Host rocks to the underground Mineral Resource include carbonaceous metasedimentary rocks, dioritic and dacitic intrusive rocks, and metavolcanic rocks. The majority portion of the underground resource is classified as carbonaceous breccia. The mineralization style is quartz-carbonate-sulfide veins and breccia fillings hosted in a major, district-scale shear zone, typical of orogenic gold deposits.

The shear zone is north to northeast trending and dips moderately to the west. In the underground resource area, the shear zone is overlain by a dioritic intrusive mass and underlain by andesitic metavolcanics rocks. The shear zone and mineralization range in thickness from several metres to over twenty metres. The planned stopesfor the C1 Underground are generally located in areas where the shear zone is thickest and contains the highest gold grades.

Primary and secondary long hole stoping using paste backfill is considered the most practical and economic method for extracting the C1 Underground Mineral Resources.

The design anticipates a nominal 2,500 t/d underground long hole mining operation using cemented paste backfill to allow for maximum extraction of the deposit. Over the potential 9.5-year LOM, a total of 7.1 Mt of mill feed would be extracted at a grade of 2.65 g/t Au.

The mill feed from the C1 Underground would be blended with open pit ore in the proposed 7,400 t/d process plant and no modifications to the process plant are included in this analysis. Over the expected 9.5-year LOM, the C1 Underground is forecast to contribute a total production of 511,000 oz Au.

A large proportion of the tailings generated from the processing of C1 Underground mill feed will be returned underground as paste backfill for the mined-out stopes. Paste fill production is estimated at 5.1 Mt. The remaining tailings (2.0 Mt) will be placed in the existing TSF.

Primary Development
The underground mine will be accessed from a portal to be established in the southwest corner of the open pit. The decline will be driven 5.0 m wide by 5.5 m high, incorporating a roof line back- excavated along the angle of the rock foliation. This heading size is the same as currently used by Equinox for declines at the Fazenda Brasileiro mine.

The main decline will be driven at a maximum gradient of -12%, and will be divided into a number of segments that will be used to connect the surface to the four major zones and the stope access sub-levels within each zone.

Over the course of the LOM, a total of 6,342 m of decline will be driven to access and extract the four major underground zones extending to a vertical depth of 592 m from the surface portal. For scheduling and costing purposes, the decline measured distances have been increased by 5% to account for miscellaneous additional development (re-muck stations, sumps, storages, ventilation raise accesses) currently not included in the design layout.

Stope Access Development
tope access development has been designed to enable direct mobile equipment access to the individual primary and secondary stopes within each zone, and provide for separate intake and exhaust ventilation circuits. The stope drifts will be driven 5 m wide x 5 m high.

When the decline is adjacent to the mineralized zones, each loop of the main decline has been designed to intersect the elevation of the stope lower sill drifts, which are spaced every 25 m horizontally. From the decline, a 50 m long access drift is driven perpendicular to the decline, extending to the end of the zone. This access drift will then be extended along the entire strike of the deposit, and becomes the lower sill for long hole drilling, blasting, and loading. Approximately 25 m from the decline along the access drift, a drift is driven perpendicular to the access drift for a distance of approximately 50 m, then turned 90° and driven an additional 25 m to intersect the zone at the upper sill drift elevation (for the adjacent down-dip primary/secondary stope). This access drift will then be extended along the entire strike of the deposit, and becomes the upper sill for long hole drilling, blasting, and backfilling of the void. Approximately 20 m along the upper sill access drift, a 5 m high by 5 m wide ventilation cross-cut is driven perpendicular to the access drift for a distance of approximately 6 m. A parallel 5 m wide by 5 m high drift is then excavated to access the exhaust raise from the sub-level above and eventually to the raise that will be excavated to the sub-level below.

Over the course of the LOM, a total of 17,330 m of stope access and stope sill drifts will be driven to access and extract the four major underground zones. Typical advance rates for headings of this size (5 m x 5 m) with bolt/mesh ground support on a multi-faced basis is one round (3.2 m length each) every eight to nine hours.

Long Hole Drilling and Blasting
Long hole drilling and blasting patterns assumed for C1 Underground are identical to those currently in use at the Fazenda Brasileiro mine. This includes drilling rings of 2.5 inches (64 mm) diameter drill holes on a pattern of 1.6 m between rows and 1.8 m between the toes of holes. This pattern results in 2.8 tonnes of ore per metre drilled. The Simba H1254 long hole drills used at the Fazenda Brasileiro mine average 250 m/d/rig thereby preparing 700 t/d/rig of stoping ore. This same productivity is assumed for the C1 Underground.

Long hole drilling/blasting are separated between the lower sill drift and the upper sill drift of each stope. For the thicker stones(>10 m) prevalent in the B-Zone, the lower sill drift is located at or slightly below the footwall contact along the down-dip stope boundary. All drill holes from this sill are drilled vertically and to the up-dip side of the sill drift. Since the up-hole slot raises needed to initiate blasting of each 25 m long stope must be successfully completed in one attempt, the raises are limited to 15 m long, which is, from SLR’s experience, the maximum recommended length for blind up-hole long hole slot raises. The upper sill drift is located higher up in the zone, below the hanging wall contact, along the up-dip stope boundary. All drill holes from this sill are drilled in a semicircular fan pattern towards the down-dip side of the upper sill drift. The downhole slot raises in this case can be any length, since they can be blasted in several lifts. Layout of the >10 m thick secondary stopes is the same as the primary stopes, except that the upper and lower sill drifts have been inset 4 m from the stope boundaries. This is to ensure that the sill drifts are not driven against primary stope backfill.

For the thinner stopes (<10 m) prevalent in the A-, C-, and F-zones, the lower sill drift is located at or slightly below the footwall contact along the down-dip stope boundary. All drill holes from this sill are drilled vertically and to the up-dip side extending to the centreline of the 25 m wide stope. The upper sill drift is higher in the zone and is also at or slightly below the footwall contact along the up-dip stope boundary. All drill holes are drilled vertically and to the down-dip side of the upper sill drift extending to the centreline of the stope.

It is anticipated that the stope extraction sequence will involve opening a 1.6 m wide slot along the entire end of the stope. The remaining mineralization would be blasted in two large blasts with the blasting of the lower sill drift rings (undercut) slightly leading the blasting of the upper sill drift rings (overcut). The powder factor at the Fazenda Brasileiro mine is 1.0 kg of explosives per tonne, and the same is assumed for the C1 Underground.

The crushing section of the plant is part of the original facility. It consists of a jaw crusher followed by a cone crusher, both of which are in open circuit, with the product conveyed to a conical stockpile.

Run-of-mine ore is fed by a front-end loader, from stockpiles on a pad adjoining the crushing plant, and into a hopper in front of the jaw crusher. Ore is withdrawn from the hopper by a vibrating feeder-grizzly, with grizzly oversize feeding the jaw crusher and grizzly undersize dropping to a conveyor that transports the grizzly undersize and the jaw crusher product to a transfer hopper, thence to a second conveyor that feeds a cone crusher. Prior to entering the grinding circuit, a third conveyor takes the crushed ore from the secondary crusher to a crushed ore stockpile.

The grinding section will consist of two mills: a SAG mill and a ball mill operated in series. The SAG mill was part of the original facility; the ball mill is new. The SAG mill, as originally installed, operated as a single-stage SAG mill to produce the final grind size. The new ball mill is a conventional overflow ball mill, and will grind the SAG mill product to the final grind size.

Ore from the stockpile is drawn by two underlying vibrating feeders onto the SAG mill feed conveyor. The SAG mill is equipped with a trommel screen that screens out plus 12 mm pebbles. The pebbles are conveyed back to the SAG mill feed conveyor and are expected to constitute approximately 5% of new feed. Trommel screen undersize will be pumped via new pumpsto the new primary mill cyclones; cyclone underflow will be recycled to the SAG mill, and the cyclone overflow will pass to the ball mill discharge pump box. From the ball mill on, all process equipment is new. The ball mill discharge pumps (one operating, one spare) will pump the combined SAG mill cyclone overflow and the ball mill discharge to the secondary mill cyclones. Cyclone underflow flows to the ball mill feed. Dry lime will be fed from a silo adjoining the ball mill pump box directly into the pump box. Cyclone overflow will flow to a trash screen. Trash screen oversize will be recycled to the ball mill pump box; trash screen undersize will flow to the plant feed sampler and thence to a pump box from which it will be pumped to the RIL circuit.

The original processing plant at Santa Luz was built and placed in operation in mid-2013 and was shut down in September 2014 after 14 months of operation. The plant did not operate well, as a result of both process difficulties and mechanical problems. The new processing facility will incorporate the crushing, crushed ore storage, and SAG mill sections of the original plant. The rest of the plant, with the exception of the refinery, will be new.

The new processing facility will incorporate the crushing, crushed ore storage, and SAG mill sections of the original plant. The rest of the plant will be new, except the refinery. The new facility will process a blend of carbonaceous and dacitic ore, using the following processing sequences:
- Two-stage crushing;
- Two-stage grinding;
- Gravity concentration and intensive cyanidation;
- Pre-aeration and kerosene conditioning;
- RIL;
- Detoxification of leached tailings;
- Containment of tailings ........