Overview

Deposit type

• Vein / narrow vein
• Breccia pipe / Stockwork
• Mesothermal
• Stratabound

Summary:

The Loulo and Gounkoto deposits can be classified as typical shear hosted Birimian style mesothermal gold deposits.

Loulo-Gounkoto is located within the Kedougou-Kenieba erosional inlier. The inlier is unconformably overlain by Upper Proterozoic sandstones towards the east and further south. Loulo-Gounkoto is predominantly underlain by the Kofi formation consisting of greywacke, sandstone, argillaceous sandstone, calcareous sandstone and tourmalinized sandstone, sheared greenstone units.

The Yalea main mineralized body is hosted by the Yalea Shear, where it is intercepted by the Yalea Structure. The Yalea Shear is a 1.4-kilometer long brittle-ductile, north-south striking, mineralized fault that transects the Yalea Structure, which is a complex, north to north-northeast striking shear zone. The Yalea mineralization is predominantly hosted in hydrothermally brecciated argillaceous pink quartzites.

Gara (previously known as Loulo 0) is hosted within an intensely tourmaline greywacke unit which outcrops on the surface due to its high resistance to weathering. Gold mineralization is strata bound and hosted by a stockwork of quartz-carbonite-pyrite veinlets that is enveloped by footwall greywacke and hanging wall (“HW”) Sheared Quartzite Rose. The higher gold grades generally occur where the veins are most intense and the range of vein orientations more complex.

Baboto is a shear hosted deposit situated along a north-south striking shear structure located approximately 14 kilometers north-northeast from the Yalea deposit. Baboto is dominated by a thick sequence of metasediments and structural breccias. Gold mineralization is mainly associated with the finely disseminated pyrite occurring in the brittle-ductile shear breccias.

Loulo 3 is located 4 kilometers north-northeast of the Yalea mine. Loulo 3 consists of four mineralized zones: a north-northwest trending main zone (“MZ1”), which is situated on the Loulo 3 structure and is transected by the north-northeast striking main zone (“MZ2”), which is situated on the Yalea structure, and two sub- parallel northwest striking footwall zones. The stratigraphy at Loulo 3 (inclusive of Loulo 2) comprises three major lithological sub units, which from east to west include: the HW package (subunits HW1 to HW5), the host package (subunits HP1 to HP4), and the footwall (“FW”) package (subunits FW1 to FW2). The mineralization in Loulo 3 is hosted in the HP4 subunit of the Main Sandstone package with a dominant vein-hosted mineralization style within MZ1 or quartz-tourmaline veins in MZ2. These vein arrays locally transition into bedding-parallel hydrothermal breccias with local semi- massive to massive pyrite, which can also include arsenopyite and hematite, and form the high-grade shoots within the Loulo 3 deposit. The position of the high grade shoots is controlled by pre-existing competence contrasts within the host rock package.

Other minor satellite deposits are present within the Loulo Permit, which exhibit similar geological characteristics to the other major deposits outlined above.

Gounkoto is a large north-northwest trending shear zone, with a complex assemblage of ductile shear breccias, shears and faults characterized by a stepped geometry, with wider zones of mineralization generally seen on the northwest trending structures and narrower zones on the north-south trending structures.

The Faraba deposit strikes north-northwest and is comprised of several zones of gold mineralization hosted within and along the contacts of north-south striking, coarse-grained, gritty sandstone units (lithic wackes) and polymictic breccias, flanked by packages of sheared argillaceous sediments. Lithological layering (transposed bedding) dips steeply westward; however, the mineralized zones (with associated silica, silica-carbonate, and late overprinting hematite alteration) dip steeply to the east. The mineralization terminates up against the west-dipping Faraba Structure at depth. Mineralization is predominantly pyrite, with subordinate arsenopyrite, local magnetite, rare chalcopyrite and pyrrhotite. The mineralization is rheological competency contrast controlled and is typically vein-hosted (i.e. massive, stringers and blebs), or occurs as dissemination in strongly altered hosts (i.e. blebs and fine grains), with semi-massive to massive sulphides typically within the lower parts of the system adjacent to the Faraba Structure. Higher-grade portions of the system appear to plunge shallowly southward in longitudinal section.

The Faraba North target consists of a series of discrete shears and hydrothermal breccia, with veinstyle mineralization associated with pyrite and arsenopyrite. The mineralized zones are sub- parallel to stratigraphy and a total of eight mineralized zones have been generated in the HW domain, and two zones of Dip Domain Boundary (“DDB”) mineralization. The eight mineralized zones in the HW domain are characterized by strong hematite alteration within the first two zones. Then, silica albite, with minor tourmaline and chlorite alternation, for the next three zones, followed by silica carbonate dominant alteration in the lower most zones. The DDB mineralization is characterized by strong silica carbonate and hematite alteration, where the highest grades are related to high strain.

Mining Methods

• Truck & Shovel / Loader
• Longhole open stoping
• Longitudinal open stoping

Summary:

The Loulo-Gounkoto complex is currently comprised of active open pits at Gounkoto, Yalea South, Gara West, and Baboto (which started mining in February 2024). Mining at Loulo 3 open pit is planned to commence in 2027 and at Faraba open pit in 2029. Additionally, the Yalea, Gara and Gounkoto underground mines are all currently in operation and are accessed via portals located in the open pits and a box cut. The mining method for the underground mines consists of long hole stoping with paste fill. Development of Gounkoto underground commenced in 2020 with the mining of the crown pillar under the North Pit occurring from the second quarter of 2023 to the end of 2025. This adds high-grade ounces to Loulo-Gounkoto from 2023.

OPEN PITS
Open pit mining is carried out using conventional drill, blast, load, and haul surface mining methods. Mining of the main pits is carried out by a mining contractor, Gounkoto Mining Services (GMS). Mining operations are carried out seven days per week, three shifts per day, utilising four shift crews.

From 2022 onwards, open pit production will be from Gounkoto, Yalea South, Gara West, Loulo 3, Faraba, and Baboto. The Gara main pit and northern portion of the Yalea pit are completely mined out. A pushback on the southern portion of Yalea is planned for 2023 in the life of mine (LOM) and is reported as Yalea South. The average LOM strip ratio is 15.0. Approximately 23.7 Mt of ore and 356.6 Mt of waste will be mined over the LOM from the combined open pit operations. Enough capacity is available for planned waste, and some in-pit dumping is planned where possible.

The upper levels of the open pits are usually in weathered material, which typically is free digging material. Once fresh (un-weathered) rock is encountered, drilling and blasting is required.

Emulsion explosives are supplied as a down-the-hole service by the mine’s explosive contractor Maxam.

Ten-metre benches are used in both the free dig material in the upper levels and in the harder ground that requires drilling and blasting. The 10 m benches containing ore are excavated in three flitches of equal height.

Production drilling is done by the contractor on a 6 m by 6 m pattern, with holes drilled to a depth of 11.6 m (10 m bench height plus 1.6 m sub-drill). Controlled presplit drilling and buffer line blasting is practised against final walls. The blasting contractor, Maxam, charges holes with emulsion which are detonated using an electronic blasting system to control the blast movement.

Dilution is controlled through blast patterns that are entirely in ore, the use of electronic blasting detonators to reduce blast movements, through the sizing of equipment and through the help of spotters who monitor the mining process.

Open Pit Design Parameters (All Open Pits):
- Accesses - Minimum of two accesses always;
- Ramps - Two single lane ramps (1 driving down, 1 driving up);
- Ramp Access - Minimising ramp access in the hanging wall, unless in a temporary wall;
- Ramp Width - 25 m for double lane and 12 m for single lane ramps, except for dumps (30 m);
- Ramp Gradient - 10%;
- Batter Angles - 60-80°;
- Switchbacks - Kept to a minimum;
- Slope Angles - As advised by a geotechnical analysis;
- Bench Basis - 10 m bench;
- Strip Ratio - Kept as low as possible;
- Final Face Benches - No ramp accesses;
- Single Lane Ramps - Used where required.

UNDERGROUND
The Loulo underground operation consists of two established underground mines, namely Yalea and Gara. A third underground mine, Gounkoto, recently commenced production and is currently in a ramp up phase. All three mines employ long hole open stoping with paste fill at a similar scale and all feed the same processing plant. The underground mines are accessed with twin declines at each site, after which stopes are accessed by multiple ramps developed at approximately 500 m intervals along strike. The sub-level spacing varies between 25 m and 20 m. Generally, newer areas are 25 m apart while older areas, crown pillar areas, and geotechnically complex areas are 20 m apart.

Yalea
The Yalea underground mine is a long hole stoping operation producing at a rate of approximately 1.4 Mtpa of ore. Development commenced in 2007, stoping commenced in 2008, and production has ramped up to 1.4 Mt in 2013.

The mine is accessed via twin declines starting in the Yalea open pits. One is a conveyor decline and the other is used for mobile equipment. The lower part of the mine has been developed through a number of single ramps for truck haulage up to crushers located approximately 350 m below surface which feed ore and waste onto the conveyors.

Gara
The Gara underground mine is a long hole stoping operation producing at a rate of 1.3 Mtpa of ore. Development began in 2010, with production gradually ramping up to 1.2 Mt in 2017 and 1.3 Mt in 2020.

Similar to Yalea, the Gara underground mine is accessed via twin declines from the pit base. One of these is a conveyor decline and the other a trucking decline. The lower part of the mines has been developed as single declines with truck haulage up to crushers which feed ore and waste onto the conveyor. Currently, the crushers are 220 m below surface at 90 Level.

Gounkoto
The Gounkoto underground mine is accessed with a single ramp, of which various other ramps access four main deposit zones. Longitudinal long hole mining method with paste fill will be used, except in the wider zone where a primary-secondary method with fill will be used. This will be at the same 25 m sub- level spacing as in the other operations. The 60 m thick crown pillar below the base of the pit will be mined first and then backfilled. A smaller 20 m sub-level spacing is planned in this zone as poor- quality rock conditions are anticipated.

Comminution

Crushers and Mills

Summary:

The Loulo processing plant processes ore from both the Loulo and Gounkoto operations. The plant uses a conventional crushing, milling, gravity, CIL, and tailings disposal circuit.

Ore material is crushed at Gounkoto with a primary Sandvik CJ815 jaw crusher and secondary cone Sandvik CS660 crusher. The final crushed product is minus 40 mm (80%) and minus 60 mm (20%) at a throughput rate depending on the final crushed size requirement. For the selected 35 mm product size the throughput rate is 360 tph.

The trucks transport ore from Gounkoto to Loulo, approximately 30 km away, using an average cycle time of 90 minutes. The trucks deliver crushed ore to the ROM pad at Loulo and feed the crushed ore directly into the hard rock circuit via the existing gyratory crusher.

Run of Mine ore from the shafts and Gounkoto operations are blended using detailed source analyses to provide a blend of ore to the plant for treatment, meeting the plant operating specifications. The ore is crushed in three stages of crushing to provide a suitable product for feed to the primary mill. Soft ore is fed to the mineral sizer, followed by ball milling. The mill products are classified using hydrocyclones, returning the course material underflow to the grinding circuit. The cyclone overflow is thickened to a suitable underflow density and pumped to the CIL plant.

Since 2014, multiple optimisation projects have been undertaken, resulting in increased throughput and improved recoveries. The upgraded processing plant remains a conventional crushing, milling, CIL, and tailings disposal circuit.

• Crushing – three stage crushing circuit for the hard rock sulphide ores and a single stage roll toothed crusher for the soft weathered oxide ores.
• Milling – one primary mill (8 MW), two identical single stage ball mills (4.5 MW), one scat conveyor system is inserted to return all mills scats back to primary mill via a cone crusher.

Crushing – Hard Ore
Hard rock is delivered to the tipping bin. Tipping can be completed from two directions.

The hard rock crusher plant consists of a primary gyrator crusher (FFE Minerals 1,300 mm by 1,750 mm) driven by a 450 kW electric motor. A tramp iron magnet is installed over the product conveyor to remove steel. A metal detector trips the conveyor if metal is detected.

The primary crusher operated at a rate of +700 tph feeds the secondary crushers, which operate in open circuit, and then the tertiary crushers operate in closed circuit. An additional metal detector is installed on the feed to the tertiary crushers.

The secondary circuit consists of two Sandvik CS660 Hydrocone crushers and the tertiary circuit consists of four CH660 Hydrocone crushing units; all are powered by a 315 kW electric motor. The secondary and tertiary crushers are housed in separate buildings connected via transfer conveyors.

The final product from the tertiary crushers discharges onto a reclaim ore stockpile, via a conveyor system, and has a live capacity of approximately 40,000 t and a total capacity of approximately 115,000 t. This is the feed to the primary mill.

Crushing - Soft Ore
A separate facility exists to crush the soft ore when it is available. The soft ore crushing consists of a tooth roll crusher (MMD 625 - 3 tooth) driven by a 250 kW electric motor. This feeds a separate stockpile area, and the roll crusher product is fed directly onto the ball mill conveyor feed.

Grinding and Classification
The milling section produces a leach feed with approximately 75% passing 75 microns. The milling circuit is composed of a ball mill operating as the primary mill (6.1 m diameter and 9.5 m effective grinding length (EGL) and installed motor power of 7,000 kW upgraded to 8,000 kW) in the open circuit. The oversize or scats are re-handled to the stockpile and re-crushed. The primary mill discharge feeds to two parallel single stage overflow type ball mills (5.5 m diameter by 8.0 m EGL) with a power rating of 4,500 kW each, operating in closed circuit with a dedicated cluster of twelve 250 mm hydrocyclones, of which eight are typically in use.

An additional High Pressure Grinding Roll (HPGR) has been installed to treat scats at a rate of 100 tph.

There is planned processing plant expansion scheduled to commence in 2027 which will expand the annual processing plant capacity to 6.2 Mtpa from 2029 onwards. The main expansion works, in parallel to the current flow sheet, will build an independent flow sheet of 4,200 tpd processing plant that include:
- A complete secondary and tertiary crushing circuit in closed circuit with the screening plant to produce a sub-12 mm product;
- A closed-circuit single stage milling circuit, comprising a 4.5 MW ball mill and a hydrocyclone cluster producing a P80 of minus 75 micron.

Processing

• Crush & Screen plant
• Carbon re-activation kiln
• Calcining
• Smelting
• Agitated tank (VAT) leaching
• Carbon in leach (CIL)
• Elution
• Carbon adsorption-desorption-recovery (ADR)
• Solvent Extraction & Electrowinning
• Cyanide (reagent)

Summary:

The Loulo processing plant uses a CIL gold extraction process with a design throughput capacity of approximately 4.8 million tonnes per annum, which has progressively reached a peak of 5.1 million tonnes per annum. Throughput capacity is expected to be increased to approximately 6.2 million tonnes per annum from 2029 onwards as a result of a planned process plant expansion that is scheduled to commence in 2027. The Loulo processing plant processes ore from both the Loulo and Gounkoto operations. The plant uses a conventional crushing, milling, CIL, and tailings disposal circuit. A gravity circuit was taken off-line in September 2017 as ultra-fine gold (-20 micrometers) was not being efficiently recovered, but it was proven to be leached post-CIL in final tails gold deportment test work. Recoveries have increased since 2019 year-on-year and further gold deportment work will be completed in 2024 to determine how efficiently this fraction is leached now. Test work in 2023 has proven longer residence time (CIL) will achieve higher recoveries and a project is in progress to evaluate the economics.

Gold recovery is maintained above 89% by blending the various ore sources (Yalea/Gara/Gounkoto) to control the copper and arsenic content within the mill feed. The current life-of-mine plan has an average recovery of 89.7%.

The upgraded processing plant remains a conventional crushing, milling, CIL, and tailings disposal circuit. It will process an average of 605 tph using the following circuits:
- Crushing – three stage crushing circuit for the hard rock sulphide ores and a single stage roll toothed crusher for the soft weathered oxide ores.
- Milling – one primary mill (8 MW), two identical single stage ball mills (4.5 MW), one scat conveyor system is inserted to return all mills scats back to primary mill via a cone crusher.
- CIL recovery process.
- Twin Zadra elution process.
- Electrowinning.
- Tailings pumping/deposition split between slime dam and paste plant.

Leaching and Adsorption
The CIL circuit consists of fourteen tanks that operate in series, each having a nominal capacity of 2,500 m3 giving a retention time of approximately 40 hours. Cyclone overflow, at a density of 35% solids, is introduced onto a linear trash screen (0.7 mm by 0.7 mm apertures) and the undersize goes to the leach feed thickener. The thickener underflow at a density of 50% solids by mass is presented as leach feed. One pre-oxidation tank (CIL Tank 1) in the CIL circuit is equipped with six high-shear reactors (Aachen REA-400) upgraded with an additional powerful unit of high-shear reactors (Aachen REA- 450). Cyanide is added into CIL Tank 2 and doses automatically to control concentration around the desired value within ± 2%. and equipped as well with six high-shear reactors (Aachen REA-400) as part of the Aachen Assisted Leach system to enhance leach kinetics. An oxygen dispersion system, consisting of power mixers (EKATO installed in Tanks 3 to 7), is installed to maintain optimal dissolved oxygen across CIL to assist leaching. The oxygen plant, operated by Air Liquide, supplies 64 tpd. Hydrogen peroxide is injected at the thickener underflow, as required, to maintain the required dissolved oxygen levels when necessary for the process. Each CIL tank is fitted with a mechanically swept cylindrical inter-tank screen (0.8 mm) complete with pumping mechanism from CIL Tank 3 to the end of the circuit.

Elution and Gold Recovery
Loaded carbon is recovered from CIL tank 3 into the acid wash cone. After elutriation, it is acid-washed using a 3% hydrochloric acid solution, followed by a caustic neutralisation/water flushing step. The rinsed carbon is transferred to one of two elution columns where the caustic/cyanide solution is circulated at elevated temperature (135°C) and pressures using the Zadra process. Loulo carbon stripping consists of two parallel circuits from harvest–elution column – heat exchangers to electro-winning cells in the gold room.

The pressure Zadra method utilises a pressure strip vessel that reverses the chemical equilibrium of the adsorbed gold-cyanide complex – calcium ion pair on the activated carbon resulting in desorption of the gold-cyanide complex from the activated carbon into the strip solution.

The pressure Zadra process is conducted in a batch-by-batch process and requires approximately eight to 16 hours to complete.

The gold is then recovered downstream from the strip column by electro-winning. Eight electrowinning cells are installed in the gold room for the electro-winning circuit where the pregnant electrolyte is introduced for gold deposition.

After a certain number of elution, the gold loaded stainless steel mesh cathodes are removed from the electro-winning cells and hosed down with a high pressure water stream. This removes the plated gold onto a hopper where it is collected, settled, decanted, and the sludge smelted after it has been dried in one of two electrically heated calcine ovens to produce doré bullion.

The barren carbon is now transferred to the adsorption circuit or to the carbon regeneration kiln, where it is regenerated at 700°C in a horizontal gas fired kiln.

The regenerated carbon is charged back into the CIL circuit.

Tailings Thickening and Paste Preparation
Tailings, discharging from No.14 CIL tank, gravitate through the tails linear screen (0.8 mm by 0.8 mm), then feed into the tails tank from where it is pumped to the Intermediate Plant. This is a technical requirement for the underground paste plants, which must use detoxified coarse tailings as backfill material to fill the stopes. The Intermediate Plant has cyanide destruction together with arsenic fixing and two-stage cycloning to remove clay and fines (if present) and discharges the coarse fraction into a tank. The coarse tailings are used for paste backfill and the fine slimes are pumped to the TSF. The tailings pump station is equipped with two streams of four stage pumps and a flow diversion valve, where the delivery line of the duty (mild steel pipe) is dedicated to high throughput deposition. At the valve station, there is a possibility to use a standby line (HDPE pipe) for low throughput operation. Mild steel pipe rotation is planned to extend the life of main delivery line.

There is planned processing plant expansion scheduled to commence in 2027 which will expand the annual processing plant capacity to 6.2 Mtpa from 2029 onwards. The main expansion works, in parallel to the current flow sheet, will build an independent flow sheet of 4,200 tpd processing plant that include:
- A complete secondary and tertiary crushing circuit in closed circuit with the screening plant to produce a sub-12 mm product;
- A closed-circuit single stage milling circuit, comprising a 4.5 MW ball mill and a hydrocyclone cluster producing a P80 of minus 75 micron;
- A high-rate thickener capable of handling the combined streams from the existing and new processing plant streams prior to feeding CIL at a total of 18,400 tonnes per hour (tph) throughput;
- Additional three 2,500 m3 CIL tanks;
- An upgrade of the current CIL circuit ancillary equipment as well as the tailings handling facilities.

Pipelines and Water Supply

Summary:

Freshwater
The Falémé River is the natural border between Mali and Senegal and provides the majority of Loulo’s freshwater requirements. Freshwater is also abstracted from the Gara Dam, and this could be used for processing requirements, but the main consistent use is for gardening and firehouse water. A main pumping station with two transfer pumps is situated in the river basin upstream of a weir on the Falémé River. Water is pumped to the raw water dam at Loulo from where water is delivered to the processing plant. The mine has a water withdrawal authorisation permit from the Organisation for Senegal River Development (OMVS) to abstract 3,024,000 m3 /year of water from the Falémé River.

The Gara Dam is a built water retention system designed to divert the Gara River around the mining pit and is used by the mine as a supply point and by the community for fishing and gardens. Water for the accommodation camp, gardens, and fire hydrants is pumped from the Gara Dam, which is also used to feed the plant during the dry season.

Gounkoto has a very low requirement for river water as dust suppression water is sourced from pit water and dewatering wells. Rainfall and pit dewatering provide sufficient water for the operation as no ore is processed there. Water is used for crushing of the ROM material before loading and for dust suppression.

Process Water
The majority of mine water is consumed by the processing plant and associated activities. Wet tails are pumped to the TSF after the CIL process and cyanide destruction at the intermediate plant, where peroxide is used. After settlement at the TSF pool, water is pumped back to the processing plant to be reused. Recycled water from the process water pond makes up 90% of total water consumption at the Loulo processing plant and the remaining 10% is made up of freshwater. The decantation water is either pumped directly to the processing plant process water pond, to the RWD or to Loulo Pit 3, where water can be stored for reuse in the processing plant or for treatment for arsenic and then discharged. Freshwater is used in the processing plant for gland service water, for the elution circuit, and for chemical mixing.

Arsenic and cyanide are the main elements of concern in the TSF water. The mine installed a plant in 2020 to treat both elements. This allows the mine to discharge excess water during the wet season that meets discharge guidelines. Cyanide destruction occurs on the whole tailings stream going out to the TSF. The plant to treat arsenic in the whole tailings stream by the addition of ferrous sulphate is being constructed.

Production

Operational metrics

Personnel

Job Title	Name	Email	Profile	Ref. Date
Deputy Mine Manager	Bouba Traoré			May 6, 2024
Environmental & Community Manager	Moussa Kante			May 6, 2024
Environmental Superintendent	Mohamed Keita			May 6, 2024
General Manager	Abbas (Cheick) Coulibaly			May 6, 2024
Metallurgical Superintendent	Lassine Diabate	Lassinediabate23@gmail.com		May 6, 2024
Mining Manager	Coulibaly Adama Bouba			May 6, 2024