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.

Pau-a-Pique underground mine is a part of a mine complex located in the southwest of Mato Grosso state, near Pontes e Lacerda in Brazil.

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.

CRUSHING
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.

The primary crusher grizzly feeder, which has an aperture of 150 mm, withdraws feed from the crusher feed bin at an average rate of 130 tph and discharges oversize material to the 1,045 mm x 840 mm primary jaw crusher, which operates at a final product size of 80–100 mm.

Grizzly feeder undersize and primary crusher product are combined on the primary crusher product conveyor, which discharges to the feed hopper. The feed hopper can also receive feed from a loader. A belt magnet removes tramp steel from the primary crusher product conveyor.

GRINDING
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 recirculating load is 4.5 times the mass of the newly crushed feed. The SAG trommel screen (15 mm aperture) removes oversize (‘pebbles’) from the mill discharge at an estimated rate of 33 tph. The pebbles are directed to the pebble recycle conveyor, which includes a belt magnet to remove tramp steel and a metal detector located after the magnet.

SAG trommel screen undersize slurry flows to the cyclone feed hopper, where water is added to adjust the solids content to cyclone requirement. The primary cyclone feed pump feeds the cyclone cluster. Cyclone overflow flows to the trash screen bypass box. Cyclone underflow reports to the cyclone discharge distributor box, which directs half of the underflow to the concentrator scalping screen (2 mm aperture) and the remainder of the underflow to the SAG mill feed chute. Concentrator scalping screen oversize (estimated to be half the scalping screen feed) returns to the SAG mill feed chute, while the undersize feeds the gravity concentrator.

Ore from Pau-a-Pique Underground will be hauled on a 47 km surface road to the Ernesto processing plant.

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.

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 go ........