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 currently comprises two underground mining operations. The bulk of the mill feed is produced from the Pilar mine. One satellite deposit, Maria Lázara, 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 SRP mining method for approximately 80% of its production. This is supplemented by traditional longhole stoping.

Mining was initiated at the Pilar mine in late 2012 and commercial production was attained in October 2014. The Maria Lázara mine has been in operation since August 2015.

The mineralized deposit at the Pilar mine comprises a series of ore lenses (only one of which is included in the Mineral Reserves) with an average thickness of 0.9 m and dips of 20° to 22°. Typically, most of the Pilar mine’s mineralization ranges from one metre to two metres in thickness.

The mine is accessed through two, five metre by five metre access ramps: one in the west and one in the east.

The Pilar mine development and production heading dimensions, as well as pillar dimensions
are listed below:

• SRP Access Drift/Ramp: 4.5 m wide by 4.5 m high;
• Longhole Access Drift: 4.5 m wide by 4.5 m high;
• SRP Primary Stoping Drift: 5.5 m wide by 1.8 m to 4.2m high;
• SRP Secondary Stoping: 6 m wide by 8 m long;
• Longhole Stopes: 10 m wide by 10 m to 15 m long;
• SRP In-Stope Permanent Pillars: 6 m wide by 3 m long;
• SRP Stope Barrier Pillar: 5 m wide surrounding stoping area;
• Longhole Stope Permanent Pillars: 4 m wide by 10 m to 15 m long.

Modifications to the SRP production headings are planned:
• SRP Access Drift/Ramp: 4.5 m wide by 4.5 m high;
• SRP Primary Stoping Drift: 3.5 m wide by 2.0 m to 3.4 m high;
• SRP Secondary Stoping: 9 m wide by 12 m long;
• SRP In-Stope Permanent Pillars: 9 m wide by 3 m long;
• SRP Stope Barrier Pillar: 5 m wide surrounding stoping area.

Extraction of the SRP stopes is as follows:

• From the main decline located in the footwall, haulage drifts are driven along strike and form the upper and lower boundaries of the mining block. These haulage drives are approximately 150 m apart.

• A maximum 15% ramp is driven, in ore, between the upper and lower haulage drifts thereby splitting the block into two roughly equal sections of approximately 150 m by 150 m. If the dip of the ore exceeds 10°, the ramp is driven across the dip. Both the haulage drifts and the in- stope ramps are 4.5 m wide by 4.5 m high, and they are driven with conventional development equipment. From each side of the in-stope access ramp, a shanty-back strike drive 1.8 m high (low side) and 5.5 m wide is excavated until it reaches the end of the mining block. This is excavated using low profile development equipment.

• A 6 m long by 3 m wide pillar is left between parallel sets of strike drives. A 6 m long by 8 m wide panel of ore between two strike drives is recovered in retreat fashion after the strike drives have reached the stoping block limits. After each panel is mined, another 6 m long by 3 m wide pillar is left and the process is repeated. Half of the panel is drilled with a jumbo from each of the two strike drives. The lower elevation half is blasted first and mucked from the lower drive. The upper half is blasted second and also mucked from the lower drive.

PRIMARY CRUSHING
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 crusher is sized for a nominal feed rate of 206 tph with a closed side setting of 75 mm. The primary crusher discharge combines with the grizzly feeder undersize and is conveyed to the crusher ore storage silo. The silo has a live storage capacity of 1,000 tonnes allowing for eight hours of mill operation at the design mill production rate of 127 tph.

PRIMARY GRINDING
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 typical mill operating power draw is reported to range between 2,200 kW and 2,600 kW. The discharge of the mill is fitted with a trommel screen with 10 mm by 10 mm openings to remove oversized pebble and ball chips. The mill operates with a 30% ball charge made up with 125 mm balls. The circulating load is estimated to be 400%. The trommel oversized material is conveyed to a cone crusher, with a 132 kW drive, positioned above the SAG mill feed conveyer. The pebble size material is reduced to –8 mm and discharged directly onto the SAG mill feed conveyor and recycled to the mill. The cone crusher capacity is 90 tph and is currently operating at approximately 20 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 cyclone overflow flows through a horizontal vibrating trash screen to remove oversize material, plastic and other debris, before reporting to the pre-leach thickener.

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.

GRAVITY SEPARATION
The concentrate from the centrifugal concentrators is treated in a ........