The Kinsevere Copper deposit is a sedimentary hosted copper deposit. The deposit is hosted in moderately to steeply dipping Neoproterozoic sedimentary formation of the Roan group of the Katanga stratigraphy in the Mine Series subgroup of Katangan African Copper belt.

On surface, the Kinsevere Copper deposit has been mapped as made of three separate Mine Series fragments (large breccia clasts of the Mine Series) whereby the first two fragments are situated along a major N-S oriented fracture and separated by a sinistral strike-slip fault, while the third fragment, called Kinsevere Hill, is situated along major NW-SE fracture and separated from the other fragments by another sinistral strike-slip fault. All these fragments are affected by fractures and breccias.

The sulphide, transitional and oxide mineralisation in the Kinsevere copper deposit are either disseminated in recrystallised layers or infilling bedding plans, reactivated bedding, fractures and joints. Sulphide mineralisation includes chalcopyrite, bornite, chalcocite and pyrite. Oxide mineralisation is dominated by malachite with lesser chrysocolla. A transitional zone exists between the primary and oxide zones with both a horizontal trend, controlled by ground water movements, and a sub vertical trend controlled by bedding and structures. Transitional copper species include chalcocite, cuprite, covellite and native copper.

Mining operations are conducted by open-pit methods. The ores mined are the oxide types malachite and cuprite with a small proportion of transitional ore and minor native copper. The current life of mine (LOM) is out to 2024 after taking into account mining from oxide resources and recovery from existing oxide stockpiles.

The mining rate is designed to feed the 2.3Mtpa processing plant with ore blending to produce a copper feed grade of around 3.7%. Depending on the mining sequence, the mining rate may differ from the processing rate due to stockpile build or withdrawal. Typical working stockpile inventory is 100,000 tonnes. Kinsevere also maintains a much higher stockpile balance of 4.8mt at 2.1% copper, partly to manage Run of Mine (ROM) head grade and partly for stockpiling low-grade ore for processing later in the mine life. Currently, all mining is from the Central pit, but the future mine plan calls for two or three pits to be mined concurrently. The total life of mine waste to ore ratio is 2:1.

MMG employs the contractor MCK for most mining functions at Kinsevere including civil works, mine development and drilling. Ore and waste haulage is by six-wheel articulated trucks with a capacity of 15-16m3 (approximately 40 tonnes). These trucks are small for a mining operation and are more commonly employed in civil applications. However, they are very suitable for wet weather conditions and provide good operating flexibility. The wet season extends from October to April, with the wettest periods in January and February. Kinsevere continues to focus on initiatives that will lead to further mining efficiencies.

Kinsevere mines and processes oxide ore. This enables the operation to use the conventional solvent extraction/electrowinning (SXEW) process (Exhibit 3) to produce A grade refined 99.99% copper cathode. Achieved capacity is just above the 80,000 tonnes per annum level.

Factors behind achieving this level of capacity (against a 60,000 tonnes per annum nameplate) include maintaining continuous power availability and a very strong emphasis on the continuous cleaning and maintenance of busbars and cathodes in the refining house. This has enabled the cells to operate at a high current density without loss of current efficiency.

The Kinsevere operation was commissioned in 2007 as a Heavy Media Separation (HMS) operation with a copper concentrate product. The current SXEW plant was completed in 2011 and the HMS plant was closed.

Elements of the current plant and SXEW process include:

Ore grinding – this uses a single stage SAG mill operating in a closed circuit. This produces a 200 micron feed, which is then directed to the leach tanks. The SAG mill operation is unusual in that sulphuric acid is added to the circuit to start the leach process early in advance of the leach tanks. The leaching process involves the extraction of copper from solid copper oxide using the sulphuric acid solution. Although the acid concentration in the SAG mill circuit is lower than that in the leach tanks, it is very effective because of the high kinetic energy in the SAG mill. The SAG mill has a mild steel shell with an epoxy coating on the inside to prevent acid erosion. The mill is topped up with concentrated acid as necessary.

Leach tanks – these are atmospheric agitated leach tanks. The residence time in the tanks is six hours. The leached slurry, which contains both copper in solution and un-dissolved copper in solids, passes to the high-grade thickener. High-grade thickener – Overflow from the thickener containing copper in solution, mainly as copper sulphate, passes to a high-grade pinned bed clarifier for further upgrading. Slurry underflow from the thickener, which contains copper not yet dissolved, passes to the counter current decantation (CCD) circuit. High-grade pinned bed clarifier – this removes remaining solids and produces a clarified high-grade pregnant leach solution (PLS), which is the feed for the high-grade circuit of the solvent extraction (SX) process. Underflow from the clarifier is recycled back to the thickener. CCD circuit – Slurry underflow from the thickener is pumped sequentially through five CCD thickeners in series. The slurry underflow liquor is diluted with wash liquor that flows in the opposite direction. The wash liquor leaches out most of the remaining copper in solids and forms the low-grade PLS. After clarification in a low-grade pinned bed clarifier, the clarified lowgrade PLS solution provides the feed for the low-grade circuit of the solvent extraction circuit.

Solvent extraction is the method used to purify the copper solution for copper refining. At Kinsevere, there are two SX trains comprising a low-grade circuit (for the low-grade PLS) and a high-grade circuit (for the high-grade PLS). This configuration has the advantage of improving copper recoveries and reducing acid consumption.

The SX process uses mixing and settling tanks to contact the pregnant acidic liquor with an organic solvent. The copper is extracted away from the aqueous phase into the organic phase, leaving most of the impurities behind. The copper bearing organic phase is then contacted with a strongly acidified aqueous solution. This causes the copper to move to the aqueous phase while the organic phase is reconstituted in its hydrogen form. The density difference between the aqueous solution and the organic solvent is used to separate the two solutions after the copper has been transferred. The copper bearing aqueous phase is then advanced to the electrowinning stage, while the organic phase, now devoid of copper, is returned to the extraction stage. The spent impure acid solution or raffinate is recycled back to the SAG mill, leach tank and CCD circuits.

In the EW process, the copper is reduced electrochemically from copper sulphate in solution and is deposited as copper metal onto a stainless steel sheet, which acts as a cathode. Electrowon copper cathodes are as pure as or purer than electrorefined cathodes from traditional smelting processes. Kinsevere has two tank houses. The EW cells run at a very high current density. Kinsevere claims the very high current density used at the refinery is the second highest in the world. Despite the high current density, the current efficiency of 91% does not appear to have fallen. When the copper deposited has achieved the desired weight, a crane is used to remove the copper cathode from the electrolytic cell. The copper is then stripped from the stainless steel cathode in an automated process. The copper cathodes are then bundled and weighed, ready for shipping. A methodical anode and cathode maintenance and cleaning regime is in place to achieve maximum current efficiencies.

There is a heap leach facility, which is now in a dormant stage. Kinsevere may look at some form of heap leach operation for the future, potentially to treat ore from additional sources, particularly lowgrade material.