BRITISH COLUMBIA – Chieftain Metals of Toronto has completed the preliminary economic assessment for its polymetallic Tulsequah Chief project 100 km south of Atlin. Pre-production capital costs are estimated at C$310.1 million. The study puts the net present value at $277 million and the internal rate of return at 25%.
The PEA outlines a project that will operate at 2,000 t/d over a nine-year mine life. Indicated resources total 6.0 million tonnes averaging 2.63 g/t Au, 96.0 g/t Ag, 6.44% Zn, 1.42% Cu and 1.23% Pb. The inferred resource is 1.1 million tonnes averaging 1.63 g/t Au, 72.0 g/t Ag, 5.02% Zn, 0.94% Cu and 0.93% Pb.
Chieftain plans to build a new underground mine adjacent to and beneath the old workings. The property was originally developed by Cominco, and it operated from 1951 to 1957.
The existing 5200 and 5400 level adits will be used as the primary access to the mine for all personnel, mine services, equipment and supplies. The adits will be enlarged to accommodate modern diesel trackless equipment.
Access to the various mining levels will be provided by a spiral ramp located in the hanging wall of the deposit. This location was selected because of the predominantly non acid-generating nature of the hanging wall stratigraphy, as compared to the potentially acid-generating footwall. Ore will be trucked to the surface.
Mining levels will be located at 30-metre vertical intervals. Each will be connected to an inclined ventilation raise to provide fresh air ventilation supply, vertical translation of services, and emergency egress to each level. Loading of trucks will be done on each mining level to minimize load-haul-dumper travel distances. The deepest mining level will be located 750 metres below the 5200 level.
Sub-level stoping will be the primary mining method employed. A minor amount of mechanized cut-and-fill stoping will be used in narrower portions of the ore body. Paste backfill and unconsolidated loose waste rock will be used for backfill for both methods. Where backfill walls will be exposed by future adjacent mining, additional cement will be added to the paste fill for strength..
Waste rock will be preferentially retained in the mine as loose unconsolidated rock fill in secondary stopes. Waste that is required to be removed from the mine will be hauled by truck to the segregated waste dumps on surface for proper storage and reclamation.
The mine will employ 4.6-m³ LHDs, 40-tonne trucks, two-boom jumbos, longhole drills, and rock bolters. All equipment will be diesel-powered, and all drilling equipment will be electric-hydraulic. Cassette carriers and multiple task-specific cassettes will be used to service the mine.
Annual production will be 69,400 oz of gold equivalent at a total cash cost (net of base metal byproduct credits) of negative US$365 per oz AuEq. Expressed another way, Tulsequah Chief will produce 74 million lb of zinc at a total cash cost of negative US$0.72/lb.
To read the PEA in full, check the company’s website, www.ChieftainMetals.com, where it will be posted shortly.