The mineralization at El Peñón is hosted by gently southeast dipping Eocene to Paleocene basaltic to rhyolitic volcanic rocks. The stratigraphic sequence consists of a lower sequence of volcanic breccia and andesitic to basaltic flows, overlain by rhyolitic to dacitic pyroclastic rocks, dacitic to andesitic flows, and volcanic breccia.

Mineralization is hosted largely by rhyolitic intrusives, domes, and associated flows that are intercalated with the other volcanic units. The distribution of Cretaceous and Eocene volcanic rocks is controlled by graben structures bounded by north and northeast trending faults. These are steeply dipping regional-scale structures with displacements in the order of hundreds to thousands of metres.

The principal direction for late dikes and many of the highest grade mineralized faults is parallel to the bounding faults. Mineralized faults dip steeply eastward on the east side of the property and westward on the west side, in a fashion implying a horst/graben extensional structure. Most of the mining takes place along north-trending veins. A minor but significant component of production has taken place along secondary northeast and northwest striking structures.

The deposits at El Peñón are low to intermediate epithermal gold-silver deposits, hosted in steeply dipping fault-controlled veins. Gold and silver mineralization consists of disseminated electrum, native gold, native silver, silver sulphosalts, and silver halides occurring in a gangue of predominantly quartz, adularia, carbonate, and clay.

Electrum is the most common form of precious metals in the deposit and occurs as micron to millimetre-size subrounded and irregular grains. Two phases of electrum are present: a primary phase, which contains approximately 55% to 65% gold, and a secondary phase, which has resulted from supergene processes that have remobilized silver and which typically consist of over 95% gold.

Sulphide minerals are relatively rare, and this may be due to oxidation, or to an initial low overall abundance such as would occur in a low sulphidation environment. Abundant iron and manganese oxyhydroxides are common with only trace occurrences of relict sulphides. In order of abundance, trace amounts of pyrite, galena, sphalerite, chalcocite, and covellite can be present. Silver sulphosalts are also common in the sulphide zone.

Gangue minerals comprise fracture and breccia-filling and replacement quartz, adularia, carbonates, and clay minerals. Vein textures often display crustiform textures, although the highest grade gold-silver mineralization is reported to be associated with massive banded quartz-adularia. Gangue minerals occur as open space filling as well as replacements of primary host rock mineral phases.

There are thirteen main vein zones and many subsidiary veins in nine vein systems that have supported, support currently, or are planned to support surface and underground mining operations. The veins strike predominantly north-south and dip steeply to the east and west. North-northeast to northeast-striking fault zones are also host to mineralized zones, and there are numerous secondary veins striking northeast and northwest, the relative proportion of the overall deposit is small.

The deposit comprises several individual tabular, steeply dipping zones or shoots that are amenable to mining by both underground and surface methods. Vein widths range from decimetre-scale to over 20 metres.

Individual mineralized shoots measure from less than one kilometre to four kilometres in strike length, and up to 350 metres in the down-dip direction. Gold grades range up to hundreds of grams per tonne but are more typically less than 30 grams per tonne. Silver grades are in the order of hundreds to thousands of grams per tonne.

The primary mining method is an underground bench and fill method and all access to the veins is by ramps and crosscuts. Main veins are separated by a distance of 100 metres to 500 metres. The application of this method will vary between veins, but it is usually applied to sublevels spaced between 10 metres and 20 metres.

A top access drift is driven for drilling, and a bottom access drift is driven for ore extraction. Depending on the vein width, the access drift dimensions are generally 3.5 metres wide by 4.0 metres high. Both the drill access drift and the lower ore extraction drift are grade-control sampled every drill, blast, load and haul cycle.

Stope width varies from 1 metre to 6 metres, depending of the width of the vein, and level spacing varies between 10 metres and 20 metres, depending on vein geometry and geotechnical conditions. Typically, open stope spans of 30 to 45 metres along strike can be achieved before backfilling.

To reduce dilution during drift development a resueing (split blasting) mining method is applied. Resue mining consists of mining the ore first in a drift and then slashing the remaining waste. Once the drifts are established and the required ground control support is applied, the production stoping of the ore body commences.

Backfilling is performed after the stope is mined out. El Peñón has employed open pit mining contractors in the past and is currently operating the Chiquilla Chica open pit, located to the south west of the core mine. There are no further significant open pits planned for the El Peñón veins, but small tonnages of near-surface, lower-grade material may be mined in the future to provide additional mill feed.

All underground mining drift, cross cut, and stope areas are first approved by El Peñón geotechnical staff before any full scale production commences. Monitoring of the production stopes and development areas is also performed by the geotechnical staff. Typical ground support includes, but is not limited to, split-set bolts, resin bolts, wire mesh and shotcrete.

The lower throughput provides the optionality to operate with one or two grinding mills, maximizing throughput when called by the mine plan. In 2019, the plant processed an average of 3,535 tpd.

ROM ore is dumped from a 7.0 m3 capacity front-end loader (CAT 988H) through a 600 mm square-grid grizzly into 100 t capacity hopper. A 1,500 mm wide apron feeder is used to transfer ore from the dump hopper to the jaw crusher. Fine material is collected and transported directly to the conveyor belt that carries primary crushed material. Coarse material is fed into a 950 mm x 1,250 mm jaw crusher that produces a product with P80 of 63.5 mm. Crushed material is transported by a conveyor belt into a 1,500 t capacity bin. Additionally, an auxiliary crushing product stockpile is located to the northwest of the bin. The stockpile has a capacity of 10,800 t and covers an area of approximately 40 m x 60 m.

The ore stored in the bin is transported by a variable speed 250 tonnes per hour (tph) capacity mill feed conveyor belt to a transfer chute that discharges onto the belt that feeds the semi-autogenous grinding (SAG) mill. Pebbles from the SAG mill are crushed in a pebble crusher. Cyanide solution and lime are added in the grinding circuit. The grinding mills are in closed circuit with hydrocyclones.

The El Peñón processing plant has been modified with the potential to increase production capacity to approximately 4,350 tpd of stockpiled and mined ore, or 1.59 million tonnes per year. Yamana has accomplished this by steadily increasing throughput through the addition of new equipment to the process plant. However, in the context of the rightsizing plan that took place in late 2016 and was put into operation in 2017, Yamana does not use the full treatment capacity of the plant and instead the focus has changed to take advantage of the increased residence time to improve recoveries for both gold and silver and reduce operating costs.

The grinding thickener underflow is leached in six mechanically agitated reactors, with a capacity of 7,279 m3, in a cyanide rich environment maintained by the addition of cyanide in the grinding and leaching steps. Oxygen is also added to favor the dissolution kinetics. The oxygen is homogenized with the pulp through recirculation pumps th ........