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, ........

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 task ........

Primary crushing:
The first step to obtain gold is crushing. The crusher used in the plant is a jaw crusher, which is fed through a vibrator feeder (220-FE-001) with the support of a wheel loader.

The vibratory feeder (220-FE-001), with opening in the 100 mm grille, removes the ore with solids mass flow with a rate of 280 t/h. The ore retained in the grille of this feeder is discharged into the jaw crusher (220-CR-001). Both the passing material in the vibrating feeder grid and the material in the crusher discharge are collected and transported to the crushed ore’s silo through the conveyor belts (220-CV-001/002), which are equipped with a metal detector (220-MD-001) and a metal extractor (220-EX-001).

Related to environmental compliance in the crushing stage, it has a dust reduction system, in all transfer. In the crushing stage only, physical processes are performed and so sodium cyanide is not used.

Grinding/ Milling and Gravimetric concentration:
The grinding/ milling circuit is intended to receive the crushed ore, with a top size of 101.6 mm and generate a product granulometrically compatible for the CIL step, with size 80% passerby in a mesh of 0.106 mm. To carry out the comminution process in the SAG mill, 5" steel balls are used.

The replacement of the SAG mill’s balls is done directly in the mill feed, through the hopper (330-BN-003). The balls are discharged, with the support of electric hoist (330-CN-003) in box (330-XM-001) and later in the hopper.

The resumption of crushed ore for grinding, in the solids mass flow with a rate of 205 t/h, is carried out by the feeders (260-FE-002/003/005) and by the conveyor belt (260-CV-003) equipped with a scale (260-SL-004).

The crushed ore (new feed) feeds the SAG mill (330-ML-001), which has dimensions of 19' x 19' (5.7 x 5.7 meters) and installed power of 2.5Mw (Megawatts). The trommel (opening 10 x 20 mm) removes the pebbles from the discharge, which return to the SAG mill through the conveyor belts, 330-CV-004 and 260-CV-003, equipped with a scale (330-SL-002), constituting the part of the circulating load. The passerby in the trommel is collected in the box (330-PB-001) where process water is added to adjust the percentage of solids in the pulp (up to 52% solids) to feed 5 hydro cyclones with 500 mm in diameter, this feeding is performed by pumps (330-PP001/001R). Hydro cyclones classify the pulp through centrifugal force into overflow and underflow.

The underflow of hydro cyclones is collected in the distribution box (330-DI-001), where half of the flow feeds by gravity the scalping sieve (360-SC-002), with opening in the 2 mm screen and the other half returns to the SAG mill, constituting another part of the circulating load. In the scalping sieve the retained material returns to the SAG mill, constituting one more part of the circulating load, while the passerby feeds the centrifugal concentration (360-CG-001). The centrifugal concentration aims at the recovery of free and relatively coarse gold, and it is predicted that 0.16 t/h (dry base) of heavy concentrate (approximately 0.14% of the feed’s plant) are transferred to the intensive leaching area. The light fraction of the centrifugal concentration returns to the SAG system, constituting another part of the circulating load. In short, the circulating load consists of the following flows: retained in the trommel, 50% of the underflow of the cyclones, retained in the scalping sieve and tailings of the centrifugal concentration.

The overflow of hydro cyclones feeds the thickening step.

The drainage of the area is carried out by the pumps (330-PS-002/003).

In the grinding stage, only physical processes are performed with a reduction from 101.6 mm to 0.106 mm and sodium cyanide is not used.

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