Overview

Deposit type

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

Summary:

The Houndé deposit predominately belong to the first deposit type as they are shear-zone hosted orogenic gold deposits as supported by occurrence of sulphide-gold mineralisation in deformed, quartz carbonatesulphide(-gold) veined and strongly metasomatised greenstone wall rocks.

On the Houndé land package, six deposits have been discovered with Vindaloo being the main and historical one leading to the construction of the Houndé mine. The six deposits are; Vindaloo, Bouéré, Dohoun, Kari Pump, Kari West and Kari Centre. Bouéré, Dohoun, and Kari Centre are small satellite deposits while Vindaloo, Kari Pump and Kari West host most of the current resources summarised in this section. In 2021, extensions of the Kari Centre deposit included the Kari Gap and Kari South deposits, a continuation of the same mineralised system. Mambo is a new discovery, located on an exploration permit approximately 14 km north-northeast of the mine.

Vindaloo
The Vindaloo deposits are hosted by Proterozoic-age, Birimian Group, intensely sericite and silica-altered mafic intrusions, similarly altered, strongly foliated and altered intermediate to mafic volcaniclastics and occasionally sediments. The mineralisation is often quartz stockwork style and is weakly to moderately pyritic. The Vindaloo trend has been drill tested for a distance of approximately 7.7 km along strike and up to 350 m in depth. The intrusion-hosted zones range up to 70 m in true thickness and average close to 20 m true thickness along a 1.2 km section of the zone called Vindaloo Main. Volcanic and sediment-hosted zones are generally less than 5 m wide. The entire mineralised package strikes north-northeast and dips steeply to the west to vertical. The mineralisation remains open both along strike and to depth.

Kari Pump
Geologically, Kari Pump is underlain by andesite flows with minor volcano-sediment and sediments that are locally intruded by few diorite sills. Gold mineralisation occurs within a sheared reverse fault (D2) that appears to be folded and dipping from (0 to 40)° to the west-northwest and northwest. Observed clear alteration consists of pervasive creamy sericite, intermittent rhodochrosite, chlorite seams and pyritised quartz/carbonate veining. The laterite and saprolite are relatively thick at Kari Pump with an average thickness ranging from (50 to 85) m.

Kari West
At Kari West the weathered bedrock and saprolite thickness vary between (25 and 75) m with thicker zones noted to the south. Laterite up to 20 m thick covers most of the area. The Kari West deposit is located in the hanging wall of a N240° trending and steep northwest-dipping lithological contact zone between dominantly meta-volcanic units (hanging wall) and a dominant metasedimentary unit (footwall). The deposit was formed under purely brittle conditions. The mineralisation of Kari West remains open down dip along the low angle structures and steeper and deeply rooted structures and open along the central extend of the deposit on the east (100 m wide) and on the west/southwest.

Kari Centre
Kari Centre area can be subdivided into three deposits which are Kari Centre Main, Kari Gap, and Kari South. The three deposits are continuous, extend up to 3.2 km in length, and cover the same structurally controlled mineralising system. The stratigraphy of those zones is composed of volcanic rocks interbedded with volcanosediments and locally by graphitic sediments. The laterite thickness ranges between (12 to 20) m and the saprolite reaches depths of 100 m in places. Most of the gold at the Kari Centre Main, Gap and South is concentrated in multiple lenses of variable length and thickness within a northeast striking shear zone. The mineralisation is associated with white quartz veins, sericite-albite alteration and disseminated pyrite. The mineralised lenses dip 50° towards the northwest. At Kari South the altered rocks commonly associated with gold mineralisation host two mineralised structures. The first structure is oriented north-northwest and dips steeply towards the east-northeast while a second structure trends 010° and dips 30° towards the east.

Bouéré
Bouéré is hosted in a mafic to intermediate volcanic sequence, comprised of fine-grained tuffs and pyroclastic andesitic flows and breccia interlayered with more massive basaltic and andesitic flows. Bouéré is structurally complex with two main phases of deformation and associated hydrothermal alteration. It is characterised by lenticular-shaped and fold-shaped mineralised zones trending east-west to northeast-southwest, steeply dipping to the north.

Dohoun
Dohoun is underlain by a package of variably deformed fine-grained volcanic rocks including lava flows‚ volcanic tuffs‚ volcanic breccia and sediments. The Birimian Greenstones are intruded by a massive granodiorite and the overall lithologies are cut by a quartz-feldspar porphyry dyke trending north-northeast. A shear zone trends north-northeast and affects the western margin of the granodiorite intrusive and hosts gold mineralisation. It is one to several metres wide comprised of quartz-carbonate veins associated with strong pervasive sericite and sulphides. Two other mineralised vein orientations are observed at Dohoun; north to south veins (interpreted to be associated with early deformational events) and east-northeast oriented fractures within the competent granodiorite intrusion.

Mambo
At Mambo, mineralised shear zones are interpreted to be exploiting the contact between a granitoid intrusive and hangingwall mafic volcanics. The mineralised trend has been defined over 1400 m and remains open to the northeast, and at depth. The mineralised lenses range between (10 to 40) m thick, with higher grades concentrated at the contacts between the volcanics and the granitoid. The gold is hosted within pyrite, with no arsenopyrite observed in drill cuttings. Graphitic shear material has not been observed, and alteration is pervasive sericite with local silica flooding and quartz veining.

Golden Hill
The Golden Hill deposit is located within the highly mineralised Houndé Greenstone Belt. This belt hosts the majority of the high-grade discovered gold ouncesin Burkina Faso, including the recently discovered Siou deposit plus the high-grade Yaramoko deposit. The Golden Hill deposit straddles the same stratigraphy and structures that host these high-grade deposits.

The property contains five north-northeast-south-southwest striking geological domains. From east to west these include: basement gneisses, migmatites, and granitoids; a belt of phyllitic metasedimentary rocks including mudstones, siltstones, phyllites, and sericitic schists; the Eastern Volcanic Domain; a Tarkwa-type sedimentary basin; and the Western Volcanic Domain.

Mining Methods

• Truck & Shovel / Loader

Summary:

The mining method at Houndé is conventional open pit mining including drilling, blasting, loading and hauling. Load and haul activities are owner operated. Contract service providers, SFTP Mining and Maxam Corp carry out drilling and blasting activities. Mining and processing began in Q4 2017.

The in-pit material excavation is conducted by a fleet of nine Komatsu excavators consisting of one PC3000-8R, three PC 2000-8R, one PC2000-11R and four PC 1250-8R. Material haulage is done by 41 Komatsu HD785-7 rear dump trucks. Key items of the ancillary fleet are nine dozers, four 50 m³ water trucks and four motor graders.

Ore mined is hauled to the ROM pad and near ROM stockpiles. Waste mined from the pit is hauled to the waste dumps and other projects requiring waste material for construction (i.e. tailing storage facility, haul roads etc.).

The ore control strategy targeting delineation of ore and waste uses RC holes piercing multiple benches. The geological and assay information, obtained from 32 m deep inclined holes are sampled and assayed every 1 m to generate wireframes from sectional interpretation, for grade control block modelling and ore outline generation. The ore outlines are then used by geologists and surveyors to determine final ore/waste boundaries and in-pit mark-up. Production drilling and blasting is performed on contract by SFTP with Sandvik DP1500s drill rigs on (9 to 10) m benches with 1 m sub-drill using (115 to 140) mm diameter drill bits. Blasted material is commonly excavated in (3 to 5) m high flitches.

Waste rock dumps associated with mining operations are constructed to meet the stipulated guidelines of the Burkina Faso Mining and Explosive and Environmental Regulations. All areas earmarked for waste dumps are sterilised before dumping commences.

Comminution

Crushers and Mills

Summary:

Crushing Circuit
RoM ore is generally loaded into the crushing circuit feed bin (RoM bin) by FEL from the RoM pad stockpiles. The system is flexible enough for direct tipping of the mined material if required. A grizzly is fitted to the RoM bin to protect the downstream equipment from oversize material. A mobile rock breaker is utilised to break oversize rocks.

RoM ore is drawn from the RoM bin at a controlled rate by an apron feeder which discharges over a vibrating grizzly. The vibrating grizzly oversize reports to the jaw crusher. The vibrating grizzly undersize and jaw crusher discharge gravitates to the primary crushing product conveyor. The primary crushing product conveyor discharges onto a transfer conveyor which runs up to surge bin, the overflow rills on to a coarse ore stockpile feed conveyor. A weightometer on the surge bin feed conveyor measures the crusher product.

Coarse spillage in the crusher area is cleaned up by FEL and transported to the RoM pad for drying or fed directly to the primary crusher. Water sprays are installed for dust suppression as required. A 10t hoist is provided over the jaw crusher to facilitate regular maintenance.

The crushing circuit is controlled locally and the FEL driver ensures feed is maintained to the crushing circuit and communicates with the crushing operator using a two-way radio to supply information on crusher feed operation. The speed of the primary feeder is controlled to a target set-point and measured using the crushing weightometer.

Grinding and Classification Circuit
The grinding circuit consists of an SABC circuit with classification hydrocyclones comprising:

• SAG Mill: A 8.50m diameter x 4.35m EGL SAG mill complete with a 6,000kW variable speed drive operates at up to a maximum 18% volumetric ball loading. Variable speed control of the mill, accomplished through a Slip Energy Recovery (“SER”) system, provides flexibility for processing of the various ore types. A speed range of 60% to 80% critical speed is available. SAG mill grinding media, typically 100mm to 125mm diameter balls, is stored in drums or bags in the plant. SAG mill grinding media is fed into the surge bin using a FEL and transferred to the SAG mill feed conveyor. The SAG mill liners and grates are handled by a mill liner handling machine capable of managing the new liners;

• Pebble Crushing: The SAG mill product discharges to a vibrating single deck heavy duty pebble dewatering screen fitted with a nominal 15mm aperture polyurethane screen deck. Undersize from the screen feeds the mill discharge hopper. The oversize pebbles (nominally +15mm) are transferred via a transfer conveyor to a pebble crusher feed bin ahead of a single 250kW pebble crusher.

A single stage of tramp metal removal via a self-cleaning belt magnet across the pebble transfer conveyor is used to remove mill balls and any other magnetic steel debris discharged from the SAG mill. Tramp metal ejected is deposited in a bunker area with concrete walls on three sides which provides access for metal removal and protection to personnel in the area. Metal detection provides a final level of protection against metal entering the pebble crusher. Upon detection of metal, the flop gate at the head of the transfer conveyor is activated and the ore stream bypasses the pebble crusher surge bin for a predetermined period and is deposited directly onto the SAG mill feed conveyor.

The pebble crusher surge bin holds approximately 25 minutes capacity to improve steady state operation of the pebble crusher. The nominal design allows for use of a single pebble crusher to meet the expected pebble load as the competence of the ore is moderate.

A variable speed pebble crusher vibrating feeder transfers the pebbles at a controlled rate from the pebble crusher surge bin into the pebble crusher. Pebbles are crushed from a nominal top size of 75mm to a P80 of approximately 12mm. The pebble crusher operates at a closed side setting of 11mm, depending on the competency of the ore, moisture content and crusher power draw. Product from the pebble crusher is transferred to the SAG mill feed conveyor and an overhead hoist is provided to facilitate crusher maintenance; and

• Ball Mill: A 6.10m diameter x 9.05m effective grinding length (“EGL”) overflow ball mill complete with a 6,000kW fixed speed motor operates at up to 35% volumetric ball loading. Product size from the grinding circuit is 80% passing 90µm on 100% primary ore. The ball mill is fixed, operating at 75% of critical speed. Ball mill grinding media is 50mm diameter balls and is stored in drums or bags within the plant. Ball mill grinding media is transferred to a kibble and loaded into the ball mill via a dedicated ball charging chute which directs the balls to the ball mill feed box from where the grinding media enters the ball mill.

Processing

• Gravity separation
• Carbon re-activation kiln
• INCO sulfur dioxide/air process
• Intensive Cyanidation Reactor (ICR)
• Smelting
• Centrifugal concentrator
• Electric furnace
• Crush & Screen plant
• Agitated tank (VAT) leaching
• Counter current decantation (CCD)
• Carbon in leach (CIL)
• Carbon adsorption-desorption-recovery (ADR)
• AARL elution
• Solvent Extraction & Electrowinning
• Cyanide (reagent)

Summary:

Construction of the processing plant commenced in April 2016 and was completed with the first gold pour in 2017. Commercial production started in Q4 2017. The processing plant at Houndé consists of a carbon-in-leach plant with a nameplate capacity of 3.0 Mt/a. The flowsheet includes a single stage jaw crusher, a two stage SAG/ball milling comminution circuit, gravity concentration for removal of coarse gold, pre-leach thickener, CIL circuit comprising six tanks, split Anglo (AARL) elution circuit, electrowinning, gold smelting and tailings detoxification.

Following commissioning, the Company launched an incremental optimisation programme at the Houndé processing plant. The crushing circuit capacity was increased via upgraded apron feeder motors and drives, pump modifications and increasing the capacity of the tailings delivery line to the TSF. The Houndé CIL processed 5.5 Mt in 2023.

Gravity
Feed for the gravity circuit is taken from the common mill discharge using a duty/standby pump arrangement. The gravity circuit feed stream is pumped to one of two single deck ‘vibrating ‘degritting’ screen to remove coarse (+2mm) material and fragments of broken mill balls and this oversize is returned to the ball mill feed. The screen undersize stream gravitates to one of two (duty/standby) 48” Knelson centrifugal concentrators and the tails slurry from the centrifugal concentrator gravitates to the mill discharge hopper. The concentrator is operated on a semibatch basis with periodic discharge of the coarse high SG material (gravity concentrate) to the concentrate storage hopper as part of the intensive leach reactor.

The intensive leach reactor (“ILR”) processes the concentrate once per day in a rotating drum leach vessel. Cyanide and caustic together with oxygen are introduced into the slurry and the drum is rotated for up to 20 hours to leach out gold and silver. At the end of this time the pregnant liquor is separated from the solids and pumped to the dedicated pregnant liquor tank. Reactor tails is pumped back to the mill discharge hopper for additional milling to recover any remaining entrained gold and silver.

A dedicated pregnant liquor pump feeds the gravity electrowinning cell in the goldroom with gold and silver recovered onto stainless steel cathodes and barren liquor returned to the pregnant liquor tank. The cathodes from the gravity electrowinning cell are treated separately to assist in metallurgical accounting and spent electrolyte is recycled to the head of the CIL circuit.

Leaching
Ore that is not recovered via the gravity circuit is screened to remove any extraneous trash (wood, plastic, etc.) then can either be sent to a thickener to increase thepercentage solids in the leach slurry, or pumped directly to a conventional carbon in leach circuit (“CIL”). The CIL circuit consists of a series of six agitated tanks where gold is dissolved in the presence of cyanide and oxygen as the slurry flows sequentially from Tank 1 to 6. The dissolved gold adsorbs on the coarse activated carbon particles which are pumped in a counter-current direction from Tank 6 to 1, becoming progressively more loaded with gold in the process;

Carbon Recovery
Once sufficiently loaded by the time the carbon reaches Tank 1, the carbon granules are pumped from the primary tank over a screen to remove the slurry. The clean carbon is then washed with hydrochloric acid to remove any acid soluble base metals and impurities, before being transferred to the elution circuit;

Elution and Gold Production
Concentrated cyanide solution is circulated in the elution column and heated to 120 degrees Celsius. After sufficient time to enable the gold to be released from the carbon, the gold bearing solution is sent for electrowinning and eventual gold bullion production;

Once the elution cycle is complete, recovery of gold and silver by electrowinning proceeds. Direct current is passed through stainless steel anodes and stainless-steel mesh cathodes within the electrowinning cells. Electrolytic action causes the gold and silver in solution to plate out on the cathodes and three electrowinning cells arranged in parallel are in operation with electrowinning taking approximately 8 to 12 hours. An overhead crane (2t capacity) is provided to assist with handling of cathodes and anodes. The cathodes are washed with high pressure spray water and the gold sludge is recovered in a vacuum pan filter. The gold sludge filter cake is dried in an oven and direct smelted with fluxes in an electric induction furnace to produce doré bars.

Tailing Detoxification and Disposal
The leached slurry, with minimal leachable gold remaining exits the CIL where the free and weak acid dissociable cyanide (“WAD”) are destroyed through a INCO cyanide detoxification process using sulphur dioxide and oxygen with a copper catalyst to destroy the remaining cyanide complexes. The detoxified tailings are pumped to a plastic lined TSF, where the solid and liquid phases separate. The liquid phase is recycled back to the process plant and the solids allowed to dry and compact in the TSF.

Water Supply

Summary:

Raw water is pumped from a water harvest dam and bores to a surge tank ahead of a treatment plant. Water from this surge tank is pumped on demand to the plant raw water tank. The raw water tank has sufficient capacity to minimize the impact of short-term supply interruptions. Duty/stand-by water pumps are provided for the raw water distribution to the plant.

Potable water is stored in the plant potable water tank and is reticulated to the site ablutions, safety showers and other potable water outlets. Transfer pumps also feed water to a separate camp potable water tank for reticulation. Additional ultra-violet sterilization units are installed on outgoing potable water distribution headers.

Process water is pumped from the TSF decant to the plant process water tank. The plant process water consists of TSF decant return water and raw water tank overflow. The process water tank is located such that the raw water tank overflows to the process water tank allowing the process water tank to be kept full at all times.

Water Demand
A water balance model is utilised to estimate the demand for raw water on site, considering the process water demand, losses and gains from the tailings storage facility, pit dewatering and dust suppression and runoff from the RoM pad and plant site. Utilisation of ground water resources from boreholes is also incorporated into the model. Any potential shortfall is assumed to be supplied from the water storage dam which feeds from a water harvesting dam. The total water demand for the site is estimated at 3.3Mm3 per year and the water demand for the process plant amounts to 2.85Mm3, which includes the minimum raw water requirement of 0.49Mm3 but excludes water in ore. Other water demands include an estimate of 0.54 Mm3 for dust suppression. The demand is met from the TSF decant, pit dewatering (including precipitation on the pit area), runoff from the RoM pad and sub-ore stockpiles. Potable water demand for the mine is directly related to the number of persons working and living on site.

Water Sourcing
The total long-term water withdrawal for the site is estimated at 2.7 Mm³/a, with 7.7 Mm³/a of water required for processing, which includes a minimum raw water make-up requirement of 0.5 m³/t of ore. Other water demands include an estimate of 0.3 Mm³/a for dust suppression. The demand is met from the TSF decant, pit dewatering (including precipitation on the pit area), runoff from the RoM pad and sub-ore stockpiles and rainfall within the water harvest dam catchment area.

Historical investigation into groundwater sources in the project area focused on the estimation of the likely volumes of water arising from open pit mine dewatering and the availability of water to meet the project demand. These concluded that the contribution from pit dewatering, including external groundwater sources of 8 L/s and precipitation on the pit surface is estimated to be up to 1.5 Mm³/a, depending on the extent of the pit development.

Decant from Tailings Storage Facility The water balance modelling indicates that for tailings pumped to the TSF at 50% m/m solids, the pond on the TSF increases during the wet season and reduces to the minimum pre-set level during the following dry season. Long-term recovery from the TSF decant is estimated to be 65% of the process water demand, or up to 5.0 Mm³/a

Surface Water
The water balance model indicates that any water demand which cannot be met from the tailings storage facility, pit dewatering or groundwater sources, is met from surface water sources. The current models are run on a monthly basis for the life of mine for average climatic conditions and tested for a 1 in 100-year dry event and a 1 in 100-year wet event occurring, when each would have the greatest impact on operations. The demand from surface water sources was highest in the year that the process plant was commissioned, when 1.75 Mm³/a was required from the water storage dam. Later in the LoMp the demand for surface water is assumed to decrease to 1.2 Mm³/a.

Water Harvest Dam
A water harvest dam ('WHD') was constructed east of the Houndé open pit. The mean annual runoff at the dam site is estimated to be 4.8 Mm³, from a catchment area of 21 850 ha. The required earth fill embankment is 8 m high and 760 m long, to create a storage capacity of 1.8 Mm³. The surface area of the dam at full capacity is 120 ha. A spillway was provided for a 1 in 100-year peak flood event.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Environmental Manager	Ibrahim Kiemtore		Apr 30, 2024
Fixed Plant Maintenance Superintendent	Ackim Lungu		May 8, 2024
Mine Manager	Alexis Brisebarre		Apr 30, 2024
Mobile Maintenance Superintendent	Jeremie Hien		May 8, 2024
Procurement Superintendent	Nina Pare		May 8, 2024
Regional Senior Buyer	Gisèle Bountoulgou		May 8, 2024