PROJECT SPOTLIGHT: Antofagasta Minerals' Centinela expansion

Friday, March 10, 2017

After some 18 months, Chilean copper mining group Antofagasta Minerals managed to secure the environmental permit for the US$4.35bn expansion of its Centinela mine in northern Antofagasta region (II).

The project is poised to become one of the key assets for Antofagasta's future, as it will allow the company to extend operations as its northern district through 2056.

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While Los Pelambres, in Coquimbo region (IV), is the company's current flagship asset with production of 355,400t in 2016, at the end of last year it had 21 years of remaining mine life, compared to 42 years in the case of Centinela, according to the most recent company presentation.

Centinela's copper output in 2016 was 236,200t and if the project is given the final go-ahead, the expansion will increase production to 400,000t in the next decade, according to the company.

Centinela (pictured) was created in 2014, following the merger of the company's Esperanza and El Tesoro mines. Japan's Marubeni owns a 30% stake in the asset.


The project involves a two-stage expansion of the copper mine by developing two pits, Esperanza Sur and Encuentro, located south of the existing Esperanza pit.

In the first stage, the sulfide ore obtained at Esperanza Sur will feed a new 110,000t/d concentrator plant, while the oxide ore will be sent to the existing Centinela SX-EW plant.

Planned investment during this stage is estimated at US$2.7bn.

In stage two, with investment of US$1.65bn, the two new pits will be jointly mined, feeding the new concentrator plant at a rate of 180,000t/d, while also continuing to feed oxide material to the SX-EW plant.

During this stage, the expansion also envisions extending the life of the Encuentro Oxides project by mining the existing oxide ore for approximately nine years.

The project also includes additional infrastructure to address the region's arid conditions, including the continued use of direct seawater in its operations, as well as thickened tailings, for which a new tailings dam will be built.

To store seawater, stage one includes construction of a 140,000m3 pool, while a second, 210,000m3 pool will be added in stage two, putting on site capacity at 350,000m3 during the length of the project.

Two new water pipelines are also part of the project's water system. Stage one includes an 850l/s duct, while in stage two a 1,650l/s pipeline will be built, which in addition to supplying extra water to Centinela will replace the existing Esperanza pipeline.

At Antofagasta's Esperanza port facilities, a desalination plant will also be built, which will be used for the filtering of the copper concentrates, potable water at the port and other uses. The reverse osmosis plant will have capacity of 38l/s.


Antofagasta has said that this year it plans to focus on lowering the project's initial capex and maximizing the value of the mining district by integrating the new facilities into Centinela.

The earliest production start-up at the revamped Centinela is targeted for 2021.

The board of Antofagasta Minerals' controller, London-listed Antofagasta plc, is expected to make an investment decision in late 2017. The company is the mining arm of Chile's Luksic group.