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.

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).

Mineralized fluids from deep intrusions moved up faults and fractures at dilational jogs along a releasing bend, percolating out into the surrounding wallrock. In places, particularly where aperture suddenly increases at lithologic contacts, at dilational jogs or at fault intersections, the fracture density increases forming wider damage (or structural) zones that are better mineralized with wide alteration halos. Some of these zones host veins and vein-breccias in more favourable fluid corridors. Mineralizing fluids were able to penetrate the host rocks away from open fractures, travelling through thin cracks and through the connected permeability of the intrusive rock and the porosity of the sedimentary host rock. The disseminate-style low-grade mineralization extends several hundred meters from the major faults and fault intersections, developing stockwork mineralization with small veinlets crisscrossing to form an inter-connected mineralization network.

In high-grade zones that are dominated by veins and vein-breccias their associated alteration halos and metal grades are continuous in directions parallel to the steeply NW-dipping NE-SW-trending faults.

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.

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.

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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 ........