The Mana district is located in the northern part of the Houndé greenstone belt. Five gold deposits, WonaKona, Nyafé, Fofina, Yaho and Siou, are hosted in different rock types. The lithostratigraphic succession is typical of greenstone belts and is characterized at the base by a major tholeiitic basaltic suite with some intercalations of argillic sedimentary rocks that are overlain by predominant pelagic and detrital sedimentary rocks (shale, sandstones, greywacke and volcanoclastics). The Mana district basalt unit has undergone submarine hydrothermal alteration with epidote, chlorite and local albite, and shows zones of strong silicification, some of which are anomalous in gold. The Paleoproterozoic formations are affected by polyphase deformation and greenschist facies metamorphism with amphibolite facies assemblages that locally occur as metamorphic aureoles around some later formed granitoids.

All deposits on the Mana property are characterized as typical West African, shear-hosted orogenic gold deposits. The major sulphides associated with the gold mineralization are pyrite and arsenopyrite. Free visible gold is encountered at the Wona-Kona and Siou deposits. Magnetite occurs as small millimetric prisms along schistosity planes in the walls of mineralized zones. The five major deposits of the Mana property are described below.

The Wona-Kona deposit is hosted in a series of deformed sedimentary, volcano-sedimentary and metavolcanic rocks. The gold mineralization has developed along a major northeast-southwest subvertical fault zone of regional extent. The shear zone is about 200m wide in the Wona-Kona pit sector. The original stratigraphic sequence is a succession of pelitic sediments with graphitic horizons and volcanoclastics. They have been affected by a pervasive schistosity associated with vertical movements along the fault (the east block rising with respect to the west one) as well as sinistral lateral movements. Those foliated rocks are cut by mafic to intermediate dykes. The mineralization appears to be associated with movement along the fault accompanied by hydrothermal fluid circulation and intense silicification.

The Nyafé and related Filon 67 deposits are hosted in a purely volcanic sequence of basalt and mafic tuffs. The original stratigraphic sequence is sub-horizontal and overturned, with pillow lava at the bottom, pillow breccias and finally massive lava at the top. Several subvertical decimetre scale dykes crosscut the volcanic sequence. The Filon 67 (F67) deposit, adjacent to Nyafé is composed of quartz veins associated to shear zones with dextral motion within a package of greenschist rocks. These composite veins show textures indicative of several successive phases of mineralization.

The Fofina deposit is divided into two sectors separated by a zone of volcaniclastic/mafic volcanic rocks. The western zones are located in a sheared sedimentary unit dipping moderately west and trending north-northeast. They are related to a rheological contact with a massive basalt unit to the east. The eastern zones are within the basaltic lavas and have similar characteristics to the Nyafé deposit.

The Yaho deposit is hosted in a wide north-striking and steeply west-dipping sandstone unit flanked by shales and siltstones to the west and basaltic flows to the east. The mineralization is associated with silicified and sericitized corridors within the sandstone which also contain increased amounts of sulphides, pyrite and arsenopyrite.

The Siou deposit is a typical shear-hosted quartz vein deposit. The two principal zones are the Siou and No. 9 zones. The Siou zone is hosted in a single quartz vein located within the Siou Granitic Intrusive, but near the contact with sandstones and shales to the west. The No. 9 zone is located at the contact between the sediments and the Siou Intrusive and generally consists of quartz veining and veinlets intruding the granitic intrusive. Both the Siou and No. 9 zones are north-striking and moderately east-dipping.

Two mining methods are employed at the Mana Mine, namely open pit and underground. Open pit mining will continue in 2021 in the Wona South pit, and underground mining at Siou. Following completion of the updated PFS, underground mining will be employed below the Wona open pit, in addition to the existing Siou underground mine.

OPEN PIT MINING
Open pit mine production at Mana averages approximately 5,000 t/d of ore (bedrock), and mining has been mainly active in the Wona and Siou pits prior to 2021.

The Siou open pit was exhausted in 2020, and open pit production will focus on the southern half of the Wona pit in 2021 and 2022, through to completion of that pit. Mining is carried out using a mix of ‘owner’ and ‘rental’ fleets. The equipment ranges from 120-250 t backhoe excavators, loading 90 t rigid dump trucks. Drilling is currently carried out using a combination of Endeavour owned and contracted drill rigs.

The current stages of the open pit mining require waste stripping (Stage 3) for approximately eight months, to remove ~8Mt of waste before reaching ore. During this waste stripping, ore supply to the plant will be from the underground mining at Siou and the open pit mining of Wona South (Stage 2).

Production drilling and blasting is carried out on 10m benches. Loading and hauling is carried out in four flitches each measuring 2.5 m. The highly weathered zone of oxide (clays and saprolite) and transitional zone with a density below 2.0 t/m3 are amenable to free digging. Emulsion is used in both wet and dry blasting for efficiency.

UNDERGROUND MINING AT SIOU
Longitudinal sublevel retreat and transverse open stope long-hole mining methods were selected for Siou underground due to the inclination of mineralized lenses and varying widths associated with wide stockwork ore zones. Cemented Rock Fill (CRF) is used to ensure safe ore recovery from secondary transverse stopes. Waste rock backfill will be used in secondary stopes in all levels other than sill levels (5070 and 4995). Large sill pillars have been left in the first horizon under 5070 level and of the second horizon under 4995 level. These will be extracted late in the mining sequence.

The mine design and planning was based on the Siou geological model results. Production ramp up to 2,000 t/d using AUMS as the contract miner was achieved in February 2020.

UNDERGROUND MINING AT WONA
Two underground long-hole mining methods will be used at Wona; longitudinal sublevel retreat and transverse open stoping. These methods were selected due to the inclination of mineralized lenses and width associated with wide stockwork ore zones. Longitudinal mining with Cemented rock fill (CRF) will be used when the orebody is narrow, where stope dimensions vary from 3.5 m to 15 m in width perpendicular to the strike of the orebody, with 20 – 40 m stope lengths along strike of the orebody and 25 m stope sublevel intervals. Each level will be backfilled prior to mining of the level above. The transverse stope dimensions vary from 15 – 30 m perpendicular to the strike of the orebody, with 15 m stope lengths along strike of the orebody and 25 m stope sublevel intervals. Primary stopes will be extracted first followed by secondary stopes once backfilling of the adjacent primary stopes are complete. It is noted that several lenses may be mined independently if there is a minimum 10 m waste pillar between them. If there is insufficient pillar material, they are either combined into a single stope, or only the economic portion is mined.

The minimum pillar dimension between orebody lenses is kept at 10 m. An external dilution of 0.5 m at the footwall side and 1 m to 2 m dilution at the hanging wall side was included. Mining recovery for the sill and crown pillars was estimated to be 75% and 50% respectively.

The Wona underground mineralization has been divided into three areas, South, Central and North. These areas will be accessed via three decline ramps developed from two portals, established on the Wona open pit footwall. The Wona underground will be developed in two phases.

Dewatering by bore holes located around the pit will still be required after surface mining has finished. These surface dewatering bore holes will assist in keeping the water table down and reduce the quantity of water to be pumped out from the underground mine. Additional waste rock will be hauled from surface, back underground, to sustain backfill operations as insufficient waste rock will be available from underground development.

The ore production rate for Wona Underground is planned to ramp up to 4,000 tpd of combined development and production stoping ore, utilising contract mining similar to the Siou Underground.

Crushing
ROM ore is loaded by a WA600 front end loader onto a static grizzly screen to handle slabby material. A rock breaker reduces the oversize material that remains on the grizzly (625 by 665 mm). Fine material drops into a 150-t capacity ROM bin. The ore is then extracted from the bin by a primary apron feeder (1,524 mm by 7,000 mm) and fed to a vibrating scalper screen (1,500 mm by 4,000 mm) to further separate the fines. Coarse material from this screen feeds directly into a 36 in by 48 in (950 mm by 1,250 mm) single toggle jaw crusher. The crusher produces a product with a size P80 of 100 mm, at a rate of 400-500 wet t/h and typically operates for 17 h/d. This schedule allows for regular maintenance to occur on a daily basis to the crushing plant.

The jaw crusher handles ROM ore with a maximum lump size of 665 mm. Fines from the scalper discharge directly onto the conveyor belt. Primary crushed material discharges onto a 48-in conveyor belt and is weighed by a scale to maintain a constant throughput to the crushing plant. A magnet located at the head pulley of the conveyor removes any trash steel. Ore is then transferred onto a mobile stacker conveyor which stockpiles around 25,000 t to 30,000 t of crushed ore. Stockpiled ore is withdrawn by two apron feeders in parallel (4,500 mm by 900 mm each) and drops onto the mill feed conveyor. Each apron feeder can handle about 200 t/h of crushed ore. Ore is weighed again to control and maintain steady throughput into the grinding circuit. Hydrated lime is added directly from a dry lime system onto the mill feed conveyor belt for CIL circuit pH control which is maintained at pH 10.5.

Grinding and Classification
The grinding circuit includes a primary semi autogenous grinding (SAG) mill in closed circuit with a vibrating screen and a pebble crusher. The 7.92-m diameter by 2.74 m Allis Chalmers SAG mill is equipped with 2,387 kW variable speed motor and operates between 10-15% ball charges depending on ore hardness. Variable speed control provides additional flexibility for processing of various ore types. The discharge from the SAG mill is split between fine and coarse material. Coarse material (?15 mm) is crushed in closed circuit by a pebble crusher (200 HP) and returns to the SAG mill for further grinding. Fine material (<15 mm) is pumped to the vibrating screen (2.1 m by 5.2 m). The material is classified by the screen with 9.5 mm by 3.2 mm slotted aperture panels. Oversize material returns to the SAG mill for further grinding while undersize material reports to the secondary ball mill discharge pump box. The circulating load for the SAG mill is around 50-60% (fine+coarse) and product size P80 is around 1,200-3,500 µm depending on throughput.

Secondary grinding is accomplished by two overflow discharge ball mills. One is a 5.3-m diameter by 7.0 m Outotec mill equipped with a 3,500 kW variable speed motor. Variable speed control of that mill provides great flexibility for processing various ore types. The second mill consists of a 3.96-m diameter by 4.88 m Allis Chalmers mill with a 1,120 kW synchronous motor. The mills operate in in closed circuit with a cluster of 16 in by 10 in GMAX Krebs classifying hydrocyclones. Nine to 12 cyclones are usually operating while four remain as spare units. Cyclone underflow reports back to the two ball mills through a splitter box while cyclone overflow at 50% w/w solids gravitates to a trash vibrating screen ahead of the leach circuit. Circulating load for the mills is typically around 250-350% and the final product P80 is targeted at 74 µm.

The Mana flowsheet comprises a standard SABC comminution circuit, CIL circuit, Zadra elution circuit and tailings disposal.

The comminution circuit consists of an open primary jaw crusher circuit followed by SAG and ball mills. The SAG mill operates in closed circuit with a pebble crusher and the product from the SAG is also screened classified prior to feeding the ball mills. The ball mill product is in closed circuit with hydrocyclones to produce a product P80 of 74 µm. Product from the grinding circuit is leached through a CIL circuit with a retention time of ±28 hours depending on throughput. Loaded carbon from the CIL is stripped through a pressurized Zadra system. The pregnant solution from the Zadra circuit is pumped to the gold room where electrowinning and smelting of the electrowon sludge occur in order to produce a gold doré. Slurry tails from the CIL circuit are pumped to the tailings storage facility (TSF) and surnagent water is recycled back to the mill. No gr ........