The Salobo copper and gold mine located at Carajas, Para is the biggest copper deposit in Brazil. Owned and operated by Vale, the open-pit mine has been producing since September 2012.
The Salobo copper and gold project has been developed in two phases, while the phase three expansion is currently underway to further unlock the production potential of the giant mine.
A final feasibility study for the project was completed in 2004 while the construction works were started in 2007. The pre-stripping activities were initiated in 2009 and the mine commenced phase one commercial production with 12 million tonnes per annum (Mtpa) throughput capacity in September 2012. The estimated investment for the Salobo I project was £1.6bn ($2.5bn).
Construction on the £1bn ($1.7bn) Salobo II expansion project was started in 2010 and completed in June 2014. It doubled the nameplate capacity to 24Mtpa.
Vale started construction on the £800m ($1bn) Salobo III expansion project in 2019. Scheduled for commissioning in 2022, the phase three expansion will increase the mine’s production capacity from 24Mtpa to 36Mtpa.
Location, geology, and mineralisation
Salobo is an iron-oxide copper-gold (IOCG) deposit located along the southern margin of the Amazon Basin, within the Carajás Mining District, in south-eastern Para, Brazil. Carajás is one of Brazil’s most prolific mining districts that measures 300km-long and 100km-wide.
The mine site lies in the Parauapebas micro-region in the Maraba municipality, approximately 80km northwest of Carajas. Marabá is approximately 240km away from the mine site by the highway.
The mineralisation at the Salobo deposit is found hosted in the upper greenschist to lower amphibolite metamorphosed rocks belonging to the Igarape Salobo Group. The thickness of mineralised zones varies between 300m and 600m.
Copper and gold reserves at Salobo
The Salobo copper and gold mine was estimated to hold 1.15 billion tonnes (Bt) proven and probable ore reserves grading 0.6% copper and 0.32g/t gold, as of December 2019.
The contained metal at the mine is estimated to be 15.3 billion pounds (Blbs) of copper and 11.6 million ounces (Moz) of gold in recoverable reserves.
The Salobo pit is also estimated to hold 193.5 million tonnes of measured and indicated resource grading 0.61% copper and 0.31g/t gold.
Mining and ore processing
The conventional open-pit mining method involving a drill, blast, load, and haul operation is implemented to extract ore at the Salobo copper and gold mine. The mining fleet includes cable shovels, large front-end loaders, hydraulic excavators, as well as 240t and 360t haul trucks.
The run-of-the-mine (ROM) ore is sent to the nearby processing facility where it undergoes two-stage crushing, two-stage screening, and ball mill for grinding before entering rougher and cleaner flotation circuits.
The tailings from the flotation circuit are directed by gravity to an on-site tailing storage facility, while the obtained concentrate material undergoes thickening, filtering, and dewatering for the production of the final concentrate.
The existing Salobo I and Salobo II plants, as well as the under-construction Salobo III plant, have 12Mtpa processing capacity each.
The mine life of the Salobo open-pit is estimated to be until 2044, while the processing complex is expected to operate by reclaiming stockpiled material until 2052.
The final concentrate from the Salobo operations is trucked to the railway terminal in Parauapebas from where it is sent to Vale’s Ponta da Madeira Maritime Terminal near the Port of Itaqui, in São Luis for shipping.
Gold stream agreements on Salobo
Vale sells 75% of the gold produced at Salobo operations to Canada-based Wheaton Precious Metals under three gold stream agreements signed in February 2013, March 2015 and August 2016.
The technical report for the Salobo III mine expansion was prepared by Wheaton Precious Metals in December 2019.
Micon Consultants and Amec Foster Wheeler (now Wood Group) were engaged to review the mineral resources and mineral reserves for the Salobo mine in 2013 and 2016, respectively.
The TSF at the Salobo mine was designed by the Brazilian company BVP Engineering.
Habtec (now part of the Mott MacDonald Group) was engaged to undertake the biodiversity impact study of the Salobo mining project.