The Candelaria Copper Mining Complex is a combined open-pit and underground mining operation located in the Atacama region of Chile. The project is under shared ownership between Lundin Mining (80%) and Sumitomo (20%).
Lundin Mining announced an 18% and a 3% increase in mineral resource and reserve estimates for the combined operation in September 2020.
The Candelaria copper mine complex comprises the Candelaria open pit and two adjacent underground mines namely, Santos and Alcaparrosa at Ojos del Salado.
The Candelaria copper mines produced 146,330 tonnes (t) of copper and 88,000 ounces (oz) of gold in 2019, while the production during the first half of 2020 included 35,060t of copper and 21,000oz of gold.
The Santos underground mine has been in production since 1929, while Phelps Dodge Corporation became the sole owner of the property in 1985 and commissioned the nearby Alcaparrosa underground mine in 1996.
The adjacent Candelaria open-pit mine that commenced production in early 1995 was discovered by Phelps Dodge in 1987. A feasibility study to develop the sulphide deposit was completed in 1990 followed by the start of construction works in 1992.
Sumitomo acquired a 20% stake in the mine in the same year. Ownership changed again with Freeport-McMoRan acquiring Phelps Dodge in 2007. Further, Lundin acquired Freeport’s interest in the Candelaria Copper Mining Complex in November 2014.
Location, geology and mineralisation
The Candelaria and the Ojos del Salado deposits are located adjacent to the Tierra Amarilla community in Region III of Chile’s Atacama Region, approximately 20km south of the city of Copiapó.
The polymetallic sulphide deposits of the Candelaria, Santos, and Alcaparrosa mines are hosted in volcanic rocks of the Punta del Cobre mining district.
The Candelaria mine is mainly comprised of the Punta del Cobre and Abundancia Formations which consists of fine-grained biotite, silica, or clinopyroxene-bearing calcareous metasandstone and mudstones.
The Santos mine is also dominated by the rocks of the Punta del Cobre and Abundancia Formations with porphyritic to aphanitic andesite of the Lower Andesite forming the basis of the lowermost rocks which are of the Punta del Cobre formation.
The Alcaparrosa mine is dominated by the Punta del Cobre Formation and is subdivided into a Lower Andesite unit, succeeded by volcanoclastic breccias, albitophyre and pyroxene- scapolite hornfels interbedded with garnetites.
Mineralisation and reserves
The mineralisation at the Candelaria Copper Mining Complex is characterised as iron oxide copper-gold (IOCG) mineralisation occurring in breccias, stockwork veinlets, disseminations in andesite, and as an internal tuff unit.
Excluding stockpiles, the Candelaria open-pit was estimated to hold 381.1 million tonnes (Mt) of proven and probable mineral reserves grading 0.49% copper 0.11g/t gold and 1.5g/t silver as of September 2020.
The total proven and probable ore reserves at the underground mines were estimated to be 160.2Mt at 0.83% copper, 0.19g/t gold, and 2.9g/t silver.
The Candelaria open-pit with a mine life of 17 years is planned to be mined in five phases with an overall strip ratio of 2.45:1.
The open-pit mine is operated with an overall extraction rate of 270,000 tonnes per day (tpd). The mining fleet comprises seven electric shovels, 43 haulage trucks, eight production drills, apart from a fleet of support equipment.
The underground mining operations are carried out using the sub-level open stoping method.
The Candelaria processing plant has a nameplate capacity of 75,000tpd and receives ore from the open-pit and as well as the Alcaparrosa underground mine, while ore from the Santos underground mine is treated at the Pedro Aguirre Cerda (PAC) processing plant which has a capacity of 3,800tpd.
The Candelaria processing plant comprises two parallel grinding and flotation process lines and utilises reclaimed process water from a conventional tailings dam.
The run-of-the-mine (ROM) ore is crushed in a primary gyratory crusher and passed on to the multi-stage closed circuit grinding process using semi-autogenous grinding (SAG) mills, ball mills, and pebble crushing. The multi-stage flotation circuit includes mechanical cells, regrind mills and column cells to produce the final copper concentrate.
The final flotation copper concentrate containing gold and silver by-products is thickened, filtered, and stored on-site for export.
The PAC processing plant has which has been operating since 1929 comprises of a closed-circuit crushing plant housing a primary jaw crusher, a secondary cone crusher, and two tertiary cone crushers.
The grinding circuit comprises three ball mills while the flotation circuit utilises conventional, multi-staged, mechanical flotation cells, and regrind milling. The obtained concentrate is cleaned in column cells and is then thickened and filtered for the production of saleable concentrate product.
The copper concentrates processed at the Candelaria and PAC processing plants are trucked to the Punta Padrones port, near Caldera for shipping.
The Candelaria mining properties are accessible via two maintained dirt roads with one passing through the Tierra Amarilla community while the other branches off from Route 5 of the Pan-American Highway.
The Candelaria Copper Mining Complex, port facilities and the desalination plant are supplied with electricity by AES Gener, a Santiago based power producer and distributor, under a contract signed in July 2012.
The Punta Padrones port facilities located at Caldera has been operational since 1995. It comprises of a covered 45,000 wet metric tonnes concentrate warehouse and a 1000 wet metric tonnes telescopic ship loader.
A 500 litres per second desalination plant was commissioned at the Punta Padrones port site in 2013 which started at an initial operating capacity of 300 litres per second. It pumps water over 110km to the mine site via a dedicated pipeline and a booster pump station.
Züblin International of the STRABAG group has been providing mining services for the Candelaria complex since 2005. Lundin extended the mining contract for four years in January 2019.
SRK Consulting prepared a technical report for the Candelaria Mining Complex in November 2018.