DRC – The results follow initial metallurgical test work from a sample of drill core from on-going exploration in the Kakula Discovery zone, in a southerly portion of the Kamoa copper project.
The tests achieved copper recoveries of 86% and produced a copper concentrate with an extremely high grade of 53% copper.
The results also indicate that material from Kamoa’s Kakula and Kansoko zones could be processed through the same concentrator plant, which would yield significant operational and economic efficiencies.
The Kamoa copper project, located approximately 25 km west of the town of Kolwezi, is a joint venture between Ivanhoe Mines and Zijin Mining Group Co. The 60 km² Kakula Discovery zone is on the Kamoa mining licence, approximately 10 km south west of the Kamoa project’s planned initial mining area at Kansoko Sud.
Testing of the Kakula sample was conducted at Zijin’s laboratory in China, using the flow sheet developed during the Kamoa pre-feasibility study (PFS). The material tested was a composite of drill holes DD996 and DD998, assaying 4.1% copper.
As a comparison, testing of a previous development composite sample from the planned, initial mining deposit at Kamoa’s Kansoko Sud zone and the adjacent Kansoko Centrale zone, assaying 3.61% copper, achieved an 85% recovery and a concentrate grade of 37% copper. The PFS circuit was optimised on this material.
Mineralogy on the Kakula sample of drill core confirmed that the material is chalcocite dominant, with lesser amounts of bornite.
“These preliminary Kakula metallurgical test results are positive as they indicate that the metallurgy at Kakula is very similar to that at Kansoko Sud and Centrale, and that mineralisation from these three areas can be successfully processed through the same concentrator plant,” says Vongani Nkuna, Kamoa’s senior process engineer.
“The next steps are to repeat and confirm the Kakula metallurgical results by running duplicate tests at Zijin’s laboratory and XPS’s laboratory in Canada. After this, we will look at minor changes to the planned Kamoa concentrator circuit to further improve recoveries. Once we have a resource model for the Kakula area, we will plan a rigorous sample selection and test work campaign.”
Kamoa is planning to start the variability tests shortly on individual drill core samples from the Kansoko Sud and Kansoko Central areas.
Metallurgical test work and concentrator design
Between 2010 and 2015, a series of metallurgical test work programmes were completed on drill core samples of known Kamoa copper mineralisation. These investigations focused on metallurgical characterisation and flow-sheet development for the processing of hypogene and supergene copper mineralisation.
Bench-scale metallurgical flotation test work carried out at XPS Consulting and Testwork Services laboratories in Falconbridge, Ontario, Canada, has shown positive results.
The most recent work was conducted on composite samples of drill core from the Kansoko Sud and Kansoko Centrale areas in the southern part of the Kamoa mineral resource area.
Two master composite samples were formulated: one was representative of the first four to five years of planned mine production and the other was representative of projected production in years five to 15.
Test work on the master composite representative of the early years of mining, and grading 3.61% copper, produced a copper recovery of 85.4% at a concentrate grade of 37% copper.
Material from the later years of mining, grading 3.20% copper, produced a copper recovery of 89.2% at a concentrate grade of 35.0% copper using the same flowsheet.
Average arsenic levels in the concentrate were measured to be approximately 0.02%, which is significantly lower than the limit of 0.5% imposed by Chinese smelters. Very low arsenic levels in concentrate are expected to attract a premium from copper-concentrate traders.
The concentrator design incorporates a run-of-mine stockpile, followed by primary and secondary crushing on surface. The crushed material, with a design size distribution of 80% passing (or P80) 9 mm, is fed into a two-stage ball-milling circuit for further size reduction to a target grind size P80 of 53 µm.
The milled slurry is subjected to rougher flotation followed by scavenger flotation. The high-grade, or fast-floating rougher concentrate, and medium-grade or slow-floating scavenger concentrate, are collected separately.
The rougher concentrate is upgraded in two stages of cleaning to produce a high-grade increment to final concentrate. The medium-grade scavenger concentrate and tailings from the two rougher cleaning stages are combined and re-ground to a P80 of 10µm before being cleaned in two stages.
The cleaned scavenger concentrate then is combined with the cleaned rougher concentrate to form the final concentrate. The final concentrate is thickened before being pumped to the concentrate filter. Filter cake then is bagged for shipment to market.
Kakula mineralisation is flat-lying, bottom-loaded and chalcocite dominant
The primary objective of the current drilling programme at the Kakula Discovery is to confirm and expand a thick, flat-lying, bottom-loaded zone of very high-grade copper mineralisation at the southern part of the Kakula Discovery area that has the potential to have a significant, positive impact on the Kamoa project’s future development plans.
Kakula’s drilling programme has seven rigs operational in the field and two rigs on standby. The planned 25 000 m of drilling are scheduled to be completed later this year.