Considerations and potential economic advantages for the in-situ recovery of gold from deep, hard-rock deposits

The combination of commodity prices and price uncertainty, coupled with ever-increasing capital and operating costs of mining and metal production create significant challenges for the metals mining industry. With current (“conventional”) technologies, it may not be feasible to extract and process many known deposits economically. This is because of declining grades, challenging mineralogies and increasingly greater depths, amongst other factors. To overcome these issues, it is appropriate to reconsider the wider application of a step-change technology, such as in-situ recovery (ISR), which reduces or eliminates mining and comminution costs significantly. Although a number of attempts have been made towards gold ISR processing, no commercial applications of this technology exist currently. In this paper, the suitability of various gold-bearing deposit types is discussed with reference to their potential for ISR processing. Solution chemistry-related issues and potential lixiviants for use in ISR are described and the challenges for gold ISR are highlighted. Despite the technical challenges presented, a preliminary techno-economic evaluation indicates the potential profitability of such a process.