According to Pearson and Speirs (2009), the La Libertad vein system is classified as a low sulphidation epithermal system. WSP has also classified the Pavón vein system as a low sulphidation epithermal system.

Gold mineralization at La Libertad is contained within vein sets along the parallel Mojón-Crimea and Santa Mariá-Esmeralda trends, which are separated by approximately 500 m. The MojónCrimea Trend is nearly 4 km long, strikes 65°, and dips on average 80° to the southeast. The down-dip dimension is commonly in the order of 200 m to 250 m. The massive quartz veins and adjacent stockwork/stringer zones range in width from 2.0 m to 70 m for an average of 15 m, often narrowing at depth. The Santa Mariá-Esmeralda Trend is discontinuous, with the Santa Mariá and Esmeralda veins separated by approximately 1,000 m. The Santa Mariá vein averages 10 m wide and is approximately 450 m long. The Esmeralda Vein has been mined out. Additional mineralization is contained within previously mined material that has been crushed and partly processed by heap leach methods.

MOJÓN
The Mojón trend forms a braided stockwork system trending 63° and dipping sub-vertically 75° to 90° to the south-southeast. Stockwork/vein zones average 22 m in width, with a range from five metres to 40 m. Numerous hanging wall splays are present that are generally narrower and less continuous than the main zone. They are oriented at 75° and have vertical to slightly north-northwest dips. Gold grades in the stockwork zones are generally 0.1 g/t Au to 0.5 g/t Au with occasional spikey values.

Massive veins/vein breccias within the stockwork envelopes have an average true width of about nine metres with a range of one metre to 20 m. Higher gold grades are associated with vuggy, drusy, and banded quartz veins. Pyrite (and its oxidized products) is closely related to gold mineralization but is present in small volumes, generally less than 1%.

Host rocks are moderately altered immediately adjacent to the stockwork and veining zones. Alteration types are typically silica and argillic with minor amounts of propylitic. Surface saprolite alteration is developed to a depth of approximately 15 m to 20 m.

JABALÍ AREA
The Jabalí low sulphidation epithermal quartz adularia vein system is hosted in a thick sequence of andesitic flows believed to be part of the Lower Coyol Group. The group consists of individual, feldspar porphyritic andesitic flows ranging in thickness from two metres to five metres to much larger flows 22 m to 50 m in thickness. Lapilli-tuff and occasionally ash tuff beds of variable thickness separate the flows.

The east-west trending Jabalí vein system has been traced on surface over a distance of more than 6 km. To date, ongoing diamond drilling has tested more than 3,950 m of the Jabalí vein system. The vein system dips to the north, varying from 60° to 80° north.

The andesite flows host the epithermal quartz veins, quartz stockworks, quartz breccia, and massive to banded quartz veins along the east-west trending mineralized structure.

Alteration associated with the deposits is typical of a low sulphidation epithermal quartz adularia vein system. Fracture-controlled quartz veining and silicification is surrounded by argillic and propylitic alteration zones within the andesite host rock.

Quartz veins consist of milky white to light grey quartz with minor amounts of adularia. Epithermal textures comprise crustiform and colloform banding, vuggy and drusy quartz, cockscomb, and bladed silica pseudomorphs after low temperature calcite.

SAN JUAN
The San Juan zone is a low sulphidation epithermal vein and stockwork system hosted by subhorizontal andesitic volcanic and volcaniclastic rocks.

The San Juan trend forms a vein and stockwork system trending at 140° and dipping subvertically 80° to 90° to the north-northwest. Stockwork zones average 12 m wide, with a range from 10 m to 20 m. Gold grades in the stockwork zones are generally from 0.1 g/t Au to 0.5 g/t Au with occasional spikey values.

Massive veins/vein breccias within the stockwork envelopes have an average true width of approximately three metres with a range of one metre to 11 m. Higher gold grades are associated with vuggy, drusy, and banded quartz veins.

Surface saprolite alteration is developed to a depth of approximately 15 m to 20 m.

LOS ANGELES
The Los Angeles vein is a low-sulphidation epithermal breccia and stockwork system.

The mineralized structure strikes at 240° and dips steeply to the north at approximately 75° to 85°. The mineralized portion is confirmed over at least 400 m and is open along strike. The zones are also open down dip. The deepest current intersection is well mineralized at 120 m vertical from surface. The stockwork zone varies from three metres to 12 m thick, while the higher-grade breccias are 1.5 m to 3.5 m thick.

The best gold grades are associated with hydrothermal breccia, quartz breccia, and wall rock breccia with >25% veins and veinlets and banded texture with fine black sulphides.

Surface saprolite alteration is developed to a depth of approximately 25 m from surface.

The Los Angeles vein was previously mined and, although the highest-grade portions of the vein are likely mined out, significant remnants in the hanging wall and footwall still contain mineralization. Drilling and long sections of historic mining confirm that there is no previous mining greater than 40 m to 50 m from surface.

Open Pit Operations
Calibre has four open pit mines currently in operation or that are planned to be within the next two years. Jabalí Antena and San Antonio are situated at La Libertad and Pavón North and Pavón Central are located at Pavón with material being trucked to the La Libertad plant.

JABALÍ ANTENA
Jabalí Antena is an existing open pit gold mine with over 351,000 t of Mineral Resources remaining as of June 2020, and over 2.7 Mt of waste to be mined. The mill feed material haul route is approximately 15 km to the existing processing plant at La Libertad, located southwest of Jabalí Antena. Mining at Jabalí Antena is currently conducted using a conventional open pit mining contractor with a total mining production schedule of 1.4 Mtpa in 2023 for Phase 2 (East Extension). RPAhas completed the mine planning of the Jabalí Antena open pit mine based on Calibre’s current pit design.The Jabalí Antena open pit was designed to be executed in two phases, Phase 1 to be completed in 2020, and Phase 2 (East Extension) to begin in 2023. The East Extension design was limited and scheduled based on a local community permitting requirement.

SAN ANTONIO
The San Antonio Project is envisioned to be an open pit with over 379,000 t of Mineral Resources as of June 2020, with over 7.4 Mt of associated waste to be mined. The haul route is approximately 8.0 km to the existing processing plant at La Libertad, northeast of the San Antonio Project.Mining will be conducted using conventional open pit mining contractor with a total mining production schedule 5.1 Mtpa in 2021, and 2.7 Mtpa in 2022. RPA has completed the open pit optimization analysis, open pit mine design, and LOM plan for the San Antonio Project.The San Antonio Project open pit design includes two phases, allowing for the balance of waste mining over the two year PEA production schedule.

Underground Operations
Calibre has four underground mines that are either in operation or will be within the next six months. Jabalí West UG is situated at La Libertad, while Santa Pancha 1, Panteón, and Veta Nueva are located at El Limón.

Jabalí West UG is located beneath the current Jabalí Antena open pit and mines the deeper extension of the same orebody. Operations at Jabalí West UG were suspended for six months while technical and community issues were being dealt with. Mining resumed in June 2020.

Santa Pancha 1 has been producing for the El Limón process plant since 2015. It is situated adjacent to Santa Pancha 2, which shut down in 2019 due to exhaustion of the deposit. Panteón is located immediately to the west of Santa Pancha 1 and was previously mined, however, has been shut down for many years. Calibre plans to mine the deeper mineralization at Panteón by accessing the deposit from an underground level in Santa Pancha 1. Veta Nueva is a new mine that is still under development. It is situated beneath an exhausted open pit with the same name and mines the deeper extension of the same orebody.

JABALÍ WEST UG
The Jabalí West UG deposit is the site of an operating underground mine that produced 111,232 t of mineralized material grading 3.93 g/t in 2019. Its blasting and mining activities were suspended in September 2019 due to surface instability caused by illegal artisanal mining, however, operations have since resumed in August 2020.

Calibre’s underground mines use two types of sublevel-stoping mining methods: longitudinal longhole open stoping and Avoca. The latter one is sometimes referred to as longitudinal retreat longhole stoping. The two methods are similar; their main difference being the timing for placing the backfill. With both methods, the stopes at Calibre’s mines extend the vein's complete length without leaving pillars along strike. Longitudinal longhole open stoping and Avoca are bottom-up mining methods that are suitable for steeply dipping vein-type orebodies.

With both methods, the vein between two sublevels is mined by drilling and blasting longholes in benches. The production drift in the lower sublevel is referred to as the undercut. The one in the upper sublevel is called the overcut. The area is mined in a retreating fashion. The benching initiates at both ends of the stope, and the bench faces advance towards the middle of the vein.

The benching at each end of the vein is initiated by drilling and blasting a slot. The slot is a raise extending between the undercut and the overcut. It provides a void for blasting the first bench. With the subsequent blasts, the bench face retreats towards the middle of the stope. At Calibre’s mines, the longholes for benching are drilled as up-holes from the undercut. Calibre prefers up-holes because gravity helps clear the holes of cuttings and rock fragments, which reduces incidences of stuck rods. Figure 16-16 illustrates a typical longhole drilling pattern from one of Calibre’s mines.

Following each bench blast, the broken material is mucked by a load, haul, dump unit (LHD) from the undercut. A portion of the blasted material can be mucked with the operator seated on the LHD, however, when the machine passes a certain distance beyond the undercut’s brow, it must be operated by remote control. When the LHD takes a bucket of broken material, it hauls it out of the stope and dumps it in a remuck bay or loads it onto a truck.

The stopes are backfilled with rockfill that is either development waste or comes from the open-pit waste stockpile. While some mines use cemented rockfill for specific applications, Calibre’s underground mines only use unconsolidated rockfill. An LHD hauls the rockfill into the stope via a crosscut in the upper sublevel and dumps its load into the open part of the stope.

With Avoca, backfilling is an integral part of the production cycle and is conducted more or less in parallel with other stoping operations. With longitudinal longhole open stoping, on the other hand, backfilling is delayed. The rockfill is placed as a separated operation after the stope has been mined out. Depending on the level design, the rockfill can be transported to the stope in two ways. It can be delivered via a central crosscut or, if the sublevel has a footwall drive, via a crosscut at either end of the stope.

Single-stage crushing with two jaw crushers capable of processing approximately 400 tonnes per hour (tph) and 200 tph, one utilized for ROM material and the other for spent heap material, followed by a crushed material stockpile.

Two-stage grinding to 70% passing (P70) 75 µm utilizing a conventional SABC (semi-autogenous grinding (SAG) followed by ball milling and pebble crushing) circuit. The grinding circuit consists of one SAG mill followed by two ball mills operating in parallel and an integrated pebble crushing circuit; the SAG and ball mills are 20 ft x 9 ft and 13 ft x 20 ft, respectively, each with a 1,680 kW motor.

The La Libertad processing plant can treat approximately 2.25 Mtpa, and current gold recoveries are approximately 94% to 95% for a blend of spent and run of mine (ROM) mill feed from the adjacent La Libertad mines.

The processing plant consists of the following unit operations:

• Single-stage crushing with two jaw crushers, followed by a crushed material stockpile.

• Two-stage grinding to 70% passing (P70) 75 µm utilizing a conventional SABC (semi-autogenous grinding (SAG) followed by ball milling and pebble crushing) circuit.

• Pre-leach thickening to 45% solids, followed by leaching in 11 leach tanks (4 x 1,500 m3and 7 x 570 m3) with oxygen addition for a total of 32 hours residence time. Carbon adsorption is carried out in six 550 m3 Carbon in Pulp (CIP) tanks.

• Tailings disposal by pumping to the lined La Esperanza tailings storage facility (TSF). The current TSF reportedly has remaining capacity for the disposal of current ........