Tenke Fungurume is classified as a strata-bound copper cobalt deposit. The Tenke Fungurume coppercobalt deposits are typical of those that comprise the Central African Copperbelt. The Copperbelt is located in a major geological structure called the Lufilian Arc, a 500 km fold belt that stretches from Kolwezi in the southern DRC to Luanshya in Zambia. The deposits of the Tenke Fungurume district are located at the northernmost apex of the arc. The arc formed between the Angolan Plate to the southeast and Congo Plate to the northwest during the late Neoproterozic, approximately 650 to 600 million years before present (Ma). Rocks in the arc are exposed in a series of tightly folded and thrusted anticlines and synclines, generally trending east west to southeast-northwest in the southern DRC. The Tenke Fungurume group of sedimenthosted copper cobalt deposits occurs near the base of a thick succession of sedimentary rocks belonging to the Katanga System of Proterozoic age (1050-650 Ma).

The Tenke-Fungurume deposits lie in the largest tectonic window of Roan Group rocks in the Central African Copperbelt (Figure 7-3). This central Roan window is surrounded by Nguba and Kundelungu lithotectonic assemblages. The Mines Series forms a series of scattered tectonic blocks referred to as ‘écailles’. These are fault bounded on all sides and tend to form tight, upright or recumbent anticlines or monocliines. The écailles can range from several 10’s to over 500 m in length and extend downdip from 20 to 200 m.

The Luflian Arc is an intensely folded zone composed of three distinct but related structural units. The outer unit, within which the Tenke Fungurume group of deposits is located, is the most northerly, consisting of tightly folded and thrust blocks of Roan age rocks which have been tectonically transported from south to north, and now rest upon a younger Kundelungu foreland.

The Tenke Fungurume concession encloses thrust slices of various dimensions and orientations. The northern portion is relatively undisturbed with a gentle northerly dip, while the southern portion is occupied by the Dipeta syncline. At its eastern extremity the syncline is closed by a series of thrust blocks which form the Fungurume section of the deposits. At the western end, the northern limb of the syncline is terminated by a major dislocation which offsets the Tenke deposits to the northeast.

Within the east west trending Dipeta syncline both the northern and southern limbs can be traced in more or less continuous ridges of Lower Roan rocks, with more resistant RSC forming the crestal spines. These ridges run approximately parallel for a distance of 14 km, apparently undisturbed. Drilling and geophysical surveys indicate that the syncline is a gently box-folded recumbent isoclinal fold with steep to overturned inside flanks and a relatively flat bottom.

As is the case with the Kolwezi Nappe, it is possible that the mineralized mega-fragments represent transported blocks of large dimension riding as nappes, or related structures, on series of decollement planes. The overall transport direction has been interpreted as being from south to north.

Both to the north and south, the Dipeta syncline is flanked by numerous écailles of Lower Roan rocks. They attain a maximum development south of the syncline where they form, in general, randomly oriented blocks. By contrast the thrust blocks to the north of the northern flank of the syncline are smaller and fewer in number, generally aligned sub-parallel to the strike of the Dipeta syncline, and are seen to rest upon the lower member of the Dipeta formation (RGS) of Upper Roan age.

The copper-cobalt mineralization at Tenke-Fungurume is mainly associated with two dolomitic shale horizons (RSF and SDB respectively), each ranging in thickness from 5 to 15 m, separated by some 20 m of cellular silicified dolomite (RSC). Primary copper and cobalt mineralogy is predominately chalcocite (Cu2S), digenite (Cu9S5) bornite (Cu5FeS4), and carrollite (CuCo2S4). Oxidation has resulted in widespread alteration producing malachite (Cu2CO3(OH)2), pseudomalachite (Cu5(PO4)2(OH)4), chrysocolla (hydrated copper silicate) and heterogenite (Co3+O(OH)).

Dolomite and quartz are the main gangue minerals present. Dolomite or dolomitic rocks make up the bulk of the host strata. Weathering of the host rocks is normally depth related, intensity decreasing with increasing depth, producing hydrated iron oxides and silica at the expense of dolomite, which is leached and removed. As a result, gangue acid consumption (GAC) is lower in the oxide zone.

Tenke Fungurume mines copper-cobalt oxide ores by open-pit mining techniques. Drill and blast is employed in the both the ore and waste rock. Conventional loaders and trucks transport the ore to the crusher or stockpiles and the waste to dumps. Larger mining equipment is currently being introduced to enable increased mining rates.

Mining at Tenke Fungurume has historically been carried out on benches of 5 m or 10 m height advancing top down in the various development phases. Recently, the bench height has been increased to 7.5 m and 15 m height. Bench operating surface widths are generally quite generous with the narrowest areas having a width of 30 m. Ore is generally broken using a continuous surface miner and excavated using a wheel loader. Waste and some low grade ore is drilled and blasted and excavated using either hydraulic excavators, front shovels or wheel loaders. Ore and waste is hauled in 85 t and 45 t capacity off-road end dump trucks. Long haul trucks will be introduced to haul ore from some of the more distant deposits. The smaller trucks are generally being phased out in favour of larger units.

Ore zones are mined first using the surface miner. High-grade ore is delivered to stockpiles near the mill feed chute. A two month stockpile of this high grade ore is maintained and loaders provide an optimized blend to the mill. The two month stockpile also allows the mine to develop in an orderly fashion without “chasing” ore in the phase to meet short-term demands.

Waste mining generally follows ore removal. Blastholes have been drilled 6 m deep on a 5 m by 5 m pattern or 11 m deep on a 6 m by 6 m pattern. A third party contractor primes and loads the holes for blasting. Originally Cat 988 front-end loaders loading into 45 tonne capacity Cat 772 haul trucks were employed to load and haul the waste. Larger Cat 992 front-end loaders and 100 tonne capacity Cat 777 haul tracks have been introduced to supplement the original fleet and increase waste stripping rates.

The major mining equipment is divided into two fleets, one for ore and one for waste, with appropriate support equipment for both.

Ore is mined by Vermeer surface miners cutting 0.625m flitches. There are currently 5 Vermeers operating with combined capacity of 12,000 tpd. Some ore is also drilled and blasted to make up the required mill feed. Fragmentation can be an issue with ore at the breaker station. Waste rock is conventionally drilled and blasted using a fleet of Atlas Copco, Furukawa and Pantera drill rigs. The current trend in drilling is a movement away from small drills and 131 mm holes to DM-45's hammer drills and 165/175 mm diameter holes. There are currently four DM-45's in the fleet with an additional unit to be added in 2014.

The current loading and hauling fleet consists of Caterpillar 988 6.4 m3 capacity front-end loaders, 18 - Caterpillar 772 45 tonne capacity haul trucks, Caterpillar 992 12.5 m3 capacity front end loaders and 32 - Caterpillar 777 85 tonne haul trucks. As part of the 14,000 tpd expansion, a larger waste mining fleet consisting of Bucyrus RH120E 16.5 m3 face shovels, Bucyrus RH90C 11m3 excavator and Cat 777 85 tonne haul trucks was introduced. This fleet delivers improved waste mining productivity. Recent additions include Caterpillar 6030 front shovels. Overland haul trucks, with 50 tonne capacity, are used to deliver ore from the outlying deposits to the mill stockpile.

Production support equipment consists of track and rubber tire dozers, motor graders, water trucks, fuel/lube trucks and a small fleet to support the Mofya quarry operation. The support fleet includes Cat D8R track dozers, Cat D10N track dozers, Cat 824G rubber tire dozers, Cat 14M motor graders, Cat 16M motor graders, Cat 740 fuel/lube trucks, miscellaneous hydraulic excavators, Cat 772 and Cat 777 water trucks equipped with Mega 11,000 gallon and 20,000 gallon tanks respectively.

Copper is extracted using standard SAG milling, sulphuric acid leach, SX-EW to produce copper cathode. Iron, manganese and aluminium are removed from a low grade residue stream from the tankhouse and a cobalt rich solution is recovered which is purified before the cobalt hydroxide product is precipitated out.

Nominal daily mill feed of oxide ore has increased from the original design of 8,000 tpd to 11,000 tpd to 14,500 tpd following several phases of plant debottlenecking and the completion of a phase 2 expansion.

The phase 2 expansion of Tenke Fungurume was completed in 2014 increasing annual copper production by 50% to a nameplate of 195,000 tonnes copper cathode and 15,000 tonnes cobalt hydroxide. The expansion included additional mining equipment, mill upgrades, acid plant expansion and a doubling of the existing tank house capacity. A second sulphuric acid plant was commissioned in early 2016.

Run-of-mine (ROM) ore is delivered by haul truck to the ROM pad. Front-end loaders feed a blend of ore to a mobile crusher which feeds a ROM bin from where it is conveyed to a single stage SAG mill. The SAG mill operates in closed circuit with a cluster of hydrocyclones.

The ground slurry is thickened, pumped to the first of five leach tanks and mixed with sulphur dioxide (SO2), sulphuric acid (H2SO4) and raffinate to achieve a leach feed pulp. Copper and cobalt leach extractions are achieved in the leach operation. The leached slurry is thickened and the overflow is clarified and pumped to the high-grade (HG) pregnant leach solution (PLS) pond. After cooling the HG PLS is re-clarified to remove residual colloidal silica and suspended solids, and then pumped to the HG solvent extractions circuit.

Thickener underflow is pumped to the counter-current decantation (CCD) circuit to recover dissolved copper and cobalt values from the leached solids. CCD 1 overflow is clarified and pumped to the lowgrade (LG) pregnant leach solution (PLS) pond. The washed solids from CCD 5 are pumped to the neutralization circuit.

CCD 5 underflow, excess CCD wash solution, and iron residue slurry are neutralized using slaked lime. Slaked lime is added to precipitate magnesium and trace heavy metals. The final neutralized slurry is pumped to the lined tailings storage facility.

The solvent extraction facility consists of a single circuit comprising six extraction and four stripping stages. The HG circuit has four extraction stages, the LG circuit has two extraction stages and the common organic stream is stripped in four stages.

Copper is extracted from the PLS solution using an organic extractant. The copper is subsequently stripped from the organic phase to produce strong electrolyte. The strong electrolyte is then filtered to remove any entrained organic solvent, prior to electrowinning. The LME Grade A cathodes are removed, washed, stripped, weighed and dispatched using semi-automatic and fully automatic stripping machines. The stainless steel cathode blanks are returned to the cells for re-use.

Fe/Al/Mn (FAM) removal.
Low-grade raffinate from the solvent extraction is neutralized using limestone. Sulphur dioxide and air are sparged into agitated tanks to precipitate iron, aluminum and manganese under oxidizing conditions. Limestone is added to each of the tanks for pH control. The resultant slurry is thickened and filtered to recover the cobalt solution. The filter cake, containing predominantly gypsum, iron and aluminum hydroxides, is repulped and pumped to the neutralization circuit.

As part of the Phase 2 Expansion, the FAM agitators, FAM thickener feed, and underflow pumps were upgraded.

Copper precipitation.
Milk of lime is added to the solution from the FAM removal circuit to precipitate the remaining soluble copper. Sulphur dioxide and air are sparged into the agitated tanks to promote the precipitation of any remaining manganese. The slurry is thickened and the solids are returned to the leaching circuit for recovery of the precipitated copper.

Cobalt precipitation.
Milk of magnesia is added to the solution from the copper precipitation circuit to produce cobalt hydroxide. Two stages of precipitation are used to improve the purity of the hydroxide precipitate and consequently reduce the consumption of magnesia. Magnesia is added in the first stage of precipitation whereas milk of lime is added in the second stage of precipitation. The thickened cobalt hydroxide from first stage precipitation is filtered and bagged as a wet product for export or flash dried and bagged as a dry product for export. Thickened solids from the second stage of precipitation are recycled to the FAM circuit. The cobalt-free solution is predominantly used as CCD wash solution, with the excess reporting to the neutralization circuit.