Alacer Gold announced in early November its intention to employ whole ore pressure oxidation to process the refractory sulphide ores at its 80% owned Çöpler gold mine in Erzincan province, eastern Turkey. Alacer currently mines and heap leaches Çöpler oxide ores, with 2013 production expected to be in the range of 192,000 to 200,000 oz.
Alacer Gold currently mines and heap leaches oxide ores at its 80% owned Çöpler mine, pictured here, with 2013 production expected to be in the range of 192,000 to 200,000 oz.
Alacer said an exhaustive technical review confirmed that pressure oxidation processing provides the best economic return from the Çöpler sulphides. The highly refractory nature of the sulphides resulted in very low gold recoveries when conventional cyanidization processing was tested, even when fine grinding was applied. Gold recoveries using these non‐oxidative processes were in the range of 15% to 40%.
Further test work during 2013 confirmed that flotation of Çöpler sulfides could recover 75% to 80% of the gold; however, the recovery came in the form of a relatively low‐grade concentrate that would be unattractive from marketing and logistical perspectives. Test work to improve concentrate grade through further flotation was unsuccessful due to a precipitous drop in gold recoveries.
Two‐stage roasting was also tested but pressure oxidation was the only process that demonstrated nearly complete oxidation of the sulphide ore (approximately 97%) with effective liberation of gold values, resulting in gold recoveries of 94%.
Alacer will take a phased approach to the development of pressure oxidation processing of the Çöpler sulphides, starting with a definitive feasibility study (DFS) of a 5,000-mt/d plant that can be scaled up in the future if conditions warrant. The company expects to complete the DFS no later than June 2014.
Upon completion of the DFS, Alacer will decide whether to proceed to detailed engineering and construction of the project. Alacer believes that the DFS will demonstrate that the pressure oxidation project is economically compelling in the current market environment.
Çöpler’s measured and indicated sulphide resource currently totals 120.9 million mt grading 1.5 g/mt gold. This resource contains approximately 6 million oz of gold, while the mine’s oxide resources currently total about 2.5 million oz of contained gold.
Alacer Gold CEO Rodney Antal said, “As evidenced by our successful heap leach operations at Çöpler, Alacer has demonstrated its ability to permit, construct, commission and operate a mine in Turkey. Alacer expects to leverage this experience to successfully deliver the next phase of Çöpler’s development.
“Importantly, we expect that most, if not all, of the up‐front capital required to construct the pressure oxidation project will be funded using existing cash and future cash flows from the high‐margin, low‐cost oxide heap leach operations at Çöpler.”