The Pau-a-Pique Deposit occurs in close association with the contact of the meta-tonalite basement and the overlying Aguapeí Group metasediments. The tonalite is metamorphosed with a foliated structure, but preserving the original igneous texture. The rocks are metamorphosed and deformed under lower green-schist facies conditions. Muscovite schist is developed in the contact between the metatonalites and metasediments and is an important host of mineralization. The muscovite schist has S-C structures and abundant shear bounded sigmoidal veins. The schist has a strong stretching lineation oriented at N20–50W that controls the form of the deposit and sub-surface mineralization.

The Pau-a-Pique Deposit is developed within brecciated-sheared host rocks which are strongly foliated and moderately metamorphosed and can be described as structurally controlled orogenic gold lode deposit.

The Pau-a-Pique gold mineralization is associated with the intensity of the hydrothermal alteration, and is proportional to the occurrence of pyrite, sulphide alteration, quartz veins and sericitization. Pyrite generally occurs in fresh rock, and at the exposed zones in the old pit there is a predominance of oxidized pyrites, products of surface weathering.

In the deeper levels (PQ-12), the most common hydrothermal alteration with gold enrichment is strong albite-anorthosic quartz veining associated with chloritization and pyrite. While in shallow levels (PQ-01, 02), the most pervasive alteration is silicification, represented by a strong injection of quartz veins and weaker gold enrichment. The albitic alteration probably represents deeper and hot sources of the hydrothermal feeder.

The envelope of the mineralized zone is approximately 550 m long, maximum of 15 m wide and 400 m deep in the largest extension (NW down plunge). The occurrence is confined to the contact between Aguapeí metasediments and the tonalite, which is the main prospective guide to the deposit, in addition to the NW plunge that can be seen in the longitudinal section.

In the NW down-plunge zone, gold enrichment associated with albitic-anorthosic metasomatism, pyrite, chlorite and magnetite is abundant. Alteration is wide and extensive and developed in contact with tonalite and conglomerate and within the sheared and deformed tonalite. The presence of sulphide and magnetite in sheared host rocks is favorable for gold enrichment with higher grade. Strong metasomatism which is developed mainly in contact and within hangingwall tonalite shows higher temperature mineral assemblage which represent a hyrothermal feeder for ascending metasomatic fluids.

Mining at Pau-a-Pique will be conducted by a modified Avoca choke blast stoping method with ore transported to the ROM pad on surface by 30 tonne haulage trucks operating through the main ramp. Ore will be subsequently hauled on a 47 km surface road to the Ernesto processing plant. Primary access to the underground mine is via a single portal located next to the main mining office.

Approximately 0.32 Mt of ore at an average grade of 3.24 g/t Au will be mined over a 17 month period at an average of 850 tpd when the Project achieves full production. Once the deposit has been depleted most of the equipment and operators will be transferred to the Ernesto operation.

The stoping method applied to the Area 7 and Area 8, NW, and P3 and P4 ore bodies will be via Hanging Wall (“HW”) access ore drives with levels spaced at 15 m and 21 m vertical intervals, for the upper and lower areas of the deposit, respectively. The upper and lower areas will be separated by a sill pillar. Unconsolidated waste rock will be used to backfill the stopes.

The majority of underground mining activities will utilize Aura’s employees, with external contractors or suppliers to undertake the supply of explosives, piping and services, ground support consumables, truck haulage underground and on surface and other specialized tasks (i.e. site security, doré bar transportation, etc.). Aura has 100% ownership of all major fixed plant components utilized at the mine.

The Ernesto gold processing plant is located next to the Ernesto Deposit and is designed to treat up to 1 Mtpy feed. The flowsheet is based on a low-risk proven technological configuration for processing gold bearing ore.

A primary crusher located at the front-end of the process plant. Run-of-mine (“ROM”) feed will be blended and fed through the plant’s primary screen. The screen oversize is crushed and the combined crushed feed is ground in a single-stage, closed-circuit semi-autogenous grinding (“SAG”) mill.

Approximately 25% of the SAG mill cyclone underflow feeds a gravity-gold recovery circuit. The grinding circuit product is thickened and then pumped to a leach tank that is followed by six carbon-in-leach (“CIL”) tanks in series. CIL tailings are treated in a cyanide reduction tank where cyanide is chemically decomposed. Final tailings are pumped to a tailings storage facility.

Loaded carbon, recovered from the first CIL tank, reports to the desorption area. Gold is stripped from the carbon into a solution and electroplated from solution onto stainless steel cathodes. Dried cathode sludge and flux are mixed and smelted to produce gold bullion.

Haul trucks deliver run-of-mine feed to the ROM pad. A front-end loader is used to feed the crusher feed bin, which is fitted with static grizzly bars with an aperture of 600 mm.

Crushed feed, pebbles, cyclone underflow, and gravity concentrator tailings are directed to the SAG mill feed chute. The SAG mill dimension is 5.8 m in diameter, 5.8 m long and has an installed motor power of 2.65 MW.

The trash screen bypass box normally feeds the trash screen (0.8 x 18 mm aperture), but also allows slurry to bypass this screen. Trash screen oversize is directed to the trash bunker, while trash screen undersize slurry flows to the pre-leach thickener feed box. Dilute flocculant is added to the pre-leach thickener feed box and to the thickener feed well.

The CIL feed pump discharges thickened slurry to the CIL feed distributor. The feed to the CIL circuit is 50-52% solids by weight after the addition of lime, barren eluate and the flow from the gold room sump pump. The average flow rate of the CIL feed is 176 m3 /h (260 tph). Thickener overflow flows to the pre-leach thickener overflow tank and is then pumped to the process water pond.

The CIL area includes seven tanks in series: one leach tank followed by six CIL tanks for a total residence time of 24 hours.

The CIL feed distributor box normally discharges to the leach tank, but can also discharge to the first CIL tank. Launders allow the slurry flow to bypass any of the CIL tanks. The final CIL tank discharges to the cyanide reduction feed box.

The CIL feed distributor box normally discharges to the leach tank, but can also discharge to the first CIL tank. Launders allow the slurry flow to bypass any of the CIL tanks. The final CIL tank discharges to the cyanide reduction feed box.

The acid-wash cycle starts when the acid-wash column is full of loaded carbon. Concentrated hydrochloric acid is added to raw water to a concentration of 3% (w/w) in the column. The acid wash column is then allowed to soak.

The strip solution pump draws solution from the strip solution tank and primes the elution column. Sodium hydroxide and sodium cyanide are added to the strip solution at a concentration of 3% w/w each.

During preheating, the strip solution is pumped through the recovery heat exchanger (cold side), through the primary heat exchanger (cold side), and into the elution column. Solution leaving the elution column returns directly to the strip solution tank. The LPG-fired solution heater heats thermal oil, which is pumped in a closed circuit through the primary heat exchanger (hot side) indirectly heating the strip solution.

Elution starts when preheating is complete. During elution, solution leaving the elution column passes through the recovery heat exchanger (hot side) and to one of the eluate tanks. Elution continues until six elution column bed volumes (“BV”) have reported to the eluate tank. Raw water makes up the strip solution tank level during elution. Solution heating stops for the last BV, cooling the column and the carbon.

Excess water drains from the carbon in the 1.0 mm slotted-aperture regeneration feed dewatering screen. A screw feeder withdraws carbon from the feed hopper and feeds the carbon regeneration kiln. Regenerated carbon is quenched with water in the carbon quench tank and is then pumped to the barren carbon sizing screen by the carbon transfer pump.

Pregnant eluate and ICR pregnant solution report to the eluate tanks. The eluate pumps feed electrowinning cells during electrowinning and transfer barren eluate to the CIL feed distributor box at the end of an electrowinning cycle. Electrowinning cell discharge flows to the eluate return hopper and is then pumped back to the eluate tank(s).

A plant operator uses the gold room hoist to lift loaded cathodes up over the off-line cell. The operator then uses a high-pressure cleaner to loosen and wash the cathode slimes into the cell. The slimes flow into the pan filter and filtered sludge is put into an oven to dry. Dry sludge is mixed with flux and smelted in the barring furnace about once a week. Bullion bars are cleaned, sampled, weighed, and stored in a vault. The electrowinning cell exhaust fan vents air and mist from the cells to atmosphere outside the building during the electrowinning process. The furnace exhaust fan vents air from the furnace to the outside atmosphere during smelting. The gold room has four vent fans to ensure adequate ventilation.