Modern Mining July 2019

COPPER/ZINC

average grades of 24 % Cu and 50 % Zn from underground mined material. Minor modifi- cations to the processing plant will allow the open-pit material to be treated at the end of the mine life, on a campaign basis, to produce sep- arate copper and zinc concentrates at average grades of 26 % copper and 36 % zinc. The flowsheet for processing underground material is similar to the flowsheet used dur- ing previous mining operations. Life-of-mine metal recoveries into concentrates are antici- pated to be 84,4 % for Cu and 83,9 % for Zn from treating underground mined material and 66,7 % and 59,4 % for Cu and Zn respectively for open-pit mined material. Water for the mining operations is planned to be supplied from the Orange River, at a rate of 4,1 megalitres per day, via the existing water pipeline. The power requirement of 38 MW is expected to be sourced from Eskom via the on-site Cuprum substation. Plans are at an advanced stage to commission the establish- ment of a renewable energy alternative source to national grid power supply, capable of poten- tially providing 52 % of the mine’s energy needs in the near term. Commenting on the results of the study, Orion’s Managing Director and CEO, Errol Smart, said: “We are delighted with the results of the BFS, which confirm the quality and scale of the Prieska project and put Orion firmly on-track to become a major new South African base metal producer. The BFS suggests that Prieska will be a high-margin, long-life

below the 957 Level; and the Central Zone, located centrally below the 957 Level. Mining methods to be deployed will com- prise Longitudinal Long-Hole Stoping with Fill (LLHOSF), Long-Hole Stoping with Fill (LHOSF); and Drift and Fill (D&F). Trackless mining methods will be used for drilling and blasting with LHD and truck haul- age to deliver rock to passes where it will be tipping onto a train haulage level. The train system will tram rock back to the shaft for hoisting. Tunnel development and declines will provide access to the orebody for produc- tion activities. Tunnel dimensions are planned to be 5,5 m wide x 5 m high for declines and 5 m x 5 m for access tunnels and production drilling drives. Paste back-filling will take place to fill the stopes once they have been mined out which assists in maximising ore extraction. With regard to the open-pit operation, the planned pit sits above previously mined out stopes (voids) and will require paste back-fill- ing. Mining will take place with conventional open-pit methods of drilling, blasting, loading and hauling. As with the underground phase, a suitable mining contractor will be utilised who will also supply the mining fleet. The open- pit operation will mine approximately 100 000 tonnes of ore and 850 000 to 1 million tonnes of waste a month. Ore processing is planned to involve con- ventional differential froth flotation to produce separate copper and zinc concentrates at

Layout of the Prieska project.

28  MODERN MINING  July 2019