Cuajone copper mine is located in the Moquegua region of Peru near the Andes mountain range, which is the largest continental mountain range in the world.

The mine is owned and operated by Southern Peru Copper Corporation (SCC), a Mexico-based mining company and subsidiary of Groupo Mexico. SCC also owns and operates the Toquepala copper mine, which is located 30km from Cuajone.

Construction work began at the mining site began in 1975, while mining by open pit methods commenced in 1976.

Cuajone copper mine location and site details

The Cuajone mine is located 30km north-east of the city of Moquega in the southern-most region of the Andes mountains range of Peru. The mine can be accessed through a highway from Moquega.

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Geology and mineralisation

The Cuajone deposit occurs in the western flank of Cordillera Occidental. The mine deposits are dated approximately 60 to 100 million years. The mine lithology contains volcanic rocks from the Cretaceous to the Quaternary period.

The copper mineralisation at Cuajone is typical porphyry copper deposits. There are 50 types of unique rocks found in the area that includes pre-mineral rocks, basaltic andesite, porphyritic rhyolite, Toquepala dolerite, Toquepala rhyolite and intrusive rocks.

The deposit is mainly composed of minerals such as chalcopyrite, chalcosine and molybdenite in addition to galena, enargite and tetraedrite.

Cuajone reserves

Cuajone is estimated to hold proven and probable reserves of 1.6Mt grading 0.497 % Cu and 0.018% Mo.

Mining at Cuajone copper mine

Mining at Cuajone mine is carried out using open-pit methods. The current Cuajone pit extends up to a depth of 950m-1,290m and is expected to reach a depth of 1,380m presenting geotechnical challenges.

SCC has adopted various measures to handle these challenges including a wall depressurisation programme, a blasting control programme and slope monitoring system. The company also carried out slope stability studies to calibrate rock mass properties and identify slope behaviour. Recommendations from the studies were implemented including slope angle reduction.

Ore processing

Mined material with a copper grade of more than 0.35% is sent to the milling circuit through an overland conveyor belt. The material is crushed to a size of 0.5in in the circuit by giant rotating crushers. The crushed ore is then sent to the ball mills where it is ground to a fine powder.

The finely ground powder is mixed with water and reagents solution and sent to flotation cells to produce copper and molybdenum concentrate, which is then treated by inverse flotation to separate copper and molybdenum.

The copper concentrate is transported by rail to the smelter located at Ilo, while the molybdenum concentrate is packaged for shipment to customers.

Cuajone copper mine infrastructure

Cuajone is well connected with a 100km long railway track including five tunnels and a 145km long road network. This allows the procurement of materials and export of finished products.

Water for the mine operations is procured from well fields at the Huaitire, Vizcachas and Titijones aquifers. SSC also holds surface water rights from the Suches Lake as well as the Quebrada Honda and Quebrada Tacalaya water courses.

The electricity needs are fulfilled by two hydro stations at the base of the Lake Suche and the 66MW Ilo thermal power plant.

Employees are accommodated in town sites, where SCC has built 3,700 houses and apartments.

Contractors

The engineering, procurement and construction (EPC) contract for the copper mine and smelter was awarded to Fluor in April 1975. Flour Daniel, a subsidiary of Fluor, was awarded another contract in 1997 for the expansion of the copper concentrator.

Abengoa was contracted in November 2019 to build a retention dam with a capacity of 40,000m3. The company is responsible for excavation, fillings, compactions, surface preparation and concrete works of the containment dam, as well as hydraulic works.

CiDRA Minerals Processing installed its SONARtrac flow meter system on a reclaimed water line at the mine.

SRK Chile performed the slope design study for the open pit.

ThyssenKrupp supplied crushing and overland conveyor systems to replace an existing railway system in 2016.

Siemens was subcontracted by ThyssenKrupp to supply gearless conveyor drive system for the project.