The Tulsequah Chief and Big Bull deposits are polymetallic volcanogenic massive sulphide (VMS) deposits of bimodal-felsic, island arc or arc related affinity, similar to the Kuroko type deposits found in Japan. These deposits are generally associated with back-arc basins associated with subduction tectonic environments. The deposit consists of several distinct lenses of massive sulphide mineralization that were deposited at or slightly below the sea floor due to precipitation from the venting of metal-rich hydrothermal fluids. These fluids typically exploit fault planes as fluid pathways and create a large zone of hydrothermal alteration in the rocks below the deposits. VMS deposits are characterized by concordant massive to banded sulphide lenses, typically occurring within a distinct stratigraphic interval.

The Tulsequah deposit will be accessed via the 120 m (former 5400 level) and 60 m (5200 level) portals. An additional portal will be driven at approximately 84 m level that will act as the SAG mill feed conveyor drift from the mine. The existing 5200 and 5400 levels will be slashed to 5.0 m x 5.0 m to accommodate the trackless equipment fleet. The main mine access will be via the 60 m level and connect to the main ramp that will access the mining levels. The main ramp is 5.0 m x 5.0 m in section and inclined to 17%. The main ramp will access sublevels 30 m apart vertically.

The deposit generally dips at greater than 60° and is variable in thickness from less than 3 m to over 25 m. Several mining blocks are planned to be opened simultaneously throughout the vertical extent of the deposit to give mining flexibility needed for sequencing and early access to higher-grade material. The deposit is favourable to a mix of mining methods with the majority coming from longhole stoping and uppers retreat with minor contributions from cut and fill.

The concentrator design includes standard crushing and grinding unit operations, gravity gold recovery and conventional froth flotation to recover mineral concentrates of chalcopyrite/tennantite (copper iron sulphide), sphalerite (zinc iron sulphide) and galena (lead sulphide) from the ground ore.

The concentrates will be transported to designated smelters worldwide for subsequent reduction into copper, zinc, and lead metal. Average mill throughput is planned to be approximately 1,100 dry tonnes per operating day (1,219 dry tonnes per day at 90% utilization). Total annual concentrate production is planned to be approximately 72,000 dry tonnes.

The primary jaw crusher is planned to be located underground which also houses the jaw crusher discharge feeder and related ancillary systems, as well as the drive system for the conveyor belt that transfers crushed ore to the storage bin. The conveyors and mill building are planned to be completely enclosed.

The ore is proposed to be delivered by truck and dumped through a grizzly that feeds a dump pocket prior to the underground jaw crusher. The ore is planned to be crushed to a nominal 100 mm product size and conveyed to the underground 2,000 t storage prior to the SAG mill.

The comminution circuit is planned to consist of one SAG mill followed by two ball mills. The ball mill grinding circuits are designed to operate in closed circuit with the cyclones. Designated cyclone underflows feed the gravity concentrators in both ball mill circuits to recover approximately 41% of the free gold.

The cyclone overflow, at approximately 30% solids, P80 of 45 microns, is planned to flow by gravity to the copper circuit. Copper, lead and zinc concentrates would be produced from a conventional sequential flotation circuit in typical rougher and cleaner configuration. The tailings from each circuit are designed to feed the next.