The mineralized veins exposed on the Coringa Gold Project are similar to those found in Orogenic gold deposits. This deposit type has been described by McCuaig and Kerrich (1998), Groves et al. (1998), and Goldfarb et al. (2001). These deposits formed over a 3 Ga time frame with peaks at 3.1 Ga, 2.7 to 2.5 Ga, 2.1 to 1.8 Ga, and 0.6 to 0.05 Ga corresponding to the episodic growth of juvenile continental crust. A large percentage of the world’s gold resource is associated with these periods.

Characteristics of an Orogenic gold deposit are as follows:
-Proximity to large scale structures which allow for large scale fluid migration. Deposits are commonly in secondary and tertiary structures.
-Magmatic-meteoric hydrothermal fluids have low salinity and moderate temperatures (200 to 600oC). High concentrations of dissolved sulphur and gold in fluids and overall fluid volumes are critical to the formation of economic deposits.
-These deposits commonly have large vertical extents (1-2 km) and can have extensive down-plunge continuity.
-Gold mineralization is hosted in quartz-dominant vein systems which have low (<3 – 5%) sulphide content. Carbonate content ranges from <5% to 15%. Pyrite is the dominant sulphide.
-Veins have high gold grades (5 to 30 g/t).
-Alteration haloes around mineralized veins include carbonate, sulphide, and sericite±chlorite assemblages.

Mineralization at the Coringa Gold Project is associated with a shear/vein system that has a strike length of over 7 km. The mineralized zones vary in thickness from <1 cm up to 14 m. Several veins (i.e., Galena, Mãe de Leite, Meio, and Come Quieto) occur along the main mineralized corridor and others, such as Serra, Demetrio, and Valdette, form subparallel zones. The average horizontal thicknesses for the veins included in the estimate of mineral resources (assuming a minimum horizontal thickness of 0.8 m) are: Serra 0.82 m, Meio 0.97 m, Galena 1.12 m, Mãe de Leite 0.98 m, Come Quieto 0.91 m, and Valdette 0.80 m.

Gold mineralization is almost exclusively associated with quartz-sulphide veining. Pyrite is the main sulphide, but minor concentrations of chalcopyrite, galena, and sphalerite are common. A genetic study of mineralization indicated that pyrite-chalcopyrite (+/- quartz) mineralization occurred first, followed by gold, with galena and sphalerite introduced late. Gold is typically free (or within electrum) and occupies fractures within sulphide grains. It is usually very fine grained and visible gold is rare (Boutillier & Rollinson, 2017). Gold in electrum is closely associated with quartz and pyrite. The bulk of the gold has a preference for deposition in the quartz matrix/groundmass (48% locking affinity) and within pyrite (31%) occurring in either fractures or as inclusions, as well as in other sulphides, oxides, and, to a lesser extent and depending on tectonic conditions, in silicates.

The Coringa Gold Project has been planned as an underground mining operation. The advantages of underground mining include:
-Underground mining helps to minimize the footprint of the mine and its environmental impacts;
-The Serra, Meio, and Galena deposits are high-grade, narrow vein deposits which are ideally suited to underground mining methods which minimize dilution from the mining process compared with open pit mining;
-Underground selectivity will help to maximize ROM feed grades.

Mining will commence at Serra with construction of a portal followed by development of a decline ramp and access to the mineralized veins. Main mine development at Serra is finished approximately in the second year of life of the Serra mine, at the end of which development of the Meio mine will start. Galena will be developed for the final year of the project.

The primary mining method for the Serra deposit is shrinkage. Having higher metal grades, the Meio deposit will be mined using a combination of shrinkage and narrow-vein longhole mining. The Meio deposit has similar characteristics to Serra, however, the higher grades will allow it to be mined with some extra dilution that the longhole mining methods might require to accommodate the mining equipment. Galena mine will use shrinkage mining similar to the Serra mine.

At Serra, upon completion of sill development, shrinkage will start. Broken ore is placed on the floor, providing a platform for the jack leg drill operator and assistant to work and for supervisors and technical services to monitor work activities. As the stope opens up, ore is only removed to accommodate the swell of blasted material and level the working platform. Pillars, with varying widths depending on the depth below the ground surface, are left in the stope as required, on a regular spacing and per Quanta’s recommendation (Quanta 2017a). Between levels, 1.5 m sill pillars are also maintained during the mining phase until stope mining is completed.

The preferred mining method for Meio is longhole mining which will be implemented per Quanta’s geotechnical recommendations. This mining method was selected mainly because of the advantage in productivity. The higher-grade content at Meio allows for the higher dilution factor that this mining method will require due to hole deviation in drilling and / or the necessary widths needed to accommodate the equipment. However, if necessary, the mining method can easily be switched to shrinkage mining method similar to the method chosen for exploiting the Serra deposit.

The ore processing facility for the Coringa Gold Project is a conventional gold cyanidation plant. It has been designed to treat 460 tpd (159,000 tpa) of ore containing 6.5 gpt gold and 13.1 gpt silver over a 4.8-year period. Annual gold production will average 32,000 ozs. The gold-silver doré product will be shipped to a refinery for further processing.

The ROM ore is stockpiled and then reclaimed by front-end loader. The loader dumps the ore into a hopper equipped with a vibrating feeder that discharges into an 800 mm by 600 mm primary jaw crusher.

The jaw crusher product discharges onto a conveyor that feeds a 4 m long by 1.5 m wide double-deck vibrating screen. The oversize from the top deck feeds a 1 m diameter Symons cone crusher while the bottom deck oversize feeds an H2800 Sandvik cone crusher. The crushed material from the secondary and tertiary crushers is collected and recycled via conveyor back to the vibrating screen.

The final crushed product (undersize from the screen bottom deck), at an average particle size of 80% passing 10 mm, discharges onto a belt conveyor that feeds the fine ore stockpile.

The ball mill grinding is in closed circuit with cyclones which classify the ground ore to a final particle size of 80% less than 105 microns. The cyclone underflow feeds a Knelson centrifugal (gravity) concentrator for free gold and silver recovery. The concentrator tails are returned to the mill for further grinding. The gravity concentrates flow to an Acacia intensive leach reactor. Acacia leach tails are pumped to the CIL circuit while the Acacia reactor gold solutions are collected, stored and then pumped to a dedicated electrowinning cell.

The grinding circuit product, cyclone overflow at 20% solids by weight, passes over a trash screen and then is directed to a 12 m diameter thickener. Thickener underflow densities are targeted to be about 41% solids by weight for leaching.

The clarified overflow water from the thickener is pumped to a tank for storage and later used as process water. The thickener underflow is pumped to a conditioning tank prior to CIL for aeration and pH adjustment to about 11.5 using hydrated lime.

After conditioning the slurry is transferred to a series of four aerated 8 m high by 6 m diameter CIL tanks, equipped with static sieve screens. The CIL tanks have a total slurry retention time of 24 hours. Gold and silver are leached with cyanide and then adsorbed by activated carbon present in the tanks.

The slurry flows downstream from tank to tank then through a carbon safety screen.

The metal-loaded carbon is transferred from the last tank up-stream to the one before, and so on, countercurrent to the slurry descending from tank to tank.

The highest metal loaded carbon is in the first CIL tank. From the first tank the carbon is transferred to a screen for preliminary cleaning/washing, then directed to the desorption column for further washing and metal stripping.

In the desorption column, carbon is washed with a weak solution of hydrochloric acid and then a caustic soda solution, then a NaCN solution for metal stripping. This strip (pregnant) solution is pumped through a dedicated electrowinning cell where gold and silver are deposited on cathodes. The cathodes are periodically removed from the cells, washed, then the gold/silver sludge is dried, mixed with flux reagents and then smelted to produce a doré’ product which is then shipped offsite for refining.

The barren (metal removed) electrowinning solution is then recycled to the leaching circuit.

After stripping, carbon is washed with water and transferred to the regeneration kiln. The carbon is heat-treated in the kiln and then returned to the last (fourth) CIL tank.

The slurry from CIL, after passing through the carbon safety screen, flows to the cyanide destruction tank that utilizes the SO2/Air process to destroy cyanide in the tailing slurry. Copper sulphate and SMBS are added to the aerated mix tank to destroy the cyanide. The detoxified slurry is then pumped to the TSF for disposal.