The Fekola deposit is an example of a disseminated orogenic gold deposit.

The Fekola Mine is hosted within an inlier of Birimian rocks of the West African craton, termed the Kédougou–Kéniéba Inlier (KKI), located on the border of eastern Senegal, western Mali and northern Guinea. The KKI is a greenstone belt characterized by sequences of approximately north–south-trending volcanic and sedimentary rocks, intruded at various stages by gabbroic suites and calc-alkaline granitoids. The major greenstone units include the Mako, Dialé–Daléma, Falémé and Kofi Series rocks. Two main crustal-scale structures; the Main Transcurrent Zone (MTZ) in the west and the Senegal–Mali Shear Zone system (SMSZ) in the east, bisect the KKI. The Kofi Series hosts significant gold mineralization on the eastern side of the SMSZ and is the primary host to mineralization in the Project area.

Kofi Series lithologies consist of phyllite, thinly-bedded calcareous siltstone-mudstone, marble, mass flow deposits (conglomerate), metapelite and diorite sills cut by quartz–feldspar porphyry dykes and breccia zones. The units have been metamorphosed to greenschist facies.

Three deformation events and corresponding foliation developments control the orientation of folding, shearing and subsequent geometries of gold-bearing zones in the Project area.

Pervasive and texturally-destructive dolomite ± albite ± tourmaline alteration is spatially associated with mineralization.

The Fekola deposit, including the Fekola North Extension, has been outlined along strike for approximately 3 km, can be as much as 200 m in width and extends based on current drilling to at least 440 m depth. Gold mineralization at Fekola is dominantly hosted within bedrock and occurs with fine-grained disseminated pyrite, commonly in association with high strain zones and fold hinges. High-grade mineralization is concentrated in a high-grade shoot (>2 g/t Au) that plunges shallowly to the north–northwest at 14° in the south end, flattening to about 5º around the Fekola North Extension area.

The Fekola deposit remains open along strike and down plunge. Work conducted in 2017–2019 identified narrow zones of hanging wall mineralization. Future exploration efforts will be designed to test for additional high-grade zones along strike to the north of the Fekola deposit where narrower intersections have been encountered at shallow depths, and north-plunging mineralization south of the current pit limits, occurring as stacked lodes.

The Anaconda Area is a collective term for the Anaconda, Adder, Cobra, Cascabel, Mamba and Boomslang zones that are situated about 20 km north of the Fekola Mine. The majority of the mineralization delineated to date is within the Menankoto Sud exploration permit; however, the Bantako Nord prospecting authorization hosts the strike extension of the Anaconda and Mamba structures that are actively being explored.

The combined Anaconda–Adder saprolite zone extends over 5.5 km along strike and up to 500 m wide at the Anaconda zone and up to 200 m wide at the Adder zone. Within these zones, mineralized saprolite varies from 2 m to >40 m thick, averaging 13.5 m true thickness. Mineralization occurs as flat-lying to slightly dipping mineralized zones within saprolite and saprock, and can locally be traced into bedrock. The Adder zone remains open along strike. The Mamba saprolite zone extends to a kilometre along strike and is about 170 m wide, with thicknesses varying from 10 m to >100 m thick, averaging 65 m true thickness. Sulphide mineralization has been discovered down plunge from, and continuous with, the high-grade saprolite zone.

The mining method for the Fekola deposit is via conventional open pit mining with the operations strategy based on owner-operator mining equipment and labour.

The base case mine production schedule involves the movement of a total 78.5 Mt/a of ore and waste to sustain a planned throughput rate of 7.75 Mt/a of high-grade ore while stockpiling as much as 5.8 Mt of low-grade mineralization and 8.3 Mt of currently sub-economic mineralization.

The mine design is based on cutback widths between 250–450 m as guided by Whittle analysis, with a minimum mining width of 40 m on all benches except the floor of the ultimate pit, where the widths will be 25 m. Nominal road and ramp widths of 27 m are used where the 90 t capacity trucks operate, and a ramp with of 35 m is used where truck fleets are mixed capacity, or the 180 t capacity trucks are in operation. The lowermost benches of phases are designed with single ramp access. The ramp gradient is designed up to 10%.

Waste storage facility design is based on 15 m vertical lifts with 36º faces and 30 m berms, when initially constructed. Facility location considerations are based on minimising haulage, surface water drainage and area availability. Large berms are designed to facilitate use of equipment during reclamation, as during the reclamation process, the faces will be re-sloped.

The total mine life is nine years for the development of a 410 m deep ultimate pit in nine stages to support nine years of processing.

Ore Receiving and Crushing
ROM ore is tipped directly into either side of the ROM pocket. A rock breaker is installed to assist in breaking down oversize material retained above the gyratory crusher in the ROM pocket. Ore is crushed by the gyratory crusher and then withdrawn from the ROM discharge pocket by a variable speed apron feeder. The crushed ore is conveyed, via the stockpile feed conveyor, to the crushed ore stockpile.

Crushed Ore Stockpile
The crushed ore stockpile has a live capacity of approximately 10,000 t (equivalent to 11 hrs of mill feed at a nominal throughput rate of 7.5 Mt/a) and a total storage capacity of 57 hours.

Crushed ore is reclaimed from the stockpile, by three variable speed apron feeders. The feeders discharge onto the SAG mill feed conveyor which conveys the crushed ore to the SAG mill feed chute.

Grinding and Classification
The Fekola grinding circuit is a traditional SABC circuit, comprising a single, variable speed, SAG mill and a single fixed speed ball mill. The SAG mill operates in closed circuit with a pebble crusher, whilst the ball mill operates in closed circuit with hydro-cyclones. The product particle size exiting the grinding circuit (cyclone overflow) contains 80% passing 75 µm material.

Crushed ore, reclaimed from the stockpile, is conveyed to the SAG mill feed chute. Process water is added to the SAG mill feed chute, to control the in-mill pulp density. The SAG mill is fitted with discharge grates to allow slurry to pass through the mill and also relieve the mill of pebble build-up. The SAG mill product discharges to a single deck vibrating screen, for pebble sizing and dewatering.

Grinding media (125 mm balls) is added to the SAG mill via direct dump onto the SAG mill feed conveyor. SAG mill discharge screen oversize is conveyed to a pebble crushing circuit. Undersize from the discharge screen flows by gravity to the cyclone feed pump box, where it combines with the discharge slurry from the ball mill.

The treatment plant design incorporates the following unit process operations:

• Single stage primary crushing with a gyratory crusher to produce a crushed product size of 80% passing (P80) of 150 mm.

• Crushed ore stockpile with a nominal 10,000 tonne live capacity to provide 20 hours of operation at design plant throughput. During extended periods of up to three days for primary crusher equipment maintenance, ore from the dead part of the stockpile is reclaimed by an excavator or dozer to feed the grinding circuit.

• Crushed ore from the stockpile is normally reclaimed by apron feeders positioned under the stockpile to feed the grinding circuit.

• The grinding circuit is a SABC type, which consists of an open circuit SAG mill, pebble crusher for SAG mill discharge oversize and a closed circuit ball mill to produce a P80 grind size of 75 µm.

• Quicklime from a silo is added onto the SAG mill feed conveyor along with the crushed pebbles. Sodium cyanide solution is added to the SAG mill feed chute to start the gold leaching process.

• Hydrocyclones are operated to achieve a cyclone overflow slurry density of 25% solids to promote better particle size separation efficiency. Subsequently, a leach thickener is included to increase slurry density to the leach circuit, minimise leach tank volume requirements, reduce overall reagent consumption, and separate gold dissolved by cyanide addition to the grinding circuit.

• Carbon columns (CIC) are included to recover gold already dissolved in the grinding circuit. The leach thickener overflow stream is pumped to this carbon adsorption circuit.

• Leach circuit with five tanks to achieve the required 24 hours of residence time at design plant throughput. Carbon-in-pulp (CIP) circuit consisting of six stages is a carbon adsorption circuit for recovery of remaining gold dissolved in the leaching circuit.

• Zadra elution circuit with gold recovery to doré. The circuit includes an acid wash column to remove inorganic foulants from the carbon with hydrochloric acid. The single elution circuit is common for both carbon adsorption circuits.

• Carbon regeneration kiln to remove organic foulants from the carbon with heat. This piece of equipment is common for both carbon adsorption circuits.

• Cyanide destruction circuit using SO2 and air to reduce the WAD Cyanide level in the tailings discharge stream to an environmentally acceptable level.

• Tailings thickener to increase slurry density for water recovery prior to tailings discharge to the tailings storage facility.