The copper-cobalt minerals hosted in rocks of the Neoproterozoic Katangan Basin in the Central African copper belt metallogenic province of the DRC are a classic example of (low energy) sediment-hosted stratiform copper (SSC) ore system deposits. These deposits are economically significant, as they account for approximately 25% of the world’s copper production and known Mineral Reserves being second only to porphyry copper deposits in terms of copper production and the most important global cobalt resource.

The copper-cobalt deposits contained in a sedimentary series of rocks are known as the Mines Group in the Katanga sequence and the Roan Group in Zambia. The sediments are shallow-water shales, dolomitic shales, reefal dolomites and possible evaporitic lagoonal mudstones, formed on a platform marginal to a subsiding basin. The rocks are exposed in a series of tightly folded and thrusted anticlines and synclines, which generally trend east-west or southeast and are often overturned to the north. In spite of this deformation overprint, the mineralized zones, although sometimes lenticular along strike and down dip, as well as showing local diapiric forms, display remarkable large-scale continuity within the Mines Group.

KTO UG operations extract mineralized copper ore from the Kamoto deposit, which is differentiated from KTE, predominantly mined in the KOV OP, but contains the same lithologies. The KTO UG is subdivided into five fragments as follows:
Principal: forms a rough L-shape syncline, flat lying to gently dipping (up to 8° to the north) in the central and northern areas and becoming steeper (15° to 25°) towards the east and west flanks. The steeply dipping area to the south is sub-vertical in places and is separated from the flatter dipping area by structurally complex zones and RAT Lilas waste intrusions.
Etang South: forms a broad open synform dipping 25° to 35° to the east on an approximate north northwest strike;

Etang North: forms a roughly rectangular slab dipping 35° to 55° to the east on an approximate northnortheast strike. It extends below the Principal fragment in the north;

Ecaille Renversee: a small reversed fragment between Principal and Etang North; and

Pringle: forms a moderately open synform dipping 35° to 55° to the southeast on an approximate north strike.

Primary mineralization, in the form of sulphides, within the Lower Roan is associated with the DSTRAT and RSF for the OBI and the SDB and SDS for the OBS and is thought to be syn-sedimentary in origin. Typical primary copper sulphide minerals are bornite, chalcopyrite, chalcocite and occasional native copper while cobalt is in the form of carrolite. The mineralization occurs as disseminations or in association with hydrothermal carbonate alteration and silicification. Supergene mineralization is generally associated with the levels of oxidation in the subsurface sometimes deeper than 100 m below surface. The most common secondary supergene minerals for copper and cobalt are malachite and heterogenite.

The deposit is currently divided into three categories of dip/plunge, and the three mining methods applied
throughout the zones are:
- RAP with Hydraulic or Cement Hydraulic Backfill at dips of less than 12º;
- TLHR with Backfill between 13º and 55º; and
- LLHR with Backfill at dips greater than 55º.

Room and Pillar
The RAP mining practised at KTO UG is applied to the OBS and OBI horizons. Access drives are developed along strike on the hanging wall contact, 6 m wide by 5 m high on 25 m centres. Cross drives (6 m x 5 m) are developed, 25 m centre to centre, along the centre of the stope for the full length thereof; connected by drifts, 25 m centre to centre, for ease of loading the broken ore and for ventilation purposes. A strike gathering drive is developed at the bottom of the stope for cleaning of ore. The cross drives are then slyped to a full width of 12.5 m and height of 5 m. Benching of drives takes place by drilling long down-holes and slots from the slyped cut to the footwall of the stope, and then blasting from the gathering drive end. Benching operations take place under a hanging wall that is supported in the development and slyping stages of mining.

The 12.5 m stopes with 12.5 m pillars are mined as primary stopes and backfilled with cemented hydraulic fill to provide support for the pillars. If fill is not used, much larger pillars would be required for a stable layout. As an indication, for a mining height of 15 m with a 12.5 m wide roadway, the required pillar width to provide a FoS of 1.2 would be close to 50 m. Overall volumetric extraction would reduce to approximately 40%. After curing, pillars can be developed and mined as secondary stopes in a similar fashion as the primary stopes. These secondary stopes are filled with waste rock or hydraulic fill for regional stability. This is a high extraction mining method with relatively minor losses and dilution. Pillar extraction or mining for the secondary stopes was not very successful historically at KTO UG due to the quality of the fill in the primary stopes. KCC has secured relevant skills to start addressing this problem. The pillar or secondary stopes account for approximately 11.8% of the total Mineral Reserve tonnages of KTO UG.

Transversal Longhole Retreat with Backfill
This method is practiced in Zones 1, 6, 7 and Etang South for dips between 12° and 55°. The stopes are 15 m to 17 m wide and pillars are 8 m wide along the strike.

The mining method requires a 6 m x 5 m drive on the hanging wall contact at 15 m to 20 m vertical intervals. Crosscuts (6 m x 5 m) are developed to the foot wall contact of the specific orebody at 23 m centres and in this position drives are again established on either side of the crosscut to eventually create one continuous drive on the footwall contact.

Crosscuts are then slyped to 16 m wide and 5 m high chambers by establishing 16 m wide stopes and pillars 8 m wide along strike. Drifts are supported with 2.4 m bolts at 1.2 m centres while the 16 m wide chambers are supported with additional 4 m long anchors at 2 m centres. A connection drive is developed to connect the chambers at the footwall contact. Slot raises and longhole blast rings are drilled from the top and bottom of the chambers to the outline of the orebody. Rings are blasted sequentially towards the slot from the top down and bottom up. Stopes are backfilled depending on the availability of waste rock from other production areas. Hydraulic fill is used if development waste is unavailable and appropriate backfill logistics exist in the area in question.

Longitudinal Longhole Retreat with Backfill
This method is used in Etang North for dips off 55° and higher. The vertical level spacing is 15 m in old areas and 15 m to 20 m in undeveloped areas. Stopes are designed at the width of the orebody, 60 m in length and with 8 m rib pillars.

Stopes are designed at the width of the orebody, 60 m in length with 8 m rib pillars. These pillars serve to provide regional support and protection for the contained access ways and infrastructure.

Level access is developed through a ramp system. Strike drives (6 m x 5 m) are developed and located at the safest position in the orebody, for that level, based on geotechnical and geological parameters. These drives are developed to the full width of the orebody. The initial development is 6 m x 5 m and is supported with 2.4 m bolts at 1.2 m centres. The orebody width slyped section is supported with 4 m bolts or anchors at 2 m centres. Down holes are drilled from the upper slyped drive for the slot and the stope. The slots and rings are blasted and cleaned from the lower level access on a retreat basis. Ore extraction is achieved using remotely operated loading equipment. On completion of ore extraction, barricades are constructed in the drill drives at each end of the panel and panels are backfilled with waste rock or hydraulic fill depending on availability.

The mixed ore milling consist of CM1 and BM1 (or CM2 and BM2), CM5, CM6 and BM6, CM7 and BM7 milling circuits.

The CM1/BM1 (or CM2/BM2) mills are operated in a closed circuit with a common cyclone clusters. CM5, CM6/BM6 and CM7/BM7 also have the same arrangement. All circuits will produce a grind of 80% -150 µm from a feed with an F80 of 150 mm. BM1/BM2, CM5, BM6 and BM7 operate with a ball load of up to 35%.

The feed to each mill circuit is measured and recorded using a weightometer installed on each AG or SAG mill feed conveyor. Process water, together with the crushed ore, is added to each AG or SAG mill to achieve a slurry solids content of 75% by mass within the mill. Scats conveyors are installed at the discharge of CM5, CM6 and CM7 to remove material from the milling area to a dedicated stockpile outside the building.

KCC is currently operating the WOL hydrometallurgical processing at their existing Luilu operation. The KCC WOL project is designed to process the mixed ore flotation tails from the KTC plant, as well as the roasted sulphide concentrate, to produce 300 ktpa of copper metal and 30 ktpa of cobalt contained in cobalt hydroxide. Further expansion is planned to achieve cobalt production capacity of 40 ktpa.

Flotation
The flotation circuit consists of two distinct parallel flotation circuits followed by a common cleaner circuit. From the surge tank slurry is distributed to the two flotation circuits via a dedicated pumping system.

The concentrate from the rougher cells 1 will gravitate to Tank TK 035, and then be pumped to Tank TK 059. The concentrate from the respective scavenger cells will gravitate to Tank TK 036, and also be pumped to Tank TK 059. The concentrate from Tank TK 059 will be pumped to the cleaner flotation cells. The tails from the rougher cells wi ........