The Keno Hill silver project is located within Keno Hill silver district (KHSD) in Canada’s Yukon Territory. Alexco Resource is the project developer, which acquired mineral rights of KHSD through its subsidiaries in 2006 from United Keno Hill Mines.
The Keno Hill silver-lead-zinc mining project includes five deposits namely Bellekeno, Lucky Queen, Flame & Moth, Onek, and Bermingham.
Alexco developed the Keno Hill silver district and constructed a new mill complex in 2010, which processed ore mainly from the Bellekeno Mine. The company, however, suspended the mining operations in 2013 and is currently focusing on conducting additional exploration to increase mineral resources at the Bermingham and Flame & Moth deposits.
Preliminary economic assessment (PEA) of the project was completed in March 2017, followed by the preliminary feasibility study (PFS) in March 2019. With an estimated operating cost of $362m, the project is expected to have a mine life of eight years.
It is expected to produce high-grade lead-silver concentrate and a zinc-silver concentrate.
Keno Hill silver project location, geology, and mineralisation
The Keno Hill silver project is a part of the Keno Hill silver district, which is one of the highest-grade silver districts in the world. It is located 330km north of Whitehorse and is also a part of the traditional territory of the First Nation of Na-Cho Nyak Dun (FNNND).
Extending in 233km², the silver district hosts numerous mineral occurrences and more than 35 mine sites with historic production. The project site covers an area of approximately 15,000ha.
The property lies along the broad South McQuesten River valley on three prominent hills namely Galena Hill, Keno Hill, and Sourdough Hill, which are collectively known as the KHSD. Galena Hill hosts the Bermingham deposit, Keno Hill hosts the Lucky Queen and Onek deposits, and the Sourdough Hill hosts the Bellekeno deposit.
The mineralization at Keno Hill is largely polymetallic silver-lead-zinc vein type with common gangue minerals including siderite, quartz, and calcite.
Keno Hill silver project reserves
As of May 2019, the project was estimated to contain proven reserves of approximately 1.18 million tonnes (Mt), grading 805g/t silver, 2.98% lead, and 4.13% zinc. It is estimated to contain 30.45 million ounces (Moz) of silver.
Mining and ore processing at Keno Hill project
Conventional underground mining methods, involving cut-and-fill and longhole stoping, will be used at all the high-grade deposits, featuring narrow vein widths.
Drift and fill method with cemented rock fill is proposed for wider areas of the ore body, while longhole stoping is proposed for areas where sill pillars can be recovered between the cut-and-fill levels.
The lead-silver concentrate is expected to have an average grade of 15,890g/t silver, 54% Pb, and 3.7g/t Au, while the zinc-silver concentrate will have a grade of 649g/t silver and 53% zinc. It is anticipated to produce 4Moz silver product annually in concentrate.
The processing plant is expected to have an average throughput of 430tpd and a peak throughput of 550tpd in the third year of operation.
The mined ore will undergo crushing, followed by two stages of primary grinding in a closed circuit with hydrocyclones to produce a P80 product size of 100µm to 120µm.
The ground produce will then pass through a grinding classification lead rougher and scavenger flotation circuits. The resultant reground and rougher lead scavenger flotation concentrates will be upgraded in the lead flotation circuit to produce the final silver-bearing lead concentrate.
The lead rougher scavenger tailings and the lead 1st cleaner tailings will be sent to the zinc rougher and zinc rougher scavenger flotation circuits to produce zinc rougher concentrate.
Infrastructure facilities at Keno Hill
Access to the project is through the Silver Trail highways, which will further connect to the 460km Alaska-Klondike highway.
Power supply will be provided by the hydroelectric plant near Mayo. Workers will be accommodated at a 90-bed camp located near the old Flat Creek town site.
Mining Plus Canada Consulting (Mining Plus) prepared the PFS and independent technical report of the Keno Hill silver project.