The Prosperity deposit is predominantly hosted in Cretaceous andesitic volcaniclastic and volcanic rocks which are transitional to a sequence of sparsely mineralized, volcanically-derived sedimentary rocks to the south. The andesitic volcaniclastics are comprised of coarse-grained crystal tuff and ash tuff, and thinly bedded tuff with lesser lapilli tuff. The upper eastern portion of the deposit is hosted by subvolcanic units of crowded feldspar porphyritic andesite and thick feldspar and hornblende porphyritic flows.

In the western portion of the deposit, the multi-phase Fish Creek Stock has intruded into a thick sequence of andesite flows which overlay volcaniclastic rocks. The steeply south-dipping, oval quartz diorite stock, which is approximately 265 m wide by 800 m long, is surrounded by an east-west trending swarm of subparallel quartz-feldspar porphyritic dikes, which also dip steeply to the south. Together the stock and dikes comprise the Late Cretaceous Fish Lake Intrusive Complex that is spatially and genetically related to the deposit. Post-mineralization porphyritic diorite occurs as narrow dikes that cross-cut all units within the deposit. They represent the final intrusive phase of the emplacement of the Fish Lake Intrusive Complex.

The deposit area is overlain by a variably thick overburden cover consisting of Wisconsinian glacial till, Miocene to Pliocene basalt flows, and Tertiary colluvium and lacustrine sediments.

The deposit is oval in plan and is approximately 1500 m long, 800 m wide and extends to a maximum depth of 880 m. A central potassium silicate alteration zone is co-extensive with the gold-copper mineralization. Along the deposit’s eastern margin, a discontinuous zone of phyllic alteration is developed at the boundary between the potassium silicate alteration zone and the surrounding propylitically altered rocks. The latter extend outward from the deposit for several hundred metres. Late stage sericite-iron carbonate alteration forms irregular zones, particularly within the potassium silicate alteration zone. Argillic alteration is localized along fault zones and overprints earlier alteration assemblages.

Pyrite and chalcopyrite are the principal sulphide minerals in the deposit. They are uniformly distributed as disseminations, fracture-fillings and sub-vertical veinlets and may be accompanied by bornite and lesser molybdenite and tetrahedrite-tenantite. The latter results in somewhat elevated levels of arsenic, antimony, and mercury in some parts of the deposit. Native gold occurs as inclusions in, and along microfractures with, copper-bearing minerals and pyrite. Latestage pyrite-base metal veins, up to several centimetres in width, are most abundant within the upper eastern portion of the deposit.

Gold-copper mineralization within the Prosperity deposit is intimately related to potassium silicate alteration and a later, superimposed sericite-iron carbonate alteration. This is particularly true within a central, east-west trending ovoid zone that hosts the majority of the mineralization.

Chalcopyrite-pyrite mineralization and associated copper and gold concentrations are distributed relatively evenly throughout the host volcanic and intrusive units in the deposit. A sedimentary unit, which is located in the upper southeastern part of the mineralized zone, is sparsely mineralized. Post mineralization porphyritic dikes are essentially barren.

Sulphide minerals show the thoroughly dispersed mode of occurrence characteristic of porphyry copper deposits. Sulphides occur in relatively equal concentrations as disseminations, blebs and aggregates in mafic sites, as fracture fillings and as veinlets. Disseminated sulphide mineralization is marginally more prevalent than veinlets in intrusive rocks while in volcanic rocks the reverse was noted.

The Prosperity open pit will be a nominal 525 m deep when complete.

The mining equipment will operate on a 15m high bench in overburden and hardrock. Wall slope design changes will be implemented by varying the berm widths and inter-berm slope angles.

Berms will be left on every bench in overburden and on alternate benches in hardrock. Berm width design will vary from 15 m to 10 m as the overall wall slope is increased from 45° to 50° in the Lower Zone.

The open pit will be mined in four phases commencing with the Phase 1 – Starter Pit. The pit will be partially pre-stripped during the preproduction development period. The starter pit will provide building materials for the tailings impoundment starter dam. The Phase 2 through Phase 4 pits are radial expansions of the mine about the Starter Pit creating a progressively deeper pit.

The mine will operate using electric cable shovels and rotary drills. Diesel electric trucks and a support equipment fleet will gradually be increased to match the production schedule that will peak in terms of total production in Year 7 through Year 9 at 200,000 tpd.

The Prosperity crushing circuit has been designed to crush on average 70,000 t/d of run-of-mine ore from minus 1,000 mm to 100% passing 350 mm and 80% passing 150 mm at a nominal rate of 4,444 tonnes/hr. The crushing system will consist of a single 1.52 x 2.79 m gyratory crusher operating at 75% utilization per 21 hour day, 365 days per year basis. The primary crusher will be located near the east corner of the ultimate pit boundary.

Product from the crusher will discharge into the surge pocket directly below. Crushed material will be drawn from the surge pocket by a variable speed apron feeder which will discharge onto a 1.8 m wide overland conveyor which will transport the crushed ore from the primary crusher 1,900 m to the coarse ore stockpile. The coarse ore stockpile is estimated to have a live capacity of 55,000 tonnes. A belt weigh scale, and a tramp iron magnet to remove tramp metal, will be installed on the conveyor.

The primary crusher will have a 10 tonne auxiliary hoist for maintenance purposes. A hydraulic rock breaker will be provided at the crusher dump pocket for breaking any oversize run-of-mine material.

Crushed ore will be reclaimed from the coarse ore stockpile via three variable speed apron reclaim feeders located in a concrete reclaim tunnel. The four apron feeders will feed directly onto the SAG mill feed conveyor.

Grinding
The primary grinding circuit will be designed to process an average of 70,000 tonnes/day at 90% utilization on a 24 hour per day, 365 day per year basis. The grinding circuit will be designed to reduce the crushed ore from 80% passing 150 mm to 80% passing 170 µm. The grinding operation will consist of a SAG mill and two ball mills.

The SAG mill will be 12.2 m in diameter (inside shell) by 6.1 m long (effective grinding length) and will be driven by a 21,000 kW variable speed wrap-around gearless drive motor. The SAG mill has been designed to operate with a nominal ball charge of 11 percent by volume. The product from the SAG mill circuit is projected to be 80% passing 2,000 µm. The SAG mill will discharge via a trommel screen into the SAG mill discharge pump box. The trommel screen oversize is returned to the SAG mill conveyor by a series of three conventional conveyors.

Provision is made to install a pebble crusher in the future if required.

The SAG mill discharge is pumped by one of two installed SAG mill discharge pumps to a gravity discharge distributor located above the mill grinding floor. The flow is split into three equal parts to feed the two ball mill circuits operating in parallel.

Each of the two ball mill circuits consists of a 7900 mm diameter by 14600 mm long ball mill with dual pinion drive. The motors are 18,000 kW wrap around motors.

The ball mills each discharge into a cyclone feed pump box and a cluster of 12 cyclones are fed by a variable speed cyclone feed pump. The cyclone underflow returns to the ball mill while the cyclone overflow discharges to the flotation circuit.

Regrind
The regrind circuit is designed with five parallel vertical stirred regrind mills. Each regrind mill circuit consists of a 1,120 kW stirred mill operating in closed circuit with a cluster of seven 250 mm cyclones.

The 80% passing 200 µm cyclone overflow will flow by gravity to the bulk flotation circuit. The cyclone underflow will be returned as ball mill feed. An on-line particle size indicator (PSI) will be provided for monitoring of the cyclone overflow streams and to provide grinding process control.

A weigh scale will be provided on the SAG mill feed conveyor for controlling, monitoring and recording the concentrator fresh feed rate. A weigh scale will be provided on the SAG mill screen oversize conveyor to monitor SAG mill circulating loads.

The process design is conventional and consists of SAG and ball mill grinding; bulk sulphide flotation, regrind and bulk rougher/scavenger cleaner flotation, cleaner flotation and concentrate dewatering. The concentrator is designed to operate 24 hours per day, 365 days per year.

Bulk Rougher/Scavenger Flotation
The bulk flotation circuit will consist of three parallel trains of bulk rougher cells.

Cyclone overflow from each of the three parallel grinding circuits will flow by gravity into a collection box and then split into three equal portions to feed each of the three rows of seven cells. The cells in each row are 200 m3 forced air cells, giving a total of 21 cells for the complete bulk rougher flotation area. This combination of cells provides the power and retention time required for flotation. The tailings from the last scavenger cells in each row are combined as bulk flotation tailings.

The flotation reagent distribution system will perm ........