The Pedra Branca project is a copper and gold mine located in Carajás mineral district in Brazil. It is owned by ValOre Metals, a subsidiary of OZ Minerals.
The mine was discovered by Noranda in 2003 and acquired by Xstrata in 2006. Avanco Resources, which took over the project in 2012, was subsequently acquired by OZ Minerals in 2019.
The copper and gold property is split into east and west zones. The initial development covers the eastern zone and will be followed by development in the western zone.
Construction at the site began in November 2019 and production is expected to begin in 2020.
The mine will have a life of eight years, including two years of ramp-up and six years of full production. It will employ approximately 100 people during the construction phase and 450 people during operations.
Pedra Branca location, geology, and mineralisation
The Pedra Branca project is located in the state of Pará in north-eastern Brazil. It lies 100km away from Parauapebas and 30km from Canaã.
It is located 72km away from Avanco’s Antas project and is accessible via the Fortaleza-Brasilia highway. It covers an area of 38,940ha, which includes 38 exploration licenses
The area north of the region has a granitic-gneiss composition.
Soil and rock tests, trenching, and limited diamond drilling showed the presence of greenstone-hosted gold mineralisation.
The Pedra Branca East (PBE) region is an iron oxide copper-gold (IOCG) type deposit in the Carajás Basement, bearing diorite and sheared granite.
Reserves of Pedra Branca
The Pedra Branca project is contains proven and probable ore reserves of an estimated five million tonnes (Mt), grading at 2.1% copper (Cu) and 0.5g/t gold (Au). Contained reserves are estimated to be 104,000t of Cu and 89,000 ounces (oz) of Au.
Mining at the Pedra Branca copper and gold project
Copper and gold mining at the site involves the development of an underground mine and an on-site pre-concentration facility. It will employ a sublevel stoping mining method, which is the best match for its orebody geometry and rock mass qualities. The bench and fill type of sublevel stoping will be implemented at the site with sublevel sill to sill intervals of 30m.
Sublevel stoping with rock backfill will be applied in a bottom-up bench stoping configuration. The stopes will be mined by long-hole open stoping and will include a drill level at the top and an extraction level at the bottom.
After stope development, a slot raise will be created between two sub-levels and will be blasted to full width. The blasted ore will be recovered by tele-remote-controlled load-haul-dumps.
The mining fleet will include 40t articulated trucks for the development phase and more efficient machines will be added after production ramp-up.
Pre-concentration and development waste will be used as back-fill for the project.
Processing at the Pedra Branca project
An ore sorting plant will be constructed for processing ore from Pedra Branca. The pre-concentrate ore will be taken to the company-owned Antas processing facility by 50t haulage trucks.
The pre-concentrate process will increase the average grade of run-of-mine (ROM) ore and reduce tonnage, resulting in reduced transport costs. It will also reduce the impact caused by trucking and tailing facilities.
Located at the Antas North open-pit copper mine site, the Antas processing facility is equipped with conventional crushing, grinding, and flotation circuits. The mined sulphide material will be processed in the concentrator, while waste rock will be stockpiled in an integrated waste landform.
Planned administrative facilities for the underground mining operation and the pre-concentration plant will be constructed in conjunction with the decline and lateral development excavation.
Underground facilities at the site include compressed air, dewatering, electricity supply, exhaust, communications and water distribution. Power for the operations is sourced from an existing transmission line.
Contractors involved in Pedra Branca development
CSA Global prepared the mineral resource estimates for both the Pedra Branca East (PBE) and the Pedra Branca West (PBW) sections.
The mineral resources estimate was prepared by Lions Gate Geological Consulting, while Minxcon was contracted to perform Joint Ore Reserves Committee (JORC)-compliant mineral resource estimations.
GE21 Consultoria Mineral prepared a preliminary economic assessment (PEA) and also developed the final pit and mine plan for the project.
Beck Engineering undertook geotechnical studies and AMC Consultants reviewed the July 2018 ore reserves estimate.
Prospectors Aerolevantanmentos e Sistemas carried out the regional, airborne magnetic and radiometric survey, while the Anglo American Geophysics Department conducted a survey for quality assurance work.