The origin of the gold in the Doyon-Bousquet-Laronde (DBL) mining camp has been extensively debated in the past and three models have been proposed: synvolcanic, multi-stage, and syn-deformation. Recent and current studies of the Laronde-Penna deposit, Westwood ore zones, and Mooshla intrusion mineralisation, combined with the geological synthesis of the DBL mining camp (Mercier-Langevin et al., 2009), have provided further insights into the synvolcanic model for the introduction of the gold.

Five deposit and occurrence styles are recognized in this camp: 1) gold-rich base metal massive sulphide lenses (Laronde-Penna, Bousquet 2-Dumagami and Warrenmac lens), 2) gold-rich vein stockworks and sulphide disseminations (Bousquet 1, Westwood and Ellison);, 3) intrusion-related Au-Cu sulphide-rich vein systems (Doyon, Mooshla-A), 4) shear-hosted Au-Cu-sulphide-rich veins (Mouska and MicMac) and 5) syn-deformation auriferous quartz-pyrite-tourmaline veins (Mooshla-B).

On the Westwood project, Zone 2 Extension mineralisation share similarities with the Doyon mine intrusion-related veins system while the Warrenmac-Westwood Corridor may be related with the volcanogenic massive sulphide lenses of the Laronde-Penna and Bousquet 2-Dumagami mines. The North Corridor mineralisation shows hybrid characteristics between the two previous corridors.

Excluding the Doyon Mine area, mineralisation in the Westwood deposit consists of multiple horizons grouped in three distinct mineralised corridors from North to south (Wright-Holfed et al., 2010; Mercier-Langevin et al., 2009): the Zones 2 Extension corridor, the North Corridor and the Warrenmac-Westwood Corridor. Gold is generally associated with the presence of base metal sulphides in each corridor.

The Zone 2 Extension mineralisation consists of quartz-pyrite veins and veinlets with variable but usually minor amounts of chalcopyrite and sphalerite. They are generally less than 15 centimetres thick and are hosted in sericitized wall rock containing 2 to 10% disseminated pyrite. The vein system is roughly oriented N85-105° with a dip varying between 60-70°S and is slightly discordant to the regional foliation and S0 planes (direction and dip). Free gold, at the origin of high-grade values, is frequently observed in those veins. The veins are highly strained and associated with a proximal sericite-pyrite-quartz-±garnet alteration assemblage. Analogies with the Doyon Mine’s intrusion-related Zone 2 may reflect a similar origin.

The North Corridor mineralisation is characterized by quartz-pyrite veins and/or concentrations with locally abundant sphalerite-chalcopyrite±pyrrhotite when approaching the Warrenmac-Westwood Corridor. The amount of sulphide is variable within centimetre- to decimetre-wide veins and veinlets. The system is generally parallel to the Zone 2 Extension corridor with a dip ranging from 70-80°S and is also weakly discordant from the regional foliation. Occasional free gold is also present in the veins. Mafic to intermediate volcanic rocks host the North Corridor. Some veins share some analogies with the Zone 2 Extension corridor veins while others are comparable to Warrenmac-Westwood veins, suggesting different, multiple or hybrid origins.

The Warrenmac-Westwood corridor consists of auriferous semimassive to massive sulphide lenses, veins and disseminations containing variable but significant amounts of Cu, Zn and Ag (Mercier-Langevin et al, 2009). The mineralisation is characterized by pyrite–sphalerite–chalcopyrite– pyrrhotite veins, stringers and massive sulphides associated with variable amount of quartz and rare visible gold and galena. The sulphides are also enriched in the epithermal suite of elements (e.g. As, Sb, Bi, Pb, Se, Te, and Hg). These ore zones are a few centimetres to more than 50 centimetres thick in a disseminated pyrite- and sericite-rich altered halo reaching thicknesses of up to 10 metres. Local massive to semimassive sulphide lenses ranging from 1 to 14 metres are also observed within the corridor. This corridor is thought to be a gold-rich volcanogenic massive sulphide horizon. The system is generally parallel to the Zone 2 Extension and North Corridor with dip ranging from 70-80°S, also weakly discordant to the regional foliation.

Development is classified as either deferred (infrastructure) development, including ramps, crosscuts and ore passes. Most of the lateral developments are mechanized, with jumbos, rockbolters, scissorlifts and 2.7m3 LHD units. Dimensions for waste drifts are generally 4.5m high and 4.1m wide. Drift dimensions in the ore lenses may vary locally according to the dip, width of the vein and mining method selected; planned drifts dimensions are 4.5m high and 4.5m wide for long hole drifts. Track drifts have been developed with wheeled long-tom crews: other than Level 840 (originally an exploration drift), dimensions are 2.9m high and 2.8m wide. No upcoming track drifts development work is out lined in the plan.

Arched backs are promoted for lateral development to enhance ground stability. Ground support varies significantly depending on the expected ground conditions and combination of static ground supports (rebars), yielding supports (hybrid bolts, debonded cables), long anchors (cables) and dynamic supports are used to control the wide spectrum of ground conditions experienced. In additions, mesh panels, straps and shotcrete are used either individually or conjointly as surface support. Ongoing monitoring of the ground support performance or possible deterioration are achieved by doing routinely workplace inspections. New ground support technologies are currently been trialled at the mine to optimize the performance of the ground support and to reduce exposure to potential ground hazard. Different bolting systems are currently been evaluated and mechanized bolters were acquired in 2018.

Vertical developments, such as ventilation raise and material handling passes,are typically inclusive to infrastructure development. Dimensions are typically 2.4 x 2.4m, although the main ventilation raise can reach up to4.3m in diameter.

Development performances are based on current performance at the Westwood Mine.
The following performances were used in the mine plan:
• Jumbo (deferred and stope prep) development: 6.0m/day/team;
• Jumbo development through paste backfill: 0.8m/day/team;
• Track drift and conventional development: 3.0m/day/team;
• Alimak raises: 2.0m/day/team;
• Conventional raises: 2.0m/day/team;
• Cables and 2": 100m/day/drill;
• Long Hole 4": 58m/day/drill (planned drilling);
• V-30 (slot) raises: 10m/day/drill

Long hole open stope (LHOS) is the primary mining method used at Westwood. Stopes are approximately 25 to30mhigh with a strike varying from 12to 15m in length. The mining width depends on the true width of the mineralization, lens configuration and geotechnical constraints applied for the area. Minimum mining width is set to 2.4m. The configuration of the access to the production stope are typically either transverse or longitudinal. Short longitudinal retreat is typically promoted for reducing delays associated to rehabilitation and exposure to induced stress.

Historically, mining sequence for long hole stopes has been carried out from bottom to top, either in a pillarless or in a primary and secondary stopes configuration. As depth increases over time in the LOM, an underhand (top to bottom) sequence is promoted for better induced stress management. Some considerations have been built in the LOM to mitigate colliding mining fronts creating diminishing pillars that are detrimental for stability. In additions, underhand sequence is known to be a mining method that is used in deep and ultra-deep mines that could reduce the exposure to seismicity on the top cut where production drilling is carried out. The main implication of an underhand retreat on the mining cycle consists in having to re-excavate the upper sill in the paste in order to allow the drilling of the underlying block. Stopes are generally being drilled down from the upper level with 100mm diameter holes. A drill pattern of 2.0 x2.0m is planned. ITH drills with V-30 heads will be used to open the slot raises.

Stopes will be blasted with emulsion explosives and electronic detonators. LHD units with remote capability will muck out the stope. Paste backfill will be poured in all stopes. A cure of 21 days is required before mining any adjacent stope and 28 days before excavating in paste. Most stopes will require cable bolts.

As part of the ground control management strategy, the seismicity is monitored throughout the mine. Westwood has a wide mine coverage micro seismic system implemented on site since 2013, with just under 100sensors been installed. Regular underground inspections and audits are performed as part of the quality assurance and quality controls programs. In additions, over 10,000m of geotechnical drilling were performed in 2019 and 2020 to refine the current geological and structural models of the mine. Table 16-1summarizes key properties for the main units and subunits.

Ore Handling and Crushing
Underground ore is hoisted to surface and hauled by truck to the processing facility located 2.5km from the mine shaft. The ore is discharged at the crusher house. The ore is fed to a single stage jaw crusher (1.07 x 1.22m) by a front-end loader through a grizzly feeder. The ore is conveyed to the mill ore bins using a belt conveyor system. Each bin has a capacity of 2,800dmt.

Grinding and Gravity
Grinding of the Westwood ore is done using a 2,700HP semi-autogenous grinding (SAG) mill in closed circuit with primary hydrocyclones. The overflow of primary hydrocyclones feeds a 1,000-HP ball mill in closed circuit with its secondary hydrocyclones. A portion of the underflow (secondary hydrocyclones) feeds the gravity separation circuit composed of a sweco screen, Knelson concentrator (30’’) and a shaking table. The tail of the gravity circuit returns to the grinding circuit and the gravity gold concentrate goes to the refinery. The targeted grind size is 80% passing 53 microns (270 mesh).

Leaching and Adsorption
The leaching circuit has 55 hours of retention time at the nominal processing rate of 3,106tpd. Leach residue is sent to cyanide destruction. At the nominal processing rate, retention time for each step of the leach and adsorption process is detailed as follows: primary leach tanks (4.7 hours), carbon-in-leach (CIL) tanks (6.6 hours), secondary leach tanks (31.3 hours) and carbon-in-pulp (CIP) tanks (12.1 hours).

Cyanide Destruction
The tailings are treated with SO2/Air cyanide destruction process. The leaches residues are split between to parallel detox reactors. In normal operation, a part of the process discharge residues is used to feed the paste backfill plant while the remainder is pumped to the Doyon open pit. A buffer tank(14h of backfill plant operation capacity) is maintained at maximum level with detoxified slurry to ensure continuous feed to backfill plant in case of temporary processing plant shutdown.

Paste Backfill< ........