The Dublin Gulch property (Eagle Gold Mine) is underlain by upper Proterozoic to lower Paleozoic clastic sedimentary rocks that have undergone regional deformation including Cretaceous age thrust faulting and subsequent granitoid intrusions. Mineralization is associated with granitic intrusive bodies, here described as the Eagle Zone and Olive Zone gold deposits, which are hosted primarily in granodioritic rocks. The gold deposits occur within the Tombstone Gold Belt, located in the eastern portion of the Tintina Gold Province, which also hosts the Brewery Creek deposit and other gold occurrences in the Yukon.

The property is located on the northern limb of the McQuesten Antiform and is underlain by Proterozoic to Lower Cambrian-age Hyland Group metasediments and the Dublin Gulch intrusion, a granodioritic stock. The Dublin Gulch Stock is comprised of four intrusive rock phases, the most significant of which is Granodiorite. The stock has been dated at approximately 93 Mega annum (Ma).

The metasediments are the product of greenschist-grade regional metamorphism. Proximal to the Dublin Gulch Stock, these metasediments have undergone metasomatism and contact metamorphism. A hornfelsic thermal halo surrounds the stock and within the halo, the metasediments have been altered to schist, marble and skarn.

The Eagle and Olive zones belong to the RIRGS class (Reduced Intrusion-Related Gold Systems) of mineral deposits.

The Eagle Zone gold occurrence is localized at the narrowest exposed portion of the stock. The Eagle Zone mineralization is comprised of sub-parallel extensional quartz veins that are best developed within the granodiorite.

Sulphides account for less than 5% of vein material and occur in the centre, on the margin, and disseminated throughout the veins. The most common sulphide minerals are pyrrhotite, pyrite, arsenopyrite, chalcopyrite, sphalerite, bismuthinite, molybdenite and galena. Secondary potassium feldspar is the dominant mineral in alteration envelopes. Sericite-carbonate is generally restricted to narrow vein selvedges, although alteration zones of this type also occur with no obvious relation to veins. Gold mineralization also occurs within the metasedimentary rock package immediately adjacent to the granodiorite.

The Eagle Zone is the principal concentration of mineralization within the property. The Eagle Zone is irregular in plan and is approximately 1,600 m long (east-west) and 600 m wide north-south. The Eagle Zone is near-vertical and has been traced for about 500 m below surface. Current drilling indicates that the mineralization is relatively continuous along this length and is open in several directions, including at depth. Mineralization occurs as elemental gold, both as isolated grains and most commonly in association with arsenopyrite, and less commonly with pyrite and chalcopyrite. The sulphide content in the veins is typically less than 5%, and is less than 0.5% within the deposit overall, with 1 to 4% carbonate (calcite) present.

The Olive Zone gold occurrence is localized at the contact zone on the northwest flank of the granodiorite intrusive and located 2.5 km northeast of the Eagle Zone. Olive measures approximately 20 to 80 m in width, 900 m in length, and has been drilled to approximately 175 to 250 m in depth. Over 97% of the gold mineralization in the Olive Zone is hosted in granodiorite.

Compared to Eagle, the Olive mineralization is more associated with sulphides and quartz-sulphide veining in an interpreted shear-zone setting. An oxidation zone and a transition zone, from near total oxidation to only sulphides, have been defined. Veins can be only sulphides or sulphides with white quartz. Pyrite plus arsenopyrite (or arsenical pyrite) and quartz-pyrite veins are common, within the overall NE trending zone of mineralization.

The Eagle and Olive deposits are being mined using open pit methods, and operate as drill, blast, shovel and haul operation with a combined nominal rate of 29,500 t/d ore and 7,500 t/d ROM ore and a remaining mine life of 11.5 years. Open pit mining operations are comprised of a fleet of 22 m3 front shovels, 12 m3 front-end loaders and 136 t haul trucks. This fleet is supported by drills, graders, and track and dozers. Benches are mined at a height of 10 m in both ore and waste with an overall 20 m effective bench height based on a double-bench final wall configuration.

Mining commenced in Q2 of 2019 in the Eagle pit to provide waste rock for construction and allow for access roads to be built. Leachate processing also commenced in Q3 of 2019 and is currently ramping up to full production in 2020. Open pit mining will focus on the various Eagle pit phases with the smaller Olive pit coming into production in 2028. Open pit mining and loading of the heap leach facilities will be completed in Q2 of 2031.

Starting from the beginning of 2020, the mine is expected to produce a total of 149.0M t of heap leach feed and 144.9M t of waste (at a 0.97:1 overall strip ratio). Ore to be crushed will be hauled to the primary crusher located towards the north-east side of the Eagle pit. ROM ore will be hauled directly to the primary HLP. ROM material will only come from the Eagle pit.

The current LOM plan focuses on achieving consistent heap leach production rates, mining of higher value material early in the production schedule, as well as balancing grade and strip ratios. Given that the secondary and tertiary crushers and HLP will only be operated between April and December of each year, stockpiles will be used when necessary for stockpiling of ore from the open pit. The handling of the ore from the crusher to the HLPs is included in the open pit scheduling and operating cost estimation.

Crushing and Ore Handling
• Primary crusher: a gyratory crusher with a stationary rock breaker in open circuit, producing a final
product P80 of approximately 115 mm;
• Secondary crusher: a vibrating screen and cone crusher operating in open circuit, producing a final
product P80 of approximately 21 mm;
• Tertiary crushers: three vibrating screens and three cone crushers operating in reverse closed
circuit, producing a final product P80 of 6.5 mm, and;
• Heap placement: crushed material is conveyed to the HLP by overland conveyor.

ROM ore is trucked from the open pits and dumped directly into a primary feed hopper. The primary crusher, a 375-kW gyratory crusher, crushes ROM material from a maximum feed size of 1,000 mm down to a P80 of approximately 115 mm.

The primary crushing plant is designed to operate 365 days per year at a rate of 29,500 t/d. During the winter months, January to March, the crushed material will be conveyed and stacked on the winter stockpile. Between April, up to the end of December, the primary crusher product is fed directly onto the secondary crushing feed conveyor. The material from the winter stockpile is reclaimed at a rate of 470 t/h by front-end loader (FEL), and conveyed to the secondary crushing feed conveyor for a combined feed of 39,200 t/d.

If the crushing plant is down, the mine haul trucks dump onto the ROM stockpile. A FEL will be used to reclaim the ROM material and deliver the material to the dump pocket. The ROM stockpile can also be used to feed the crusher, if the mining operations are suspended.

Ore from the secondary crushing feed conveyor is transported to the secondary vibrating double deck screen. Screened undersize material is conveyed to the tertiary crushing feed conveyor. The screened oversize feeds the 932-kW secondary cone crusher. The secondary cone crusher product discharges onto the tertiary crushing feed conveyor.

Ore from the tertiary crushing feed conveyor is transported to the tertiary ore stockpile. The material from the stockpile is reclaimed by belt feeders to three tertiary vibrating double deck screens. The oversize material from the screens feeds the tertiary crushers, each installed with 932 kW motors. The crusher product returns to the tertiary crusher feed conveyor. The undersize material, with a target P80 of 6.5 mm, is transferred by overland conveyors to the HLP for stacking, by a series of grasshoppers that feed a radial stacker.

Lime is added to the stockpile feed conveyor from the 200-t lime silo by screw conveyor for pH control, at a rate of 1 kg/t to 1.5 kg/t.

The gold recovery process was designed on the basis of leaching approximately 13M t of ore per year with an average gold head grade of 0.64 g/t (ROM and crushed ore combined) at an overall gold recovery of 77%.

The three-stage crushing plant operates at a nominal primary crushing rate of 29,500 t/d, 365 days per year and a secondary and tertiary crushing rate of 39,200 t/d, 275 days per year. During the coldest part of the year (January through March), fine crushing and HLP loading activities are suspended. Barren solution, made up of a cyanide-caustic mixture, is pumped at a nominal rate of 2,070 m3 /h to a network of supply piping and drip emitters on the HLPs. Pregnant solution is collected in a sump near the bottom of the HLPs and pumped to the 8 t/d carbon ADR plant for gold extraction and the production of gold doré.

The gold ore processing facilities include the following unit operations:

Crushing and Ore Handling
• Primary crusher: a gyra ........