The gold deposits within the Youga, Ouaré and Balogo properties can be described as epigenetic, mesothermal (“lode”) gold deposits, demonstrating a strong structural control and relationship to regional scale shear zones. Similar deposits can be found in other areas of the late Proterozoic Birimian terranes of West Africa.

At Youga and Ouaré, gold mineralisation is intimately associated with pervasive silicification, quartz veining and sulphidation (predominantly pyrite), although sulphide content is extremely low (generally <1%).

The majority of the Youga gold deposits are hosted within the Tarkwaian sandstones, while Ouaré is hosted along the sheared contact between mafic volcanics to the north and quartz-feldspar porphyritic rocks to the south.

Within the Youga deposit, there are two distinct styles of mineralisation:
• Moderately to weakly silicified arkose with quartz stockwork veining and pyrite is the predominant sulphide which generally grades between 0.5 g/t and 2 g/t
• Intensely silicified arkose with abundant quartz veins and more diverse sulphides which generally grades >3 g/t.

The Ouaré mineralisation is on the Bitou 2 Exploration Permit and has been delineated in three zones, along a strike length of 2 km.

At the Ouaré Main zone, mineralisation occurs as quartz veins within shear zones at the contacts between felsic and mafic volcanics. Orpailleur workings have been developed along mineralised structures in two orientations: 090° and 315°. The 090° portion of these workings have multiple parallel quartz veins along shears in an interpreted dilation zone. The 315° portion is interpreted as a 100 m wide deformation zone, terminating the 090° trend.

The gold mineralisation appears to preferentially follow the lithologic contacts between felsic volcanics and mafic volcanics, particularly within a shear zone of inter layered quartz-feldspar porphyritic and intermediate to mafic volcanic rocks. Gold mineralisation appears to be confined to a major 090° trending deformation corridor of dextral strike slip.

The proposed method of mining for Youga and Ouaré is a conventional open pit method using drilling and blasting, loading with excavators, and hauling with articulated dump trucks. The ore will be extracted by small hydraulic excavator (30 t to 40 t) to maximise selectivity where the orebody is narrow, and the waste will be loaded by slightly larger hydraulic excavators (70 t to 80 t) to allow for higher productivity.

There is potential for additional Mineral Resources to be exploited by open pit mining methods, although this is dependent on improved project economics and/or reclassification of the Inferred Resources through additional drilling. Consideration of underground mining has not been necessary at this stage of the Project, although if mineralisation were found to continue at depths beyond economic open pit limits then this could be considered in the future.

The evaluation of Youga and Ouaré assumes that the ore will be transported to the main processing facility at Youga. The optimal production rate is therefore constrained by the capacity of this plant, which is nominally set at 1.1 Mt/year. However, provision is made for the addition of an oxygen plant in January 2018, which will increase the plant throughput by 8% to 1.2 Mt/a.

The Youga processing plant uses the conventional gravity/CIL gold recovery process, similar to various facilities in operation in West Africa. This consists of a 3-stage crushing operation, ball milling, gravity concentration and cyanidation by carbon-in leach (CIL). Pressure Zadra elution is utilized for recovery of gold from loaded carbon.

Crushing Circuit:

Run of Mine (ROM) ore is delivered to the primary crusher feed bin by front-end loader (FEL). Ore is withdrawn by a variable speed apron feeder to the primary (jaw) crusher. The crushed ore is conveyed to the secondary (cone) crusher, which operates in open circuit. The secondary crushed product is fed to a single deck screen (14 mm openings to produce a nominal -12.5mm crushed product), with the screen oversize reporting to the tertiary crusher section (two cone crushers in parallel) feed bins, while the screen undersize reports to the fine ore stockpile feed conveyor. The tertiary crushed products report back to the single deck screen, completing the circuit.

Milling Circuit:

The crushing circuit product reports to the fine ore stockpile, from which feed to the grinding circuit is withdrawn by one of three vibrating feeders onto the mill feed conveyor. Hydrated lime is added via a rotary valve onto the conveyor to ensure the ground ore is fed to the leaching circuit at the correct pH (>10.5). The ball mill discharge is pumped to a ‘cluster’ of hydro-cyclones, the overflow product from which forms the feed to leach circuit. The underflow product returns to the mill feed after a portion (approximately 20%) is diverted to the gravity circuit.

Gravity Circuit:

The bleed stream is passed over a vibrating scalping screen to remove coarse (+2mm) particles, which gravitate back to the mill inlet chute. The underflow feeds the centrifugal bowl type concentrator for recovery of the coarse free gold and other particles of sufficiently high specific gravity. Concentrator tails gravitate to the mill feed inlet, while the concentrate is periodically discharged from the concentrator and flows into a storage tank located in the gold room for upgrading by further gravity devices.

Leaching circuit:

The cyclone overflow slurry flows onto a linear trash screen for removal of natural and mining debris such as woodchips, cloth, plastic and wire which can cause operating issues in the downstream stages. The slurry gravitates through a sampler and into the first leach tank (mechanically agitated) where cyanide solution is added. From there it overflows and gravitates through five subsequent, mechanically agitated, Carbon-in-Leach (CIL) tanks to enable maximum possible dissolution of gold as a cyanide complex and subsequent adsorption onto activated carbon. Each CIL tank is equipped with an interstage screen mechanism, with a cylindrical basket-type stainless steel wedge-wire screen surface for retention of activated carbon in the tank. Air blowers installed on the top of the CIL tank platform provide air in the slurry through the agitator shaft in order to improve oxygenation of the slurry and enhance the dissolution process. By the end of the year this will be supplemented by the addition of an oxygen plant, which should further increase oxygen transfer into the process.

Tailings:

The barren slurry from the last CIL tank gravitates to a vibrating screen (Carbon Safety Screen) prior to a sampler, and then to the tailings pumping station from where it is pumped to the slimes dam. Any carbon recovered from the screen will be re-circulated as required.

Carbon Treatment:

Barren carbon is added to the last of the CIL tanks and advanced through to the first where the loaded carbon is routinely removed from the circuit, washed in acid, and the adsorbed gold removed by washing in cyanide under pressure and temperature. The desorbed gold is recovered by electrowinning onto steel wool. The electrodes are routinely ‘harvested’, and, combined with the separately collected gravity concentrate, converted to bullion by smelting.

The current mine plan is projecting the material from Ouaré to be processed in 2018, 2019 and 2020 in the proportions of 34, 73, and 53 percent respectively, of the proposed mill annual throughput of 1.18 million tonnes.