The Voro deposit is mined solely by open-pit mining methods and this is expected to continue until the end of its mine life. Ultimately, the mine design is the excavation of two pits: a 240 m deep pit to the north; and an 80 m shallow pit to the south. A conventional truck-and-shovel method is employed with drilling and blasting primarily used in the deep pit. Both primary and oxidised ore are stockpiled and blended near the pit and then transported to the processing facilities located 6 km away. Waste dumps are located 1 to 2 km from the pit.
|Location||Sverdlovsk Region, Russia|
|Processing||950 Ktpa CIP circuit, 1,000 Ktpa HL with CIC|
|Reserves (JORC)||0.8 Moz GE at 2.3 g/t|
|Resources (JORC)||1.0 Moz GE at 4.9 g/t|
|Production start date||2000 (HL), 2005 (CIP)|
|Life of mine||2028 (CIP)|
Voro is one of Polymetal’s very first key gold assets acquired in 1998, and despite its current mature stage of operations and a planned decrease in production, it continues to demonstrate excellent operating and financial performances with significant contributions to free cash flow. Today, Voro comprises an open-pit mine, a 950 Ktpa carbon-in-leach processing plant and a seasonal 1000 Ktpa heap leach circuit that accommodate the processing of both primary and oxidised ore.
Voro is located in Russia’s Sverdlovsk region, approximately 370 km north of the regional centre of Ekaterinburg (population of 1.5 million) and 25 km south of the city of Krasnoturinsk (population of 65,000). Voro is easily accessible from Ekaterinburg via the federal highway that runs 7 km from the site. The industrialised and moderately populated area around the deposit is home to several mining companies, ensuring good access to the grid and other infrastructure. In addition, there is good railway access with a Group-owned spur located 18 km from the site.
The deposit was first discovered in 1985. In 1998, the Group acquired the company that held the mining licence for Voro. In 1999 mining resumed and heap leaching circuit for oxidised ore was launched in 2000. In 2005, the CIP plant was commissioned with a capacity of 450 ktpa. The plant was expanded to 600 ktpa in 2007 by replacing three-stage crushing with one-stage crushing and SAG milling. The plant was further expanded to 940 ktpa in 2008 by removing bottlenecks from thickening, leaching and filtration sections. In 2010, mining started on the new southern pit to extract ore from an extension of the main deposit.
The Voro deposit is a fracture zone where the ore body generally lies in the footwall of the fault.The main mineralised zones occur within brecciated limestone and are erratic in shape, not visually identifiable and require dense grade control drilling for final delineation prior to mining. A highly variable weathering pattern is developed across the deposit, with a broad oxidation surface developed to a depth of 65 m, but zones as deep as 100 m are developed where karstic features have formed in the limestone. An extension to the main Voro deposit of mainly oxide material has been outlined in the south.
Oxidised gold at Voro occurs mostly in free form. In primary ore, gold occurs in a variety of forms. These include free, inter grown with host minerals, associated with pyrite and attached to silicates. The highly variable mineralogy of primary ore requires careful selection of processing regimes.
Two processes are used to extract gold from the two types of ore mined at Voro. Oxidised ore is processed by heap leaching with a capacity of 1,000 ktpa, while primary ore is processed by milling/CIP with a capacity of 950 ktpa.
The primary ore is crushed in a jaw crusher and further treated in a three-stage milling circuit (one SAG mill and two ball mills). A standby circuit, which operated before the expansion (three-stage crushing), is available during the SAG mill downtime. After milling, slurry is thickened and leached (approximately 48 hours residence time) in a CIP circuit. Further processing includes desorption, electrolysis and smelting to doré. Tails are filtered and transported to a dry-stacking tailings storage facility immediately adjacent to the plant.
|Ore Reserves||Tonnage, Mt||Gold grade, g/t||Silver grade, g/t||Copper grade, %||GE grade, g/t||Gold, Koz||Silver, Moz||Copper, Kt||GE, Koz|
|Mineral Resources||Tonnage, Mt||Gold grade, g/t||Silver grade, g/t||Copper grade, %||GE grade, g/t||Gold, Koz||Silver, Moz||Copper, Kt||GE, Koz|
- In 2017, the Company increased Voro’s mineral resources by 28% to 1.0 Moz GE with the discovery of a new gold deposit at Pesherny (30 km from the CIP plant). An initial resource estimate comprised 449 Koz of gold at an average grade of 6.7 g/t. In 2018, we plan to continue exploring this highly promising property that may significantly extend the life-of-mine and halt production decline at Voro.
- At Saum, mineral resource grew to reach 67.4 Kt of copper equivalent at an average grade of 2.9%. In 2018, we plan to complete the feasibility study for the property.
- At Voro open pit, exploration focused on the assessment of mineralisation below the ultimate pit floor. Mineral resources grew by 86 Koz of gold equivalent at 2.6 g/t. The results suggest feasibility of underground mining after open pit mining is completed. Ore bodies are open along strike with drilling to continue in 2018.