The Antamina Mine is nested at more than 4,300 m altitude in the Antamina valley in the Andes Mountains of north-central Peru. It is located in the department of Ancash some 270 km north-east of Lima.
The deposit is one of the largest copper-zinc ore bodies in the world. Antamina employs 1,850 people directly and 3,350 indirectly.
The US$2.2 billion construction program was one of the largest new mine development projects ever undertaken. In order to reach the mineral deposits, tops of several mountains had to be removed and a lagoon drained. It took four years of work.
It is an open pit truck/shovel mine, currently 2,000 meters long, 1,000 meters wide and 500 meters deep. Roads, a pipeline and the port had to be developed. Antamina mine operations began in late 2001 with an estimated mine life of more than 20 years.
The mill has a rated capacity of 70,000 tonnes per day. A 302 km long slurry concentrate pipeline transports concentrates to the port facility. The operations produce separate copper, zinc, lead and molybdenum concentrates.
In 2004 productivity increased as a result of a comprehensive employee training program as employees gained operating experience at this relatively new mine. The number of expatriates declined from 66 to 28 and further reductions are expected.
In 2008, following a 77% increase in mineral reserves, Antamina was evaluating expansion alternatives with expanded production capacity of around 30 percent indicated from a pre-feasibility study.
In 2010 announced that a major expansion is expected to increase ore throughput by approximately 38% to 130,000 tonnes per day, and annual production of copper and zinc by approximately 30% on completion in late 2011.
Copper concentrates produced at Antamina are transported by a slurry pipeline to a port at Huarmey, Peru and from there by ship to customers in Asia and Europe.
Antamina is located in the Andes, in north central Peru. It is situated in the Western Cordillera range at an altitude of 4,300m. By road it is about 485km north of Lima.
The mine site is about 12 kilometers east of the town of San Marcos, about one hour trip by car, and over 1500m high in elevation. The Antamina mine, mill, and related support facilities are located at an elevation between 3500m and 4500m in the Andes, in the headwaters of two small streams which are tributaries of Rio Pucha, which is part of the upper Amazon Basin. A highway has been built to the port near Huarmey.
The mine is very close to the Huascaran National Park, which is 340,000 hectares in size and a biosphere reserve and Natural World Heritage Site. El Huascaran, which is in the park, is the highest peak in Peru at 6,768m. The park is popular with mountaineers and there is a well developed system of trekking and mountaineering routes.
The mean annual temperature of the area is about 3°C, with a minimum of -30°C. Mean annual precipitation is approximately 884mm (recorded at 3,980m), is mainly between October and May. Topography ranges from humid forest in the valleys and alpine fluvial tundra to very wet sub-alpine formations at higher levels.
Peru has 1,804 species of birds, more bird species than found in all of North America and Europe combined. Tourism in the area centers around trekking, archeology, and birding.
The Antamina deposit is the largest known copper-zinc skarn in the world with zinc, silver, lead, molybdenum and bismuth mineralisation. It has a southwest to northeast strike length of more than 2 500 metres and a width of up to 1 000 metres. The deposit sits at the bottom of a U-shaped glacial valley surrounded by limestone ridges.
The Antamina polymetallic deposit is skarn hosted. It is unusual in its persistent mineralization and predictable zonation, and has a SW-NE strike length of more than 2,500 metres and a width of up to 1,000 metres. The deposit is located mainly between elevation 4,350 and 3,790 metres, but outcrops up to elevation 4,650 metres. The deepest drill hole, which terminated at 3,632 metres elevation, was still in mineralized skarn.
The skarn is well zoned symmetrically on either side of the central intrusion with the zoning used as the basis for four major subdivisions being a brown garnet skarn, green garnet skarn, wollastonite/diopside/green garnet skarn and a marbleized limestone with veins or mantos of wollastonite. Other types of skarn, including the massive sulphides, massive magnetite, and chlorite skarn, represent the remainder of the skarn and are randomly distributed throughout the deposit.
The deposit formed at approximately 10 Ma by the emplacement of quartz monzonitedeposit model intrusions into Mid to Late Cretaceous limestones of the Celendin and Jumasha Formations. Mineralisation is hosted as a series of zoned green and brown garnet endoskarns and exoskarns, in the form of chalcopyrite, bornite and sphalerite. Economically recoverable metals are Cu, Zn, Mo, Ag, Bi, and Pb.
Mining & Operation
The mine is an open pit, truck/shovel operation. The ore is crushed within the pit and conveyed through a 2.7 kilometre tunnel to a coarse ore stockpile at the mill. It is then processed utilizing a SAG mill, followed by ball mill grinding and flotation to produce separate copper, zinc, molybdenum and lead/bismuth concentrates. A 302 kilometre-long slurry concentrate pipeline, approximately 22 centimetres in diameter with a single pump station at the minesite, transports copper and zinc concentrates to the port where they are dewatered and stored prior to loading onto vessels for shipment to smelters and refineries world-wide.
The main challenge of drilling and blasting is to obtain optimally fractured material. Once the material is fractured, the loading process begin. Fractured material is sent on a conveyer belt through a 2.6 km tunnel that crosses the mountain between Antamina and Yanacancha canyons. Material is stockpiled by ore type.
Crushing is done by a single 60" x 89" gyratory crusher which has an average capacity of 80,000 tons a day. Huge blocks of ore are reduced to 5-inch blocks suitable for the concentrator plant.
Ore at Antamina is of two general types: copper ores producing copper and molybdenum concentrates, and copper zinc ores producing copper and zinc concentrates. Proven reserves include stockpiled material which is expected to be processed later in the life of the mine.
The operations produce separate copper, zinc, lead and molybdenum concentrates. Long-term concentrate sales contracts have been entered into with smelters and refineries in Japan, Canada, Australia, Germany, Korea and Spain.
The mine is expected to produce an average of 675 million pounds of copper and 625 million pounds of zinc annually over its first 10 years of production, and will have an operative life of 19 years.
The ore deposit is comprised of six distinct ore types, classified by their elemental content and grindability. As a result, Antamina process the various ore types through specific campaigns of differing lengths. The overall operation consists of four plants: grinding, copper flotation, zinc flotation and bismuth/molybdenum flotation. The zinc and bismuth/molybdenum plants operate only when the ore type justifies it. Specific reagent schemes were developed in the pilot plant to optimize the metallurgical performance of each ore type.
The Antamina Concentrator processes six ore types using conventional grinding and differential flotation techniques: two copper-only ores with varying levels of bismuth and molybdenum; two copper and zinc ores, again with varying levels of bismuth and molybdenum; and two bornite ores with varying levels of zinc.
Processing is conventional grinding in a 38 foot semi-autogenous grinding (SAG) mill and three 24 foot diameter ball mills and flotation to produce concentrates. The ore is batch treated by ore type through a conventional grinding and flotation mill with a nominal design capacity of 70 000 tonnes a day.
The concentrator is capable of processing 70,000 tonne per day at an operating availability of 90% for all ore types. Six concentrates are produced; three copper concentrates (2 chalcopyrite copper concentrates containing a low or a high bismuth content, and a bornite copper concentrate), a zinc concentrate and to a much lesser extent, a molybdenum concentrate and a bismuth-lead concentrate.
Each ore type is tracked separately, as well as on an overall production basis. Performance evaluation and accounting are performed and made available on a campaign basis as well as on a daily, month-to-date and year-to-date basis. Metallurgical reports are generated automatically.
The operative life of the mill was estimated to extend to 2028.
The tailings dam is the highest in the world (135 m for now) and has the capacity to store 550 million tons of sterile material or 330 cubic meters during the mine's operative life. Built in the Huincush Canyon, the dam has an interior reinforced concrete plate that is also protected with high-density geo membranes to avoid any possible leaks. Drainage tunnels and rainwater collection channels complement this state-of- the-art operation that guarantees environmental protection and structural stability. In the second phase the tailngs dam will reach 165 meters and in the third and final phase, it will be 250 meters high and 750 meters long. Its resistance is 0.48 Gp or maximum credible earthquake. It was designed by Golder Associates Ltd.
A 300-kilometre underground pipeline transports copper and zinc slurry concentrates to the port of Punta Lobitos, where they are dewatered, stockpiled, and shipped by sea. The pipeline includes a parallel fiber optic network that sends information about the mineral's progress through the pipeline and inter-connects the entire company.
Molybdenum and bismuth-lead concentrates are trucked to Lima for shipment to local customers.
The Punta Lobitos Port is located one km West of Huarmey, a town 140 km South of Chimbote and 300 km North of Lima. The port's facilities include storage tanks, agitators, pressure filters, water treatment plant, a 160,000 tonnes concentrate storage building; and marine facilities: a 271 m long dolphin-type dock with a transport conveyer belt, a 1,400 t/h ship loader, a service platform and six buoys for incoming ships.