Eldorado Gold has provided updates for its 95% owned Olympias gold project in northern Greece and its 80.5% owned Certej gold project in western Romania. Eldorado acquired both projects when it acquired European Goldfields in early 2012. Both projects have been previously mined.
Olympias: Eldorado is redeveloping Olympias in three phases. Phase I is currently in operation and is reprocessing previously deposited tailings to recover a gold concentrate through an existing concentrator. Eldorado expects to complete Phase I operations by the end of 2015.
Phase II involves rehabilitation of previously mined underground operations and conversion of the concentrator to differential flotation to allow production of separate lead, zinc and gold concentrates. Plant throughput will average 385,000 mt/y.
Production of metal in concentrates during the first four years of full operation is expected to average 60,725 oz/y of gold, 1.1 million oz/y of silver, 12,200 mt/y of lead, and 12,900 mt/y of zinc. Operating costs are estimated at $309/oz of gold, net of byproduct credits.
During preparations for Phase II, the concentrator will be shut down for installation of the three flotation circuits. Prior to the shutdown, rehabilitation work will be carried out in a number of areas, including replacement of crushing facilities for mined ore, modifications to the thickening and filtration circuits, and installation of a new ball mill.
Cost to complete the Phase II plant conversion is estimated at $45.6 million.
Development of the underground mine to support Olympias Phase II production has involved rehabilitation of existing drives and development of new access to the ore. A total of 13,000 m of mine development had been completed as of early June.
Drift-and-fill stoping with paste backfill has been selected as the most effective mining method. Sufficient mine development and infrastructure are expected to be in place to support ramping up of underground ore production starting in the second quarter of 2016. Phase II is planned to operate for six to eight years.
Planning for Olympias Phase III is currently in progress and includes a new concentrator and new mine development to access the bottom of the Olympias orebody. Plant throughput is being planned at 800,000 mt/y.
Certej: A recently completed feasibility study supports development of the Certej project as an open-pit mine and pressure oxidation processing plant producing an average of 140,000 oz/y of gold and 830,000 oz/y of silver in a gold-silver doré over an operating life of about 15 years. Plant throughput would average about 8,000 mt/d.
Certej has 2.4 million oz of gold and 7 million oz of silver in proven and probable reserves at grades of 1.69 g/mt gold and 10.9 g/mt silver. Total initial capital costs to develop the project are estimated at $449 million.
Having evaluated several options for dealing with the refractory nature of the Certej ore, Eldorado selected pressure oxidation as the best available technology. As part of the feasibility study, the company evaluated and implemented several process optimizations and simplifications to reduce capital requirements.
Certej ore will comminuted by crushing, followed by SAG and ball milling. The ground ore will be subjected to simple rougher flotation to separate the gold-bearing sulphide fraction from the host andesite. Flotation concentrate will then subjected to pressure oxidation. The oxidized solids will be treated with limestone and lime at elevated temperatures to facilitate silver recovery, prior to conventional precious metal recovery by carbon-in-leach cyanidation, carbon stripping, and electrowinning.
Carbon-in-leach tails will be subjected to further treatment to ensure residual cyanide is destroyed before the tails are impounded. Eldorado is a signatory member of the International Cyanide Management Code and will work toward certifying Certej as compliant with the code.