Environmental impact of increasing production of gold from hydrothermal resources

Abstract

As the Witwatersrand Basin of South Africa loses its dominance in world gold production, and production from hydrothermal resources continues to increase so there is an upward trend in the exploitation of the so-called refractory zones associated with these deposits.

These ores are pyritic in nature, often containing appreciable quantities of arsenic as arsenopyrite. Much of the gold is occluded in the crystal structure of the sulphide minerals, particularly the arsenopyrite. As a consequence, a much higher level of processing is required when compared to conventional “oxidised” ores, with greater pressure on the environment.

Together with this trend in gold production, significant advancements have been made in the development of alternative recovery technologies. From the environmentally hazardous Edwards roasters through the more sophisticated fluosolids system, to second generation hydrometallurgical processes of pressure and biological oxidation.

The paper demonstrates how technological developments have not only been driven by the normal quest for lower costs and higher recoveries, but in this case by consideration for plant safety and the environment. The modern plant is considered ‐Cenvironmentally safe” with respect to current discharges. However, will they be just as safe in the long term?