The Kemess Underground deposit is a large copper-gold porphyry deposit and is typical of calc-alkaline porphyry copper-gold deposits in the western cordillera. The deposit has a low grade ore zone at a depth of 150 metres below the surface on its western flank and a higher grade zone 300–550 metres below surface on the eastern side, which forms the Kemess Underground Project. The Kemess Underground deposit is hosted by potassic altered Takla Group volcanic rocks and Black Lake plutonic rocks. The deposit is centered on a mineralized porphyritic monzodiorite/diorite pluton and associated WSW trending dykes, which extend to the southwest. Higher-grade copper-gold mineralization is characterized by secondary biotite alteration in volcanic and the eastern plutonic host rocks.

Porphyry style copper-gold mineralization occurs within the Takla volcanic rocks and intermediate intrusive rocks associated with weak to pervasive propyllitic, phyllic, and potassic (biotitic) alteration assemblages. The latter is associated with better copper and gold grades. Alteration of Toodoggone assemblages ranges from fresh to weak propyllitic and is generally barren of significant sulphides and ore grade mineralization.

Gold-copper mineralization forms an inclined tabular zone that is centred on the East Cirque porphyritic monzodiorite, which from structural contours, strikes east-west and dips 20° to the south. The quartz diorite/quartz monzonite intrusive exhibits an irregul ........

The opportunity to exploit the Kemess Underground (KUG) gold-copper-silver deposit by underground mining methods such as longhole open stoping, sub-level caving, and block cave mining methods, with the block cave approach recommended due to superior economics. As a result, AuRico (then Northgate Minerals) elected to conduct a Feasibility Study (FS) for the Kemess Underground (KUG) deposit based on block caving.

The planned production schedule calls for 107.3 Mt of ore mined at a head grade of 0.27% Cu and 0.54 g/t Au and 1.99 g/t Ag.

Triple declines will be developed from surface comprising access, intake air, and conveyor declines. The access decline will provide access for personnel, equipment, and materials/consumables.

The final design establishes a single extraction level at the 1140 mRL (Figure 5.3) that includes 582 drawpoints (291 drawbells) over a footprint that is approximately 570 m eastwest and 90 m to 300 m north-south. The cave will be initiated in the highest grade ore in the east of the orebody and progress to the southwest over the life of the mine. An 18 m high undercut will be established above the undercut level, with this level at the 1158 mRL and accessed via ramps from the extraction level.

Ore will be recovered on the extraction level using 8.6 m³ (17 t) load-haul-dump (LHD) machines and dumped into one of four 55” x 42” jaw crushers located to the south of the footprint. Transfer conveyors will then transpo ........

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The KUG project intends to process 12.7 Mt/y (35,000 t/d equivalent) through the grinding circuit, with one of the two original KS rinding circuits that processed KS ore was removed, so additional mills will be installed to achieve the required capacity.

The Kemess grinding circuit is expected be used to process the KUG ore following primary crushing underground and stockpiling ahead of the process plant. The original flotation facilities remain; however, these will be retrofitted to incorporate both cleaner and cleaner scavenging. In addition, additional regrind capacity will be added to the circuit to achieve a finer grind size. Thickening, and concentrate handling facilities remain from KS operations. The tailings will be pumped to the KS open pit, which is permitted for use as a tailings storage facility.

The KS open pit has a capacity for approximately 107 Mt tailings and 3.0 Mt waste rock from KUG mine development. To achieve this storage capacity, a 25m ........