The gold deposits in the Val-d’Or area are consistent with the orogenic gold model. Orogenic gold deposits are typically distributed along first-order compressional to transpressional crustal-scale fault zones that mark the convergent margins between major lithological and/or tectonic boundaries such as the Larder Lake–Cadillac Fault Zone.

Most orogenic gold deposits in Archean terranes are hosted in greenstone belts. In the Lamaque Project area, competency contrasts are the most important localizing host rock control. At Lamaque and Triangle the intersection of shear zones with late diorite to granodiorite plugs host the main gold-bearing veins, whereas at Sigma and Ormaque a syn-volcanic diorite (the C-porphyry) hosts mineralization near the sheared contact with the surrounding volcaniclastic rocks.

Orogenic gold deposits develop in response to shear failure, extensional failure and/or hybrid extensional shear failure. In the Lamaque Project area both shear veins and extension veins are widely recognized, and their identification is important to constrain vein geometries and ore shoots. In the Triangle deposits the main C vein structures are steeply dipping shear veins and host the bulk of the resource, whereas in the Ormaque deposit gently dipping extension veins contain most of the ore.

Sigma Mine
Auriferous veins at the Sigma mine consist of quartz and tourmaline with lesser carbonates, muscovite, pyrite, scheelite, chlorite and chalcopyrite (Robert and Brown, 1986a, b). Four types of veins can be distinguished based on their host rock associations and geometries: (1) steeply to moderately dipping fault-fill veins within shear zones; (2) subhorizontal extensional veins; (3) arrays of subhorizontal extensional veins hosted within the feldspar porphyry dykes, referred to as dyke stringers; and (4) moderately north-dipping extensional-shear veins, referred to as the North Dipper veins.

Lamaque Mine
Gold mineralization at Lamaque consists of quartz-tourmaline-carbonate-pyrite veins, stringers and stockworks. These gold-bearing veins occur within all rock types but are most abundant in late intrusions. Roughly 85% of the gold mined historically at Lamaque was from veins hosted by the Main Plug. The quartz-tourmaline-carbonate veins, as at Sigma, are associated with brittle-ductile reverse shear zones, and occur in multiple orientations and styles. The veins were classified into three main types namely shear veins, flat veins, and stringer veins (Karvinen, 1985). The shear veins are generally thick (up to 10 m) and have strike lengths of over 500 m. They are best developed in the volcanic rocks away from the plugs in the upper parts of the mine. Typical thicknesses of flat veins are less than 0.5 m but these also extend for hundreds of meters in strike. They dip gently (10 to 20°) to the west and intersect shear veins at 75 to 85 °. Stringer veins are essentially stockwork veins and veinlets found predominantly in the two productive plugs and in several zones these veins were so numerous that bulk mining was possible. These stockwork zones were very prolific at the Lamaque Mine and produced most of the ore. They were developed usually near the intersection of sub-vertical south dipping shear zones with the intrusion. The resulting geometry created large zones of gold bearing veins and veinlets that could be as large as the intrusion itself and therefore were very economic to extract.

Triangle Mine
Gold mineralization in the Triangle deposit occurs primarily within quartz-tourmaline-carbonate- pyrite veins in the Triangle Plug and 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 have an east-west strike and developed within ductile-brittle reverse shear zones that dip 50-70° to the south. They are classified as C-veins (shear veins) and at least twelve discrete C-veins (C1 to C10 and C8b and C9b) have been identified to a depth of greater than 1500 m. Smaller extensional shear veins form splays to the C-veins and dip 20-45° south and are commonly associated with sub-horizontal extension veins. The bulk of the gold occurs within the quartz veins, but lower grades also occur in the strong muscovitecarbonate-pyrite alteration selvages. In and below C8, C9 and C10 veins a lower faulted portion of the Triangle Plug contains intense stockwork veins similar in style to zones within the Lamaque mine that were previously bulk mined.

Plug No. 4 Deposit
The Plug No. 4 deposit is located 550 m north of the Triangle deposit and 1 km southwest of the historical No.3 Mine shaft, to which it is connected by drifts on the 450’ and 700’ levels. Plug No.4 is a fine- to medium-grained magnetic gabbro intrusion measuring roughly 100 to 150 m in diameter. It is enveloped by an older syn-volcanic diorite and diorite breccia similar to the C- porphyry. These intrusions are cut to the west by a fine-grained porphyritic felsic diorite dyke which extends northwest towards the No. 3 Mine area. Gold mineralization at Plug No. 4 is restricted to the gabbro intrusion.

Parallel Deposit
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 the Parallel deposit is hosted within fine- to medium-grained Cporphyry diorite. The diorite is medium greenish-gray and contains 1 to 5% disseminated pyrite commonly in a chlorite-silica pervasive alteration. The ore zones at the Parallel deposit occur as subhorizontal extension veins at shallow depths (70 m to 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. Fine pyrite within the vein commonly amounts to 1-3% and rarely up to 5 %. Traces of chalcopyrite occur locally. In wider veins, pyrite and gold are typically confined to vein margins and/or vein contacts, especially in veins composed mainly of quartz and carbonate. The sub-horizontal veins are laterally extensive (up to 300 m) and occur in en-echelon arrays that exhibit pinch and swell geometries. Adjacent wall rocks contain carbonate-albite-muscovite-pyrite alteration. In general, the veins form stacked sets which are 10-25 m thick and contain up to 8 individual veins. Shear veins also occur in clusters. Typically, up to four en-echelon south dipping veins occur within a 75 m wide vertical corridor that cuts across the porphyritic diorite. The shear veins most commonly range in width from 15 cm and 1.5 m but can be up to 2.6 m thick locally.

Ormaque Deposit
The Ormaque vein system occurs within the C-porphyry at the contact with volcaniclastic rocks to the north. Gold mineralization occurs dominantly in gently south-dipping quartz-tourmaline-carbonate extension veins and localized breccia zones. Individual extension veins have widths ranging from several cm up to 2 m and have east-west strike lengths of up to 650 m. The veins form vertically stacked clusters from a depth of about 150 m to at least 600 m below surface.

The deposits that currently make up the Lamaque property include:
- Upper Triangle (zones C1 to C5);
- Lower Triangle (zones C6 to C10);
- Parallel;
- Ormaque;
- Plug No 4.

The primary mining method that is currently used at Lamaque is mechanized longhole stoping. The existing mobile equipment fleet of conventional equipment, mine infrastructure, and services, as well as workforce skillsets are based on longhole, and this method will continue to be used. Ore is transferred to surface using 45-tonne rated underground haulage trucks in the newly developed Sigma Ramp to the surface ore pad near the Sigma mill facility.

The current longhole stoping mining method will be maintained in the proposed mining of the Lower Triangle deposit.

In the proposed mining of the Ormaque deposit, drift and fill (DAF) mining methods will be employed due to the shallowly-dipping orientation of the mineralized zones, allowing for near-complete recovery of mineralization and providing better selectivity while allowing low grade material to be left in the stopes. New low-profile mining equipment will be required to reduce mining heights to 2.4m and reduce external dilution.

The mine operation is currently using cemented rockfill (CRF) and unconsolidated rockfill as backfill. In the proposed Lower Triangle and Ormaque mine plans, addition of a paste fill plant is included in the growth capital to provide cemented paste fill. Mineralized material will continue to be transferred to surface using 45-tonne rated underground haulage trucks. The newly developed Sigma-Triangle decline to the surface ore pad near the Sigma mill facility is a recent improvement for material handling to the mill. Where practical, waste rock will remain underground for use as backfill.

The ore from the mine is trucked to the Sigma mill site 24 hours per day. The crushing circuit is only operated during a 12-hour day shift and consists of a grizzly screen, a rock breaker, a Metso C110 jaw crusher and a 294 kW (400 hp) secondary cone crusher in closed circuit with a triple deck screen. The final screened product is conveyed to the covered stockpile.

The grinding circuit includes a 2.74 m × 3.65 m, 300 kW (9 × 12 ft, 400 hp) rod mill and a 3.51 m × 4.27 m, 750 kW (11.5 × 14 ft, 1000 hp) ball mill. The rod mill operates in open circuit and the primary mill is closed with cyclones. A portion of the cyclone underflow is sent to the gravity circuit with the remainder returned to the primary ball mill. The cyclone overflow, with a grind size P80 of 75 to 100 µm, proceeds to the secondary ball mill pumpbox.

The secondary ball mill is 3.66 × 4.27 m, 930 kW (12 × 14 ft, 1250 hp) and operates in closed circuit with a second set of cyclones. The targeted grind size from the secondary ball mill is a P80 of 40 µm. The secondary cyclones underflow is returned to the mill for further size reduction while the overflow flows to the trash screen to remove debris. The trash screen undersize is pumped to the production thickeners.

A lead nitrate system, incorporating a bag discharge hopper, mixing tank, transfer pump, storage tank and dosage pumps, is installed in the grinding circuit but it is currently not being used

The annual treatment rate is anticipated to ramp up to 862,000 tpa by 2024, based on an average daily production of 2,500 tpd from the Upper Triangle mine. This corresponds to a plant throughput of 110 tonnes per operating hour. Minor debottlenecking improvements are planned to ensure that the mill throughput capacity and availability correspond to the mining production rate.

The Sigma gold plant is situated at the East entrance of the city of Val-d’Or. This plant started operation in 1937. The plant capacity and the flowsheet were modified several times over the years. The flowsheet uses gravity concentration, cyanide leaching and carbon-in-pulp to recover gold.

The Sigma mill operates a conventional process including crushing, grinding, gravity concentration, leach, and carbon-in-pulp (CIP) circuits, as well as elution, carbon regeneration and refinery areas. Metallurgical recoveries through the Sigma mill averaged 96.8% over the last twelve months.
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