The mineral deposits at Kipushi are an example of carbonate-hosted copper-zinc-lead mineralisation hosted in pipe-like replacement and tabular zones. This deposit type tends to form irregular, discordant mineralised bodies within carbonate or calcareous sediments, forming massive pods, breccia/fault-like fillings and stockworks (Trueman, 1998). They often form pipe-like to tabular deposits strongly elongate in one direction. Zinc-lead rich zones can project from the main zone of mineralisation as replacement bodies parallel to bedding, as is the case at Kipushi.

This deposit type is associated with intracratonic platform and rifted continental margin sedimentary sequences which are typically folded and locally faulted (Cox and Bernstein, 1986). The host carbonate sediments were deposited in shallow marine, inter-tidal, salt flat, lagoonal or lacustrine environments and are often overlain unconformably by oxidised sandstone-siltstone-shale units. The largest deposits are Neoproterozoic in age and occur within thick sedimentary sequences.

The Katanga Supergroup hosts a number of epigenetic zinc-copper-lead deposits developed within deformed platform carbonate sequences. While many of these are relatively small (e.g. Kengere and Lombe in the DRC; Bob Zinc, Lukusashi, Millberg, Mufukushi, Sebembere, and Star Zinc in Zambia), Kipushi and Kabwe in the DRC and Zambia respectively represent world class deposits with predominantly massive sulphide mineralisation contained within dolomitic limestone (Kampunzu, et al., 2009). These deposits are polymetallic with a typical Zn-Pb-Cu-Ag-Cd-V association and contain variable concentrations of As, Co, Mo, Rh, Ge, and Ga.

Mineralisation at Kipushi is spatially associated with the intersection of Nguba Group stratigraphy with the Kipushi Fault and occurs in several distinct settings:
• Kipushi Fault Zone (copper, zinc, and mixed copper-zinc mineralisation both as massive sulphides and as veins);
• Série Récurrente:
- Disseminated to veinlet-style copper sulphide mineralisation);
- A high-grade pod (massive copper and zinc sulphides);
• Copper Nord Riche (mainly copper but also mixed copper-zinc sulphide mineralisation, both massive and vein-style);
• Big Zinc (massive zinc sulphide with local copper sulphide mineralisation), and
• Southern Zinc (poly-metallic massive sulphide) mineralisation and replacement.

Mineralisation at the Kipushi Project is generally copper-dominant or zinc-dominant with minor areas of mixed copper-zinc mineralisation. Pyrite is present in some peripheral zones and forms massive lenses, particularly in the Fault Zone. Copper-dominant mineralisation in the form of chalcopyrite, bornite, and tennantite is characteristically associated with dolomitic shales both within the Fault Zone and extending eastwards along, and parallel to, bedding planes within the Série Récurrente and adjacent Upper Kakontwe Formations.

Zinc-dominant mineralisation in the Kakontwe formations occurs as massive, irregular, discordant pipe-like bodies completely replacing the dolomite host. These bodies exhibit a steep southerly plunge from the Fault Zone and Série Récurrente contacts where they begin, to their terminations at depth within the Kakontwe Formation. This southerly orientation, observed across all the mineralised zones, is oblique to the north-west plunging intersection of the Kakontwe Formations with the Fault Zone, inferring a persistent structural control at the Kipushi deposit.

Mining zones included in the current Kipushi Mine plans occur at depths ranging from approximately 1,200 mL and 1,590 mL with 0 mL being the surface. Access to the mine will be via multiple vertical existing shafts and internal decline. Mining will be performed using highly productive mechanised methods and CRF utilised or backfilling of open stopes. Depending on the required composition and available material, excess waste rock, and dense media separation (DMS) tailings will be used in the CRF mix as required.

Mining is planned to be a combination of Transverse Sublevel Open Stoping and Pillar Retreat mining methods. The Big Zinc area stopes are planned to be mined as Sublevel Open Stopes to be extracted in a Primary and Secondary sequence and filled with CRF. The sill pillars are to be mined on retreat once the stopes below and above have been mined.

The primary and secondary stopes are each 15 m W x 30 m H, with panels of two sublevels separated by a 15 m high sill pillar every 75 m vertically. Stope lengths vary from 5–60 m (maximum). Ore drives are developed perpendicular to the strike of the orebody, at a spacing of 15 m centre to centre. Drill drive dimensions are 6.0 m W x 6.0 m H and extraction drives are 5.5 m W x 5.0 m H, both with an arched profile.

On the sill pillar levels stopes are 15 m W x 15 m H, with stope lengths varying from 5–60 m. Drill drive dimensions are 6.0 m W x 6.0 m H, with drill drives located in permanent pillars designed at 8.0 m W x 6.0 m H, to maximise ore extraction.

The Southern Zinc area is predominantly planned to be extracted by the same Transverse Sublevel Open Stope method. Additionally, a thinner area at the base of the Southern Zinc zone is planned to be mined by longitudinal open stoping on retreat, bottom-up with unconsolidated fill.

Stopes within the Big Zinc and Southern Zinc areas are required to be backfilled to maintain the structural integrity of the mine and allow for maximum recovery of the ore. Backfill has been specified as either Cemented Rock Fill or Rock fill depending on the strength required in that stope.

Ore and waste are crushed underground to a product top particle size at P100 of 280 mm and hoisted to surface using the refurbished P5 Shaft system.

Both crushed ore and development waste will be intermittently (and separately) hoisted to surface, depositing into a single bin on surface, within the P5 Shaft headframe. Material is reclaimed from the bin via a vibrating feeder, which discharge onto a single existing 900 m overland conveyor T5A connecting Shaft 5, via a series of four overland transfer conveyors (T5, T6, T7 and T8), to the waste and ore stockpiles area at the Old Kipushi Concentrator (OKC).

Crushing plant
The crushing and screening circuit receives ROM ore onto the ore stockpile, via a series of overland transfer conveyors, as primary crusher product, from the Kipushi underground mine.

Ore is withdrawn from the ore stockpile using a FEL to feed a two-stage crushing plant at a nominal solids feed rate of 140 t/h. The crusher circuit design has been set up to minimise the production of fines (–1 mm). To this end, an open circuit secondary jaw crusher is used in conjunction with a closed-circuit tertiary cone crusher.

Screened crushed ore product, at –12 mm size fraction, is transferred and discharged into a DMS feed bin from where the DMS plant is fed.

Milling Circuit
DMS concentrate from the sinks screen oversize is transferred to the mill feed bin. The mill is fed from the bin at a controlled rate, with steel balls added manually onto the mill feed conveyor. DMS effluent, together with –1 mm fines, is pumped into the mill discharge sump.

The milling circuit is designed as a closed-circuit variable speed ball mill with a classification cyclone cluster. The milling circuit comprises a single 1,1 MW ball mill. The milling circuit is designed to achieve a P80 of 106 µm. The cyclone overflow gravitates to the flotation feed tank via a trash linear screen.

The concentrator plant is designed to process a nominal 800 ktpa of run-of-mine (ROM) ore, from a high-grade zinc zone orebody of the KICO underground Zinc-Copper Mine in the Central African Copperbelt in the DRC, to produce a saleable zinc flotation concentrate.

The metallurgical test results indicate that the Kipushi mineralisation is amenable to a process involving pre-concentration by dense media separation (DMS) and bulk flotation to produce suitable saleable zinc sulfide concentrate. ROM ore and waste material from underground mining facility are hoisted through the existing P5 shaft system and transferred to the stockpiles area. Ore is withdrawn from the stockpile to feed the process plant, whilst reclaimed waste material is loaded into trucks for disposal.

The new process plant, consisting of crushing and screening, DMS, milling, flotation, tailings and concentrate handling circuits, is located at the existing Kipushi Mine facility with limited free space ........