Gold mineralization at the Pilar and Guarinos Greenstone Belts is typical of orogenic gold deposition. The mineralization is related to, and controlled by, major faults and shear zones. At the Pilar mine, these structures are mainly low angle thrust faults and at Guarinos, they are mainly high angle transpressional structures and boudins, both probably related to the final stages of Archean-Paleoproterozoic deformation.

Strong silicification and sulphidation are the main forms of hydrothermal alteration. Host rocks and most carbonaceous meta-sedimentary rocks are well silicified and contain shear-related quartz veins. Arsenopyrite is the main sulphide related to the gold mineralization, while pyrite, and minor chalcopyrite, and pyrrhotite are also present. Gold is present both as free grains in clusters related to quartz veining, and in association with arsenopyrite and other sulphides.

Mineralization at the Pilar mine is located in three main zones:

• HG1 (Basal zone): the most continuous and important style of mineralization in the deposit. The Bazal zone is controlled by carbonaceous schists and intercalated chlorite schists. It is hosted on the basal contact of the chlorite schist with the graphite schist.

• HG2 (Upper zone): an important zone with similar volume to HG1 but with lower grades. The zone is essentially controlled by quartz veins inside the chlorite schists. It is located in the hangingwall portion of the main thrust fault.

• HG3 (Upper zone): the smallest and most discontinuous zone at the Pilar deposit, with location and average grades similar to HG2.

The upper zone is continuous along the Pilar – Três Buracos trend, with a width of up to 60 m. This zone is characterized by the presence of thin quartz veins and associated sulphides, mostly pyrite.

The basal zone is characterized by strong silicification and sulphidation. Arsenopyrite, the main sulphide, commonly constitutes up to 5% of the rock. The basal zone averages 10 m wide and is continuous along the main trend. The highest grades are closely associated with high sulphide (arsenopyrite) and quartz content and are associated with structurally controlled mineralized shoots distributed along the trend.

Detailed field mapping, examination of garimpo workings, core logging, and assay results received for drill holes have led Yamana to a preliminary interpretation of three main mineralization levels at Três Buracos. All three levels have been investigated by an extensive chip sampling campaign and followed by detailed geological interpretation:

• The uppermost level comprises chlorite schist with thin quartz veins and hydrothermal alteration. It is approximately 30 m thick and shows encouraging results for gold grades along strike. Chip sampling at this level shows low, but consistent, gold grades of about 1.4 g/t Au to 2.6 g/t Au.

• The intermediate level comprises intensely silicified and sulphidized rocks, with up to 20% arsenopyrite as the main sulphide. Sericite and fuchsite are common and concentrated in a 1.0 m thick layer. Gold grades are high, mainly in highly sulphidized, sericite-fuchsite-rich layers, ranging from 13 g/t Au to 85 g/t Au. The main mineralized horizon is at the contact zone between the upper level and the underlying graphite schist. The intermediate level is at least 3 m thick, and is characterized by strong hydrothermal alteration.

• The basal level of graphite schist is close to the contact with quartz sericite schist, is mineralized, and was mined during the 18th century.

Mineralization at Maria Lázara is hosted by silicified biotite-chlorite-sericite schists and with quartz veins concordant with the main foliation. These schists show an average thickness of 2.0 m in diamond drill holes and mine openings. The mineral assembly contains sericite, chlorite, biotite, tourmaline, albite, quartz, and sulfides, mainly arsenopyrite with minor pyrite, pyrrhotite, sphalerite, galena, and chalcopyrite. The schists exhibit a porphyroblastic texture, containing porphyroblasts of garnet and occasionally magnetite. Native gold occurs associated with arsenopyrite and quartz or quartz-albite veins.

Diamond drilling has outlined an area of gold mineralization with a strike length of 3.6 km, a width of 720 m, and a thickness ranging from less than one metre to ten metres.

Gold mineralization at the Caiamar mine occurs in four parallel zones and in a set of small shoot-like structures related to a transpressional shear zone. They are described as follows:

• Zone A0: small zones of discontinuous mineralization not related to hydrothermal alteration, hosted by quartz-biotite-graphite schist.

• Zone A1: the most important and continuous zone in the deposit. The zone is hosted in a hydrothermally altered meta-greywacke and the mineralization is associated with quartz-albite-arsenopyrite veinlets. Contains small, scattered higher-grade zones associated with porphyritic intrusions.

• Zone A2: similar setting and slightly less tonnage than zone A1. It is separated from A1 by an amphibolitic metasediment. Contains small, scattered higher-grade zones associated with porphyritic intrusions.

• Zone A3: small, scattered patches of mineralization in a similar environment to A1 and A2.

Diamond drilling has outlined zones of steeply plunging gold mineralization within an area with a strike length of approximately 1.4 km, a vertical extent measuring 600 m, and thicknesses ranging from one metre to 20 m.

The Pilar complex comprises two underground mining operations. The bulk of the mill feed is produced from the Pilar mine. The Maria Lázara satellite deposit currently supplements the Pilar mine production. At the Maria Lázara mine, ore is extracted using traditional longhole sub-level open stoping. The Pilar mine utilizes a custom step room-and-pillar (SRP) mining method for approximately 80% of its production. This is supplemented by traditional longhole stoping.

The Maria Lázara mine is located approximately 15 km from the Pilar processing plant. At the Maria Lázara mine, sub-level longhole open stoping is used to extract ore. Each mining panel consists of a main lower level and two sub-levels, accessed with 4.0 m wide by 4.5 m high drives. The vertical distance between the roof of the main level and the floor of the first sublevel is 15 m.

The Caiamar mine is located approximately 42 km from the Pilar processing plant. At the Caiamar mine, sub-level longhole open stoping was used to extract ore. Each mining panel consists of a main lower level and two sub-levels, accessed with 4.0 m wide by 4.5 m high drives.

The overall process flowsheet consists of the following unit processes:

• Primary jaw crushing;
• Semi-autogenous grinding (SAG) mill feed bin;
• Single stage SAG mill grinding;
• Pebble crushing;
• Gravity concentration using centrifugal concentrators; treating the underflow the grinding cyclones;
• Intensive cyanide leaching of the gravity concentrate using Acacia reactor;
• Grinding circuit thickening producing a leach feed of 55% solids;
• Cyanide leaching using six tanks in series;
• Carbon in pulp gold recovery using eight tanks in series;
• Cyanide detoxification using sodium metabisulphite in five tanks in series;
• Anglo American Research Laboratory (AARL) stripping of the carbon;
• Electrowinning of the carbon eluent and gravity concentrate leach solution;
• Casting of gold bars in an induction furnace.

Ore is delivered from the Pilar mine using 14 t haul trucks. Ore from the Caiamar mine is delivered in over-the-road haul trucks. The ore is stockpiled and then loaded into the primary crusher feed hopper using a front end loader. The feed hopper is equipped with a static grizzly with 800 mm openings.

Ore is drawn from the feed hopper using a vibrating grizzly feeder and fed to the primary crusher. Grizzly feeder undersize material bypasses the crusher and falls directly onto the crushed ore conveyor. The primary crusher is a 1,000 mm by 760 mm single toggle jaw crusher with a 110 kW drive. The primary crusher discharge combines with the grizzly feeder undersize and is conveyed to the crusher ore storage silo.

Ore is drawn from the storage silo by two vibrating feeders, which feed the fixed speed SAG mill feed conveyor. The SAG mill is 5.8 m diameter by 5.8 m long with a 3,000 kW drive and a capacity of 165 tph.

The SAG mill operates with a slurry density of approximately 75% solids and discharges into the cyclone feed sump where it is diluted and pumped to a cluster of eight 380 mm cyclones for classification. The cyclone feed slurry density is controlled to approximately 53% solids to obtain a cyclone overflow density of 34% solids and a target particle size distribution of 80% passing 125 µm. The cyclone underflow slurry is typically 76% solids and flows by gravity to the feed of the SAG mill. A portion of the cyclone underflow is diverted to two centrifugal concentrators for gravity gold recovery. The tailings from the centrifugal concentrators recombine with the cyclone underflow and return to the mill feed chute, closing the circuit.

The concentrate from the centrifugal concentrators is treated in an Acacia intensive cyanide leach reactor, located in a locked section directly beneath the concentrators. The Acacia reactor is an automated system providing security for the processing of gravity gold concentrates. The concentrate is leached at 54°C in a 2.5% sodium cyanide and 1.5% sodium hydroxide solution to recover the gold. The pregnant Acacia leach solution is then pumped to a storage tank in the carbon stripping area in preparation for electrowinning. The tailings from the Acacia leach reactor is pumped to the cyclone feed sump for re-processing.

The cyclone overflow, at 34 % solids, flows through a horizontal vibrating screen to remove oversize material, plastic and other debris, before reporting to the pre-leach thickener.

The thickener underflow slurry is adjusted to 55% solids and pumped to the leaching and CIP circuit. The leaching circuit consists of six 700 m3 tanks in series for a total retention time of 20 hours to 23 hours. Leach tank No. 1 is used for pre-aeration. Lime is added and air is spared into the tank to oxidize weekly bound sulphur that would combine with cyanide during leaching to form thiocyanate, CNS, increasing cyanide consumption. Lime added during preaeration reacts with the oxidized sulphur to form calcium sulphate. The slurry overflows the pre-aeration tank to leach tank No. 2 where cyanide is added and leaching continues through leach tank No. 6.

The leach slurry overflows through a launder to he CIP circuit where it is diluted to 45% solids and contacted with activated carbon for gold recovery. The CIP circuit consists of eight, 400 m3 tanks in series for a total retention time of eight hours. Activated carbon is added to tank No.8 and is transferred from tank to tank counter current to the slurry flow using vertical recessed impeller pumps. The target carbon concentration is 30 g carbon/L slurry and the carbon is loaded to approximately 2,000 g/t Au as it advances from tank No. 8 to tank No. 1. The loaded carbon is pumped from CIP tank No. 1 to the loaded carbon wash screen where the carbon passes over the screen. The washed loaded carbon is re-pulped with water and pumped to the loaded carbon storage bin in the carbon stripping area. The screen underflow slurry returns to the CIP tank No. 1.

The gold is desorbed from the carbon using the AARL process. The process treats the carbon in 2.7 t batches. The carbon is acid washed before each elution, however, the eluted carbon is only regenerated every third batch (3 elution to 1 regeneration).

The pregnant solutions from the Acacia intensive cyanide leach reactor and from the carbon elution circuit are combined and circulated though the electrowinning cells to recover the gold. The gold in solution is plated out onto stainless steel cathodes. Once the cathodes are loaded and the circulating electrolyte is reduced to five ppm gold, the cathodes are removed from the cells and the gold mud is washed from the cathodes with high pressure water. The gold mud is filtered, dried, and fluxes are added. It is then smelted in a gas fired furnace to produce gold doré bars. The barren electrolyte is pumped back into the CIP circuit.