The deposits on the Cordero property do not fit neatly into a single deposit type in any of the systems commonly used to categorize mineral deposits into groups with a similar genesis. This is partly due to the fact that the property is large and hosts many different types and ages of intrusive igneous as well as extrusive igneous rock; but even within the Cordero Main area, observations from surface mapping and core logging are consistent with overlapping deposit types. Of the deposit types that have been described and named in the technical literature, the ones with most relevance to Cordero are as follows:

• extensional intermediate sulphidation epithermal systems like Real de Angeles in Zacatecas;
• carbonate-hosted Pb, Zn (Ag, Cu, Au) in manto-style (skarn) and crosscutting chimney-style and felsic intrusive igneous contact-related massive sulphides like those at Santa Eulalia in northern Chihuahua.

Although breccia-hosted deposits like Peñasquito have sometimes been used as an analogy for Cordero, the Peñasquito deposit has several characteristics not yet observed at Cordero.

The Cordero project area has limited outcrop up to approximately 20%, with a subdued topographic surface that averages approximately 1,550 m above sea level. Resistant Tertiary-age silicic volcanic/subvolcanic rocks pierce the horizontal landscape comprised of recessive and easily eroded marine sediments.

The Cordero property is a shallow-level magmatic system emplaced into an isolated sedimentary basin comprised of a series of compositionally similar, interconnected hypabyssal bodies. Emplacement- related textures have provided favourable permeability loci for mineralization, including a variety of intrusion-related structures.

The Cordero magmatic-hydrothermal system and emplacement-related structures have had a complex history while developing its shape into a disc-shaped laccolith with a deep keel, and a series of interconnected sills and dikes, with magmatic flow-related structures (flow-foliation/flow- banding), contact-related structures (bimictic breccia) syn-magmatic in origin, and fragmental structures in collapse breccias.

At Pozo de Plata, a polymictic rhyolitic intrusive breccia (IBX) is cut by mineralized hydrothermally altered milled matrix breccia. The IBX can occur elsewhere as unmineralized bodies. Additionally, the creation of space and permeability is provided by reactivated NNW- to NNE- trending axial planar shears along fold axes, where bedding plane faults and manto-replacement bodies have formed in favourable sedimentary horizons, as well as in extension-related faults where openspace fill is dominant in veins and vein breccias.

The Cordero Intrusive Complex that hosts most of the project’s current mineral resource comprises a rhyodacitic laccolith, sill, dike and breccia complex. A domal feature forms a resistant hill, the product of intense silicification. In this area, fluids from deep magma found interconnected pathways along several deep basement fault zones, such as the NE-SW trending Cordero, Todos Santos
and Josefina faults, that control mineralization. Sheeted dikes have exploited the same northeast-trending Cordero Fault Zone and parallel fault strands; these dikes typically have a quartz- feldspar dacite composition, and are marked by clusters of coarse feldspar crystals, a texture known as “glomerophyric”.

The best-developed mineralization in the Cordero Main area occurs where intrusive igneous dikes and shallow-dipping sills are inter-fingered with marine sediments of the Mezcalera Formation, which consists of interbedded limestones, and sedimentary rocks composed of grains of fine clay (shale) to fine silt (siltstone) as well as larger grains of sand or quartz in sandstones.

The Ag-Au-Pb-Zn content at Cordero is in sulphide minerals, with pyrite, sphalerite and galena accounting for the significant majority of metal content; lesser amounts of the metals of potential economic interest are contained in arsenopyrite, chalcopyrite, freibergite, argentite, rare pyrrhotite, and in the sulphosalts tetrahedrite and tennantite.

The primary gangue minerals are Ca-Fe-Mg carbonates and rhodochrosite in Mn-carbonates, adularia, quartz, barite, calcite, sericite, fluorite and chalcedony.

The rocks were altered as hydrothermal fluids percolated through interconnected faults, fractures, stockwork and along permeable lithologic contacts. The principal type of chemical alteration was caused by fluids that removed certain minerals and replaced them with their potassium-bearing cousins: adularia (a potassium-bearing alumino-silicate), potassium feldspars (orthoclase or sanidine), illite (a potassium-bearing clay), and the potassium-bearing micas: muscovite, biotite and phengite. Potassium-rich alteration is widespread throughout the main Cordero magmatic hydrothermal belt and accounts, in part, for the strong coincidence between the potassium spectral band on the radiometric geophysical survey and the intensity of Ag-Au-Pb-Zn mineralization.

Other alteration minerals include chlorite, chalcedony (a micro-crystalline form of reprecipitated silica) and buddingtonite, an ammonium mineral sourced from sedimentary rocks and associated with epithermal deposits.

The other type of alteration observed at Cordero is due to weathering and the percolation of oxygen-rich waters through the near-surface permeable layer. The common alteration minerals at shallow depths are jarosite, (iron hydroxy sulphate) goethite (iron oxyhydroxide), hematite (iron oxide), kaolinite and smectite (swelling clays) and gypsum (hydrated calcium sulphate).

Mining of the Cordero deposit will be done by open pit methods utilizing a traditional drill, blast, load and haul sequence to deliver mill feed to the primary crusher for processing through the sulphide plant or placed on the heap leach pad. Waste material will be sent to either the rock storage facility (RSF) southeast of the pit or to the tailings storage facility (TSF) to the west of the pit.

The current geotechnical dataset is considered sufficient for PEA level-designs. Interramp pit slope angles (measured from bench crest to bench crest) range from 40° at the southwest side of the ultimate pit to 59° at the northeast side of the ultimate pit. Bench face angles range from 69° to 80°. Bench widths range from 8.5 to 16 m and have been designed to adequately retain rockfall.

Four pit phases were developed for the single open pit. Mining occurs on 10 m lifts with safety benches every 20 m using the provided geotechnical parameters by sector. Haul roads are designed at 35.4 m wide to accommodate 230-tonne class haul trucks. The operating width used for the truck is 8.3 m. This means that single-lane access is 27.1 m (twice the operating width plus berm and ditch) and double lane widths are 35.4 m (three times the operating width plus berm and ditch). Ramp gradients are 10% in the pit and RSF for uphill gradients. Working benches were designed for 35 to 40 m minimum mining width on pushbacks.

Phase 1 will start being mined in Year-2 and will be utilized as quarry material for construction purposes. Phases 1 and 2 target the highest-grade areas of the deposit and are target the same pit shell target for the two areas. Phase bench elevations will range from 1640 masl to 1340 masl. All waste and mineralized material accesses will be on the southeast side of the phase, where the RSF and process destinations will be located.

Phase 2 will also be accessed from the southeast side of the pit. Phase bench elevations will range from 1630 masl down to 1480 masl.

Phase 3 extends the initial phases to the north, with pit bottoms at 1340 and 1420 masl. Pit exits at the north and northeast ends allow for short waste hauls to the TSF and RSF from the upper benches. The 1570 masl pit exit at the south end of the pit can be used for shorter mill and heap leach hauls. Phase bench elevations will range from 1630 masl down to 1340 masl.

Phase 4 is the final pit phase and therefore represents the ultimate pit. The pit exit at 1570 m elevation pit is where the mined material will leave the pit at the southeast side of the pit. Phase bench elevations will range from 1600 masl down to 1120 masl.

Mine Equipment Selection
The mining equipment selected to meet the required production schedule is conventional mining equipment used by contract miners in Mexico.

Drilling will be completed with down-the-hole (DTH) hammer drills with 140 and 200 mm bits. This will provide the capability to drill patterns for the 10 m bench heights. The smaller drill bit will be used for preshear holes and the larger drill bit for production blasting.

The mining contractor is expected to use a loading fleet of 13.7 m3 excavators and 13.8 m3 loaders to load the 91-tonne rigid body trucks. This fleet configuration remains the same for the entire mine life. Pre-production mining will use one excavator and one loader with five trucks. Production from Year -1 onwards will have a peak fleet size of two production excavators and three production loaders. The truck fleet will peak at 37 units. It is expected one of the loaders will be used at the at the primary crusher and stockpiles full-time.

The support equipment fleet is sized to provide sufficient coverage for the usual road, pit, and dump maintenance requirements. In addition, smaller road maintenance equipment is included to keep drainage ditches open and sedimentation ponds functional.

The mine schedule plans to deliver 199 Mt of sulphide mill feed grading 31.1 g/t Ag, 0.09 g/t Au, 0.75% Zn and 0.46% Pb over a mine life of 14 years. Heap leach material processed included 20 Mt of leach crush material grading 41.5 g/t Ag, 0.09 g/t Au, 0.40% Zn and 0.34% Pb along with 9.1 Mt of ROM leach material grading 23.6 g/t Ag, 0.06 g/t Au, 0.37% Zn and 0.25% Pb. Waste tonnage totalling 491 Mt will be delivered to either the tailing storage facility or the rock storage facility.
The overall strip ratio is 2.2:1.

The mine plan calls for the staged delivery of various feed types to the primary crusher. In Years -1 to 3, the crusher will size 5 Mt/a of oxide material suitable for heap leaching. Sulphide feed to the mill will start in Year 1 and continue at a rate of 20,000 t/d until Year 3. The sulphide plant will be expanded in Year 3, achieving a rate of 40,000 t/d in Year 5 (Year 4 is a ramp up year from 20,000 tpd to 40,000 tpd). This rate will be maintained for the remainder of the 16-year mine life. The peak mining rate will occur in Years 1 and 2 at 67 Mt/a, but holds steady thereafter at 65 Mt/a until Year 6 when it declines as the mine matures. Three sulphide stockpiles with a peak capacity of 64 Mt will be used to primarily store low-grade sulphide mill feed.

Crushing Plant
ROM material is directly tipped into the primary crusher dump pocket which has a capacity for 1.5 truckloads. The dump pocket is equipped with a hydraulic rock breaker to break any oversized rocks. The feed material flows by gravity into the primary crusher.

The primary gyratory crusher is designed to reduce the 100% passing feed size (F100) of 900 mm to an 80% passing product size (P80) of 100 mm when only operating the oxide operation at the beginning of the mine life. Later a product size (P80) of 125 mm is achieved when both oxide and sulphide mineralization are processed. The crushed material is discharged onto the stockpile feed conveyor which can discharge to either the coarse oxide stockpile or the coarse sulphide stockpile. The initial design conveys the crushed mill feed directly to the oxide stockpile. Once the sulphide operation also begins, a diverter system is used to direct the sulphide material towards the coarse sulphide stockpile.

Oxide and sulphide operations have dedicated secondary and tertiary crushing systems. The coarse product from each stockpile is fed to their respective double-deck secondary screen, and the screen oversize is crushed by the secondary cone crusher, operating in an open circuit. The oxide secondary crushing stage reduces the 80% passing size of 125 mm to 43 mm, whereas the sulphide circuit produces a P80 of 56 mm. The secondary crusher discharge combines with the secondary screen undersize, and the material is conveyed to two double-deck tertiary screens. Oversized material from the screen decks report to the tertiary cone crusher bins. Vibrating feeders reclaim stored material and feed the tertiary cone crushers. The tertiary crushers are operated in closed circuit and reduce the F80 of 43 mm to a P80 of 13 mm in the oxide circuit and from the F80 56 mm to a P80 18 mm for the sulphide circuit. The tertiary crushed product is combined with the secondary crusher product prior to returning to the double-deck tertiary sizing screens. The undersize of the tertiary screens provides the final product of each crushing circuit, resulting in 80% passing crushed products of 7 mm in the oxide circuit and 12 mm in the sulphide circuit.

Once the heap leach oxide operation has been completed, the crushing equipment utilized for the oxide processing is reallocated to the sulphide operation to accommodate the increase in sulphide processing throughput. Feeder and conveyor additions will be required during the expansion to redirect the fine feed from the fine oxide stockpile to the new sulphide flotation plant.

The major equipment and facilities include the following:
• primary crusher dump pocket (348-tonne live capacity);
• rock breaker;
• 1,370 mm 54x75 gyratory crusher;
• stockpile feed conveyor.

Oxide
• two apron reclaim feeders;
• 3.05 m x 7.32 m vibrating banana double-deck secondary screen; 75 mm top deck aperture and 30 mm bottom deck aperture;
• 1,780 mm head secondary cone crusher, 30 mm closed side setting (CSS);
• two 3.05 m x 7.32 m vibrating banana double-deck tertiary screens; 30 mm top deck aperture and 13 mm bottom deck aperture;
• two tertiary crusher feed surge bins;
• two tertiary crusher vibrating pan feeders;
• two short head, 1,780 mm tertiary cone crushers, 15 mm CSS;
• screen feed and discharge conveyors.

Sulphide
• two apron reclaim feeders;
• 3.05 m x 7.32 m vibrating banana double-deck secondary screen; 75 mm top deck aperture and 40 mm bottom deck aperture;
• 1,780 mm secondary cone crusher, 45 mm CSS;
• two 3.05 m x 7.32 m vibrating banana double-deck tertiary screens; 40 mm top deck aperture and 20 mm bottom deck aperture;
• two tertiary crusher feed surge bins;
• two vibrating grizzly feeders, 1.6 m wide;
• two short head, 1,780 mm, tertiary cone crushers, 18 mm CSS;
• screen feed and discharge conveyors.

The feed to the crushers is controlled by adjusting the speed of the vibrating feeders.

Crushed Material Handling
The crusher circuits differ between the oxide and sulphide operations in terms of tertiary crusher setting but otherwise follow the same three-stage crushing flowsheet. The oxide operation reclaims the fine material and processes the material through an agglomerator in preparation for the heap leach. The resulting agglomerates are discharged onto a conveyor before reaching a series of grasshopper conveyors. The grasshopper conveyors convey the agglomerates until they reach a radial stacker, which deposits the agglomerates onto the heap pad. The sulphide circuit utilizes feeders to reclaim the fine crusher product and use a ball mill feed conveyor to supply the flotation plant.

The crushed sulphide mineralization is fed by means of a belt feeder to a belt conveyor. A ball mill feed conveyor weightometer is used to control the throughput of material into the mill. The major equipment and facilities in this area include the following:
• crushed product reclaim feeders;
• rotary drum agglomerator;
• heap leach grasshopper feed conveyors;
• radial stacker conveyor;
• ball mill feed conveyor and weightometer.

Grinding
The grinding circuit consists of a ball mill and cyclones operating in closed circuit. The grinding circuit is designed to grind the ball mill feed from an 80% passing size of 12 mm to 200 µm.

The ball mill consists of a double-pinion overflow mill operating in a closed circuit. The mill has an inside diameter of 7.32 m and an effective grinding length of 12.19 m. The mill receives crushed mineralized material and process water at a variable flowrate to achieve the correct discharge pulp density of 72% solids w/w. Soda ash, sodium cyanide, and zinc sulphate are also dosed to the ball mill to condition the feed prior to the flotation circuit, when the carbon pre-float circuit is bypassed. The ball mill discharge passes over the discharge trommel screen with an aperture size of 10 mm x 25 mm. The ball mill is charged with high chrome grinding media at a diameter of 50 to 80 mm by means of the grinding building hoist and ball kibble.

The major equipment and facilities in this area include the following:
• 7.32 m diameter x 12.19 m single-pinion overflow ball mill with a 12,500 kW motor;
• hydrocyclone pack and pumping system, 12 cyclones;
• grinding media handling system.

The process plant design is based on a stage-wise expansion approach to treat the variable grades in the recovered mineralization while also considering a future increase in mill throughput. Initially, a heap leach operation is used to treat oxide material mined initially from the deposit and to produce silver-gold doré bars. Following this, lower-grade ROM mineralization is used as heap leach feed and will bypass the crushing circuit.

A sequential flotation process plant operates in parallel to treat the sulphide mineralization from the open-pit, producing a lead-silver concentrate and a zinc concentrate. Two expansions to the sulphide flotation capabilities will be completed later in the mine life, the first when the sulphide material throughput is doubled and the second will be driven by the compounded impact of future increasing feed grades on the doubled process plant throughput.

The sequence of the process plant development over the course of the life of mi ........