operating conditions and tallying the impact. Relevant impacts can include lost recoveries, lost throughput, and ineffective use of reagents such as cyanide, or combinations thereof. The current work is the first instance that directly combines SGS and DRS within a single framework, representing an industrially relevant context that is low-sulphidation epithermal gold-silver deposits. The framework is comparable to an inventory stockpile simulation, typical of a manufacturing context, except that the supply uncertainty is subject to geological complexity, e.g. a fault-laden paleo-phreatic surface separating overlying oxide ores from underlying sulphide ores, which complicates the downstream cyanidation process, as in the El Peñón Mine (Chile). Operating policies can be formulated and parametrised within the framework and tested against geological scenarios that are based on drill samples taken from the workface, and considering critical geological features such as structural transitions in mineral assemblies. Sample computations demonstrate that refined stockpiling and blending can result in a 14% decrease in cyanide consumption during a demanding stage of the mine life, while maintaining other key performance indicators such as gold and silver recovery, and throughput.