The Tiger Deposit represents a distal variety of the reduced intrusion related gold deposit (RIRGD) model. The following is based on a paper completed by Craig Hart (Hart 2007) and work completed by Eric Theissen for his Master’s thesis (Theissen 2013).

RIRGDs are best developed around small, cylindrical-shaped plutons that have intruded sedimentary or metasedimentary host rocks. Plutons are typically emplaced between 5 and 9 km depth. Fluid flow and mineralization is largely controlled by structural features impinging upon the thermally driven hydrothermal system. The dominant structural control on RIRGDs is weak extension that forms arrays of parallel fractures in the brittle carapace. These are filled with auriferous, low-sulphide quartz veins that form extensive, intrusion-hosted sheeted arrays.

Mineralization often extends beyond the limits of the intrusion and locally beyond the limits of the thermal aureole. RIRGDs exhibit predictable zonation and differing deposits styles outward from the central, mineralizing pluton, with increasing structural control on the more distal mineralization.

Low-sulphide contents (0.1 to 2.0%) are common in intrusion-hosted systems, and is dominated by pyrite, pyrrhotite and arsenopyrite, with accessory scheelite and bismuthinite. Arsenopyrite is more abundant in veins outside of the intrusion and is commonly associated with pyrrhotite in replacement-style mineralization.

Several types of mineralization are known to occur on the Property including:
1. sediment-hosted replacement-style gold
2. zinc ± silver ± lead ± gold ± bismuth in limonite-rich veins and replacement bodies
3. scheelite in tremolite skarns
4. pyrrhotite ± scheelite ± chalcopyrite in actinolite-diopside ± garnet skarns
5. wolframite ± tantalite in granite
6. gold bearing quartz-boulangerite veins
7. pyrite-sphalerite-galena in carbonate replacement deposits.

Sediment-hosted replacement style gold mineralization is the most significant economic mineralization explored on the Property to date. Known showings of this type include the Tiger Deposit.

The open pit mine will utilize a conventional truck-and-excavator fleet. Based on the geotechnical recommendations provided by Golder (2016), blasting will be performed on non-oxide rock only, while oxide material will be excavated directly by a hydraulic excavator.

The mining schedule was developed based on a nominal processing capacity of 1,500 t/d for 365 d/a. Oxide and sulphide material above the economic cut-off will be scheduled for processing. Oxide and sulphide material below the economic cut-off will be handled as waste.

Over the eight-year mine life, the pit will produce 3.2 Mt of mineralized material and 15.6 Mt of waste rock. The LOM average gold grade of oxide and sulphide material is 4.06 g/t and 2.99 g/t, respectively. The LOM stripping ratio (defined as waste material mined divided by mineralized material mined) is 4.9.

The proposed 1,500 t/d processing plant will utilize conventional crushing, grinding, cyanidation by carbon-in-pulp (CIP), and gold recovery from loaded carbon to produce gold doré from the Tiger mineralization. Although previous heap leach test work showed promising results from oxide mineralization, and extensive engineering studies were conducted using a combined heap leach and tank processing treatment to extract the gold from the mineralization, there are numerous potential technical risks and challenges associated with the heap leach option. Therefore, a conventional cyanidation circuit consisting of grinding and agitated cyanide leaching for both the sulphide and oxide resources is proposed for this study.

The process plant will co-process two types of mineralization: oxide mineralization and sulphide mineralization. The overall design philosophy was to select proven equipment, with a simple and single line flowsheet that can be operated and maintained effectively in a cold environment.

A mineral sizer in the crushing circuit will reduce the run-of-mine (ROM) material to a particle size of approximately P80 120 mm.

The crushed material will be transported by a conveyor to a 1,500-t surge bin and then reclaimed and fed to a primary grinding circuit consisting of a semi-autogenous (SAG) mill and a ball mill in closed circuit with hydrocyclones. The grinding circuit will further reduce the crushed mill feed to a particle size of P80 75 µm.

The hydrocyclone overflow from the primary grinding circuit will be thickened, and the underflow of the thickener will be diluted with process water to the optimum solid density, and then cyanide leached in a CIP circuit to recover the gold from the mineralization.

The thickener underflow with a solids density of 55 to 60% w/w will be pumped to the head of a bank of cyanide leach tanks. The overflow of the leach residue thickener will be added to dilute the cyanide leach feed to a solid density of approximately 45% w/w. Cyanidation will be performed in a CIP circuit consisting of six leach tanks and five CIP tanks. Each of the leach tanks, with a dimension of 10 m diameter by 10 m high, will be equipped with an agitator. These leaching tanks will be insulated and located outdoors. The five CIP tanks will be located inside the mill building. Both the leach tanks and CIP tanks will provide a total leaching retention time of 38 hours. The tanks will be aerated with compressed air from two oil-free compressors (one operation and one standby). The CIP tanks will be equipped with in-tank carbon transferring pumps and inter-stage screens to advance the loaded carbon to the preceding CIP leach tank. The activated carbon will be added into the last CIP leach tank and the loaded carbon will leave the CIP circuit from the first CIP tank.

Sodium cyanide will be added to the leach tanks to extract gold. Lime will be added to maintain the slurry pH at approximately 10 to 11.

The loaded carbon leaving the first CIP tank will be transferred to the carbon stripping circuit, while the leach residue will be sent to a carbon safety screen to recover any coarse carbon grains. The screen undersize will report to the residue thickener prior to being pumped to the cyanide destruction circuit.

The loaded carbon will be treated by acid washing and a modified Zadra pressure stripping process for gold desorption in one stream, which is capable of processing approximately 2.0 t of loaded carbon in each batch.

The loaded carbon will be acid washed by diluted hydrochloric acid solution to remove inorganic contaminants, such as calcium scale, prior to being transferred to the elution vessel. The acid washed carbon bed will be rinsed with fresh water.

The stripping process will include the circulation of the heated barren solution through the carbon bed. The barren solution will be heated by passing through two heat exchangers, one heated by the pregnant solution and the other by steam from a boiler. The barren solution will then flow up through the bed of the loaded carbon in the elution vessel and overflow near the top of the stripping vessel. The pregnant solution will be cooled by exchanging heat with the barren solution and flow to the pregnant solution holding tank for subsequent gold recovery by electrowinning. The eluded carbon will be discharged from the bottom of the vessel through a regulating valve to the stripped carbon tank.

The gold in the pregnant solution will be recovered by electrowinning. The barren solution from the elution circuit will be circulated back to the elution/leach circuit. The gold sludge produced from the electrowinning circuit will be smelted to produce gold doré bullion that will be shipped offsite for refining.

The residue from the leach circuit will be thickened to recover the leach solution for reuse as process water in the cyanidation circuit. The thickener underflow will be sent to a cyanide destruction circuit employing a sulphur dioxide/air process to destroy the residual weak acid dissociable (WAD) cyanide. The treated residue slurry will be pumped to the lined tailings management facility (TMF) for storage.