The Mumbwa licence area lies within the extreme southern portion of the Neoproterozoic Lufilian Arc. The Lufilian Arc is a large arcuate fold and thrust belt covering northwestern Zambia, the southern Democratic Republic of Congo and eastern Angola.

The geology of the Mumbwa area is described by Cikin and Drysdall (1971). The region is dominated by metasedimentary rocks of the upper units of the Neoproterozoic Katanga Sequence. These rocks are intruded by the large syn- to post-tectonic 566-533 Ma Hook Granitoid Suite and by younger post-tectonic syenites, diorites, porphyry granites, granites, diorites and gabbros. The east-northeast trending MSZ runs along the southern margin of the Hook Granitoid Suite.

The Mumbwa district represents an IOCG province that is related to voluminous anorogenic (Atype), alkali and granitoid magmatism and tectonic activity that took place from 570-500 Ma along a Pan-African transform plate boundary that separated the Congo and Kalahari Cratons (Pelly, 2001). IOCG systems associated with the Hook Granitoid Suite and related intrusions in the Mumbwa district display many of the typical characteristics of IOCG systems.

IOCG deposits comprise a broad and ill-defined clan of mineralisation styles, which are grouped together chiefly because they contain hydrothermal magnetite and/or specular hematite as major accompaniments to chalcopyrite ± bornite. Apart from copper and byproduct gold appreciable amounts of Co, U, REE, Mo, Zn, Ag, Nb and P may also be present.

Deposits vary between magnetite-apatite deposits with actinolite or pyroxene (Kiruna type) and hematite magnetite deposits with varying amounts of copper sulphides, Au, Ag, uranium minerals and REE (Olympic Dam type). Typically, these systems are characterized by >20% iron oxides. Iron-rich zones, breccias and alteration halos associated with IOCG systems can reach hundreds of metres in width and many kilometres in length.

Deposits are localized along high- to low-angle faults which are generally splays off major, crustal-scale faults. Structural control can vary from the intersection of highly permeable units with fault zones, dilational jogs, duplexes, splays on faults and shears, folding or complex intercalation of high and low permeability units all influencing fluid flow regimes and ultimately the position of alteration zones, breccias and/or ore deposition.

The mining study considered sub-level caving (SLC), a combination of SLC and sub-level open stoping (SLOS) and block caving mining methods. Previous studies considered open pit mining and SLOS.

SLC was selected as the preferred and most suitable mining method for the project.

The factors influencing the mining method selection were:
• The massive geometry of the deposit.
• Near surface mineralisation has been leached of copper.
• A geotechnical assessment that indicates that caving can be induced in areas overlying the orebody.

The flowsheet for the Kitumba Copper Project has been designed to process 3 Mtpa of ore to produce nominally 60,000 tpa of copper cathode, although peak copper output of 70,000 tpa may be achieved by increasing the plating current density from a design 310 A/m2 up to 357 A/m2.

The process plant for treatment of the Kitumba ore includes the following unit operations:

• Primary crushing and milling in a SABC circuit to achieve a nominal P80 of 150 µm.
• Rougher flotation of the mill product to produce separate concentrate and tails streams.
• Pressure oxidation (POX) leaching of the flotation concentrate in an autoclave to produce
sulphuric acid, ferric species, and heat.
• Mixing of the flotation tails with heated raffinate solution and POX leach discharge slurry.
• Leaching of this combined slurry in an atmospheric acid leach circuit to yield a copper rich pregnant leach solution (PLS).
• Separation of the PLS from the barren leach solids in a six stage counter-current decantation (CCD) circuit.
• Extraction of copper from the PLS using solvent extraction.
• Recovery of copper as copper cathode using electrowinning.
• Precipitation and subsequent recycle of copper hydroxide from a bleed stream of solvent extraction raffinate using milled limestone. Recycle of the neutralised raffinate as wash solution in the CCD circuit.
• Neutralisation of the final CCD stage underflow slurry, using limestone and lime, prior to disposal.