The Houndé deposits are shear-zone hosted orogenic gold deposits as supported by occurrence of sulphide-gold mineralisation in deformed, quartz carbonate-sulphide(-gold) veined and strongly metasomatised greenstone wall rocks.

A strong, northeast-trending, dextral shear zone cuts through the Houndé area. This shear zone lies approximately three kilometres west of the Vindaloo Zone and has a very sharp western edge, as defined by the magnetic data. The eastern edge of the structure is not well defined; however, magnetic data suggests that the shear zone may be four to six kilometres wide. To the east of this strong structure, shearing is focused along unit contacts with preference along the sediment volcanic, volcanic-gabbro and sediment-gabbro contacts. Sediment units are often strongly deformed and display local graphitic shear zones, gouge and healed breccias.

Vindaloo-Madras
The Vindaloo and Madras mineralised zones are predominantly hosted by altered magnetitebearing gabbro and to a lesser extent, andesitic volcanic rocks and sediments. The gabbrohosted zones range up to 70m in true thickness and average close to 20m true thickness in a section of the zone called Vindaloo Main. Volcanic- and sediment-hosted zones are generally less than five metres wide. The mineralised system is zoned with initial propylitic-style alteration along the outer edges of the system with the addition of chlorite and calcite stringers concurrent with the destruction of pyroxene, amphibole and plagioclase. In a poorly defined area, located to the west of the Vindaloo Main zone, the propylitic alteration is overprinted by a reddish hematitic alteration comprising disseminated hematite and hematite veinlets. Fine grained to millimetre-size pyrite crystals are associated with:
• Trace to 10%, up to 2cm wide, quartz veins (trace to 2% overall in mineralised zones);
• Pyrite-enriched haloes to the quartz veins; and
• Occasionally as disseminations within the host gabbro.

Bouéré
Gold mineralisation at Bouéré is associated with hydrothermal alteration zones and related quartz-carbonate veining, that appear to have occurred in protracted fashion throughout D1 and D2 deformations. The hydrothermal alteration at Bouéré evolved through D1 carbonatization (associated with no or very low-grade mineralisation) towards sericitization and silicification which occurred in pulsative fashion at a transitory late-D1 to syn-D2 stage of deformation (associated with significant mineralisation). Gold mineralisation is coeval with a progressive increase in the D2 deformation and a variably intense sericite – silica - carbonate (ankerite + calcite) ± albite alteration and zones of quartz – carbonate veining, both associated with sulphides dissemination in the altered rocks and in quartz veins. Gold veins were emplaced during a continuum of deformation between late D1 and syn-D2. High to very high gold grades are systematically associated with massive and/or laminated milky quartz (± carbonate ± albite) veins from one metre to multiple metres thick occurring in the silica-sericite-carbonate-sulphide alteration zones. Visible gold is nearly exclusively seen in theses quartz veins. Bouéré is characterised with low continuity of mineralisation over short along-strike distances and relay-type patterns of mineralisation resulting in fragmented/discontinuous lenses of mineralisation.

Dohoun
Gold mineralisation at Dohoun is intimately related to the shear zone along the western edge of the granodioritic intrusive. The gold is hosted in a brittle-ductile context with mainly pyritictype sulphides. The pyrite grain geometry is highly variable, though gold is generally associated with fine- to medium-grained pyrite in a hydrothermal alteration halo of sericite and quartzcarbonate veins. Richer and thicker mineralisation have been observed in volcanic rocks in direct contact with the intrusive where the shear zone thickens; however, the portion of the shear zone crossing the intrusive is low to medium grade (<2g/t Au).

Kari Centre
Kari Centre gold mineralisation is developed mainly within the volcanics, associated with whitish sulphide-sericite-albite alteration and fine disseminated pyrite at the hanging wall of the volcanic/sediments contact (N60° strike, dipping 45° to the northwest). The mineralisation is diffuse, locally high grade (>2g/tAu) but generally lower grade when hosted in the oxide horizon. In brittle sedimentary units, gold grades are structurally controlled, and locally can be high grade (>5g/tAu). These mineralised zones tend to occur in narrow, tension gash type structures. To date, neither visible gold nor arsenopyrite have been observed in drill cuttings.

Kari Pump
Gold mineralisation occurs at Kari Pump within a sheared reverse fault (D2) that appears to be folded and dipping from zero to 40 degrees to the west-northwest and northwest. The mineralisation exhibits good continuity over 1.3km along section and displays typical pinch and swell characteristics. The highest-grade areas of the quartz veins are typically thicker, and alternate with thinner vein areas which are typically lower in grade. Kari Pump gold mineralisation is associated with the pyrite occurring as veinlets and disseminated grains within the silica altered and quartz vein bearing host shear.

Kari West
Kari West hosts multiple stacked mineralised lenses that are sub-parallel to the lithological foliation, reflecting both strong structural and lithological control. The mineralised lenses trend in a general west to west-southwest direction with shallow and moderate dips to the north. The lenses vary in thickness from a few metres to locally tens of metres, displaying pinch and swell characteristics both along strike and down dip; structural observations suggest that the thicker zones may represent the intersection of two mineralised lenses with varying dip and strike characteristics. The gold mineralisation in Kari West is associated with pyrite occurring as veinlets and disseminated grains within the quartz veins and SASE and SEAL alteration.

The mining method employed at Houndé Gold Mine is conventional open pit excavator-truck operation with the production unit operations (drilling, blasting, loading, hauling and dumping) carried out by mixed owner contractor mining personnel and equipment. Load and haul activities are owner operated and contract service providers, SFTP Mining and African Explosive Limited (“AEL”), carry out drilling and blasting activities.

Mining and processing of transition/fresh ore began in Q4 2017. Mining activities transitioned from mainly oxides in early 2018 to mainly fresh ore by the end of 2019. Ore was mined from the Vindaloo Main Pit Stages 1, 2 and 3 and Vindaloo Central and Bouéré pits to feed the process plant in 2019.

The in-pit material excavation is conducted by a fleet of eight Komatsu excavators consisting of one PC3000-8R, three PC 2000-8R and four PC 1250-8R. Material haulage is done by thirty-one Komatsu HD785-7 rear dump trucks. Key items of the ancillary fleet are seven D375A-6R track dozers (two D375A track dozers are being mobilised from Ity Gold Mine in April/May 2020) and four GD825A-2 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 32m deep inclined holes are sampled and assayed every 1m to generate wireframes from sectional interpretation, for grade control block modelling and ore outlines generation. The ore outlines are then used by geologists and surveyors for final ore/waste discrimination and in-pit mark-up. In 2018 Houndé Gold Mine introduced blast movement simulation technology (“BMT”) to better predict movement of ore resulting from blasting as a key measure in reducing ore loss and dilution.

Production drilling and blasting is performed on contract by SFTP with Sandvik DP1500s drill rigs on 9m benches with one-meter sub-drill using 115mm diameter drill bits. Blasted material is excavated in 3m high flitches. African Explosives Limited (“AEL”) provides in-the-hole blasting services. The AEL plant on site consists of an ammonium nitrate mixing shed for the manufacturing of bulk explosives and four 30 tonne capacity iso-tank containers for storage. The supply of detonators, boosters, bulk explosives, initiating systems and other explosives material into the site-based magazines for storage is the responsibility of AEL.

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 sterilized before dumping commences.

The production drilling and blasting operations are carried out at 9m benches that is then double battered to 18m double benches in fresh rock. Each 9m bench is then excavated in 3m flitches to ensure maximum selectivity and equipment productivity. The average blasting powder factor is between 0.90kg/bcm to 0.98kg/bcm (ammonium nitrate/fuel oil “ANFO” equivalent) for the transitional and fresh rock with a density above 2.0t/m3 and emulsion is used in both wet and dry blasting. The highly weathered zone (clays and laterites) and transitional zone with a density below 2.0t/m3 is classed as free dig as per the current mining practice.

Dust suppression is undertaken by water carts fitted with spray bars. Water for dust suppression is available from sumps in the pits in first instance and from the Turkeys Nest on the surface if the pit sumps run dry.

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.

The “Houndé Process Plant” consists of a Carbon-in-Leach (“CIL”) plant with a nameplate capacity of 3.0Mt per annum (now operating at 4.0Mtpa) with Semi-Autogenous Ball Mill Crusher (“SABC”) milling circuit to produce an 80% passing 90-micron grind size. Ground fresh ore is fed to continuous centrifugal gravity concentrators to recover free and occluded gold in heavy particles (pyrite) to a low mass gravity concentrate. This gravity concentrate is processed through an intensive cyanide leach reactor followed by electrowinning to recover the gold. The CIL feed has the potential to be thickened and fed into a standard CIL circuit, with leach tails passing into a cyanide destruction process before being pumped to the Tailings Storage Facility (“TSF”).

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; and

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 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.