The copper-gold sulphide mineralization found at the Candelaria Copper Mining Complex is generally referred to as iron oxide copper gold (IOCG) mineralization.

The sulphide mineralization occurs in breccias, stockwork veinlets, disseminations in andesite, and as an internal tuff unit. There are also some localized controls to mineralization in the form of faults, breccias, veins, and foliation. Candelaria has become an exploration model for Andean-type IOCG deposits that display close relationships to the plutonic complexes and broadly coeval fault systems. Depending on lithology and the structural setting, the polymetallic sulphide mineralization can occur as veins, hydrothermal breccias, replacement mantos, and calcic skarns. The Candelaria IOCG system lies within the thermal aureole of the Lower Cretaceous magmatic arc plutonic suite in the Candelaria-Punta del Cobre district.

The main mineralized body at the Candelaria mine is hosted in rocks of the Punta del Cobre Formation. Specifically, the host rocks are massive andesite and breccias of the lower andesite, and volcanic tuffs and volcaniclastic rocks at the base of the upper andesite. In the metasedimentary rock, the mineralization is confined to a few isolated layers (mantos).

The mineralized body is up to 400 metres thick in its central part and thins towards the edges. In east-west sections, the mineralization has a lenticular, downward concave shape with a steep eastern limb and a shallowly dipping western limb. The shape of the mineralized body in north-south section is irregular. In plan view, the extent of the mineralization is approximately 1,400 metres by 2,400 metres. The mineralized body was folded after its formation. The north-northeast-trending fold axis corresponds to the Tierra Amarilla anticline.

The mineralization assemblage in the Candelaria mine consists of chalcopyrite, magnetite, pyrite, pyrrhotite, and sphalerite. Biotite, calc-silicate minerals, and potassium feldspar constitute the gangue minerals. Pervasive potassic alteration is associated with the mineralization.

Chalcopyrite is the only primary copper sulphide present in the Santos mine. Additionally to copper mineralization, there are economic values of gold. Most frequent gangue minerals are pyrite, magnetite, actinolite, k-feldspar, chlorite, biotite and hematite.

In the Santos mine, three types of mineralized bodies are observed: veins, mantos, and breccia bodies. An important vein in the Santos mine is the Isabel, which is oriented northwest-striking, and extends over 1 kilometre in length and between 4 and 30 metres in width. Manto-type mineralization occurs as tabular bodies hosted in two sedimentary horizons located in the floor and roof of the albitophyre. The manto mineralization is characterized by variable iron contents with magnetite common in the north and deeper areas, and specular hematite in the south. Mineralization occurs within breccia bodies is typically contained with the albitoforo and lower andesite and is formed by steeply west-dipping and north-northwest- to northwest-striking bodies.

Mineralized bodies at the Alcaparrosa mine have a manto-type geometry that trend to the northeast and dip to the west. Ore and gangue mineralogy consists of chalcopyrite, pyrite, and magnetite, with trace pyrrhotite, molybdenite, and arsenopyrite.

Mineralization styles at the Alcaparrosa mine also occurs as veinlets defining dense stockwork, breccias (hydrothermal potassium feldspar and magnetite), as well as fine dissemination in biotite meta-andesites. High grade bodies are also found in massive veins striking north-northwest, north, and east.

Minera Candelaria consists of the Candelaria Open Pit and the Candelaria Underground mines. Minera Ojos del Salado consists of the Santos and Alcaparrosa underground mines. The Candelaria and the Minera Ojos del Salado facilities are close to each other.

The Candelaria Open Pit mine operates with an overall mining rate of approximately 310,000 tonnes per day over the next 10 years including an average of 45,000 tonnes per day of ore sent to the Candelaria processing plant together with substantial quantities of ore recovered from the WIP stockpiles. The average grade of the ore that will be mined from the open pit over the remaining life of mine (LOM) is estimated at 0.49 percent copper, while stockpiled work-in-progress material is estimated to have an average grade of 0.33 percent copper.

The Candelaria Underground mine is forecast to produce 9,000 tonnes per day of ore in 2018, ramping up to a steady state of 14,000 tonnes per day by 2021 as per the LOM plan. The average LOM grade is 0.85 percent copper. The Alcaparrosa mine currently produces 4,300 tonnes per day of ore and is expected to maintain that rate in the LOM plan. The LOM average grade is 0.79 percent copper. The Santos mine will continue to produce at its current rate of production of 5,200 tonnes per day of ore with an average LOM grade of 0.91 percent copper. The mining method in all three underground mines is sublevel open stoping.

The LOM plan for the Candelaria Copper Mining Complex is largely driven by supplying ore to the Candelaria processing plant from the Candelaria and Española open pit open pits although higher grade underground sources are of increasing importance. Surface WIP stockpiles are fed to the plant once the open pit Mineral Reserves have been depleted. The open pit and work-in-progress stockpile Proven and Probable Mineral Reserves are estimated at 499.9 million tonnes at an average grade of 0.45 percent copper, 0.11 gram of gold per tonne, and 1.47 grams per tonne silver.

The Candelaria open pit was designed to be mined in several phases of development. As of June 2018, five phases of development remain in the LOM plan (Phases 9 to 13). The overall strip ratio is expected to be 2.45:1 including ore that is initially delivered to stockpiles. The total in-pit waste is 939.6 million tonnes and the overall life of the open pit mine is 17 years.

For the Española project the total in-pit waste is 83.2 million tonnes and the overall life estimated in 7 years.

The three underground mines (Candelaria Underground, Santos, and Alcaparrosa) utilize a sublevel stoping mining method for ore extraction. This method is ideal for relatively large, vertical, as well as thick deposits with favourable and stable host rock. Stopes can typically be up to 180 metres high with sublevels at 20 to 60 metre intervals. The length of the stopes is generally 40 to 100 metres with widths varying between 20 to 30 metres. Stopes are drilled down from the sublevel drilling drifts as benches using 114 to 140 mm diameter down-the-hole holes. The holes are loaded and blasted in vertical slices towards an open face created by the slot blasting. The blasted ore gravitates to the bottom of the stope and is collected in draw points at the production level below. This lower level also consists of the haulage (transport) drift. The undercut levels, which feed the draw points, are 15 to 20 metres high and inclined at 50 to 60 degrees to allow the blasted ore to flow easily by gravity. An Epiroc Simba tophammer rig drills 64 mm up holes within the undercut, which are loaded and blasted with the downholes. Once the stope is mined, a remaining rib pillar, which can be another 20 to 30 metres wide, may be blasted into the stope to increase the extraction tonnage. Typically, a 20-metre structural pillar remains between each stope and no backfill is used at these operations. Mucked ore is dumped into 60 tonne underground trucks or 30 tonne highway type trucks (being replaced by the former trucks) and hauled up the ramp to a surface stockpile for subsequent re-handling and processing

Minera Candelaria
Run-of-mine ore is trucked to a primary gyratory crusher. The crushed product is transported using an overland conveyor belt to a coarse ore stockpile with a combined live and dead capacity of 500,000 tonnes. Semi-autogenous grinding (SAG) mills are followed by pebble crushing, with separate grinding of a portion of the crushed pebbles and the remainder brought back to the SAG mills. This circuit is followed by closed-circuit ball milling with hydrocyclones to classify the flotation feed size.

Minera Ojos del Salado
The concentrator flowsheet comprises a closed-circuit crushing plant including a primary jaw crusher (48 by 60 inches), a secondary cone crusher and two tertiary cone crushers.

The grinding plant has three ball mills (one 9 by 9 feet and two 10.5 by 13 feet) operating in parallel and in closed-circuit with hydrocyclones.

The Candelaria processing plant receives ore from the Candelaria Open Pit and the Candelaria Underground (North Sector) and Alcaparrosa underground mines. It has a nameplate capacity of 75,000 tonnes per day. The Pedro Aguirre Cerda (PAC) processing plant receives ore from the Santos underground mine and has a design capacity of 3,800 tonnes per day.

The Candelaria processing plant flowsheet is conventional, comprising two parallel process lines for grinding and flotation, reclaimed process water from a conventional tailings dam, final concentrate filtration, and shipping of bulk copper concentrates. Run of mine ore is trucked to a primary gyratory crusher. Grinding takes place in a multi-stage closed circuit using semi- autogenous grinding (SAG) mills, ball mills, and pebble crushing. A multi-stage flotation circuit using an arrangement of mechanical cells, regrind mills and column cells produces copper concentrate. Final flotation copper concentrate with gold and silver by ........