Overview
The Constancia copper property is located in the south-eastern Andes of Peru, in the Chamaca and Livitaca Districts, Province of Chumbivilcas, Department of Cusco.
The deposit was first explored in the 1980s by Mitsui and Minera Katanga. Rio Tinto joined Mitsui in 2003 and completed a drill program on the property. Norsemont Mining Inc. entered into an option agreement with Rio Tinto in 2005 and acquired the balance of interest from Mitsui in 2007. Norsemont exercised their final option and acquired 100% interest in the property in 2008 ? total acquisition costs amounted to US$22.8 million.
Norsemont Mining is a Canadian exploration and development company headquartered in Toronto, Canada.
The project's global Proven & Probable mineral reserve was estimated at 372 Mt grading 0.39% copper, 105g/t molybdenum, 3.6 g/t silver, and 0.05 g/t gold.
The mining process at Constancia will be a conventional modern hard rock open pit operation, supplying the nominal concentrator production capacity of approximately 70,000 to 76,000 tonnes per day (tpd). Concentrate will be transported by truck from site to the nearest port, Matarani, located 475 km by road from Constancia.
Average annual production is 170 million pounds of recovered copper, 2,960 tonnes of recovered molybdenum, 1.8 million ounces of recovered silver, and approximately 10,800 ounces of gold as a by-product credit over the 16 year mine life.
Total cash cost including sustaining capital is $1.02 per payable pound of copper.
The total capital cost is estimated at $920 million in development capital.
Location
Peru is a Spanish speaking developing country that straddles the Andes and encompasses a strip of the Pacific coast to the west and a flat terrain covered by the Amazonian jungle to the east. It is approximately two-thirds the size of Mexico and it is the fourth most populous country in South America.
The Constancia copper project is located at high altitude (over 4,500 m asl) in the south-eastern Andes of Peru, in the Chamaca and Livitaca Districts, Province of Chumbivilcas, Department of Cusco. A translation of the Inca name for the Chumbivilcas province was the 'holy scarf'.
The most important rivers in the province are Rio Velille and Rio Santo Tomas.
Less than 80,000 Quechua people inhabit the province, which is regarded as one of the poorest regions of the country.
An 82.5 km access road links the proposed mine site to Yauri, which is the closest community.
Results from the environmental baseline studies indicate that no endangered species of plants are located within the mining area.
Geology and Mineralization
The property is located in the Yauri-Andahuaylas metallogenic belt which hosts large copper-gold-molybdenum porphyry deposits like Antapaccay and Los Chancas, and copper skarn deposits.
The Constancia deposit is a porphyry copper-molybdenum system which includes copper-bearing skarn mineralization. Multiple phases of monzonite and monzonite porphyry have intruded a sequence of sandstones, mudstones and micritic limestone of Cretaceous age.
The majority of the mineralization is associated with potassic alteration and quartz veining, occurring as chalcopyrite-(bornite)-molybdenite-pyrite mineralization.
At the contact between the intrusives and limestones skarn mineralization was developed. While volumes are small grades are high.
Structural deformation has played a significant role in preparing and localizing the hydrothermal alteration and copper-molybdenum-silver-gold mineralization, including skarn formation.
Supergene enrichment occurs immediately beneath, and occasionally as remnants within, a leached cap. The highest copper grades in the Constancia porphyry are typically associated with this and with the skarn zone.
Two individual porphyry-style deposits are known within the project area, Constancia and San José, separated by some 350 m. The total mineralized zone extends about 1200 m in the north-south direction and 800 m in the east-west direction. Mineralization occurs to surface at San José, but is deeper at Constancia. Glacial moraines cover the northern and eastern margins of the Constancia deposit: to the east these moraines cover potentially important extensions of copper mineralization along broad east-west structural zones.
Mining Operation
The mining process at Constancia will be a conventional modern hard rock open pit operation, supplying the nominal concentrator production capacity of approximately 70,000 to 76,000 tonnes per day (tpd).
Pit access ramps are 30 m wide with 1:10 gradient and are designed to accommodate 220 t sized trucks including allowances for the construction of safety windrows and drainage. A 15 m single lane ramp has been designed for the last 60 vertical metres of pits and sub-pits. A minimum mining width of 50 m is maintained.
Mine fleet would include: Two 32 m3 shovels; Thirteen 220 t Dump Trucks; One 18 m3 FEL; Two 391 KW Track Dozers; One 362 KW Wheel dozer; Two 209 KW Graders; One 12 m3 Excavator; One 279 mm Production Drill Diesel; One 127 mm Pre-split Drill; One Service Truck; Fourteen light Vehicles and other support equipment.
Processing
A civil construction fleet would be by used by the owner to build the tailings management facility, waste dumps, water management structures and internal access roads.
The primary gyratory crusher is fed by rear-dumping from two dump points by haul trucks, or fed by FEL from a stockpile. Crushed ore is conveyed to a 50 278 t open stockpile ahead of the concentrator plant.
The grinding circuit consists of a single line SABC circuit using a variable speed SAG Mill in closed circuit with pebble crushing and two fixed speed ball mills.
A slaked lime copper feed reports to two rougher flotation banks. Flotation concentrate is reground prior to three cleaning stages. The copper cleaner circuit consists of three
stages of cleaning and one bank of cleaner scavenger flotation cells.
The bulk copper/molybdenum concentrate reports to a thickener for removal of reagents that are present from copper flotation. After conditioning it is being sent to a flotation circuit which consists of one roughing stage and seven cleaning stages.
The tailing from the molybdenum flotation roughers and molybdenum cleaner scavengers reports to a copper concentrate thickener.
The copper concentrate is conveyed to an undercover storage shed. The concentrate is transferred from the stockpiles via FEL onto trucks for transport from the mine site to the terminal warehouse facility at the port facilities in Matarani located some 475 km away.
A waste rock facility would store waste rock mined from the San José and Constancia Pits. The facility would hold some 295 Mt rock characterized as having the potential to generate acid; another 55 Mt non-acid generating waste rock.
The tailings management facility would be developed behind an embankment dam that has a 277 Mt capacity and would reach an ultimate height of 130 m. The facility would be lined by a geomembrane.
The existing 82.5 km road would be upgraded to an unsealed all-weather road of 6m and a maximum gradient of 9%.
Total raw water requirements have been calculated at 365 m3 per hour and are to be met by ex-pit and in-pit dewatering operations.
A $30.27 million 1,800 bed camp would be constructed at the site of the mine.
Environment and Community
Results from the environmental baseline studies indicate that no endangered species of plants are located within the mining area.
A total of 46 archaeological sites had been identified on the property.
A resettlement plan would be developed according to international best practices for involuntary resettlement.
Six air quality monitoring stations have been proposed: four adjacent to the open pit, and one each in Uchucarco and Chilloroya. Twelve surface water quality monitoring stations have been proposed in the area.
The closure plan includes the reclamation and regarding of the open pit area. After closure the pit lake water will need to be treated in perpetuity, by lime treatment of water prior to discharge into the Chilloroya during the wet season.
Waste rock dump would be capped by a low permeability layer and topsoil. Tailings would be covered by a layer of impermeable desulphurized plant tailings that would form a layer of inert and impermeable cover.
