Overview

Deposit type

• Breccia pipe / Stockwork
• Vein / narrow vein
• Volcanic hosted
• Sediment-hosted

Summary:

Young-Davidson is situated within the southwestern part of the Abitibi Greenstone Belt. The Abitibi Greenstone Belt consists of a complex and diverse array of volcanic, sedimentary, and plutonic rocks typically metamorphosed to greenschist facies grade, but locally attaining amphibolite facies grade. Volcanic rocks range in composition from rhyolitic to komatiitic and commonly occur as mafic to felsic volcanic cycles. Sedimentary rocks consist of both chemical and clastic varieties and occur as both intravolcanic sequences and as unconformably overlying sequences. A wide spectrum of mafic to felsic, pre-tectonic, syntectonic, and post-tectonic intrusive rocks are present. All lithologies are cut by late, generally northeast-trending Proterozoic diabase dikes.

The Abitibi Greenstone Belt rocks have undergone a complex sequence of deformation events ranging from early folding and faulting through later upright folding, faulting, and ductile shearing resulting in the development of large, dominantly east-west trending, crustal-scale structures that form a lozenge-like pattern. The regional Larder Lake-Cadillac Fault Zone (“LLCFZ”) cuts across the Young-Davidson Project area. The LLCFZ has a sub-vertical dip and generally strikes east-west. The LLCFZ is characterized by chlorite-talc-carbonate schist and the deformation zone can be followed for over 120 miles from west of Kirkland Lake to Val d’Or, Québec.

There are three important groups of Archean sedimentary rocks in the district. The oldest is Pontiac Group quartz greywacke and argillite, which occur as thick assemblages in Québec, while interbedded within the Larder Lake Group volcanic rocks are turbiditic siltstones and greywackes of the Porcupine Group. Unconformably overlying is Timiskaming Group Conglomerate, turbidite, and iron formation with minor interbedded alkalic volcaniclastic units.

Archean intrusive rocks are numerous in the district but are largely manifested as small stocks, dikes, and plugs of augite syenite, syenite, and feldspar porphyry occurring in close temporal and spatial association with the distribution of Timiskaming Group sediments. The main syenite mass, which hosts most of the gold mineralization on Young-Davidson, measures almost 900 m east-west by 300 m north-south.

Huronian Proterozoic sedimentary rocks onlap and define the southern limit of the Abitibi in Ontario. In the project area, these rocks are correlative to the Gowganda Formation tillite. Post-Archean dike rocks include Matachewan diabase and younger Nipissing diabase, which respectively bracket the Huronian unconformity in the project area.

Essentially all of the historical production at the former Young-Davidson Mine and approximately 60% of the production from the MCM Mine was from syenite-hosted gold mineralization. Most of the current underground Mineral Resources are also related to syenite-hosted gold. The syenite-hosted gold mineralization consists of a stockwork of quartz veinlets and narrow quartz veins, rarely greater than a few inches in thickness, situated within a broader halo of disseminated pyrite and potassic alteration. Visible gold is common in the narrower, glassy-textured quartz veinlets. In general, gold grades increase with quartz veinlet abundance, pyrite abundance, and alteration intensity. Mineralized areas are visually distinctive and are characterized by brick red to pink K-feldspar-rich syenite containing two to three percent disseminated pyrite and several orientations of quartz extension veinlets and veins. The quartz veins and veinlets commonly contain accessory carbonate, pyrite, and feldspar.

Mining Methods

• Longitudinal stoping
• Transverse stoping

Summary:

Open pit mining commenced in November 2011, and ceased in June 2014, upon depletion of the in-situ open pit Mineral Reserve. While the mining of the open pit has ceased, a sizeable stockpile of open pit ore was used to augment underground production until early 2020 but has now been depleted. Over the life of the open pit, approximately 20.9 Mt of waste rock was generated by the open pit and placed in the waste dump to the north of the pit. Commercial production was declared for the Young- Davidson open pit mine and mill effective September 1, 2012.

In October 2013, the Company commissioned the mid-shaft loading pocket and shaft hoisting infrastructure and began hoisting underground ore to surface via the Northgate shaft. Prior to October 2013, ore was being trucked to surface through the exploration ramp. On October 31, 2013, commercial production at the Young-Davidson underground mine was achieved.

The underground deposit is located approximately 210 m to 1,500 m below surface. During 2013, AuRico completed the sinking of the Northgate shaft down to the mid-shaft loading pocket to access the first eight years of mine production. The Company has since completed vertical access in the underground mine below that of the mid-shaft loading pocket, to the ultimate depth of 1,500 m. In 2017, raise boring of the Northgate shaft was completed to the ultimate depth of 1,500 m and ground supporting of the shaft was completed in 2018. Completion of the Lower mine development and the tying in of the Northgate shaft extension was completed in mid-2020. In 2015 the existing MCM #3 shaft was extended to a depth of 1,500 m to provide for the hoisting of personnel, materials, and ore and waste. Commissioning of the MCM #3 shaft was completed in the first half of 2016. The mine is also accessed by a ramp, which was extended to the bottom of the mine from the existing exploration ramp and was completed in the first half of 2020. The mine design has taken into consideration the existing MCM #3 and the Northgate shafts and other existing openings for ventilation. Additional ventilation raises to surface have been established and the underground ventilation circuit continues to be upgraded as the mine deepens.

The underground mine has been designed for low operating costs using large modern equipment, gravity movement of ore and waste through raises, shaft hoisting, minimal ore, and waste re- handling, high productivity bulk mining methods, and paste backfill. The mining method employed is a combination of transverse and longitudinal stoping, followed by paste backfill, on 30 m sub- levels. Below the 9,400 m level sub-levels are being developed on 35 m intervals. Given the significant orebody widths, it is expected that approximately 90% of the remaining Mineral Reserves will be transversely mined. The mine operates scoop trams to load, haul and transfer stope production to the ore pass system from where it is hoisted to the surface via two 24.5 tonne skips in the Northgate shaft.

With the commissioning of the Lower mine, the Northgate shaft hoisting capacity is approximately 10,500 tpd of ore and waste.

Lateral development of the underground mine will average approximately 11,000 m per year including capital, operating, and ore categories for the first ten years of the underground mine operation. In the last five years of the underground mine life, the development requirements drop off sharply as the mine is close to being fully developed.

The average underground hourly mining personnel requirements at 8,000 tpd are estimated to be approximately 380 persons. The mine operates seven days a week with two 10.5 hour shifts per day working five days on and four days off followed by four days on and five days off schedule. The mine is fully owner-operated with only diamond drilling and raising being contracted.

Comminution

Crushers and Mills

Summary:

Pit Ore Reclaim
Open pit stockpiled ore is crushed in a jaw crusher to a P80 of 150 mm. Crushed ore is then conveyed to the coarse ore bins feeding the processing plant grinding circuit. The surface crusher is capable of crushing over 8,000 tpd and was the sole source of mill feed prior to the commissioning of the underground mine.

The surface crushing for the open pit will be carried out by an independent contractor and material to the plant will be fed by mine trucks, which will dump the material atop a grizzly fitted with scalping bars set on a 250 mm x 300 mm grid. All the sized material reports into a hopper above on a vibrating grizzly feeder.

The vibrating grizzly feeder drops the open pit ore onto the pit ore feeder conveyor which feeds the coarse ore bin feed conveyor. This coarse ore bind feed conveyor receives the crushed product from both the underground mine and the open pit and is designed for a rate of 550 t/h. A fixed magnet is located at the transfer chute between the two conveyors to capture tramp metal. Each conveyor discharge point is fitted with an extraction hood connected to a dust-collecting bag house. The dust is dropped back on the subsequent conveyor belt through mechanical shaking of the bags.

Underground Ore Crushing Circuit
The mined ore is dropped into an ore pass from which it is metered by a grizzly feeder with 600 mm x 600 mm openings to an apron feeder which drops into the underground jaw crusher with a 160 kW (200 hp) motor size. A fixed magnet mounted above the discharge of the apron feeder to the jaw crusher retrieves any tramp metal. The crushed ore is sent to two underground ore bins each 1500 tonnes in capacity. The product of these two bins reports to two apron feeders which discharge to a conveyor leading to the skip loading system.

The material skipped to surface is fed into one of two 500 t surge bins (1 ore, 1 waste) at the headframe. From there, the mill material is transferred via an apron feeder onto the coarse ore bin feed conveyor. This overland conveyor allows filling of a 6,000 live tonnes capacity bin. The bin is insulated to prevent wet material from freezing against the bin wall, while the top of the bin is covered and fitted with a bag house to extract air moisture and prevent freezing. An electric hoist mounted on a beam extending over the edge of the bin outline assists in bringing maintenance supplies to the top of the bin, facilitating the maintenance of the head pulley and idlers at the discharge point of the coarse ore bin feed conveyor.

Coarse Ore Reclaim
Feed from the coarse ore bin discharges onto the SAG mill feed conveyor via two apron feeders fitted below elongated slots at the bottom of the coarse ore bin. Both feeders are normally in operation to achieve the plant design feed rate and to provide some blending capability for managing the SAG mill feed size distribution. In case of a feeder being out of operation, the total ore flow required by the grinding plant can still be obtained with only one feeder in service.

The SAG mill feed conveyor is fitted with a belt scale, providing plant feed tonnage control through the variable speed capability of the apron feeders.

Grinding Circuit
The grinding circuit is in a single-stage SAG mill configuration.

One of the Kemess ball mills was modified to function as the SAG mill in the Young-Davidson grinding circuit. The resulting unit has 6,710 mm ID ø x 11,130 mm (22’ ID ø x 36.5’) of flange-to-flange (FF) length, and is fitted with two 4,474 kW (6,000 hp ) synchronous motors taken from the mills at Kemess.The fresh material from the coarse ore bin feeds the SAG mill at the design rate of 370 t/h, equivalent to 8,880 t per operated day, which meets the average nominal capacity of 8,000 t/d and a plant availability of 91%. Process water is added to the SAG mill feed chute to achieve a pulp density of 75% solids in the mill.

The SAG mill discharge reports to the cyclone feed pump box.

A centrifugal pump (with one stand-by) with a 298 kW (400 hp) VFD drive delivers the slurry from the cyclone feed pump box to a battery of three (two are typically in operation) ø660 mm (26”) hydrocyclones fed from a common manifold. The cyclone battery works in closed circuit with the SAG
mill, with the cyclone underflow returning as a circulating load to the mill feed. The cyclone overflow stream proceeds forward to the flotation circuit at a slurry density of 35% solids.

The grinding circuit is designed to operate with circulating loads fluctuating between 100 and 150% relative to the fresh SAG mill feed rate, using the variable speed capability of the cyclone feed pump to maintain the pump box level and the number of cyclones for feed pressure control to the cyclones.

An automatic sampler was installed to collect incremental samples of the cyclone overflow in order to provide a composite shift sample that is used for metallurgical accounting purpose. The secondary sampling stage and collection of the shift composite is achieved by the multiplexer provided with a particle size analyzer (PSA). The PSA is installed at this position to provide feedback to the grinding circuit operator of the grinding product size being achieved. The shift composite sample is also collected for analysis of its precious metal content.

A pebble crusher was added to the mill circuit in the fourth quarter of 2017.

Processing

• Hydrochloric acid (reagent)
• Carbon re-activation kiln
• INCO sulfur dioxide/air process
• Crush & Screen plant
• Flotation
• Agitated tank (VAT) leaching
• Carbon in leach (CIL)
• Carbon adsorption-desorption-recovery (ADR)
• Dewatering
• Solvent Extraction & Electrowinning
• Cyanide (reagent)

Summary:

The metallurgical test programs supported the selection of single stage semi-autogenous grinding circuit followed by flotation. The flotation concentrate is further ground and leached in a conventional carbon-in-leach circuit. The flotation tailings are also leached in a carbon-in-leach circuit. The gold is recovered from the carbon followed by electro-winning and pouring doré bars.

The combined leach tailings were used for the cyanide destruction test work. The Young-Davidson carbon-in-leach tailings are treated with the SO2/Air cyanide destruction method.

The Young-Davidson mill can be considered a standard flotation/CIL gold mill. The mill was commissioned during Q1 of 2012 and the first gold pour occurred on April 30th, 2012. Ore is currently sourced from two sources, the underground mine and from low grade surface stockpiles, produced by the open pit between 2011 and 2014.

The cyclone overflow feeds a trash screen prior to feeding the flotation conditioner. The flotation conditioner overflows into the first flotation cell. The flotation circuit is comprised of four tank cells.

The flotation concentrate is pumped to the concentrate thickener. Thickener underflow is pumped to the regrinding circuit. The thickened concentrate is pumped to the regrinding circuit, comprising a vertical tower mill, where the solids are reduced to a size distribution with a nominal P80 target of 15 µm, operated in closed circuit with a cyclone cluster. The cyclone underflow returns to the tower mill box while the cyclone overflow flows directly to the concentrate CIL circuit.

The flotation tailings are pumped to the flotation tailings thickener. The flotation tailings thickener underflow is pumped to the combined CIL circuit. Thickener overflows from both thickeners report to the mill process water tank for reuse.

The flotation concentrate from the regrind circuit reports to a pre-leach tank. The slurry overflows from the pre-leach tank into a series of four CIL tanks providing a total of 48 hours of retention time.

The loaded carbon extracted from the first tank of the concentrate CIL tank is pumped to the carbon stripping circuit for carbon elution.

The flotation tailings, along with the previously leached flotation concentrate are fed to the combined CIL circuit consisting of five leach tanks providing an overall retention time of 24 hours. The combined leach circuit tailings report to the cyanide destruction circuit.

The carbon elution circuit has been sized for processing 4 t/d of carbon. The loaded carbon is pumped from the first flotation concentrate leach tank across a loaded carbon screen. The loaded carbon flows by gravity into the acid wash vessel where the loaded carbon is rinsed by a solution of hydrochloric acid followed by neutralization. The loaded carbon is transferred by a recessed impeller pump to the elution vessel. The stripped carbon is reactivated in an electric kiln and reused in the CIL circuit.

The carbon stripping circuit elutes the precious metals into the pregnant solution. The pregnant solution feeds the electrowinning circuit. Pregnant solution is pumped through the electrowinning circuit to produce sludge on the cathodes containing the precious metals. The cathodes are washed, dewatered and dried. The dried cathode sludge is melted in an electric induction furnace and poured into doré bars.

The combined leach circuit tailings report to the cyanide destruction circuit using the SO2/air process and copper sulphate solution. The treated tailings slurry is pumped to the tailings impoundment area for settling or to the paste fill plant and a portion of the reclaim water is sent back to the process plant as process water.

Pipelines and Water Supply

Summary:

Mine Water Settling Pond
The mine water settling pond is an irregularly shaped, single-celled, above grade lined facility, measuring approximately 100 m x 170 m, surrounded by 2 m high berms. The mine water settling pond is located to the north of the mill and to the east of the open pit.

Pipeline to the West Montreal River
The pipeline to the West Montreal River is a 355 mm diameter high density polyethylene pipe of approximately 4.6 km length (with environmental approval for water takings and discharge; Environmental Compliance Approval #6336-ACNH2J and Permit to Take Water for shaft dewatering #6234-AF6JL7)

Fresh Water and Fire Protection Water
Fresh water for both the process plant and fire water are supplied from a water intake on the West Montreal River. The fire and fresh water reserves are in a combined tank with an active holding capacity of 1,185 m3 .

Fresh water is consumed at an instantaneous rate of 64 m3 /h. The majority of this water is consumed at the gland seals (46 m3 /h), while another 18 m3 /h will be used to make-up a variety of reagents and shower water in the mine and mill dry.

A 6 hour reserve is provided to cover short term interruptions in supply. Adding appropriate design factors, a fresh water surge capacity of 660 m3 is installed. The tank has level controls to ensure that the water level does not drop below the necessary storage volume for fire protection purposes at any time. Water flow is based on the demand for the largest fire hazard area. A fire water reserve of 525 m3 is specified to allow for three hours of fire-fighting at a rate of 175 m3 /h.

Process Water
There are four types of water service specifically required by the plant:
- fresh/fire protection water
- process water
- reclaim water
- gland seal water
- potable water.

Process water is required for mill operations, and sufficient water storage within the tailings impoundment area is available for recycling. Recycled water from the TIA is stored in the mill water tank and transferred to the processing plant and other required areas as needed.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Engineering Superintendent	Jean Collard		Jan 18, 2024
Health & Safety Superintendent	Dan Demers		Apr 26, 2023
Maintenance Superintendent	Greg Rooney		Apr 26, 2023
Mine General Manager	Léon G. LeBlanc		Apr 26, 2023
Underground Superintendent	Joey Santi		Apr 28, 2023
VP, Technical Services	Chris Bostwick		Apr 26, 2023