The Lamaque Project is located in the southeastern Abitibi Subprovince of the Archean Superior Province in the Canadian Shield. The region has several large-scale strike faults and/or shear zones, trending W to WNW and dipping steeply to the north. The Cadillac Tectonic Zone (“CTZ”) is one of the most prolific structures in terms of gold mineralization.

The Triangle deposit is hosted by volcaniclastic rocks and minor volcanic flows of the Val-d’Or Formation, which have been intruded by numerous intrusions, dykes and sills of compositions varying from mafic to intermediate.

Gold mineralization at Triangle occurs within quartz-tourmaline-carbonate and pyritic gold veins in the Triangle Plug and in the adjacent massive mafic lapilli-blocks tuffs. The veins are localized in a series of shear zones and fractures that cut both units. The thickest and most continuous veins are localized with E-W striking ductile-brittle reverse shear zones dipping 50-70° south. Veins also occur as extensional shear vein splays dipping 20-45° south as well as subhorizontal extension veins. The latter generally are not volumetrically significant. Gold also occurs in sericite carbonate-pyrite alteration selvages along the veins, which are commonly foliated to schistose within fault zones.

The Plug No. 4 deposit is located 550m north of the Triangle deposit. No. 4 Plug is a fine- to mediumgrained magnetic gabbro intrusion measuring roughly 100 to 150 m in diameter. A series of E-W striking reverse shear zones dipping between 45° and 75° to the south cuts all units at Plug No. 4. The shear zones are spaced roughly 25 to 50 m apart and have been identified to a depth of more than 1000m from surface in the gabbro. Gold mineralization at Plug No. 4 is found in quartztourmaline carbonate-pyrite veins. Sub-horizontal extensional veins also occur in this deposit as vein arrays or clusters that extend for tens of meters down the center core of the gabbro intrusion. At Plug No. 4 these vein clusters can carry significant but quite erratic gold concentration. The Parallel Deposit is located 650 m northwest of the No. 3 Mine and 900 m east-southeast of Lamaque Mine main shaft. Gold mineralization at Parallel is hosted within fine- to medium-grained porphyritic diorite, similar to the host rock at the Sigma Mine. The ore zones at Parallel occur as subhorizontal extension veins at shallow depths (70-200 m) and as east-west striking shear veins dipping approximately 30° south at deeper levels. The mineralized veins consist of quartz and carbonate with lesser amounts of tourmaline, chlorite and sericite.

Archean greenstone-hosted orogenic lode gold deposits are typically distributed along first order compressional to transpressional crustal scale fault zones characterized by several strain increments (e.g., Larder Lake–Cadillac Fault Zone) that mark the convergent margins between major lithological boundaries. However, they are seldom located within these first order structures. Major or first-order faults are interpreted as primary hydrothermal pathways to higher crustal levels (Eisenlohr et al., 1989; Colvine, 1989; McCuaig and Kerrich, 1998; Kerrich et al., 2000; Neumayr and Hagemann, 2002; Kolb et al., 2004; Dubé and Gosselin, 2007);

Significant mineralized quartz veins are commonly hosted in second- and third-order shear zones (Eisenlohr et al., 1989). Structurally, these shear zones vary from brittle–ductile to ductile, depending on their depth of formation (Hodgson, 1993; Robert and Poulsen, 2001). At depths greater than 10 km, quartz veins are seldom located within shear zones, whereas gold mineralization is mostly associated with disseminated sulphides (Witt and Vanderhor, 1998).

The volcanic sequence at Lamaque strikes E-W and dips steeply south, with tops facing south. It consists of andesitic basalt lapilli tuffs mixed with lesser andesite flows and flow breccia and mafic lavas. The oldest intrusive rocks at Lamaque are porphyritic diorite dykes and stocks.

Numerous chimney or plug-shaped intrusions varying from mafic to felsic compositions occur at Lamaque, with the Main Plug being the most productive host rock. The Main Plug is roughly elliptical (250 m E-W by 100 m N-S), plunges northeast at 70° and has been traced to a depth of 1,800 m. The core of the Main Plug is medium to fine grained, dark grey and homogeneous tonalite-diorite, which grades outward to quartz diorite and finally diorite. The West and East plugs have the same composition as the Main Plug, but the West plug is coarser grained.

Gold mineralization at Lamaque consists of pyritic quartz-tourmaline-carbonate (QTC) veins, stringers and stockworks. These gold bearing veins occur within all rock types, but are mostly abundant in intrusions. Roughly 85% of the gold mined historically at Lamaque was from veins hosted by the Main Plug. The QTC veins, as at Sigma, are associated with brittle-ductile reverse shear zones, and occur in multiple orientations and styles. Historical nomenclature for the different veins sets include i) “major veins” (strong subvertical shear vein), ii) “lesser veins” (extensional shears or Riedel shears), iii) “stockworks and stringers” (horsetail structures) and iv) three types of “flat veins”, each distinguished by their host rocks or their spatial and temporal relationships with the shear zones.

The Triangle Zone will be the only area of extraction representing the most advanced part of the property.

From the early phases of the project it was recognized that the reserves in Triangle would be optimally recovered through a haulage ramp system to surface, as opposed to a vertical shaft which could not be economically justified at this time. The ramps will be used to haul ore and waste and provide access for personnel, equipment, materials and services, and form part of the exhaust air circuit.

The Triangle Zone long-hole stopes are designed within four sub-parallel major zones (the C zones) dipping 50-70° to south. Approximately 95% of all reserves are located within these zones, whereas a minor portion (5%) of the reserves are located in low-dipping (20-45°) splays off the main shears (C-splays). Each of the C-zones (C2 West, C1-C2 East and C4) will be serviced by a dedicated haulage ramp. A total of 36 levels are required to extract the reserves over the vertical extent of the orebody. The total lateral development requirements are estimated at 54,000 meters over the LOM. Sector C2 West and C1-C2 East are connected via level 184 and 148. Sector C2 West and C4 are tied together at level 328.

A longitudinal retreat long-hole mining method was selected for the Triangle zone based on the orebody characteristics, including grade, dip, continuity, thickness, etc. Although some part of the C-zones have hanging walls dipping shallowly (as low as 43 degrees), the approach in this study has been to promote the application of long-hole mining where possible.

Long-hole Method:

Sublevels will be developed along the vein strike with an 18.0 m vertical separation.

The stope preparation sequence involves marking all the reference lines on the walls for drilling, followed by raise boring an initial opening raise using a V-30 boring head1. Production drilling is then carried out following a pattern defined by the engineering group. The blasting sequence will generally involve two separate firings; the first blast will increase the initial void according to the available volume for broken material whereas the second will encompass the remaining stope volume. Production blast holes will be typically 64-mm (2.5”) or 76-mm (3.0”) in diameter following a pattern parallel to the walls. Mucking will be performed longitudinally from the ore drift using remote controlled loades. Each stope will be filled with a combination of cemented rock-fill and free running waste material.

Room-and-pillar method:

A minor portion of the reserves in shallow dipping areas such as the upper part of C1 will be mined using the room-andpillar mining method, and backfill will not be required.

The proposed room-and-pillar stope configuration is based on typical industry practices for currently operating mines with similar vein geometry. The typical mining height will vary from 1.8 m to 3.0 m. The room and-pillar mining method involve the excavation of a series of “rooms” following the vein, leaving “pillars” (columns) of rock in place to support the mine roof. In conventional room and pillar mining, drilling is achieved using hand held drill equipment and holes are loaded with explosives. After blasting, bolts are then installed in the mine roof to ensure the roof is properly supported. The broken rock is moved to either a raise or a drawpoint using an electric slusher with a scraper. The broken material is the recovered by an LHD to be hauled to surface by truck. A room-and-pillar design is proposed for the upper part of the C1 Zone using 6 m wide rooms with 3 m x 6 m pillars. Mechanized sublevel development from which the blasted material is loaded by LHDs will be completed at 60 m intervals along the vein.

Ore will be hauled by 45 tonnes underground mining trucks via the main access ramp to the surface ore pad. The broken ore will then be transported by a local contractor via an off road route from the Triangle ore pad to the Sigma mill site.

The production rate will ramp-up in pre production from 165 tpd of mineralised material in 2018 to 1,200 tpd in 2019. The mine plan has a duration of approximately 8 years including the preproduction period. The average production rate from the Triangle Zone is 1,481 tpd over the commercial period, calculated on a 360 operating days per year.

The Sigma Mill will process an average 575,000 tonnes per year, with toll milling at the Camflo and Westwood mills in 2018, Sigma mill start-up in Q4 2018 and processing of about 440,000 tonnes in 2019.

The Sigma Mill is composed of crushing, grinding, gravity concentration, leach and carbon-in-pulp (CIP) circuits, as well as elution, carbon regeneration and refinery areas. The crushing circuit includes a jaw crusher, cone crusher and a screen which needs to be replaced. The grinding circuit is composed of a primary rod mill and two ball mills. The circuit will be rearranged to use one ball mill as the secondary grinding step and the other as a tertiary grinding step, with each mill in closed circuit with its own cyclone, to be able to achieve a 50 µm grind size.

The gravity circuit is currently composed of two static screens and two 20-inch Knelson gravity concentrators operating as parallel units to recover free gold. For the first year of operation, the XD20 unit will be rehabilitated and the CD20 unit dismantled. The Knelson concentrate will be treated on the existing shaking table. The table concentrate is then further processed in the refinery.

In 2019, two new 20-inch gravity concentrators will be installed each preceded by a new vibrating screen. One gravity concentrator will be installed in the primary ball mill circuit while the other will be installed such that it can be fed by either the primary or the secondary ball mill circuits. The old XD20 gravity concentrator will be dismantled at that time. As mentioned previously, the new gravity recovery equipment will be fed directly from the ball mill pump boxes as the existing plant height does not allow installation of all equipment underneath the cyclones. For the time being, it is planned to install the new gravity equipment in a building extension to the grinding building.

A new intensive leach reactor skid will also be installed in 2019 to treat the gravity concentrate. This includes a concentrate feed tank, the intensive leach reactor, an agitated solution tank as well as solution and slurry pumps.

The trash screen underflow is pumped to the thickener feed box. A sampler and particle size monitor are installed on this line. The plant is equipped with two 30 ft diameter high rate thickeners. It is assumed that both will need to be rehabilitated although based on thickening test results, for a production rate of 575,000 tpa, one might be sufficient. Operation at lower tonnage the first year will enable us to confirm thickener performance. Flocculant is supplied to the thickeners by a flocculant preparation system.

After thickening, the slurry will go to a new agitated pre-aeration tank before being sent to the leach circuit where cyanide is used to dissolve the gold. The circuit is composed of five tanks for a total of approximately 5,100 m³ of active leach volume. The pre-aeration tank will be the same size as the leach tanks. Slurry flows from one tank to the other by gravity. Every tank can be by-passed to allow maintenance on any given tank. Each tank will be equipped with an agitator mechanism and compressed air lines. Currently, one agitator is missing and needs to be replaced. As mentioned before, the plant will be equipped with a new milk of lime system, which will enable fine tuning of the leach circuit pH.

The plant is currently equipped with a sodium cyanide receiving and storage tank and sodium cyanide dosing pumps. They are still in good condition but are located in the middle of the plant with no separate containment area and fairly close to the diluted HCl tank. In order to prepare the plant for potential compliance to the International Cyanide Management Code, Eldorado are moving the sodium cyanide tank to a new annex of the mill building where it will have its own containment area and access to the area can be restricted. A new truck delivery pad with containment will also be added. The same pad will be used for both sodium cyanide and sodium hydroxide deliveries.

The discharge of the leach circuit first flows through a sampler. It then goes on to the carbon-in-pulp (CIP) circuit, composed of one larger 280 m3 tank and six smaller 170 m3 tanks. Four of the smaller tanks will need to be replaced due to their poor condition. The slurry goes from one tank to the other by gravity. Every tank can be by-passed to allow maintenance on any given tank. Inter-stage screens prevent carbon from being transferred with the slurry. These screens will also be replaced, the existing ones being in poor shape. All tanks are equipped with agitators. As part of the CIP circuit rehabilitation, all tanks will also be re-equipped with compressed air lines and air distribution cones.

Carbon is pumped counter-current to the slurry using existing vertical pumps. Fresh carbon is fed to the last tank via the regenerated carbon vibrating screen which removes carbon fines prior to feeding the carbon to the CIP circuit.

After going through the CIP circuit, the slurry proceeds to two parallel safety vibrating screens to recover any smaller carbon particles that may have passed through the inter-stage screens. The screen underflows feed into a pump box whereas the overflows, which contain fine loaded carbon, are loaded into bags.

The combined volume of the leach circuit and CIP tanks is about 6,400 m3. At 575,000 tpa, this provides a residence time of about 66 hours.

Loaded carbon is pumped from the first CIP tank onto a screen, which returns the underflow slurry to the same tank. Carbon is screened out and then drops into a bin prior to the acid wash column, whose purpose is to eliminate carbonates fouling the carbon. Hydrochloric acid is used for the acid wash.

From the acid wash, the carbon goes into a 3 tonne capacity pressure elution column where a high temperature, high pressure sodium cyanide and caustic solution desorbs gold from the carbon. The elution solution is pre-heated by the hot pregnant solution via a heat exchanger and then further heated using an electric heater.

Carbon from elution is regenerated in an electric rotary furnace, cooled in a quench tank, and returned to the regenerated carbon screen which feeds the last CIP tank. As required, fresh carbon will be fed to a new agitated carbon attrition tank and pumped to the CIP circuit via the regenerated carbon quench circuit. Carbon fines collected from the regenerated carbon screen, the kiln feed dewatering screen and other carbon transfer waters are collected in two fine carbon tanks, one overflowing into the other. A new fine carbon filter press will be added to process the tank underflows. This fine carbon will then be sold.

The plant is equipped with two hydrochloric acid (HCl) tanks: one for receiving of the concentrated HCl and one for dilute acid at the concentration used in the acid wash. A new truck delivery pad with containment will be added for acid delivery. This pad is on the other end of the plant from the sodium cyanide delivery pad to avoid any possible contact between the two chemicals.

The existing caustic soda tank will remain where it is currently located. As mentioned before, trucks delivering the caustic soda will use the same truck delivery pad as for sodium cyanide.

The cooled pregnant solution from elution is sent to the electrolysis cells located in the refinery. There are two electrowinning cells running in parallel. Gold forms on steel wool cathodes. A fan is used to evacuate fumes from the electrowinning cells.