The Côté Gold deposit is a new Archean low-grade, high-tonnage gold (± copper) discovery. It is described as a synvolcanic intrusion-related and stockwork disseminated gold deposit (Kontak et al., 2012, Katz et al., 2015, Dubé et al., 2015, Katz, 2016). Deposits of this type are commonly spatially associated with and/or hosted in intrusive rocks. They include porphyry Cu–Au, syenite- associated disseminated gold and reduced Au–Bi–Te–W intrusion-related deposits, as well as stockwork-disseminated gold.

Certain features of the Côté Gold deposit resemble those characteristic of gold-rich porphyry deposits (as described by Sillitoe, 2000). These include:

- Emplacment at shallow (1–2 km) crustal levels; frequently associated with coeval volcanic rocks
- Localized by major fault zones, although many deposits show only relatively minor structures in their immediate vicinities
- Hydrothermal breccias are commonly associated with the deposits, and consist of early orthomagmatic as well as later phreatic and phreatomagmatic breccias
- Gold is fine-grained, commonly <20 µm, generally <100 µm, and is closely associated with iron and copper–iron sulphides (pyrite, bornite, chalcopyrite).

Two different types of gold mineralization are recognized on IAMGOLD’s Chester township properties. The historically important mineralization can be termed quartz vein and fracture associated (Type 1), while the Côté Gold deposit is interpreted by Kontak et al. (2012) and Katz (2016) as an Archean intrusion-related gold (±copper) deposit (Type 2).

Property Mineralization (Type 1)
The Type 1 quartz vein and fracture mineralization occurs in the Chester 1, 2, and 3 areas on the Chester property and elsewhere in the Project area at the Shaft Zone on the Falcon Gold Option property.

Côté Gold Deposit Mineralization (Type 2)
The Côté Gold deposit-type gold mineralization consists of low- to moderate-grade gold (±copper) mineralization associated with brecciated and altered tonalite and diorite rocks.

Several styles of gold mineralization are recognized within the deposit, and include disseminated, breccia-hosted and vein-type, all of which are co-spatial with biotite (±chlorite), sericite and silica-sodic alteration.

Disseminated mineralization in the hydrothermal matrix of the breccia is the most important style of gold (±copper) mineralization. This style consists of disseminated pyrite, chalcopyrite, pyrrhotite, magnetite, gold (often in native form), and molybdenite in the matrix of the breccia and is associated with primary hydrothermal biotite and chlorite after biotite. In contrast, disseminated biotite and chlorite (after biotite) alteration are not typically associated with gold mineralization. However, when present, disseminated gold and chalcopyrite are intergrown with biotite–chlorite (Katz et al., 2015). Disseminated mineralization is typically associated with sericite or silicasodic alteration (Katz, 2016).

The nature of the veins and fractures vary from stockworks to closely-spaced, planar, subparallel sheeted vein sets. Stockwork mineralization cuts through all major rock types, but is most prominent in the more brittle tonalitic phases compared to the dioritic phases and formed during the biotite alteration event (Katz et al., 2015; Katz, 2016). The mineralized sheeted veins and stockwork zones cut the hydrothermal breccia and therefore post-date the breccia-controlled mineralization. Miarolitic-like cavities, which consist of millimeter to centimeter size openings lined with feldspar, carbonate and sulphide, can also contain gold. Importantly, the gold-bearing sheeted veins have been shown to be syn-intrusion in timing based on a structural study in the deposit area (Smith, 2016). In addition, Re-Os molybdenite dating of one of these gold-bearing veins returned an age of 2746.8 ± 11.4 Ma, which overlaps with the age of the intrusive events.

Visible gold is observed in several settings within the deposit:
- Quartz ± carbonate ± biotite–chlorite veins: gold is observed to be hosted within the vein quartz and also along fractures cutting the vein. Sulphides include pyrite, chalcopyrite and pyrrhotite
- Sheeted syn-intrusion-related veins: a set of subparallel, sheeted, millimeter to decimeter scale quartz ± carbonate ± chlorite veins with 0.5% to >50% pyrite ± chalcopyrite ± pyrrhotite that commonly contain millimeter to centimeter scale barren sericite alteration haloes. Gold is also observed marginal to these veins within sericite ± silica–sodic ± biotite–chlorite alteration halos. These veins have been interpreted to be syn-intrusion in timing (Smith, 2016) and are also found outside the deposit within the CIC (e.g., Chester 1)
- Magmatic–hydrothermal breccia: gold is more commonly observed in larger, welldeveloped breccia units but is also present in small, <1 m units. At hand-sample scale, gold appears to have some correlation with biotite–chlorite, sulphides, and magnetite
- Miaroles: gold is observed hosted within miarole quartz, in fractures cutting primary miarole minerals, and within the host rock, proximal to the host/miarole interface commonly within a moderate to intense silica and/or sericite alteration halo
- Alteration related/disseminated: gold is also observed in moderate to intense hydrothermally- altered tonalite and diorite. Typically, this mineralization occurs in silica–sodic and/or sericite alteration of the host, but it may also be associated with biotite/chlorite.

The hydrothermal breccia and the associated hydrothermal alteration zones are the material component of the mineralization providing the mineable widths and grades to the deposit. Areas outside of its significant development are likely not a significant contribution to economically important mineralization. The various gold-bearing quartz vein systems, also found immediately adjacent to the proposed open pit, serve to upgrade the hydrothermal envelope where they are present. The amount of gold contributed by these quartz vein systems to the deposit is difficult to determine but is thought to be of some significance to overall metal content.

The Base Case mine plan is designed as a truck- shovel operation assuming 220-t autonomous trucks and 34 m3 shovels. The pit design includes four phases to balance stripping requirements while satisfying the concentrator requirements.

The design parameters include a ramp width of 35 m, road grades of 10%, bench height of 12 m, targeted mining width between 90 m, berm interval of 24 m, variable slope angles by sector and a minimum mining width of 40 m.

The smoothed final pit design contains approximately 203 Mt of mill feed and 492 Mt of waste for a resulting stripping ratio of 2.4:1. The 203 Mt processed fits within the maximum capacity of the TMF. The average grade of this material is 0.98 g/t Au. These tonnages and grades were derived by following an elevated cut-off strategy in the production schedule.

The Mine Rock Area (MRA) will be constructed southeast of the planned open pit to store mine rock from the open pit excavation. The rock piles will be built in 10 m lifts with 25.5 m benches to provide an overall safe slope of 2.6H:1V. The inter-bench slopes will be at the angle of repose of the rock. In its ultimate configuration, the MRA will store 350 Mt of mine rock with its final crest elevation at an approximate elevation of 480 m.

Collection ditches and six runoff collection ponds/sumps will be built at topographical low points around the MRA perimeter to collect runoff and seepage, which will then be pumped to the polishing pond.

The overburden storage, which will be located to the southwest of the pit, will have a storage capacity of approximately 8.2 Mm3.

The stockpiles will contain stripped materials from all excavations from the project development. The stockpiled materials will be used for rehabilitation applications at closure. Sedimentation ponds will be built to settle out solids before release to the environment.

The ore stockpiles will be located on the north side of the pit and have a total storage capacity of 23 Mm3 , which is enough to satisfy the maximum stockpiling capacity of approximately 48 Mt required in the production schedule.

Crushing
The 54 x 75 primary gyratory crusher will crush the ore at an average rate of 2,143 t/hr to a P80 of 140 mm. Selection of this crusher was based on volumetric throughput and power requirements.

Run-of-mine (ROM) ore from the trucks will be discharged to a dump pocket with a capacity of 330 t or the equivalent to 1.5 times the size of a truckload. The dump pockets will have an agglomerative dust suppression or “fogging” water spray system. The apron feeder discharge chute at the crusher exit will have a baghouse-type dust collector. Crushed ore product from the primary crusher will be transferred to the covered coarse ore conveyor and conveyed, approximately 300 m, to a coarse ore screen distributor located in the screening building.

Primary crusher product will be sized on the coarse ore screens consisting of two double-deck multi-slope vibrating screens. The coarse ore screen oversize will be sent to the 1,250 hp secondary cone crusher. Secondary crusher product will be sent back to the coarse ore screens through the coarse ore conveyor.

Coarse ore screen undersize will be conveyed to the covered COS, which will have a live capacity of 20,157 t, or 12 hr of nominal process plant operation. Total live and dead storage capacity will be 74,720 t, equivalent to 44 hr of normal operation. Using a bulldozer will enable the process plant to continue operating during primary/secondary crushing circuit maintenance shutdown or upset conditions.

The COS will be equipped with three reclaim apron feeders, sized in a way that two feeders can deliver the design rate. A 93 m diameter dome structure will cover the stockpile for weather and dust containment. Additionally, apron feeder discharge chutes will be equipped with filter cartridge-type dust collectors to control dust in the tunnel. Reclaim apron feeders will discharge onto an approximately 260 m long covered stockpile reclaim conveyor.

Combined ore from HPGR screens’ oversize will report into the HPGR feed bin via two covered transfer conveyors of approximately 90 m and 70 m long respectively.

The screening building will be an insulated structure. The screen building will contain two coarse ore and three fine ore screens, apron feeders to each screen, product transfer conveyors and chute works. Dedicated dust collectors for each set of screens will be located outside of the building.

The crushing building will also be an insulated structure. Equipment will include the secondary crusher and the HPGR with respective apron feeders and a shared 100 t/20 t crane. Dedicated feed bins and dust collectors will be located adjacent to the main building.

HPGR and Grinding Circuits
The selected flowsheet to achieve 36 kt/d with a final passing P80 product of 100 µm consists of a closed HPGR circuit, a primary grinding with ball mill circuit, and secondary grinding with vertical mills circuit.

The HPGR will have 2,400 mm diameter by 2,400 mm width rolls, and two variable speed motors with a total installed power of 7,776 kW. The HPGR discharge will fall into a discharge conveyor and feeds a scalping screen feed distributor. The crushed ore stream will be evenly split into three double deck dry-scalping screens with 12 mm and 4 mm apertures, to achieve a transfer P80 of 2.4 mm. Oversized material will be recycled back to the HPGR feed, while undersize will be sent to the primary grind ball mill circuit via a 16 m diameter fine ore bin capable of storing two hours of plant feed. This bin will receive ore from the screening building via a 166 m long covered conveyor. A dust collector system will be installed in the discharge to the bin. Ore will be reclaimed from the bin using two reclaim feeders, which will discharge onto a 240 m long ball mill feed covered conveyor.

The 7.92 m diameter by 12.3 m EGL ball mill, powered by two motors of 8,000 kW each, will operate in a closed-circuit configuration with a 12-way radial cyclone cluster. Fresh circuit feed will be fed directly to the ball mill and the product will be discharged by gravity through the mill trommel to the cyclone feed pumpbox, where the slurry will then be pumped to the cyclone cluster. A total of ten 750 mm diameter cyclones will work in closed circuit with the ball mill, with two cyclones on stand-by. All coarse cyclone underflow material will report to the ball mill with an estimated circulating load of 300%. Overflow fine material from the primary cluster cyclones will report to the secondary grind cyclone feed pumpbox with a passing P80 of 235 µm.

The secondary grind circuit will consist of two vertical stirred mills with a total installed power of 6,700 kW. Stirred mills will operate in closed circuit with the secondary grind cyclone cluster consisting of 13 operating 750 mm diameter cyclones. Underflow material from the cyclones will fed the stirred vertical mills. A 40% split from the cyclones underflow will fed the gravity concentrators for gold recovery. Tailings from the gravity circuit will be returned to feed the vertical mills. Secondary cyclone overflow will be directed to the whole ore leach circuit with a final passing P80 product size of 100 µm. A particle size analyzer will monitor the performance of the entire grinding circuit.

Plant throughput will be 36,000 t/d and it is expected that a ramp-up period of 10 months will be required to reach the design throughput.

The Base Case process plant will consist of:
- Primary (gyratory) crushing
- Secondary cone crushing and coarse ore screening
- Coarse ore stockpile (COS)
- Tertiary HPGR crushing
- Fine ore screening and storage
- Two milling stages (ball mill followed by vertical stirred mills)
- Gravity concentration and intensive leaching
- Pre-leach thickening
- Whole ore cyanide leaching
- CIP recovery of precious metals from solution
- Cyanide destruction
- Tails thickening
- Elution of precious metals from carbon
- Recovery of precious metals by EW
- Smelting to doré.

Gravity Concentration and Intensive Leach
Material from the secondary cyclone underflow up to a maximum of 1,600 t/hr will be directed to the gravity concentration circuit. The stream will be e ........