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Mayskoye

Long-life high-grade refractory gold mine with 3 Moz in additional resources

Quick facts

Location Chukotka, Russia
Ownership 100%
Mining open-pit/underground
Processing 850 Ktpa flotation plant, third-party offtake/Amursk POX
Reserves (JORC) 1.4 Moz GE, 6.9 g/t average grade
Resources (JORC) 3.2 Moz GE, 11.9 g/t average grade
Production start date 2011
Life of mine 2034
Employees 977
Key highlights 2016
116 Koz Total gold production
6.9 g/t Average reserve grade
761 Kt Ore processed
94.4% POX recovery

Overview

Mayskoye is one of Russia’s top high-grade refractory gold deposits that was brought into the Group’s production profile in 2011 as part of the Amursk Hub project. Mayskoye comprises of an operating underground mine and a 850 Ktpa on-site flotation concentrator, launched in 2010 and 2013, respectively.

The operation primarily produces gold concentrate via the conventional floatation method, which is then shipped to third party off-takers or the Amursk POX plant for further processing into gold dore bars.

In 2016, Polymetal initiated a project to extract crown pillars at zones 1 and 2 via open-pit mining. The open-pit will deliver oxide and transitional orese that will be processed through the retrofitted on-site processing plant which includes new cyanide leaching tanks and a tailing detox.

Location History Geology and Mineralisation Operations Reserves and Resources

Mayskoe is located in North-Eastern Russia, in the Chaun distrct of the Chukotka Autonomous Region, in a remote unpopulated area covered by Arctic tundra. The deposit is accessible all-year round via 187 km of improved unpaved roads from the town of Pevek (population of 4,000), which also happens to be a major seaport, and holds a local airport that is capable of accommodating a variety of commercial aircrafts. Spare parts and other supplies are delivered through the port of Pevek, from July to early November each year.

Location

Mayskoye was first discovered in 1972 and was extensively explored between 1974 and 1986, mostly by surface diamond drilling. The deposit was the subject of several statutory feasibility studies conducted by both the Soviet Union and Russia. In 2004, Highland Gold acquired the licence for the deposit through a public auction, and by 2008, substantial infrastructure was built on site, including road access and accommodation. In the same year, a feasibility study was completed by Aker Kvaerner and the development of the underground mine commenced in the first quarter of 2008.

The Group acquired the property from Highland Gold in 2009 and incorporated Mayskoye into the Amursk POX hub in order to reduce capital costs necessary for the construction of a stand-alone processing plant. Construction of the Mayskoye concentrator began in 2010 and it was commissioned in 2012.

Gold mineralisation at Mayskoye is of the medium-sulphide, gold-pyrite-arsenopyrite type and is mostly associated with the steep quartz-feldspar dykes. Economic gold mineralisation is confined to high-grade gold-quartz-sulfide veins. Only 46 of more than 300 veins were subject to gold resource assessment, which were grouped into six mineralised zones to prioritise further mining operation scheduling. The average ore body width is 0.8 to 5.2 m and the zone of oxidation can be traced to a depth of 300 m. Gold in the oxidized zone can be found both in free and sulphide-associated forms.

Flowcharts

Mining

Current reserves at Mayskoye have an estimated depth of 300 m from the surface, with resources extending to a depth of 1,000 m. The primary ore that makes up more than 90 % of the total reserves, is accessed with three separate sets of twin spiral ramps in the central, eastern and western parts of the deposit. This technique allows for greater mining flexibility in terms of tonnage, grade and metallurgical characteristics (sulphur content and organic carbon content).

Several underground mining methods are used at Mayskoye, but more than 80% of ore is mined by sub-level open stoping. Oxidised ore is mined in a series of shallow open pits, as well as the underground. However, due to persistent problems with ore stability that was partly responsible for fatal accidents at the mine, we accelerated a planned changeover from drift-and-fill mining to sublevel open stoping with backfill. The new mining system was designed to ensure that employees are not exposed to the falling rocks in the partially broken stopes since all development and production drilling will be done from waste openings. This new mining method has demonstrated positive dynamics, ensuring lower dilution from secondary stopes and reduced primary stope length.

Processing

Primary ore from Mayskoye will be processed via conventional floation at the 850 Ktpa circuit based on on-site. The circuit comprises single-stage crushing followed by three-stage grinding (in one SAG mill and two ball mills) and three-stage conventional flotation. The flotation concentrate is then thickened, filtered, dried and packed into big bags, which are then transported to the port of Pevek, for further transportation to the Amursk POX hub and third party off-takers.

Oxidised ore, on the other hand, is processed using conventional RIL cyanidation. This process uses the same crushing and milling equipment as the flotation circuit, where slurry is subject to thickening, leaching, resin, resin deactivation, electrolysis and smelting. The cyanidation tailings are then filtered and dry stacked in the lined tailings storage facility.

Due to refractory nature of Mayskoye ore, pre-treatment oxidation processing is required, which is done at the Amursk POX hub that was launched in 2012. In the process of choosing an optimal processing method for refractory ores, autoclave leaching (POX) was selected as the most viable option. All research and test work carried out in the process was done by SGS and our in-house engineering team. For more details on the Amursk POX hub, please click here.

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
Total 6.5 6.9 - - 6.9 1,429 - - 1,429
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
Total 8.5 11.9 - - 11.9 3,239 - - 3,239

Gallery