The Brucejack Deposit is interpreted to be a deformed porphyry-related transitional to intermediate sulphidation epithermal high-grade gold-silver vein, vein stockwork, and vein breccia deposit that formed between 184 to 183 Ma (Board and McNaughton 2013; Tombe et al. 2018; Board et al. submitted). High-grade gold-silver mineralization was formed in association with a telescoped, multi-pulsed magmatic-hydrothermal system beneath an active local volcanic center (Board et al. submitted).

The Brucejack Deposit has many characteristics in common with intermediate sulphidation epithermal systems. Intermediate sulphidation epithermal systems occur in calc-alkaline andesite-dacite arcs and can be spatially associated with porphyry systems and individual volcanic centers (Sillitoe and Hedenquist 2003).

The Brucejack Project area is largely underlain by volcano-sedimentary rocks of the Lower Jurassic Hazelton Group. These rocks unconformably overlie volcanic arc sedimentary rocks of the Upper Triassic Stuhini Group along the western-most part of the Brucejack Project area. The rocks are variably altered and deformed, with zones of intense quartz-sericite-pyrite (phyllic) alteration being associated with increased deformation due to preferential strain partitioning in sericite-rich zones. A north-south trending, broadly arcuate, concave-westward 0.5 to 1.5 km wide band of variably phyllic-altered rocks and associated quartz stockwork extends over 5 km across the Brucejack Property area. The band straddles the Brucejack Fault across the Brucejack project area, shifting from the west side of the fault in the north of the Brucejack Project area to the fault’s east side further south. The phyllic alteration typically contains between two and 20% pyrite, affects rocks from the bottom to the top of the lithological sequence (see Section 7.3.1), and, depending on the alteration intensity, can preclude protolith recognition. More than 40 mineralization showings, associated with the alteration band, have been identified on the Brucejack Project area, highlighting the exceptional exploration potential of the area (McPherson 1994; Board et al. submitted).

Ten mineralized zones are currently recognized on the Brucejack Project area, extending from the Hanging Glacier Zone in the north to the Bridge Zone in the south. Although five of these zones have been explored in some detail (West Zone, Valley of the Kings Zone, Bridge Zone, Gossan Hill Zone, and Shore Zone), mining is focused on just the two zones for which there are current Mineral Resources and Reserves: the Valley of the Kings Zone and the West Zone.

Visible gold and silver mineralization in the Brucejack Deposit occurs as electrum and is predominately hosted in quartz-carbonate to carbonate vein and vein breccia structural corridors within broader stockwork zones (McPherson 1994; Kirkham and Margolis 1995; Tombe et al. 2018; Board et al. submitted). Additionally, lowgrade (less than 5 g/t) gold mineralization occurs sub-microscopically in vein- and wall rock-hosted arsenian pyrite (invisible gold) throughout the Valley of the Kings Zone and possibly within the West Zone as well. Electrum-bearing quartz-carbonate veins and stockwork overprint and are co-spatial with earlier porphyry-related phyllic alteration in the Brucejack Deposit.

The Valley of the Kings Zone is currently defined over 1,200 m in east-west extent, 700 m in north-south extent, and 650 m in depth. Deep drilling has indicated that the alteration, mineralization, and veining in this zone extend to a depth of at least 1,100 m. Mineralization in the Valley of the Kings Zone is open to the east, west, and at depth. Deep exploration drilling conducted under the Flow Dome Zone in 2018 was successful in confirming the presence of Valley of the Kings Zone-style mineralization from the eastern edge of the Valley of the Kings Zone to beneath the Flow Dome Zone, which lies approximately 1,000 m further east. The West Zone is currently defined over 590 m along its northwest strike, 560 m across strike, and down to 650 m in depth, is open to the northwest, southeast, and at depth to the northeast. The Valley of the Kings Zone contains higher gold and lower silver grades than the West Zone.

Precious metal mineralization is ubiquitous throughout the vein systems, however, its continuity is not correlated to any specific geologic continuity; although mineralized structural corridors can be continuous on the meters- to tens-of-meters scale, the within-vein gold and silver distribution is highly erratic. Nevertheless, the distribution and grade of precious metal mineralization within the mineralized structural corridors within the broader stockwork system is of significant economic interest.

Brucejack Gold Mine development has been ongoing since the start of commercial production in 2017. The execution of the mine plan closely matches the mine plan as disclosed in the 2014 FS (Ireland et al. 2014). Locations for some infrastructure items have been adjusted to improve practicality as the mine has developed. These changes include the location and type of the main dewatering system and the utilization of settling sumps to pump the sediment and slimes directly to the mill clarifier. The explosives magazine was moved to isolate the location from the main works and to allow direct ventilation exhaust to surface in the event of combustion or explosion. The layout for the underground service facilities was also modified.

The updated underground mine design supports the extraction of 3,800 t/d of ore through a combination of transverse and longitudinal LHOS. Paste backfill is integral to the mine plan to maximize both orebody recovery and mining productivity. Modern trackless mobile equipment is employed in the majority of mining activities.

A main decline, designated as the Valley of the Kings access, extends from the surface portal near the concentrator and is used to access the mine and as a conveyor way. The conveyors installed have a combined length of 800 m. The existing West Zone portal will continue to provide access (and egress) to the mine and serve as the main access for large underground equipment and waste haulage.

A fleet of LHD and underground trucks are used for material loading and transport from the underground working areas and through an internal ramp system that connects all levels to the centrally located crusher.

Major underground infrastructure includes crusher, conveyors, ventilation raises, fans, heating system, pumping stations, electrical substations, explosives magazines, paste fill booster pump station, refuges, mine communications, and other ancillary installations that include an underground maintenance service facility and a fuelling facility.

The Valley of the Kings Zone is currently accessible via internal ramps between the 1,050 m and 1,470 m elevation levels via both the Valley of the Kings ramp and the West Zone ramp from surface. The continued infrastructure development program will utilize this existing infrastructure. The Valley of the Kings access decline joins the main surface portal to the Valley of the Kings ramp at the 1,290 m and at the 1,320 m elevation levels on the West Zone access ramp. The West Zone will likewise be accessed from the existing bulk sample access drive during the latter half of the LOM.

For ease of entry and exit, ramps have been developed with a 25 m turning radius and a 15% gradient, levelling out to a 0% gradient in proximity to a level access intersection. Passing bays are incorporated where required in the main Valley of the Kings Zone and West Zone access ramps.

Level development follows the general strike of the various lenses of the Brucejack Deposit, providing access to the mineralized zones in a manner that allows for either transverse or lateral mining; whichever is more suitable for that zone of the deposit. Level development is generally in the footwall and includes excavations for sumps, refuges, transformers, remucks, paste fill line, and raise accesses. Stope-access cross-cuts located outside of the Brucejack Fault Zone are on 15 m spacings for transverse stope blocks, while the multiple access configuration of lateral mining stopes is determined based on efficiency and mining sequence. This excludes those levels where sill extraction or near-surface weathered ore is recovered in smaller stopes that are designed to geotechnical criteria. Likewise, all Brucejack Fault Zone ore is developed on 10 m spacings to accommodate poorer ground conditions. These spacings are modified as geotechnical experience is gained.

The LOM plan includes 671 stopes in the Valley of the Kings Zone and 135 stopes in the West Zone. The number of stopes may vary if stopes are combined or split for optimization during operations.

Stopes that are planned to not be re-exposed by adjacent mining and are below the 1,350 m elevation level may be backfilled with unconsolidated waste and/or by paste fill with sufficient binder to remove any risk of future liquefaction (low-strength paste fill). High-strength paste fill will be required in the lower portion of all primary and secondary stopes that will be undercut by sill extraction from below.

The Brucejack Gold Mine tailings paste fill mixes responded very favourably to the slagbased and fly-ash binders. The test program demonstrated a significant difference in the strength values for the paste fill mix with GP cement compared to the slag-based (MC and SS) and FA mixes.

The primary crushing facility has an average process rate of 264 t/h at a crushing availability of 60% to meet the increased mill throughput of 3,800 t/d at a closed-side setting of approximately four inches. The current primary crushing unit is located underground and includes the following major units:
- Hydraulic rock breaker;
- Stationary grizzly;
- Jaw crusher (150 kW);
- Vibrating grizzly feeder;
- Associated dump pocket and belt conveyor;
- Belt scales;
- A dust collection system.

The ROM ore is trucked from the underground mine to the underground primary crushing facility. The particle size of the jaw crusher feed is typically less than 700 mm. The jaw crusher reduces the ROM material to 80% passing 120 mm or finer.

The crusher product is transported by a conveyor system from the underground primary crushing facility to the SAG mill feed surge bin located on surface. The primary crushing and conveying facilities are equipped with a spray water dust suppression system to control fugitive dust generated during crushing and conveyor loading. The crushing and conveying system are monitored through closed-circuit television (CCTV) and can be controlled by the local control system or from the process central control room located in the process plant.

The SAG mill feed surge bin has a live capacity of 2,500 t. The crushed product from the underground primary crushing facility is first conveyed to the transfer tower, which is part of the portal building on the surface. From there, it is further transported to the SAG mill feed surge bin. The ore from the mill feed surge bin is reclaimed by two 1,067 mm wide by 15,000 mm long apron feeders onto the SAG mill feed conveyor at a nominal rate of 172 t/h. The stocking and re-handling system for the crushed ore includes the following major components:
- One jaw crusher discharge belt conveyor;
- Two belt conveyors located in the underground and one conveyor located at surface to feed the SAG mill feed surge bin;
- One SAG mill feed surge bin with a live capacity of 2,500 t;
- Two apron feeders, 1,067 mm wide by 15,000 mm;
- Local dust collection systems.

The crushed ore conveyor transfer points at the portal and at the SAG mill surge bin are equipped with a dust collection system to control fugitive dust generated while transporting the crushed material.

A SABC grinding circuit has been installed at the mine site and incorporated with two centrifugal gravity concentrators to recover gold/silver nugget grains that are liberated or partially liberated from their host minerals. The upgraded primary grinding circuit has an average feed rate of 172 t/h at a 92% availability to meet the increased mill throughput of 3,800 t/d and maintain a target product size of 80% passing approximately 100 µm.

The grinding circuit includes:
- One SAG mill, 6,096 mm diameter by 3,048 mm long (20 ft. by 10 ft.), driven by a 2,013 kW VFD;
- One ball mill, 3,960 mm diameter by 7,260 mm long (13 ft. by 23.8 ft.), powered by a 2,013 kW VFD;
- One hp 100 cone crusher.

The process plant reached full operation in Q4 2017. Since then, new test programs have been conducted to further improve the mill operation. In 2018, further throughput increase reviews and test work were conducted by mill metallurgists and engineers, equipment suppliers, and independent consultants to improve the mill operation in an effort to increase the mill throughput to 3,800 t/d. Most of the mill upgrading has been completed, excluding the installation of the third cleaner flotation cell and the new flocculant system, which are currently being installed. As reported, the mill was operated at 4,065 t/d in Q4 2019.

The process flowsheet originally developed for the Brucejack Gold Mine uses a combination of conventional bulk gravity concentration and sulphide flotation. The gravity concentrate is refined in the gold room on site to produce gold-silver doré by directly smelting the upgraded gravity concentrate. The doré is shipped by air to precious metal refineries loca ........