Primary gold deposits in Burkina Faso occur within the Paleoproterozoic Birimian belt. Mineralization was synchronous with regional metamorphism and deformation. Gold deposits found within the Birimian greenstone belts of the West African shield are typically late orogenic hydrothermal deposits that exhibit a strong relationship with regional arrays of major shear zones. The gold mineralization is typically associated with an organized network of quartz veins containing subordinate amounts of carbonate, tourmaline, sulphides, and native gold. In these deposits, the gold is typically free milling. Alternatively, gold mineralization can also be associated with disseminated sulphides in strongly deformed alteration zones. In the alteration zones, gold may be free milling, but also refractory.

Gold mineralization is related to regional arrays of alteration and deformation zones, commonly located at major lithological discontinuities. The local controls on the distribution of the gold mineralization are structural and lithological.

In Burkina Faso, the weathering profile is deep and typically results in extensive surface oxidation of bedrock to a depth reaching more than 100 metres locally. In such areas, gold deposits typically comprise a surface oxide zone, an intermediate transition zone, and a deeper fresh rock zone. Gold is typically free milling in the oxide zone.

The gold mineralization found at the 55 Zone and Bagassi South Zone deposits is associated with low sulphide quartz veins and is free milling. The weathering profile over the deposit is shallow and ranges from approximately 10 to 30 metres.

Property Geology
The north-northeast trending Boni shear zone divides the Yaramoko Gold Project between predominantly Houndé volcanic and volcaniclastic rocks to the west and the minor volcanic rocks of the Diébougou granitoid domain to the east.

The eastern assemblage contains several intrusive bodies, including a diorite body east of the village of Yaramoko, a large quartz bearing granitoid which stretches south from the town of Bagassi, and a smaller granitoid body to the east of Bagassi. The granitoid body east of Bagassi hosts the 55 Zone gold deposit. A diabase (dolerite) dike trends north-northeast across the southern portion of the property.

Outcrop and core observations document the main lithological units present on the Yaramoko Gold Project as mafic volcanic rocks, felsic dikes, and late dolerite dikes. The mafic volcanic rocks constitute the main country rock, and are locally strongly magnetic and in places affected by calc- silicate skarn alteration (garnet, calcite, epidote, and magnetite). The mafic rocks are crosscut by multiple generations of felsic dikes with aplitic, pegmatitic, or porphyritic textures. Late dolerite dikes crosscut mafic volcanic rocks, felsic dikes and gold mineralization (SRK, 2013b).

Mineralization
Gold is the main mineralization of economic interest found on the Yaramoko Gold Project. The main areas of gold mineralization are the 55 Zone, Bagassi South Zone, 109 Zone, and 117 Zone. The 55 Zone and Bagassi South Zone are the two main zones, both of which are hosted in the Diebougou granitoid domain.

Both the 55 Zone and Bagassi South Zone deposits occur along dextral shear zones and gold is primarily associated with quartz veining. The bulk of the gold mineralization occurs in dilational segments of the shear zone where quartz veins are thicker and exhibit greater continuity. Gold typically occurs as coarse free grains in quartz and is associated with pyrite. The gold bearing veins range in size from a few centimetres to over 5 metres in width, and contain only minor concentrations of disseminated pyrite (frequently less than one percent). Adjacent sheared vein wall rock locally contains a small percentage of pyrite.

At the Bagassi South Zone, the gold mineralization is associated with laminated quartz-carbonate veins developed in two shear zones: QV1 and QV'. The average thickness of the gold mineralization at QV1 varies from less than one metre to over 18 metres and extends from the surface to over 300 metres depth; gold mineralization remains open along strike and at depth. Gold mineralization at
the Bagassi South Zone is associated with quartz and pyrite alteration in similar structural settings as at the 55 Zone.

Four mineralogically distinct hydrothermal veins were defined from samples from the 55 Zone: quartz rich veins, iron-dolomite rich veins with quartz and muscovite, iron-dolomite and quartz veins with albite, and albite rich veins with quartz and iron-dolomite (GeoMinEx, 2013). Native gold is present in each vein type, with accompanying sulphides of pyrite and trace tellurides. The most abundant sulphide mineral, pyrite, occurs in veins and altered wall rock. Textural and chemical complexity of pyrite document a protracted period of crystallization from a compositionally evolving hydrothermal fluid. Native gold occurs in numerous textural associations and at a wide range of grain size ranging from less than 1 and up to 300 micrometres.

The second type of gold mineralization encountered is also associated with pyrite, occurring in zones of conspicuous shearing primarily in the volcanic rocks, with minimal to no significant quartz veining. These two styles of mineralization represent two end-members of brittle-ductile deformation within the 55 Zone where coarse gold in veining, usually seen in a granitic host, defines a more brittle environment while pyrite and shearing in the volcanic rocks is typical of a ductile domain.

Mining operations at Yaramoko are comprised of the 55 Zone underground mine, which was commissioned in 2016, and Bagassi South underground mine, which was commissioned in 2019.

Longitudinal longhole stoping with delayed cemented rockfill is the primary mining method adopted for both underground mines. Other than sill pillar stopes, up holes are drilled to breakthrough and surveyed to ensure drilling accuracy prior to production blasting. Sill pillar stopes are drilled as blind up hole stopes as these are the final level to be mined in a panel of four or three for 55 Zone and Bagassi South respectively. A longitudinal stope mining sequence, along strike from vein extremities retreating to a central access in an east and west direction.

Each stope is mined in this fashion over a 25 m strike length for 55 zone and 10 m strike length for Bagassi South.

Blast holes generally consist of parallel up holes utilizing a dice five or zipper drilling pattern due to the narrow nature of the orebody. Holes range from 12 m to 17 m in length, with some drillholes fanned out where vein widths exceed 5.0 m. Drill factors average 2.5 t to 3.5 t per drill meter, common factor for narrow vein ore bodies. Blast holes are loaded with ammonium nitrate fuel oil (ANFO) and low-density ANFO for perimeter control to a powder factor ranging from 1.00 to 1.50 kg per tonne for the initial void firings and 0.50 to 1.00 kg/t for ring firings. Any wet holes are charged with in-hole liners due to sensitivity of ANFO to water. Stope slots are opened by multiple methods depending on location and stope type. Stopes at the extremities utilize airleg rising or downhole longhole drilling with vertical retreat firings, whereas adjacent stopes utilize airleg rising or firing against cemented rock backfill.

Standard stope dimensions for 55 Zone are 25 m up to 40 m on strike, 20 m height based on sublevel heights, and vein width with the inclusion of planned dilution. A standard stope at 55 Zone yields on average 3,000 t to 3,500 t. Production loading is undertaken via 3.1 cubic meter (m3) bucket load, haul, dump loaders (LHD)s, with tele remote loading for final stope cleanup. Mineralized material mucked from stopes brows is trammed along the vein by the LHD to stockpiles located on each level close to the main decline and re-handled by LHD’s with 5.7 m3 bucket onto truck for hauling to the run of mine (ROM) pad.

Longhole stopes are backfilled with 6.0 percent cemented development waste rock for the first 4m to 5 m, followed by 4.0 percent cemented development waste rock for the next 10 m and then filled with uncemented waste rock for the remainder of void, the higher strength fill at the bottom to ensure minimal overbreak occurs from firing sill panels from below. The current LOMP indicates that waste generated from development can supply all the backfill needs of the 55 Zone mine and Bagassi South but in instances where there is insufficient waste generation from development for filling stopes, waste is backhauled from the waste dumps for filling activities.

Access to the underground mine is by decline development. 55 Zone and Bagassi South decline gradients are different due to level spacing differences in each mine. 55 Zone on an average is at a gradient of minus 1:7.25 to maintain a level spacing of 20 m floor to floor and Bagassi South on a gradient of minus 1:8.3 to maintain a level spacing of 17 m floor to floor. Development profile for decline has dimensions of 5.3 m width by 5.8 m height, optimized to the selected haul trucks.

Recent exploration drilling and a review of mine engineering designs in 2020 and 2021 supports the development of an open pit mine, at the completion of the 55 Zone underground mine, which includes the mining of near surface mineralization remaining in the crown pillar and remnant mineralization from earlier underground mining. Open pit mining would only commence at the conclusion of underground mining due to the need to remove certain key surface infrastructure associated with the underground mine.

Crushing Circuit
The crushing circuit is fed with a CAT966 front end loader via the ROM bin. The crushing circuit is based upon two stage crushing (primary jaw and secondary cone) at 1,100 tpd, with secondary crushing operated in open circuit at a design feed rate of 100 tph. The crusher circuit produces a final product particle size of P80 of 20 mm. Feed control into the crushing circuit is via a variable speed feeder to a jaw crusher, with choke fed secondary crushing operations maintained by a surge bin and variable speed feeder prior to the secondary crusher. The crushing circuit also includes a belt magnet for tramp steel removal, a metal detector prior to secondary crushing, and a weightometer.

Reclaim, Grinding and Classification Circuit
An apron feeder inside the stockpile tunnel reclaims crushed ore from under the stockpile and discharges onto the mill feed conveyor, which feeds the (4.2-meter diameter by 4.8-meter effective grinding length) Ball mill at the designed feed rate of 50.2 tph. The mill feed conveyor is fitted with a weightometer for control and accounting purposes. The quicklime handling system located next to the mill feed conveyor doses quicklime on the mill feed conveyor to control the process pH. The total mill feed consists of crushed ore (fresh feed), cyclone underflow (recirculating load), scats recycle and dilution water.

A vibrating reclaim feeder can be used as an emergency feeder loaded by a front-end loader in situations where the main reclaim apron feeder is under maintenance.

The addition of grinding media into the Ball mill is a manual process onto the mill feed conveyor. The SAG mill operates with a ball charge of between 20 to 27 percent volume/volume and a maximum total load of 35 percent with pinion power draw of 996 kW. A variable speed drive is installed on the mill to vary the mill speed, so that it caters for changes in ore characteristics. The ball mill discharge product passes through a trommel screen, with oversize (Scats) reporting to a bunker. Scats are recycled back into the mill feed with front-end loader via the emergency feeder.

The Yaramoko processing plant was upgraded in January 2019 and designed for a throughput of up to 401,600 t per year (1,100 tpd).

The process circuit is simple and robust and comprises the following components:
• A 2-stage crushing circuit with a throughput of 100 tph and availability of 70 percent, on a 24-hour-per-day operation.
• An open stockpile receiving crushed product, which has a live capacity of 810 t. An underlying apron feeder and emergency vibrating feeder provides ore feed directly to the milling circuit.
• A milling circuit with a throughput of 50.2 tph, operating at 91 percent availability, with a design grind of 80 percent passing 90 micrometers.
• A gravity circuit on cyclone underflow consisting of two centrifugal concentrators and two intensive leach reactors for treatment of the gravity concentrate, treating 68 percent of the cyclone underflow.
• A carbon-in-leach (CIL) circuit consisting of one leach tank and seven adsorption ta ........