Mineralization at Santo Domingo occurs primarily as iron oxide–copper–gold (IOCG) deposits with related vein and skarn bodies.

To date, four deposits, three of which support Mineral Reserves, and a number of prospects have been identified in the Project area.

Santo Domingo Sur
The andesitic flows and tuffs are the primary host to mineralization at Santo Domingo Sur. Mineralization consists of thick semi-massive to massive iron oxide mantos that have replaced the tuffaceous rocks. The stratigraphic sequence of andesitic flows and tuffs dips gently (at an angle of approximately 15°) towards the north–northwest under gravel cover.

Mineralization occurs in the form of copper-bearing semi-massive to massive iron oxide mantos with minor veins and breccias. The mantos are zoned from an outer rim of specular hematite toward a magnetite-rich core.

Drilling has identified a 150 m to 500 m thick, copper-bearing, specularite–magnetite sequence covering an area of approximately 1,300 m by 800 m, and traced to a depth of approximately 525 m below surface. Mineralization consists of stacked chalcopyrite bearing, specularite-magnetite mantos within tuff and tuffaceous sediments overlain by andesitic flows.

The mantos consist of semi-massive to massive specularite and magnetite layers with clots and stringers of chalcopyrite, that range in thickness from approximately 4 m to 20 m. The upper parts of the manto sequence directly below the overlying andesite flows are frequently oxidized and contain various amounts of copper oxides and chalcocite.

Iris
The Iris deposit is essentially blind, covered by a sequence of Quaternary gravel. The elongated shape of the deposit and textures observed in diamond drill holes indicate that the Iris deposit has formed in a north-northwest striking fault zone that is bounded by a west-dipping fault that can be traced along most of the deposit’s western side. The eastern side of the deposit is bordered by a steeply dipping fault that divides andesitic tuffs on the western side from calcareous sedimentary rocks and limestone to the east.

The Iris deposit footprint, when projected to surface, is approximately 500 m wide, has a strike length of 1,800 m, and has been traced from surface to a depth of approximately 670 m below surface. When the dip and plunge of the zones is considered, the real width of the deposit is of the order of 200 m.

The deposit consists of iron oxide mantos and breccias developed along a north–northwest-striking fault zone. The dominant iron oxide at Iris is hematite and the main copper mineral is chalcopyrite.

There are some old mine workings at the southern end of the deposit where copper oxides such as brochantite and chrysocolla were mined at surface. The oxide mineralization is hosted by a specularite manto that is cut by steeply-dipping structures. The extent of oxide mineralization at surface is approximately 100 m by 60 m.

The Iris Mag zone is located between the Iris deposit and the SDS deposit in a separate structural block. Mineralization in the zone consists of magnetite and chalcopyrite with a very high magnetite content (40% and more) and typically low copper content (approximately 0.1% Cu on average). The host rocks are andesitic flows and andesite breccias with a much smaller tuff component than the other zones. It appears that this part of the deposit has been subject to the initial high temperature magnetite event, but shows little evidence of a later oxidizing overprint that has introduced high copper and gold elsewhere.

Iris Norte
The Iris Norte deposit is located about 600 m to the north of the Iris deposit and is also blind, being entirely covered by a gravel sequence. The deposit is very similar in character to Iris, and occurs on the eastern edge of a pronounced gravity anomaly. The deposit is approximately 500 m wide and has been tested over a strike length of 1,600 m and to a depth of 320 m below surface.

Mineralization is primarily hosted in andesitic flows, which differs to the tuff host at Santo Domingo Sur and Iris. The Iris Norte deposit is also elongated in shape and seems to have formed in a structural zone. The deposit displays a northeasterly strike which is a rotation of approximately 55° clockwise versus the strike of the Iris deposit.

Mineralization consists of mixed magnetite and hematite mantos. The main sulphides in Iris Norte are pyrite and chalcopyrite, with the latter providing the copper content of the deposit. Iris Norte contains a higher proportion of magnetite than the Iris deposit and there are a higher proportion of intrusive rocks.

Estrellita
Estrellita comprises an east-west striking, flat lying to shallow north-dipping tabular body lying approximately 3.5 km northwest of Santo Domingo Sur. Mineralization is interpreted by Capstone geologists to occur at a higher stratigraphic level than Santo Domingo Sur, Iris and Iris Norte, which are hosted in tuff sequences below the level of mineralization at Estrellita. Drilling at Estrellita has shown that the host package of andesitic porphyries and flows has a thickness of up to 200 m. In the Estrellita area this package is underlain by a sequence of volcaniclastics with minor intercalations and interbeds of andesite porphyry, limestone and altered tuff.

Estrellita has been faulted into a series of four blocks which step downwards to the north, with displacement across the faults ranging up to approximately 75 m. The overall footprint of the zone measures 900 m long by 450 m wide and is up to 100 m thick.

The character of mineralization at the Estrellita deposit is a mixture of manto style, iron oxide and structurally-controlled, vein-style mineralization. The central part of the Estrellita deposit consists of a more or less horizontal tabular body of iron oxide manto that appears to have formed at the intersection of a flat-lying and a steeply-dipping set of specularite structures.

Copper mineralization typically consists of copper oxides such as brochantite, chrysocolla, almagre, cuprite, and chalcocite. The oxidized mineralization at surface becomes gradually less oxidized with depth and transitions through a mixed zone of oxides and sulphides into a sulphide zone where the main copper mineral is chalcopyrite.

The mine is scheduled to work 7 days per week, 365 days per year. Each day will consist of two 12-hour shifts. Four mining crews will cover the operation.

The final pit design was based on a LG shell that used a copper price of $3.00/lb and $100/t for magnetite concentrate. Two pits, the Santo Domingo pit and the Iris Norte pit, were designed. The Santo Domingo pit will have four phases; three mining phases are planned for the Iris Norte pit. These values were used only for mine design not the economic analysis.

A road width of 40 m was selected to accommodate 290 t trucks. NCL used a 10% road gradient which is common in the industry for this type of truck. The current mine plan is designed with 12 m benches stacked to 24 m (i.e. double benching) for the fresh rock material. Mining costs are based on blasting 12 m benches for the waste zones and for the ore.

Additional 40 m wide safety berms were included in the design when the slope height exceeds 100 m at the east wall and 150 m elsewhere and are in accordance with geotechnical recommendations.

The Santo Domingo pit will have two exits on the west side to provide access to the run-of-mine (ROM) pad area and the primary crusher. On the east side there will be another exit to access the main waste rock storage area. The final pit will be 2,200 m long in the north–south direction and 1,500 m wide in the east–west direction. The pit bottom will be at the 676 m elevation. The highest wall will be about 552 m and is situated on the southeast side of the pit. The total area disturbed by the pit will be approximately 229 ha.

The Iris Norte pit will have one exit on the west side to provide access to the ROM pad area and primary crusher. On the east side there will be an exit to access the waste rock storage area. The final pit will be 1,600 m long in the north– south direction and 900 m wide in the east–west direction. The pit bottom will be at the 664 m elevation. The highest wall will be about 315 m and is located on the north side of the pit. The total area disturbed by the pit is about 124 ha.

Mine equipment requirements were calculated based on the annual mine production schedule, the mine work schedule and equipment hourly production estimates. The study is based on operating the mine with 42 m3 capacity hydraulic excavators (shovels) and trucks with a capacity of 290 t. The fleet will be complemented with drilling rigs for ore and waste. Auxiliary equipment will include tracked dozers, wheel dozers, motor graders and a water truck. A small drill rig was also included for presplitting purposes.

The primary crushing plant will process ROM feed in open circuit. Trucks will be able to unload material simultaneously to the 450 t capacity feed hopper that will have a fixed rock breaker. Primary crushing will be carried out in a 600 kW, 60” x 89” gyratory crusher. The crushed product will fall into a 450 t hopper which will unload onto a plate feeder that feeds the conveyor transporting material to the coarse ore stockpile. The stockpile will have a live capacity equivalent to six to eight hours of operation. The stockpile will discharge onto three feeders located within the reclaim tunnel, which then will feed the primary SAG mill.

The grinding circuit will receive fresh feed from the coarse ore stockpile and desalinated water from the water storage pond. The 24 MW (at the shell), 40’ x 26’ EGL SAG mill will operate in a direct (DSAG) mode. The SAG mill will discharge onto a screen. The oversize pebbles from the discharge screen will be recycled to the SAG mill without being crushed. The screen will be a conventional, double deck, 12’ x 24’, vibratory screen with screen openings of 1” on the top deck and ½” on the bottom deck. The oversize pebbles will be transported by a conveyor system to the SAG mill feed conveyor. The undersize from the discharge screen will be fed to secondary grinding circuit pump box.

The secondary grinding circuit will consist of two 24’ x 36’ ball mills each with a 12 MW twin pinion drive system. The ball mills will operate in closed circuit with two cyclone clusters of ten 33” hydrocyclones with 20% spare cyclone flow capacity. The coarse (underflow) fraction from the hydrocyclones will be returned to the ball mill feed and the fine material (overflow) fraction will be the final comminution circuit product with a P80 of 150 µm.

The main process design criteria include:
- Design capacity (first 5 years): 65,000 t/d
- Nominal capacity (after 5 years): 60,000 t/d
- Operating period: 365 days per year.

Copper Flotation
Copper rougher flotation will be carried out in a single bank of six 600 m3 mechanical, forced air tank cells arranged in a 1-1-1-1-1-1 configuration. Flotation rougher concentrate produced from the rougher cells will flow by gravity to the regrind mill feed box where it will be combined with first cleaner scavenger concentrate and then fed to the regrinding stage which will consist of a single vertical mill and cyclone cluster operating in closed circuit.

The overflow from the hydrocyclones will feed a single conditioning tank preceding the first cleaner and cleaner scavenger flotation circuit. First cleaner stage flotation will be carried out in a bank of four mechanical, forced air 250 m3 tank cells; the concentrate will be pumped to the second cleaner ........