The Mato Bula gold-rich VMS deposit is the main deposit discovered to date within the Adyabo Project, and covers the Mato Bula North, Silica Hill North, Silica Hill, Mato Bula, Jasper Hill and Halima Hill mineralized zones.

Two mineralized structures are present at Mato Bula Hill; the Main lode and the Upper lode.

The Main lode at Mato Bula is located south of the crest of the Mato Bula Hill, and is a narrow high-grade gold shoot extending over a strike length of 120 m at surface. Numerous active artisanal gold bedrock workings are present at Mato Bula exploiting this gold lode, and an upper lode, reportedly to a depth of 46 m.

The shoot has steep dip, vertical plunge, and maximum true width of 3 m. At depth the maximum strike of the shoot is reduced to 80 m, but the structure remains open at depths greater 220 m below surface.

Silica-pyrite alteration is extensive laterally (750 m strike) and in thickness (159 m wide), and zones of silica-pyrite are present in the hanging wall and along strike, in a zone up to 150 m wide and 750 m long.

Mineralization is hosted within a shear zone that contains abundant quartz veining, silicification, sericitization and carbonate alteration. Gold is associated with chalcopyrite-rich veins in intense silica alteration, and also the presence of possibly V-rich mica (roscoelite). The Main lode averages 5.5 g/t gold and 0.61% copper, and has a high gold:silver ratio of 10.2. Lead and zinc concentrations are negligible.

The Jasper Hill zone (sometimes known as Mato Bula South) contains structurally controlled gold lodes (vein/wall rock porphyry hosted), and extend from the Mato Bula zone in the north towards Halima Hill in the south. The upper and main lodes within this zone exhibit more complex geometry due to possible faulting (or slumping) and wall rock interaction. Mineralization is lithologically controlled with the gold-bearing zones within a jasperoid alteration zone. Gold concentration decreases, with increasing zinc concentration, moving away from the jasperoid unit. Gold-bearing veins have also been identified perpendicular to the long core axis.

The Main lode at Jasper Hill is located 40 m southeast of the Upper lode, southwestwards along strike from the Mato Bula zone, and outcrops along strike for 80 m. The structure has a maximum true thickness of 9 m, and an average gold grade of 4.53 g/t and copper grade of 0.85%. It has the highest gold:silver ratio in the Mato Bula prospect of 5.3:1, and a low gold:copper (x10) ratio of 0.56:1. The average silver concentration is low, 0.85 g/t, and only trace amounts of lead and zinc are present. The lode plunges at approximately 60 to 70° to the southwest, and remains open down plunge below depths of 200 m from surface.

The most southerly manifestation of the Mato Bula Trend is the mineralized zone at Halima Hill, 320 m to the southwest of the Jasper Hill zone. Halima Hill was targeted due to the presence of artisanal trenching, with lower order gold-copper geochemistry present within an alteration zone. Apart from a zone of subcrop at Halima Hill, much of the southern part of the trend is covered in thick (50 cm to 2 m) transported colluvium, thus reducing the geochemical signature at Halima Hill relative to the hilltop workings of Mato Bula North, Silica Hill and Mato Bula.

Mineralization was present as pyrite- chalcopyrite bearing quartzveins within altered tuffs. The assay results and visual interpretation of alteration at Halima Hill indicate the Mato Bula system is weakening to the south near surface, however the IP survey is suggestive of additional increasing potential at depth.

Open pit mining is planned as conventional truck and shovel open pit mining with drill and blast.

The PEA open pit contains the following:
• 3.3 Mt of potential mill feed
• 30 Mt of waste rock (including mineralized material below cut-off grade)
• 322,000 tr oz of gold
• 75,000 tr oz of silver
• average NSR US$111/t processed.

The pit consists of three distinct sections, namely a northern satellite pit with high grades, a central pit from which much of the mill feed will be sourced and a southern limb which mines shallow mineralisation with lower grade.

The pit slope design is based on a maximum overall slope of 49°. The bench heights for mining are designed at 5 m high, with triple benching between catch benches of 5 m wide. Haul roads are designed around the width of 25 t articulated dump trucks and are planned as 15 m wide.

Mining will be managed by qualified engineering professionals such that the operations are conducted safely and efficiently. The management of operations will include mine planning, surveying of open pits, assaying of rock to be mined for minerals, and geotechnical engineering for pit walls and WRSF stability.

Mining will be done by first drilling and blasting the rock so that it can be loaded by loader onto haul trucks. Waste rock will be transported by haul trucks to designated WRSF, while rock containing mineralization will be transported to the crusher for subsequent processing.

Drilling and blasting has been considered for the PEA. It is assumed to consist of drilling of 5 to 10 m bench heights with 89 and 115 mm holes. Tetra Tech has made provisions for track mounted drill rigs for drilling blast holes.

The holes would be charged primarily with ammonium nitrate and fuel oil (ANFO) where possible and cartridged emulsion explosive if holes are wet. Initiation is assumed to be carried out using nonel systems with pentolite boosters. Explosives will be stored onsite, with blasting carried out at the end of shifts to ensure minimal disruption to other pit activities.

For this PEA, loading was assumed to be done by excavator with support from a wheeled loader. The minimum mining width has been included in the design as 15 m based on selected equipment operating widths.

Tetra Tech conducted a high-level assessment of underground potential for Mato Bula. The objective was to determine if underground mining could replace areas of the open pit with high strip ratios, as well as evaluating the potential to mine tonnes below the extent of the open pit.

Tetra Tech concludes that a combination of underground mining and open pit mining has good economic potential. Further optimisation between underground and open has the otential to produce the following advantages:
• reduced strip ratios
• higher head grades
• reduces waste rock volumes
• extended LOM
• ability to store or discard waste rock or tailings in mined out excavations.

CRUSHING CIRCUIT
The crushing circuit will reduce the mined material size from a nominal top size of 500 mm to a product size of 80% passing (P80) 10 mm in preparation for the grinding process. The crushing circuit facility will contain the following main items of equipment:
• stationary grizzly
• run-of-mine (ROM) surge bin
• vibrating feeder to jaw crusher
• jaw crusher, 93 kW
• conveyor belts
• belt magnet and metal detector
• sizing screen
• cone crusher, 224 kW
• belt scale
• crushed mill feed bin.

Haulage trucks with a nominal capacity of 25 t will bring ROM material to the crushing plant. The material will be dumped directly from the trucks for crushing, although provision has been made for material to be dumped onto a temporary ROM stockpile in the event of unscheduled crusher plant stoppages.

The trucks will dump the ROM material onto a stationary grizzly. This grizzly will prevent oversize rocks from entering the ROM surge bin. The surge bin will have a nominal capacity of 40 t (live capacity). The surge bin will be equipped with a vibrating feeder which will feed the ROM material to the jaw crusher. The jaw crusher will reduce the feed size from finer than 500 mm to a size 80% passing approximately 60 mm. The crushed material will be discharged onto the conveyor belt together with the vibrating feeder undersize material to the sizing screen. A belt magnet will be installed to remove tramp metal, followed by a metal detector which will activate an alarm and stop the conveyor belt, allowing tramp metal to be manually removed or by-pass the cone crusher. The crusher plant utilization will be 75%, and the design throughput will be 116.7 t/h.

The sizing screen will receive the crushed material from the jaw crusher. The sizing screen will be a vibrating screen with a final product size P80 of 10 mm. The screen oversize will be conveyed to a cone crusher for additional crushing. The crushed material from the cone crusher will be returned by conveyor belt to the sizing screen feed conveyor. The screen undersize, less than approximately 13 mm material, will be discharged onto a conveyor, which will transport the fine crushed material to the crushed ball mill feed surge bin. The bin will have a live capacity of 1500 t, equivalent to approximately one day’s operation.

GRINDING CIRCUIT
The grinding circuit will reduce the size of the crushed material to a final product size of 80% passing 75 µm, suitable for subsequent copper and gold recovery by flotation processes. The grinding process will be single-stage with a ball mill in closed circuit with classifying cyclones. The grinding circuit will have the following main items of equipment:
• conveyor belt
• conveyor belt weigh scale
• ball mill, 4.2 m diameter by 5.3 m long
• mill discharge pumpbox
• cyclone feed slurry pumps
• classification cyclone cluster

The material in the ball mill feed surge bin will be drawn from the bin under controlled feed rate of approximately 64.8 dmt/h new feed using a belt conveyor. A belt scale will control the feed to the ball mill. The cyclone underflow will also constitute part of the total feed to the mill. Process water will be added as required to maintain the slurry density in the ball mill at approximately 72% solids. The ball mill will operate at a rotational speed that is approximately 75% of the critical speed.

The Mato Bula processing facilities is designed to process a nominal 500,000 t/a, or 1,400 t/d, of gold-copper-bearing material from an open pit mining operation. The concentrator is designed to produce a copper concentrate containing a high level of gold and a gold concentrate produced by gravity concentration that can be sold directly. A gold-bearing by- product of the flotation process contains a sufficient level gold that will be treated using agitated cyanide leaching to maximize gold recovery. This material is planned to be treated off site at the nearby Da Tambuk process plant, which is proposed for development, or other facilities.

GRAVITY CONCENTRATION
The gravity concentration circuit, consisting of a centrifugal concentrator and a table, will produce a concentrate containing coarse gold recovered from the grinding circuit. The shaking table will upgrade the gravity concentrate suitable for onsite/offsite smelting at a refinery.

Approximately 30% ........