La India
The La India Vein Set comprises two cross-cutting structures. The bulk of the mineral resource is hosted by the India-California structure, a normal fault striking 330° and dipping ENE at approximately 70° in the southern zone, 50-60° in the central zone and 45° in the northern zone. The India-California structure displays evidence of trans-tensional movement with a sinistral transverse component inferred.

In the hangingwall zone, a series of steep-dipping veins have formed in contact with the main structure that are interpreted as tension gash fill. The result is a thick mineralised sequence of anastomosing quartz veins and breccias. At the southern strike extent of the structure the mineralised veins do not reach surface, but drilling has demonstrated that the mineralised fault system remains open along strike at depth.

A smaller mineral resource is contained within the approximately EW striking Teresa-Agua Caliente-Arizona veins. These veins form a set of discrete, parallel, and vertical to steeply north dipping veins. The Company has produced a series of detailed geological sections which show the various volcanic lithologies, which have been used as a basis for the geological and mineralisation models.

America Mine
The gold mineralisation at America occurs along the faulted contacts which separate three structural blocks. The America-Escondido structure forms two of the three recognised block boundaries. The structure is characterized by a 60° bend between the America fault which strikes 300° and dips approximately 55° to the northeast and the Escondido fault which strikes north and dips at approximately 45° to the east. Both the America and Escondido fault limbs are planar normal faults, typically 1-3 m wide and characterized by the development of sand to gravel-grade cataclastic textures on the principal fault plane and small, metre-scale tension gashes in the hangingwall. A wider quartz breccia has developed at the flexure zone. The Constancia veins are hosted by a steeper dipping structure striking at 270-290° and dipping at approximately 70° to the north.

Central Breccia
The Central Breccia is a multi-stage hydrothermal breccia deposit hosted by a massive porphyritic andesite located at the centre of the graben-like structure that runs down the axis of the America Vein Set near the intersection with the regional cross-cutting NE-Fault. Drilling has shown that the andesite overlies a felsic pyroclastic breccia. Two stages of hydrothermal breccia development are recognised, an early hydraulic breccia with evidence of clast movement and rotation and a silica-cemented microbreccia matrix, and a later crack and fill brecciation with calcite-cement containing anomalous gold values formed under a more passive dilational regime.

Gold mineralisation is associated with a later calcite and quartz calcite crack and seal breccia. The breccia typically has grades of 0.1 to 0.2 g/t Au, within which high-grade zones (interpreted as shoots within the wider breccia pipe) typically over 10 m thick and grading between 2 g/t and 7 g/t Au occur. The high-grade zones are often associated with sulphide minerals and intense argillic alteration and quartz veins.

The gold mineralisation at La India is interpreted as to have been deposited in a high level, low sulphidation epithermal system. The mineralisation itself occurs associated both with quartz vein systems and within well-confined hydrothermal breccias.

The veins and stockwork zones are hosted within massive andesites, andesitic and felsic tuffs or felsic lava flow deposits. Veins are typically less than 3 m in width, but stockwork zones and stacked stockwork-vein zones can be up to 25 m wide. Quartz veins, often including a brecciated component, vary in thickness and are most typically between 0.7 m and 2 m in thickness.

In many areas, the wallrock hosts a breccia or stockwork zone with vuggy quartz veinlets up to 5 cm thick and accounting for up to 70% of the rock mass. The breccia/stockwork zone is typically up to 10 m thick and is associated with silica-haematite alteration. The quartz in the breccia zone may be gold mineralised, although the country rock component means that gold grades are diluted compared to the veins.

The grade of gold and silver can vary from a few grams per tonne to significant intersections with grades in excess of 30 g/t Au (>1 oz/t). Gold mineralisation occurs as fine gold-silver amalgam with a gold to silver ratio of 1 to 1.5. The “Central Breccia” Deposit is interpreted as a gold-mineralised hydrothermal breccia with, low grade gold mineralisation is associated with carbonate breccia cement and high-grade gold mineralisation is associated with argillic alteration and sulphide mineralisation.

The open pit mining consist of four deposits: La India, America, Mestiza, and CBX.

The study envisages the development of a large open pit to exploit the La India deposit, which is planned to be approximately 1,275 m long, 475 m wide, with a maximum depth of 370 m. The main geotechnical challenge to the project is the variability in rockmass strength. Several large-scale structures exist in the pit area. Most of these are favourably orientated; however, a few structures are unfavourably orientated or positioned, and thus may affect the stability of some of the slopes.

SRK proposed the following slope geometry for all fresh rock slopes to be used when developing the engineered pit, to achieve the recommended inter-ramp angle:
• 20 m bench height;
• 75° bench face angle;
• 8 m berm width;
• 100 m maximum stack height;
• 30 m ramp/geotechnical berm width; and
• 56° inter-ramp angle.
The overall slope angle is therefore governed by the overall slope height and overburden thickness.

An overall slope angle of 40° has been assumed when developing optimised pits for America, Mestiza and CBZ.

All OP mines are expected to be conventional drill, blast, load and haul operations, with material hauled to the WRD, LG stockpile, or directly tipped at the crusher.

Two Mining Contractors, Espinoza Ingenioros S.A. and Explotec, were approached by the Client in 2019, to provide quotes for the potential mining operations. The Mining Contractors would be responsible for separate operational functions and therefore both would be required on site. The functions for Esina and Explotec include loading and hauling and drill and blast, respectively.

Approach and Parameters
SRK has developed an OP strategic schedule, optimising the extraction of La India, Mestiza, America and CBZ to maximize NPV on an annual basis. the OP schedule was developed in Maptek Evolution and Chronos. The mining sequence was optimised in Evolution to maximize NPV.
The key scheduling parameters and targets applied are listed below:
• a targeted mill feed rate of 1.225 Mtpa case A;
• a maximum sink rate of 60 m per year per pushback (12x5 m benches);
• mill feed set at 80% capacity for the first three months of year 1, ramping up to 100% thereafter;
• primary target was to maximize NPV by mining higher Au grades and low strip ratio areas first;
• secondary target was to balance the total material movement; and
• a single pre-stripping year included to allow the schedule to bring ore tonnes forward into year 1.

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Process Description
The process plant flowsheet includes unit operations that are standard to the industry, including: primary crushing, SAG, CIL cyanidation, carbon elution, electrowinning, refining and final tailings detoxification.

Pre-leach Thickening
Cyclone overflow will gravitate to the trash removal screen. The trash screen will remove any coarse ore particles, wood fragments, organic material, plastics, and lime slurry grits that could otherwise blind the inter-tank screens. The screen oversize (trash) will be collected in a bunker or bin, and the undersize (slurry) will gravitate to the high rate pre-leach thickener where it will be combined with flocculant in the feed well. Thickener underflow will be pumped to the CIL circuit, and thickener overflow will report to the process water tank.

Leach and Carbon Adsorption Circuit
The thickener underflow will be pumped to the leach distributor feed box passing through a two-stage cross-cut feed ........