The Prairie Creek Lead-Zinc-Silver Project is located close to the Nahanni National Park Reserve, approximately 500km west of Yellowknife in the Northwest Territories (NWT), Canada. It hosts two surface leases and 12 mining leases, covering a combined area of 7,487ha.
The project is wholly owned by Canadian Zinc Corporation (CZN). The prefeasibility study (PFS) for the project was completed in June 2012 and was further updated in March 2016. The definitive feasibility study (DFS) for the project is scheduled for completion in mid-2017.
Approximately $244m is estimated to be invested to bring the project into production and the mine is estimated to have a life of 17 years.
Prairie Creek Lead-Zinc-Silver Project geology and mineralisation
The lead-zinc-silver project is located on the western flank of the Prairie Creek antiform, also known as the Main Zone, dominated by interbedded chert and dolomite. The Main Zone hosts four main types of base metal mineralisation, including the main quartz vein (MQV), stratabound sulphides (SMS), stockwork (STK) and Mississippi Valley type (MVT) mineralisation.
Mineralisation at the site occurs along the entire 16km north-to-south length of the property, while the project will involve the extraction of minerals from the MQV, SMS and STK zones.
Reserves and production
As of March 2016, the project was estimated to hold combined proven and probable reserves of 7.6 million tonnes (Mt), grading 127.58g/t silver, 8.33% lead and 8.93% zinc.
As of September 2015, the project was estimated to hold combined measured and indicated resources of 8.7Mt, grading 136g/t silver, 8.9% lead and 9.5% zinc.
Inferred resources were estimated to be 7.049Mt, grading 166g/t silver, 7.7% lead and 11.3% zinc.
Based on reserves, the project targets an average annual production rate of 60,000 dry metric tonnes (dmt) of zinc concentrate and 55,000dmt of lead concentrate, containing 86 million pounds (Mlb) of zinc, 82Mlb of lead and 1.7 million ounces (Moz) of silver.
Mining and processing at the NWT mine
The mining method envisaged for the project is the underground long-hole open stoping method (LHOS) and the mechanised drift-and-fill (DAF) method. The latter will particularly be used to extract the ore from the SMS zone. Tailings material from the deposits will be disposed underground as paste backfill.
The project’s processing plant will integrate a two-stage crushing circuit, dense media separation (DMS) facility, single-stage grinding circuit, lead sulphide circuit, zinc sulphide flotation circuit, lead oxide flotation circuit, concentrate dewatering and load-out systems, and tailings dewatering and paste backfill preparation systems.
Infrastructure for the Canadian lead-zinc-silver project
The project benefits from the presence of existing infrastructure, including a 1,000t/d mill, 5km of underground workings and related equipment, surface fleet, 1,000m airstrip, 180km access road, 50km of exploration roads, administration and warehouse buildings, an accommodation camp for 120 people, a 6.8 million litre fuel tank farm, 450,000m³ water storage pond, and a 200-year storm-protective Dyke system.
Tower and heat requirements for the project will be met through five 1.5MW each diesel-powered generators, leased from third parties.
The project will further involve construction of an additional on-site accommodation facility for 150 people, a concentrate shed and an incinerator, a water treatment plant, and upgrade of existing buildings and infrastructure. A new all-seasoned road is also proposed to be constructed to connect the mine site to the existing Liard Highway.
Concentrate transportation and off-take agreements
The concentrates will be transported in enclosed haul trucks, using the new mine access road and Liard Highway, to a rail line at Fort Nelson, and further by train to the Port of Vancouver, for final shipment to smelters abroad.
In March 2016, CZN entered two separate memorandums of understanding (MoUs) with two smelting companies for off-take of zinc and lead concentrates from the project.
Under the first MoU, CZN will supply Korea Zinc with approximately 20,000 to 30,000 wet metric tonnes (wmt) of zinc sulphide concentrates, 15,000wmt to 20,000wmt of lead sulphide concentrates, and 5,000t of lead oxide concentrates a year for a minimum period of five years.
As part of the second MoU, CZN will supply Boliden approximately 20,000dmt to 40,000dmt of zinc sulphide concentrates a year, for a minimum of five years.
Key players involved
The updated PFS was compiled by AMC Mining Consultants, in collaboration with Tetra Tech, and P.Eng., whereas the 2012 PFS was compiled by SNC-Lavalin, in collaboration with AMC.
HCF International Advisers was appointed as adviser by CZN to secure debt financing for the project, in February 2017.
CZN signed a memorandum of understanding (MOU) with Northwest Territories Power Corporation (NTPC) to determine the options for the supply of electrical power for the project, in February 2017.