The Hope Bay Property is located within the Hope Bay volcanic belt which is part of a massive structural-geological complex called the Slave Structural Province.

The Hope Bay deposits (Doris, Madrid, and Boston), as well as a large number of other prospects, are considered to be typical of orogenic-type mesothermal lode gold deposits, greenstone-hosted quartz carbonate vein deposits.

• The Doris gold deposit is a typical Archean lode deposit which occurs within an over 3 km long, steeply dipping quartz vein system, in folded and metamorphosed pillow basaltic rocks.
• The Madrid deposit area lies within a north-south striking package of mafic volcanic rocks, comprising a sequence of Fe-Ti tholeiitics, Mg tholeiitics, komatiitic basaltic, synvolcanic to late gabbroic, and ultramafic rocks.
• The geology in the area of the Boston deposit is a bimodal assemblage of mafic and felsic volcanic rocks in contact with sedimentary rocks, all of which are complexly folded about a large-scale synformal-anticline. The core of the anticline is occupied by mafic volcanic rocks that host the Boston deposit and these are in turn overlain by sedimentary rocks.

THE DORIS AREA
The Doris Deposit is located at the north end of the north-south trending Hope Bay greenstone belt of Archean age near Cambridge Bay in Nunavut. Gold mineralization is contained within predominantly sub vertical quartz veins hosted within mafic volcanic rocks.

Mineralization
The Doris Vein system is characterized by a series of north–south striking, sub vertical, goldbearing, brittle-ductile structures that commonly host wide, stylolitic, ribboned, or bull quartz veins.

Within the veins, gold is commonly associated with narrow tourmaline chlorite septa oriented parallel to and along the vein margins. Veins are not consistently mineralized along strike. Gold is distributed throughout vein structure but is usually concentrated near the footwall side of the vein, where visible gold is relatively common. Gold mineralization includes visible and disseminated gold occurring primarily with quartz veins ranging from a few centimetres to approximately 10 m in scale. Visible gold includes coarse leafy free milling grains located along vein margins, tourmaline septa, and wallrock fragments which are commonly associated with pyrite. Gold is also associated with disseminated sulphides at the margins of the quartz veins, or with sulphide clusters within the vein. Occasionally, gold is present within brecciated zones adjacent to the quartz veins. Sulphide mineralization consists of trace to 2% pyrite, trace chalcopyrite, rare sphalerite, and pyrrhotite.

THE MADRID AREA
The Madrid deposit area is located in the northern area of the Hope Bay volcanic belt, south of the Doris deposit. It includes the Wolverine-Madrid corridor which is defined as the belt of rocks extending from the southern end of Wolverine Lake to the northwest end of Patch Lake (Sherlock et al., 2002).

The Madrid deposit area includes the Naartok East, Naartok West, Rand, Spur, Suluk, Wolverine and Patch 14 deposits. The Madrid trend also includes the Suluk T3, and Patch 7 prospects.

The style of mineralization at Madrid is different from the Doris or Boston deposits and can be generally characterized by sulphidation and replacement of favourable stratigraphic units. The most favorable lithologies are Fe-rich tholeiitic mafic volcanics which have been extensively brecciated. Hydrothermal alteration at Madrid is characterized by an early assemblage of sericite micas and carbonate alteration, consisting of magnesite and ankerite with quartz-carbonate stockwork veinlets. The main gold-bearing alteration assemblage consists of secondary albite and paragonite with lesser carbonate as ankerite and quartz-ankerite stockwork veinlets. The higher gold tenor is associated with over 10% fine grained pyrite, intense albite flooding and hematite discoloration (Sherlock et al., 2012).

The gold mineralization within Naartok West, Naartok East, Rand, Suluk, and Patch 7 consists of quartz-carbonate stockwork veining, which overprints dolomite-sericite-albite-pyrite altered mafic volcanic rocks of the Patch Group. The gold mineralization is characterized by multi-stage brecciation and alteration with at least two separate gold mineralization events. Gold occurs within north-northeast, east, southeast, and north-northwest trending brecciated and carbonate altered zones and is associated with disseminated pyrite which has replaced brecciated mafic fragments

THE BOSTON AREA
Boston mineralization has been subdivided into the B2, B3, B4, and B5 zones.

The strongest mineralization in the Boston deposit is found within the B2 zone, particularly the section investigated by the underground workings. The B2 zone has been intersected to a depth of 1,000 m, with the highest grades located in the central part of the zone.

Compared with the B2 zone, mineralization in the B3 zone is less continuous and lower grade. The B4 and B5 zones are the smallest of the three main Boston ore zones. The B4 zone is a relatively small zone hosted on the eastern contact of the volcanic core, while the B5 zone comprises several mineralized horizons located south of the Newton Deformation Zone.

Fingas (2018) recognizes at least 6 styles of mineralization in the Boston deposit, which include: vein stringer sets hosted in transition breccia; discrete veins at geological contacts; fault-hosted veins; shear-hosted mineralization; vein domains at picrite contacts; internal picrite-hosted mineralization.

Vein stringer sets hosted in transition breccia is the most important mineralization style in the B2 zone and has been exposed in underground drifts. Mineralization consists of sulphide-bearing quartz-carbonate veins, typically hosted in both volcanic- and sediment-dominated transition breccia. Zones are typically planar, from 2 to 10 metre wide, with ore shoots plunging steeply to the southwest (e.g. ore shoots within the B2 zone with an apparent plunge of 77° to 225°).

During 2018 and 2019 a small open pit was mined near Doris Lake where the hinge outcropped at surface.

A small open pit is currently being mined on the Naartok East Limb.

Mining at the Hope Bay Project incorporates longhole mining methods in order to address the deposit geometry and anticipated ground conditions. Mining will take place under permafrost conditions where the mineralization is located away from any water bodies and under nonpermafrost conditions in what is known as the talik in the vicinity and under the lakes in the area.

Doris North will be under permafrost while the Connector and Central zones at Doris will be beneath the lake. A portion of the Madrid North deposit (part of Naartok) as well as the Madrid South deposits (Patch and Wolverine) are situated beneath the lakes and therefore will not be under permafrost conditions.

The deposits will be accessed, and services will be provided by a decline from surface with an average grade of 13%. The ramp will also be used for ore and waste haulage from the underground operations.

The Doris deposit is currently in production, with an existing ramp decline reaching active mining areas. Mining will continue as per current methods until depletion. Transverse and longitudinal longhole mining is planned for Doris. Madrid North (Naartok and Suluk) and Boston will be mined using longhole stoping methods with sub-levels placed at 20-m vertical intervals (16-m drilling heights). Both longitudinal and transverse accesses are used, depending on width of the ore zones. The Madrid South (Patch and Wolverine), where ore zones are much narrower, will be mined using longhole stope method with sub-levels placed at 16-m intervals (12-m drilling heights). The majority of stopes in Madrid South will have longitudinal accesses.

Sill pillars are placed throughout the deposit to improve the mining sequence by providing additional stoping fronts. Sill pillars will be recovered at the end of the sequence using up- holes.

Stopes will be backfilled using a combination of CRF and unconsolidated rockfill (UCF). The CRF will generally contain 5% binder, except 10% in sill pillars. The CRF will be mixed on surface and trucked to the stopes.

The primary, secondary and tertiary crushing circuits reduce Run of Mine (ROM) ore to a size where grinding and separation processes can effectively operate. A wet surge bin is installed between the crushing circuit and the grinding circuit to allow for approximately 45 minutes of operational capacity to be built up, in order to ensure that the downtime in the crushing circuit does not disrupt grinding and flotation operations.

PRIMARY CRUSHING AND STOCKPILE
ROM material is hauled by trucks to the ROM pad to designated high-grade, intermediate, and low-grade stockpiles adjacent to the primary crusher area. A front-end loader reclaims ore from the ROM pad and feeds it onto the 600 mm primary crushing static grizzly to scalp oversize material into, a 26 m3 dump hopper. Oversize is removed and crushed by a mobile rock breaker.

A vibratory grizzly feeder scalps out minus 80 mm ore via a fines feed chute, and feeds the oversize into the primary jaw crusher, a Metso Nordberg C100, with a product that is 95% passing (P95) 125 mm. The vibrating grizzly undersize and crusher discharge are conveyed by the primary crusher discharge conveyor (CV), under a self-cleaning belt-type tramp metal magnet t to the stockpile. A weightometer is installed on the stockpile feed conveyor for throughput measurement and control.

The primary crushing circuit product has a P80 of 100 mm. At 50% utilization, the nominal operating rate is approximately 200 t/h but crushing rates can exceed 250 t/h if required. The stockpile has a live storage capacity of 4 hours and can store and total capacity of 36 hours. The crushed ore stockpile was completely enclosed by a steel-fabricated structure following the plant start up.

Crushed ore is reclaimed to feed each concentrating line, CL1 North and CL2 South, via separate reclaim tunnels for each train using two reclaim tunnel apron feeders, discharging onto two plant feed conveyors. A weightometer is installed on each plant feed conveyor for feed rate control. The secondary and tertiary crushing circuits are low profile, modular construction supplied by Gekko systems, known commercially as the Python crushing trains. Both North and the South concentrating lines are nearly identical.

SECONDARY AND TERTIARY CRUSHING
The plant feed conveyor discharges to the secondary crusher feed conveyor and onto a vibrating grizzly feeder. A fixed-type electromagnet is installed to remove tramp iron at the transfer point between conveyors. The vibrating grizzly removes minus 50 mm material and the secondary jaw crusher, Metso model C80 crushes the oversize to a P95 of 50 mm. A metal detector is will stop the conveyor travel when metal is detected in the conveyed material. Metal can be groundengagement steel from mobile mining equipment, as well as ground support material from underground.

The secondary crusher discharge reports to a vibrating feeder that combines the crusher product with the grizzly undersize, and the blended feed is then to the secondary dry horizontal screen, 1.2 m x 2.45 m, for sizing at 40 mm. The oversize is returned to the secondary jaw crusher for further crushing. A fixed-type magnet has been installed the head end of screen feed conveyor, along with metal detection. The undersize product is transferred to the wet tertiary screen.

The tertiary screen is fitted with panels having a 4 mm aperture by 25 mm long. The oversize from tertiary screen, is conveyed to one of the duty/standby tertiary crushers, Remco model 1530 vertical shaft impactor (VSI-type), 260 kW, for further size reduction. The transfer conveyors are fitted with a fixed-type magnet for removal of scat metal. Each train with two sets of crushers is fitted with a dedicated hydraulic changeover system, and the VSI set are run off a common Variable Speed Drive (VSD), intended to allow for adjustment of the speed to increase rock breakage, or alternatively reduce wear on the rotors. The tertiary crusher product is conveyed to the tertiary screen for closed circuit operation.

The tertiary screening operation is a critical unit operation to provide feed appropriately sized for the grinding circuit, and for coarse gold in the gravity circuit. One of the two wet tertiary screens was replaced by a new 1.8 m x 6 m Con-Weld screen in November 2019. Maintenance management of the tertiary screen will likely require the presence of a rotatable spare on site, or further monitoring to ensure delivery in the year of replacement by sealift.

The crusher product at a design transfer size of approximately P80 1.7 mm reports to the tertiary screen undersize hopper from which it is pumped by one of two duty/spare pumps to the dewatering cyclones. The dewatering cyclones return water to the tertiary screen feed box for mixing with new feed, while the underflow discharges in the surge tank feed pump hopper.

The availability of the secondary and tertiary crusher is a critical factor in establishing the achievable throughput to the plant. While originally designed for 92% availability by the supplier, actual operating hours of the circuit are considerably lower. Nominal design criteria of 55 t/h per train have been regularly reported, and to some extent, the operation team compensates by operating the crushing circuit at up to 62 t/h when available.

PRIMARY GRINDING AND GRAVITY CONCENTRATION
The primary milling circuit grinds ore to a target of P80 of 150 µm for flotation. The primary ball mill operates in closed circuit with the primary cyclones, with the overflow reporting onto the continuous gravity concentrator and the flotation circuit. Like the crushing circuit, the grinding and gravity concentration circuits are duplicated.

The surge tank underflow pump feeds the grinding circuit by transfer of slurry into the primary mill discharge pumpbox. This pumpbox originally had a volume of 2.5 m3 but was increased to 7.5 m3 during the gravity circuit upgrade in 2018. The duty/spare primary mill discharge pump feeds the primary grinding cyclone cluster in closed circuit. The cyclone distributor feeds the six Weir Cavex 250CVX20 cyclones mounted parallel to each other. Normally 3 cyclones are run to produce the target cut size to the cyclone overflow, allowing 3 cyclones to be on standby or for the completion of maintenance. Automated valves feeding the cyclones can be remotely opened and closed from the mill supervisory control and data acquisition system (SCADA)

The underflow slurry from the cyclones return to the primary mill at 78-80% solids for further grinding, while the overflow at 28-32% solids reports to the agitated 5 m3 rougher flotation feed tank at a grind target of P80 of 150 µm, which was lowered from the original design criteria of 212 µm.

The primary mill is a frame-mounted overflow-type Outotec model 15-04 which is 2.7 m in diameter and has a 4.88 m long effective grinding length (EGL). The mill is installed with a 450 kW variable voltage variable frequency (VVVF) drive.

From 2015 to 2017, ore produced by the Doris Mine was stockpiled while the first concentrator line of the Doris Plant was constructed. Construction of the first concentrator line of the Doris Plant was completed in December 2016 and commissioning completed in June 2017. The first concentrator line provided the Doris Plant with a capacity of 1,000 t/d. The Doris Plant capacity was upgraded to 2,000 t/d when the planned second concentrator line was completed in August 2018. The Doris Plant initially consisted of two Python concentrator lines followed by a concentrate treatment plant (CTP) which produces gold dore bars for sale. The Doris Plant has been upgraded from its original design with expanded gravity recovery and leach scavenger capabilities.

ORIGINAL DESIGN CRITERIA
- Concentrator availability was 92% (8,059 hours per annum), which included availability in the CTP.
- CL feed was 2 x 62.5 t/h (IPJ con bypassed mill), 9.8 g/t, 2 x 605 g/h Au.
- Plant thro ........