In its 2021 guidance and three year outlook, just released, Centerra Gold outlines the near future for its flagship operations, including developments and production predictions for the next few years at Kumtor gold mine in Kyrgyzstan and the Mount Milligan copper-gold mine in BC, Canada.
Looking first at Kumtor, operated by Kumtor Gold Company (KGC), Centerra expects an increasing gold production profile at Kumtor over the 2021-2023 period, with 556,000 oz produced in 2020 but with planned production of 550,000 to 600,000 oz by 2023 after a dip in 2021. “While the mid-point of gold production in 2021 is expected to be approximately 12% lower than 2020 gold production at the mine, Centerra expects 2022-2023 gold production levels to return to or exceed 2020 levels.” Kumtor is one of the highest gold deposits in the world, situated in the southern region of the Central Tien-Shan at an altitude of 4,000 m above sea level in a permafrost zone. The deposit is located 350 km from Bishkek, the capital of the Kyrgyz Republic.
Kumtor gold production in 2021 is expected to be in the range of 470,000 to 510,000 oz and reflects lower average grades in the ore stockpiles available for processing compared to 2020. Gold production is expected to rise steadily throughout the year with the first quarter of 2021 contributing approximately 15% of annual gold production rising to approximately 35% in the fourth quarter of 2021. Total tonnes mined are expected to increase to a rate of approximately 550,000 tonnes per day from the average mining rate of 280,000 tonnes per day in 2020 due to the addition of new mining equipment, a resumption of waste rock dumping at the Lysii waste rock dump and fewer expected restrictions due to COVID-19. Mine operations are expected to be focused mainly on waste stripping from cut-back 20 during the first half of 2021, accessing greater amounts of ore in the second half of the year and accessing the high-grade ore in the fourth quarter.
Expansion of the mine fleet capacity will play a big part in allowing Kumtor to exceed 2019 mining levels. In the 2021 Kumtor Technical Report, the fleet additions are outlined – the main haulage fleet includes 71 Caterpillar 789 haul trucks and 26 Caterpillar 785 haul trucks. To maintain production requirements with longer hauls KGC added 11 used Caterpillar 789 haul trucks in 2020; and is adding another 10 new Caterpillar 789D haul trucks in early 2021. A further eight trucks were to also be added later in 2021 but have now been deferred to 2022. The mine is also seeing mill improvement projects, including a tower mill project for regrinding of flotation tails is expected to allow Kumtor to achieve higher targeted gold production levels.
Sustaining capital expenditure is projected at $55 to $65 million in 2021 and relates primarily to major overhauls, purchase of mining equipment, replacement of regrind mill motor, and dewatering projects. Non-sustaining capital investment at Kumtor for 2021 is forecast at $60 to $70 million which includes, expansion of the leach circuit, the tower mill project for regrinding of flotation tails to improve future recoveries, and additional capital expenditures for mine life extension related to development of the cut-back 21 and Hockey Stick zones, including mine fleet expansion and raising of the tailings dam.
A new LOM plan expects open pit mining to continue uninterrupted until 2028 with a final year of Central Pit mining in 2031 to mine out reserves associated with the Central Pit step out adjacent to the process plant, and processing operations of the Kumtor Mine to end in 2031. The LOM plan is based solely on open pit Mineral Reserves and has no provision for production from any underground mining activities.
Open pit mining at Kumtor is performed using conventional open pit bulk mining methods with hydraulic shovels and mining trucks on 10 m benches. Blast holes are drilled using three diesel-powered Sandvik DR460 rigs and five Drilltech D55SP rotary-percussion drill rigs, with a hole diameter of 200 mm. Loading of the blast holes is undertaken by bulk explosives trucks delivering either ANFO or an emulsion explosives blend. The average explosives consumption is approximately 0.21 kg per tonne of bedrock material. Ice and moraine are considered free-dig materials. Management of the on-site explosive plant is outsourced to Orica.
The main loading fleet operating in 2020 consists of five Hitachi EX3600 29 m3 shovels and nine Liebherr 9350 26 m3 hydraulic face shovels, one of which has been converted to a backhoe excavator. Each of the Hitachi 3600 shovels has an expected average productivity of 47,000 t/d while the Liebherr 9350 shovels are expected to yield 42,500 t/d per shovel. The productivity in rock, till and ice varies due to the digging characteristics of each material. Cat 992K wheel loaders are utilised for handling material on stockpiles and various auxiliary operations. The main haulage fleet includes 71 Caterpillar 789 haul trucks and 26 Caterpillar 785 haul trucks.
The top mining elevation in the current ultimate pit design is at 4,520 m, and the deepest part of the final pit excavation will be at 3,510 m in the southwest part of the Central Pit. The crushing plant to which ore is delivered is at an approximate elevation of 4,050 m. Waste haulage profiles are a combination of both uphill and downhill hauling. Management of the entire mining fleet (including auxiliary equipment) is undertaken using a MineSense dispatch system supplied by Peru’s MS4M.
Over to Mount Milligan, Centerra expects strong gold and copper production over the 2021-2023 period. The Mount Milligan mill is expected to maintain a stable average daily throughput of approximately 60,000 t/d, the maximum permitted rate. Installation of Woodgrove Staged Flotation Reactors is expected to contribute to achieving targeted gold and copper production levels in 2022 and beyond. The mine produced 162,000 oz of gold in 2020 – for 2021, the company expects to achieve an average daily throughput of approximately 60,000 t per calendar day. Mill maintenance downtimes are scheduled for the first quarter and third quarter to complete SAG Mill reline replacements and other maintenance work. Mount Milligan’s total 2021 gold production is forecast to be in the range of 180,000 to 200,000 oz. For copper, the mine produced 83 Mlb in 2020 and is set to produce 70-80 Mlb in 2021 before increasing to 90-100 Mlb in 2022.
Sustaining capital expenditure in 2021 is forecast to be $65 to $70 million and relate primarily to tailings storage facility costs, major overhauls and water management costs. Non-sustaining capital investment at Mount Milligan for 2021 is forecast at $5 to $10 million for the installation of the Staged Flotation Reactors to improve future metal recoveries.