Citing lower recoveries, Eldorado Gold has revised its 2017 guidance for the Kisladag gold mine in Turkey to 170,000 ounces (oz) to 180,000 oz at cash costs of $500/oz to $550/oz. At the beginning of the year, the company was expecting Kisladag to produce 230,000 oz to 240,000 oz. Guidance for 2018 and beyond, according to the company, is currently under review.
Kisladag is a low-grade, bulk-tonnage, open-pit operation that uses heap leach for gold recovery. While placing ore on the leach pad as planned during June, the company reported the gold solution grade and consequently gold recovery from the leach pad had lagged internal expectations. Initial laboratory and in situ tests, where solution chemistry was adjusted, indicated normal recovery rates were still expected. Eldorado also believed that more time for a solution to flow through the current stack height of the leach pad (approximately 80 meters at the highest point) was required.
During the third quarter, a significant amount of laboratory test work was undertaken, primarily focused on the zone of mineralization located around the base of the open pit where mining is currently under way. Monthly composite samples from material recently placed on the pad, even with adjusted solution chemistry, have indicated lower gold recoveries. Final recoveries in the low 40% range are now anticipated for this material and that will reduce the recoverable leach pad inventory by approximately 40,000 oz of gold.
Further metallurgical test work on heap leaching is ongoing to determine the extent of the impact on gold resources and reserves. The company is also investigating alternative treatment methods for this material, which includes studies on finer particle breakage, either through milling or high pressure grinding roll (HPGR) crushers. The company has previously contemplated construction of a mill at Kisladag and historic and ongoing test work using bottle rolls and other metallurgical tests indicate that milling should result in consistently higher recoveries compared to heap leaching throughout the orebody.