Katanga, Dem. Rep. Congo
Super Porphyry Cu and Au|
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The Kinsevere sediment hosted copper-cobalt deposits are located ~35 km NNE of Lubumbashi in Katanga Province of the Democratic Republic of Congo (DRC). It is 25 km NE and 35 km NNE of the Luiswishi and Ruashi-Etoile deposits respectively, and is in the south-eastern part of the ~350 km long Congolese Copperbelt, part of the larger Central African Copperbelt that extends south into Zambia (#Location: 11° 21' 36"S, 27° 34' 17"E).
Kinsevere is based on three main deposits, distributed over a ~3 km long, NW-SE trend, from NW to SE: Tshifufiamashi (also known as "Mashi"), Tshifufia (comprising Tshifufia North, Central and South, sometimes collectively referred to as "Central") and Kinsevere Hill/Kilongo (Kilongo extends north westward from Kinsevere Hill towards Tshifufia, and is sometimes referred to as "Kinsevere Hill Extended") (Booth et al., 2010).
The Kinsevere deposits were first discovered around 1920, and were subsequently exploited in several phases for copper and cobalt by UMHK ("Union Miniére du Haut Katanga"). The first phase of modern exploration in the area was during the 1990s, by the state owned Gécamines and EXACO (a local Congolese company), interested primarily in exploiting near-surface, high-grade, oxide cobalt mineralisation within 30 m of surface. This exploration was centred on the Tshifufia and Tshifufiamashi prospects. Gécamines also undertook a preliminary investigation for copper, which included limited drilling at the three Kinsevere prospects. However, most drill holes were vertical, parallel to the dip of the orebodies, and were not conclusive. Subsequently, an open pit was developed at Tshifufia South, to a nominal depth of 30 m, although no formal exploitation of the other deposits was undertaken (Booth et al., 2010).
In 2004, Anvil Mining, in joint venture with the Mining Company of Katanga, and under an agreement with Gécamines, the owner of the mineral rights, began exploration for Cu and Co at Kinsevere. After preparing a JORC/NI 43-101 compliant resource estimate, and signing the necessary agreements, mining commenced in late 2006. In late 2011, Anvil Mining was taken over by MMG Limited/Minmetals Resources (Booth etal., 2010).
For details of the regional setting of the Kinsever deposits, the Central African/Congolese Copper Belt and the Lufilian Arc, see the Central African Copperbelt - Congolese/Katangan Copperbelt record.
The main deposits within the south-eastern section of the Congolese Copperbelt are hosted within elongate slivers of Roan Group sedimentary rocks, exposed within the cores of a series of parallel, NW-SE trending antiforms. The crests of many of these antiforms, have been attenuated by axial plane reverse faults, resulting in exposures of Roan Group slivers over lengths of tens to >75 km, with widths of <200 m to locally >5 km, following the curvilinear trend of the Lufilian Arc. To the SE, all of these structures coalesce on the rim of the Luina Dome within the Domes Region of the Lufilian Arc.
The Kinsevere deposits lie adjacent to such a sliver, towards the outer eastern margin of the Congolese Copperbelt. The Luiswishi and Ruashi-Etoile deposits are in the next parallel antiformal crest, which is ~20 km to the SW, while Sase, Lupoto and Kasonta follow the crest of the next parallel antiform, a further 20 km to SW. The Kipushi Cu-Zn-Pb deposit is in a fourth anticlinal crest, 15 km to the SW, on the southwestern margin of the Copperbelt.
A number of parallel subsidiary anticlines are mapped between these main structures, the axes of some of which are the focus of artisanal mining. Not all of these anticinal crests expose the mineralised sections of the Roan Group sequence.
The Kinsevere orebodies are hosted by reduced carbonate rich rocks of the Mines Subgroup, which overlie the oxidised predominantly clastic sequence of the R.A.T. Subgroup. These are the lowest two units of the Neoproterozoic Roan Group. The host rocks occur within écailles (French for 'fish-scales', a local structural term for tabular tectonic megabreccia blocks) of a Roan Group megabreccia. At Kinsevere, the stratigraphic succession is as follows, from the base (after Kazadi, 2012 and Booth et al., 2010):
R.A.T. Subgroup (Roches Argilo-Talqueuses; R-1) - subdivided into:
i). R.A.T. Rouges, which stratigraphically underlies the Mines Subgroup, and comprises 15 to 20 m of pinkish-white, massive, moderately fractured sandstone, with pervasive talc impregnation and manganese oxide in fractures, becoming bedded towards the top, overlain by 15 to 18 m of a pinkish-white, talc-rich and dolomitic siltstone that is fractured and diffusely bedded, grading into massive dolomitic siltstone with hematite staining along bedding planes and manganese oxides in fractures. The stratified R.A.T. siltstones are usually barren or poorly mineralised, although the top 1 to 3 m often contain malachite and heterogenite in fractures. The unit has been brecciated, producing a 1 to 2 m thick cross-cutting layer of monomictic crackle breccia, containing angular clasts with strong limonite staining toward the top, and often hosting malachite mineralisation.
ii). R.A.T. undifferentiated, comprising other oxidised R.A.T. Subgroup rocks separated by faulting and breccia zones that cannot be readily allocated to specific stratigraphic sub-units. These consist of massive to diffusely laminated dolomitic siltstone with a greenish-pink colouration due to the presence of significant chlorite alteration, usually containing calcite veins parallel to the bedding, and pinkish red-purple massive sandstone. They are rarely mineralised, except for some malachite along a few discrete fault planes in open pit exposures.
iii). R.A.T. Grises (G.R.A.T.), which is variously regarded as the reduced upper facies of the R.A.T. Subgroup (R-1; Hitzman, 2008) or the lowest member of the Mines Subgroup (R-2; Cailteux, 1977; 1978; François, 1974; Cailteux et al., 2005). In general, the G.R.A.T. and R.A.T. Rouges are made up of the same main rock-forming and accessory minerals (detrital, diagenetic and metamorphic). In the Kinsevere area the G.R.A.T. consists of massive, tannish-yellow to orange-grey, medium-grained slightly dolomitic siltstone, with a gradational lower contact into the underlying R.A.T. Rouges, and a generally conformable contact with the overlying dolomitic rocks of the D.Strat. It can be locally strongly deformed and fractured, with minor copper mineralisation within the fractures in the oxide zone, occurring as malachite, mixed with heterogenite and manganese oxides, although more intense fracturing at the upper contact is accompanied by strong mineralisation.
The G.R.A.T. occurs as essentially two facies:
* Proximal facies, the upper part, which is 3 to 4.5 m thick and occurs immediately below the D.Strat. When not weathered, it comprises partially bedded, reduced, pale olive to pale greyish-olive and beige argillite, with a minor sandy component, and erratically distributed medium-grained quartz particles. This facies is variably developed and is completely absent in the Tshifufia écaille.
Around 1 to 2 m from the upper contact, a zone of 2 to 4 cm spaced, thin (2 to 8 mm) lenticular siliceous bands or short lenses, sometimes with a worm-like appearance are developed, following diffuse bedding planes. These siliceous bands are often replaced by very fine-grained pyrite and locally by chalcopyrite, weathering to limonitic or hematitic layers. Less commonly, the same zone also carries ellipsoidal evaporitic nodules (<20 mm long), which are often replaced by chalcopyrite or pyrite. This zone is well developed at Tshifufiamashi where continuous unbroken laminae occur over an interval at least 50 cm thick.
This facies normally has a sharp lower contact, with an increase in reddish hematitic staining towards the base.
* Distal facies, that is 3 to 16 m thick, and occurs in the lower part of the unit. It comprises a cream to ivory, to very pale grey to beige, massive and homogeneous argillite, that weathers to a very pale red or pinkish colour, with prominent hematite staining locally dominating the rock, especially towards the top. Locally, rare minor, diffuse, almost anastomosing bedding planes are evident, frequently containing >10 to 30% very small pseudomorphs that form tiny vugs where weathered. In proximity to well-mineralised younger sediments, in the zone of oxidation, this facies contains joints and veinlets of malachite increasing towards the stratigraphic top.
Mines Subgroup (R-2) - which constitutes the main host rocks to the Kinsevere copper deposit. Of the five regional Mines Group facies recognised by François (1973) to be progressively developed from north to south across the Copperbelt, namely the Musonoi, Long, Kilamusembu, Kalumbwe and Menda (see the "Mineralised Facies" paragraphs in Congolese Copperbelt record), only the Menda facies is represented at Kinsevere. This facies is characterised by the absence of the siliceous stromatolitic dolomite (R.S.C.) and the presence of three graphitic beds within the dolomitic shales (S.D.) sequence. The Mines Subgroup is divided, from the base, into:
i). Kamoto Dolomite Formation (R-2.1), the lowermost formation of the Mines Subgroup which either conformably overlies the G.R.A.T. or is discordantly underlain by the heterogeneous Roan or R.A.T. Breccia (see below). It comprises:
* Dolomie stratifiées; D.Strat. (R-2.1.2) and Roche Siliceuse Feuilletées; R.S.F. (R-2.1.3), which together host/comprise the Lower Orebody. The D.Strat., which is observed to conformably overlie the G.R.A.T. is 2 to 3 m thick and comprises a massive to crudely laminated suite of grey-green to dark grey, silicified, impure dolomite with an algal or bacterial band of stromatolitic nodules in the top metre. Moderate-to-high concentrations of sulphides, mainly chalcocite and bornite, are hosted in dolomitic lenses and nodules. When weathered, it occurs as a coarsely-bedded siliceous dolomite, alternately clayey, grey, brownish-yellow or whitish with distinct bedding planes.
The R.S.F. is a thinly and regularly laminated silicified dolomite, which has a dark grey colour, due to its high concentration of copper sulphides, principally chalcocite and chalcopyrite. Where weathered, it is a greyish-brown, thinly laminated and strongly silicified dolomite, often with high concentrations of malachite and heterogenite. The thickness of the unit varies and can exceed 3 m. At Kinsevere these strata have consistent characteristics and their combined thickness only varies between 5 and 6 m. Both are locally strongly fractured, and are characterised by a high concentration of Mg-dolomite (>20%), detrital and authigenic quartz, chlorite and sericite. The RSF in particular, is characterised by the presence of muscovite (François, 1973; Cailteux, 1978, Batumike et al., 2006).
ii). Dolomitic Shale Formation (R-2.2),
* Schistes Dolomitiques; S.D., which varies from 75 to 110 m in thickness, and is essentially a strongly carbonaceous unit, composed of fine-grained micritic cemented clastics rocks which hosts the Upper Orebody. At Kinsevere, the bulk of the S.D. is a succession of slightly greenish-grey dolomitic shale, with finely-banded, weakly carbonaceous, silty dolomite, alternating with dark, mostly carbonaceous shale/siltstone, progressing upward into largely carbonaceous, finely pyritic siltstone and shales with occasional 1 to 3 m thick mid-grey, diffusely bedded dolomites and dolomitic shales. Bedding is parallel, laminated and sharp to diffuse in the carbonaceous shales and siltstone, although the fine laminated texture is not always apparent until the framboidal pyrite within it starts to oxidise and the shale swells. More dolomitic beds have thicker, less obvious bedding with minor dolomitic pseudomorphs, while non-carbonaceous dolomite shale and shaley dolostone have a weak crystalline texture, often with associated 1 to 3 mm lath-like pseudomorphs after sulphates.
In detail, mapping of the S.D. within both the Tshifufia and Tshifufiamashi écailles has differentiated the following succession (Hillbeck et al., 2007), from the base: S.D.B. - Basal dolomitic shale; B.O.M.Z. - Black ore mineralized zone; S.D.2a - carbonaceous dolomitic shale; S.D.2b+2c dolomitic shale to shaley dolostone; S.D.2d - carbonaceous dolomitic shale; S.D.3a - dolomitic shale to shaley dolostone; S.D.3b - carbonaceous dolomitic shale. The individual units are between 5 and 15 m thick.
At both Tshifufia and Tshifufiamashi, ~10 to 20 m above the base, there are occasional narrow (<2 m thick) zones containing minor siliceous dolomite nodules, occurring as irregular, flattened, bedding parallel "blebs" (<10 x 5 to 35 mm). At Tshifufiamashi, these nodules are typically replaced or rimmed by pyrite with very subordinate fine chalcopyrite.
Where weathered, the S.D. generally has a light grey colour, in places grading to brownish-yellow to reddish-white, and is well-laminated with coarser-grained dolomite bands. In the open pit, it is a light grey to dark reddish, regularly bedded dolomitic shales package, which is strongly fractured (veins, fractures and joints). These fractures are filled by copper and manganese oxides, mainly malachite, heterogenite and other black iron oxides. Structurally reactivated bedding planes are filled mainly by malachite. Where fresh, fractures (tension joints and fractures) are filled by calcite/dolomite and copper sulphides, including chalcopyrite, bornite and chalcocite.
iii). Kambove Dolomite Formation (R-2.3), previously more commonly known as the Calcaire á Minerai Noir (C.M.N.), is the uppermost unit of the Mines Subgroup. It is essentially a well laminated, cryptalgal-stratified, recrystallised and coarse grained dolostone, with the appearance of a medium to thickly stratified, bedded and interlayered unit with intervals that are more carbonate dominated, versus intervals with silt contamination. When un-oxidised, it is moderately carbonaceous. It has been regionally subdivided by Oosterbosch (1962), into a lower unit of dark-coloured organic dolostones and an upper suite of clean dolostones interbedded with chloritic siltstones. Cailteux (1977; 1994) further subdivided each of these into 3 further sub-units based on drilling at Kambove (120 km to the NW). However, at Kinsevere, the C.M.N. is relatively thick, locally exceeding 160 m, and can be subdivided into three sub-units:
* Lower C.M.N., which is a 40 to 80 m thick sequence of homogeneous and diffusely bedded, to sharply laminated, crystalline dolostone, and dark, carbonaceous, finely laminated, shaley dolostone, alternating with subsidiary black shale bands. When weathered, it becomes a yellowish-brown to grey siliceous dolostone with dark purplish vuggy shale.
* Intermediate C.M.N., a 25 to 35 m thick interval, commencing with 3 to 6 m of weakly carbonaceous, banded to irregularly finely-bedded dolostone, with significant bedding-parallel dolomite veining/alteration. This passes up into a cyclic unit composed of well-defined dark to medium grey well-bedded dolostones (which becomes less carbonaceous upwards), alternating with very pale, olive coloured massive shales. Each lithological band is from <2 to 5 m thick, with a gradual increase in the proportion of shale upwards. The shales are poorly bedded (rarely anastomosing, mostly diffuse and irregular), with poorly sorted medium grained sand to coarse grit and rare fine pebble layers less than 1 to 4 cm thick occurring at the base of many of the units. Contacts are mostly sharp.
* Upper C.M.N., composed of white to cream, variably bedded dolostones with occasional very pale olive dolomitic shales. Zones of very pale lilac beds that are <2 to 3 cm thick containing large, ill-defined crystals resembling anhydrite occur within the lower to central sections. The presence of occasional small stromatolites, possible evaporite collapse breccias and pseudomorphs imply a shallow water environment. Much of the unit is characterised by monotonous sharp to diffusely and thickly bedded dolostones with minor flattened, bedding-parallel nodules and lenses of chert. When weathered, it becomes a yellowish to reddish-brown siliceous dolostone with patches of green-grey chloritic conglomeratic sandstone (greywacke).
The C.M.N. has been deformed by isoclinal micro-folds with axial planes dipping at 10° to the SW and W in the Tshifufiamashi and Tshifufia open pits respectively. Similar folds are also evident at Kinsevere Hill. The C.M.N. has also been fractured, with joints and veins filled with copper oxides (chiefly malachite and heterogenite), manganese oxides and black iron oxides.
Below the base of oxidation, the fractures are filled with dolomite/calcite veins and associated copper sulphides (chalcocite, bornite and chalcopyrite) and occasionally pyrite. Copper sulphides also occur along bedding planes and as disseminations and replacement of stratiform evaporitic nodules in dark grey laminated, coarse-grained dolostone of the Lower C.M.N. The C.M.N. hosts the Mines Subgroup Third Orebody which is well developed in the Kinsevere copper deposit.
Key lithologies of the Mines Subgroup at the MMG Kinsevere deposit - The lowest member is the Grey R.A.T. (Roches Argilo-Talqueuses - middle left), a grey, largely structureless dolomitic silt to sand rock, which may be brecciated, as in this image. This is overlain by thinly developed D.Strat. (Dolomie stratifiées - middle-centre) which represents the Lower Orebody position, and comprises a massive to crudely laminated suite of silicified, impure dolomite, followed by the R.S.F. (Roche Siliceuses Feuilletées - middle right), a thinly and regularly laminated silicified dolomite. The R.S.C. (Roches Siliceuses Cellulaires), normally found above the R.S.F., representing a stromatolitic reefal facies, is absent at Kinsevere. Instead, the overlying S.D. (Schistes Dolomitiques - upper image) follows the R.S.F.. At Kinsevere, the S.D. is thicker than normal, and is characterised by well bedded, black, carbonaceous, fine-grained micritic cemented clastics rocks, and hosts the main Upper Orebody. This unit also carries pyritic intervals which produce sulphur blooms on exposure to the atmosphere (see upper image). The next unit above the main ore, is the C.M.N. (Calcaire á Minerai Noir - lower-left), which is slightly coarser and more dolomitic than the S.D., and also hosts part of the Upper Orebody. The upper margin of the Mines Subgroup is marked by the Heterogeneous Breccia (bottom-centre), which at Kinsevere has a matrix rich in kaolinite and rock flour, enclosing clasts of a range of Mines Subgroup lithologies. Photographs by Mike Porter, 2014.
Breccias - Two types of Roan Group breccias are encountered in the Kinsevere area:
i). Monomictic Breccia, which occurs within the units of the Mines Subgroup. Locally, these breccias are found separating Mines Subgroup stratigraphic units, and are mostly composed of angular clasts of CMN, cemented by a clayey, malachite, and manganese and iron oxide matrix when weathered. This breccia was interpreted to be a tectonic breccia resulting from internal thrusting of Mines Subgroup layers (Cailteux and Kampunzu, 1995; Kampunzu and Cailteux, 1999; Kazadi, 2004) and hosts high-grade copper oxide mineralisation.
ii). Heterogeneous (or R.A.T.) Breccia, is a significant lithology within the Roan Group (Cailteux, 1995; Kampunzu and Cailteux, 1999; Wendorff, 2000; 2003; 2005; Jackson et al., 2003). It separates different Roan Group and Mines Subgroup outcrops at the Kinsevere copper deposit, surrounds all the Mines Subgroup écailles and occurs along a fault zone separating the Tshifufia and Tshifufiamashi écailles. It is a massive, mostly light red to pink to white and mottled rock, that is fragmental and brecciated. Clasts are of rounded to sub-angular Mines Subgroup lithologies, ranging from millimetres to more than a hundred metres (e.g., the >100 m long C.M.N. clasts to the west of the Tshifufia écaille), which are contained in a kaolinitic to sandy dolomitic matrix. At Kinsevere, the R.A.T. breccia occurs as dyke-like bodies of very variable width, with an average thickness that varies from 10 to 160 m. In pit faces it can be seen to have structural contacts with the adjacent rocks and commonly contains allochthonous fragments of those wall rocks. It is strongly fractured, in places with a banded fabric, giving it a laminated appearance. Fractures are filled by hematite, calcite and dolomite, and rarely by quartz. It is also affected by calcite-dolomite veining referred to as "hydro-fractures" (Cailteux and Kampunzu, 1995). The breccia has been interpreted to result from halokinetic (salt migration/diapiric) deformation of an evaporitic dolomite unit (Hitzman, 2008), while Cailteux and Kampunzu (1995) suggested the "hydro-fractures" are a result of de-watering due to tectonic compression, and suggested a faulting origin for the mega-breccia. However, Jackson et al., (2003) pointed out that faulting alone cannot explain the vast extent of the heterogeneous breccia because of the difficulty of forming large discordant diapirs without a mobile substrate, nor the strata-bound geometry of clast contacts.
Regionally and within the district, the Mines Subgroup is overlain by the Dipeta and Mwasya subgroups, and by the Nguba and Kundelungu groups. However, in the immediate deposit area, only the Kundelungu Group is represented. It occurs in the form of the Gombela Subgroup (Ku-1), previously known as the Kalule Subgroup (Batumike et al., 2007), which includes the basal Petit Conglomérat (Ku-1.1), and a sequence of dolostones, sandstones/mudstones and shale. These rocks outcrop to the east, SE, south and west of the Roan Group block that hosts the Kinsevere deposit, where they are represented by the Ku-1.2 (Lusele Formation) rocks, which consist of alternating purplish and grey, finer grained sandstone, with a thick bed of dark grey dolomite-poor sandstone/schist.
The Kinsevere deposits are hosted by three contiguous, steeply dipping to overturned and dislocated écailles of Mines Subgroup (R-2) rocks, overlying the R.A.T. (R-1) Formation and heterogeneous R.A.T. Breccia in the east. These écailles occur within an internally folded, but continuous, ~2.5 x 0.3 to 1 km block of R.A.T. and Mines subgroup rocks (Kazadi, 2012).
This Roan Group block is bounded on all sides by steeply to moderately inward dipping, reverse faults/thrusts, and is interpreted to be internally segmented by ESE-WNW to NNW-SSE striking rotational faults, mainly reverse, but also normal. These faults converge downward, and have exhumed and emplaced Roan Group strata at a shallower level. The R.A.T. Subgroup rocks are interpreted to have included significant evaporites which facilitated the exhumation and formation of the R.A.T. Breccia (HItzman, 2008).
The Roan Group rocks structurally overlie the younger Kundelungu Group unit Ku-1.2 of the Gombela Subgroup, above the inwardly dipping reverse faults/thrusts that define the margins of the Roan Group block (Kazadi, 2012).
The contiguous and overlapping Tshifufiamashi, Tshifufia and Kinsevere Hill/Kilongo écailles that host the ore deposits are ~750, 900 and 1100 m long respectively, 150 to 200 m thick, and are separated by faults and R.A.T. Breccia. The Tshifufia écaille persists for >400 m down dip. The Tshifufiamashi and Tshifufia écailles are aligned in a NNW-SSE to north-south direction, while Kinsevere Hill/Kilongo to the SE, trends WNW-ESE to NW-SE (Kazadi, 2012).
Each of the écailles comprises a west to SW facing sequence, from R.A.T. Grises, through D.Strat.-R.S.F. and S.D. to C.M.N. formations, the highest unit preserved. Heterogeneous R.A.T. Breccia surrounds and separates the different écailles of Mines Subgroup rocks (Kazadi, 2012; Booth et al., 2010).
The upper C.M.N. Formation passes westward into R.A.T. undifferentiated, via heterogeneous R.A.T. Breccia, which interfingers with large, lensoid clasts/blocks and semi-detached fingers of C.M.N (Kazadi, 2012; Booth et al., 2010).
All the Kinsevere écailles can be considered as partially preserved limbs of a large-scale fold complex. Within these limbs, bedding planes were locally exploited as faults, suggesting layer-parallel slip to accommodate folding. As a consequence, the strata at Kinsevere are highly fractured and faulted, and are either overturned, dipping to the east (Tshifufia), or right-way-up dipping west (Tshifufiamashi and Kinsevere Hill). These opposite-dipping fragments are separated by two sinistral strike-slip faults and are surrounded by heterogeneous R.A.T. breccias within the undifferentiated R.A.T. (Kazadi, 2012).
Similarly, internal rotational faulting has dislocated the Tshifufia écaille, where the stratigraphy at Tshifufia North and Tshifufia Central strikes north-south, but is rotated westwards along a fault offset, immediately north of Tshifufia South. At Tshifufia North, bedding is upward facing and dips steeply to the west, while at Tshifufia Central it is overturned and dips at a moderate angle to the east. The bedding in the Tshifufia South pit is sub-vertical, but the stratigraphy appears to wrap around a central "core" of R.A.T. Subgroup rocks. Faulted contacts between rocks within the écailles are marked by monomictic breccia (Kazadi, 2012).
Hypogene mineralisation is hosted in three main stratigraphic positions within the Mines Subgroup écailles (Kazadi, 2012 and Booth et al., 2010). These include the:
Lower Orebody - within the G.R.A.T. unit of the R.A.T. (or lower Mines) Subgroup, and the D.Strat.-R.S.F. units of the Mines Subgroup, Kamoto Formation. Only weak sulphide mineralisation is found within the G.R.A.T. unit, occurring as finely disseminated pyrite and minor chalcopyrite within a zone of lenticular siliceous bands following bedding in the upper few metres of the unit, and sometimes replacing ellipsoidal evaporitic nodules in the same zone.
The D.Strat. unit generally contains moderate-to-high concentrations of sulphides, mainly chalcocite and bornite, hosted in dolomitic lenses and nodules, while the R.S.F. unit is a very fine laminated, silty dolostone with a distinct, leafy foliation that has a dark grey colouration, due to the high concentration of copper sulphides it contains, principally chalcocite and chalcopyrite. Together the D.Strat. and R.S.F. units have a relatively consistent combined thickness across the deposit, only varying between 5 and 6 m.
Upper Orebody - within the S.D. unit of the Mines Subgroup, Dolomitic Shale Formation, which varies from 75 to 110 m thick and contains both stratabound and fracture controlled mineralisation.
Third Orebody - within the C.M.N. unit of the Mines Subgroup, Kambove Formation. Like the S.D., the C.M.N. has been fractured with joints and veins filled with dolomite/calcite veins and associated copper sulphides (chalcocite, bornite and chalcopyrite) and occasionally pyrite. Copper sulphides also occur along bedding planes and as disseminations and replacement of stratiform evaporitic nodules in dark grey laminated, coarse-grained dolostone of the Lower C.M.N. Mineralisation is predominantly localised in the coarsely recrystallised dolomitic layers.
The hypogene sulphide mineralisation occurs as (after Kazadi, 2012 and Booth et al., 2010):
i). Stratabound copper sulphide mineralisation, typically occurring as,
* replacement of early diagenetic pyrite and anhydrite nodules by copper sulphides, including chalcopyrite, chalcocite and bornite.
* volumetrically dominant, discrete, bedding-parallel and bedding-oblique stratabound veins, filled predominantly with chalcopyrite and only minor quartz and calcite, generally within zones of very finely disseminated chalcopyrite in black, fine-grained calcareous carbonaceous siltstone.
* broad intervals (>3 m) of light grey coloured, coarsely crystalline, silty dolostone, with coarse grained disseminated chalcopyrite, which locally coalesces to form discontinuous stratabound boudinaged veins. Disseminated sulphides are most apparent in dolostone beds.
ii). Veins, mainly cross cutting quartz-carbonate-sulphide veins following fractures and joints. Vein controlled and stratabound mineralisation tend to spatially coexist, although stratabound mineralisation may occur locally as the sole style. Veining tends to have the same sulphide and gangue proportions, and mineralogy, as the stratabound mineralisation. The vein and fracture hosted sulphides overprint the disseminated and bedding controlled mineralisation.
iii). Breccias, which are variably mineralised and interpreted to have been developed by remobilisation during faulting. Their mineralogy and relationship to the stratabound mineralisation is as for the veining.
At Tshifufia and Tshifufiamashi, all three primary orebodies are steeply dipping, and are juxtaposed, to form an unusually thick mineralised package that occupies a stratigraphic thickness of more than 200 m (Hitzman et al., 2012; Booth et al., 2010).
Supergene/oxide mineralisation. The regolith profile at Kinsevere includes a near-surface veneer of bleached clays, underlain by a zone in which the country rocks are progressively less oxidised downward. The base of oxidation is typically at a vertical depth of ~110 m, although it is commonly an irregular surface which varies with the rock fabric and degree of deformation. The transition to fresh rock is not always sudden, although the oxide interval is generally of significantly higher copper grade than the primary zone, with bonanza grade oxide mineralisation (large blocks of > 120 m long and >50 m thick of >7.5% Cu in section) in the central parts of the Tshifufia deposit. The oxide zones are also more erratic, and tend to form laterally discontinuous layers cross cutting bedding surfaces. The bonanza grade block outlined above in the Tshifufia pit, is underlain by hypogene ore with grades of 0.7 to 3.5% Cu (Booth et al., 2010).
The supergene ore forms a well defined horizontal layer from just below the surface to the base of oxidation at 60 to 100 m depth, cross-cutting the steeply dipping primary orebodies at a high angle (Booth et al., 2010).
Stratigraphically, oxide mineralisation is first seen in the stratified red R.A.T. siltstones, which are usually barren or poorly mineralised, although the top 1 to 3 m often contain malachite and heterogenite in fractures. Minor copper oxide mineralisation is found in the G.R.A.T. within fractures, comprising malachite mixed with heterogenite and manganese oxides, increasing upwards towards the top contact, where the hosts are highly fractured and can contain strong copper oxide grades. However, in some cases, as at Tshifufia Central, large tonnages of oxide mineralisation are hosted in fractures and veins within the G.R.A.T., immediately below the D.Strat. contact. Within the D.Strat., and particularly the R.S.F., there are high concentrations of malachite and heterogenite over the 3 to 6 m of the combined width of the units. Over much of the width of the succeeding S.D., particularly the lower half, copper and manganese oxides, mainly malachite, heterogenite and other black iron oxides fill a network of fractures, and structurally reactivated bedding planes, related to high-angle faults and widespread bedding-parallel fault breccias. The C.M.N., which has been deformed by isoclinal micro-folds with shallow axial planes, has also been fractured with joints and veins within the lower half of the unit filled with copper oxides (chiefly malachite and heterogenite), manganese oxides and black iron oxides. The C.M.N. is characterised by a combination of stratabound malachite, irregular veinlets and nodules of malachite, in addition to black heterogenite associated with the malachite.
These mineralised units are structurally juxtaposed in the three écailles, and terminated to the west by barren R.A.T. Breccia. Monomictic breccia separating Mines Subgroup stratigraphic units, may also be mineralised, mostly composed of angular clasts of CMN, cemented by clayey, malachite, and manganese and iron oxide (Kazadi, 2012; Lawlor et al., 2008; Booth et al., 2010).
Mined surfaces reveal little cross-strata dispersion of supergene ore minerals, and small scale interleaving of mineralised and unmineralised beds (Lawlor et al., 2008; Booth et al., 2010).
The oxide ore mineral assemblage at Tshifufia, Tshifufiamashi and Kinsevere Hill is predominantly composed of malachite (Cu2CO3(OH)2) and pseudomalachite (Cu5(PO4)2(OH)4), with minor chrysocolla (Cu,Al)2H2Si2C5(OH)) and rare intergrown heterogenite (CoO(OH)). These are found as disseminations and/or in veins and veinlets, and sometimes coalesce into prominent "clots".
Malachite commonly occurs as coarse (0.2 to 0.7 mm) variably bladed crystals. A significant proportion is also observed within goethite, quartz and phyllosilicate gangue minerals. Noticeably finer-grained pseudomalachite is also identified within principal gangue phases together with heterogenite. No primary sulphides have been identified at the surface, although minor amounts (typically chalcopyrite) can occur within oxide ore zones, where it is usually restricted to fresh rock beneath, or within 10 to 20 m thick transition zones, separating weathered and unweathered material.
The fresh to oxidised transition is not defined by an appreciable supergene blanket type spike in Cu mineralisation, and the presence of native Cu, secondary suphides and other Cu oxides, but tends to correspond to more erratic, laterally discontinuous layers, which transect bedding planes, although such Cu and Co assemblages (chalcocite, cuprite and inter-grown heterogenite) are preserved in oxidised domains as either disseminated, fracture or cleavage-controlled phases within certain favourable host rocks (Lawlor et al., 2008; Booth et al., 2010).
The mineralised zone at surface at Tshifufiamashi has a strike length of ~200 m and is ~160 m wide, bounded to the north, east and west by the margin of the écaille, and to the south by a rotational fault zone, although the same stratigraphy continues south across this structure with diminished grades. The high grade mineralisation at Tshifufia forms an inverted 'V', closing to the north, where the ore zone is over 200 m wide. The strike lengths on the eastern and western limbs is ~400 and ~550 m respectively, with each limb having a width of ~140 m. The limbs are separated by a wedge of barren R.A.T. Breccia. The Mines Subgroup rocks between the Tshifufiamashi and Tshifufia ore zones have elevated grades, which are largely <1% Cu (Booth et al., 2010).
While these standard Lower, Middle and Third orebody stratigraphic subdivisions have been applied to geological descriptions, Booth et al. (2010) and Lawler et al. (2008) subdivided the orebodies in their geological model for the purposes of calculating mineral resources, into a Lower Orebody within the G.R.A.T. unit only, an Upper Orebody in the D.Strat.-R.S.F. and S.D. units and a Third Orebody in the C.M.N. unit. The absence at Kinsevere of the barren/low grade R.S.C unit separating the Upper and Lower orebodies elsewhere in the Congolese Copperbelt, and the similarity in ore style in both makes the differentiation unnecessary. However, the difference in nature of ore in the G.R.A.T., is sufficient justification for its separation.
Published JORC compliant mineral resources and ore reserves are as follows:
As at 31 December, 2009 (Booth et al., 2010 for Anvil Mining Limited):
Oxides - at a 0.7% Cu Total cut-off
Tshifufiamashi measured resources - 1.97 Mt @ 3.45% Cu Total, 3.06% Cu Acid Sol.
indicated resources - 4.18 Mt @ 2.70% Cu Total, 2.08% Cu Acid Sol.
inferred resources - 0.62 Mt @ 2.55% Cu Total, 1.91% Cu Acid Sol.
Tshifufia measured resources - 7.37 Mt @ 4.30% Cu Total, 3.64% Cu Acid Sol.
indicated resources - 5.81 Mt @ 5.0% Cu Total, 3.95% Cu Acid Sol.
inferred resources - 0.92 Mt @ 4.73% Cu Total, 3.42% Cu Acid Sol.
Kinsevere Hill indicated resources - 6.41 Mt @ 2.88% Cu Total, 2.53% Cu Acid Sol.
TOTAL oxide measured + indicated resources - 25.74 Mt @ 3.78% Cu Total, 3.14% Cu Acid Sol.
inferred resources - 1.54 Mt @ 3.85% Cu Total, 2.81% Cu Acid Sol.
Sulphides- at a 0.7% Cu Total cut-off
Tshifufiamashi indicated resources - 0.61 Mt @ 2.40% Cu Total, 1.59% Cu Acid Sol.
inferred resources - 1.05 Mt @ 2.37% Cu Total, 1.49% Cu Acid Sol.
Tshifufia measured resources - 0.06 Mt @ 2.16% Cu Total, 0.97% Cu Acid Sol.
indicated resources - 3.09 Mt @ 3.99% Cu Total, 2.60% Cu Acid Sol.
inferred resources - 11.59 Mt @ 3.64% Cu Total, 1.85% Cu Acid Sol.
TOTAL sulphide measured + indicated resources - 3.76 Mt @ 3.70% Cu Total, 2.41% Cu Acid Sol.
inferred resources - 12.64 Mt @ 3.54% Cu Total, 1.82% Cu Acid Sol.
As at 30 June, 2012 (MMG Limited Mineral Resources and Ore Reserve Statement, 2012):
Oxides - at a 0.5% Cu Total cut-off
measured resources - 15.7 Mt @ 3.9% Cu Total, 3.1% Cu Acid Sol.
indicated resources - 14.5 Mt @ 2.8% Cu Total, 2.3% Cu Acid Sol.
inferred resources - 1.1 Mt @ 2.1% Cu Total, 1.8% Cu Acid Sol.
TOTAL oxide measured + indicated + inferred resources - 31.4 Mt @ 3.3% Cu Total, 2.7% Cu Acid Sol.
Sulphides - at a 0.5% Cu Total cut-off
measured resources - 1.6 Mt @ 2.6% Cu Total, 0.9% Cu Acid Sol.
indicated resources - 10.4 Mt @ 2.8% Cu Total, 0.7% Cu Acid Sol.
inferred resources - 8.9 Mt @ 2.4% Cu Total, 0.6% Cu Acid Sol.
TOTAL sulphide measured + indicated + inferred resources - 20.8 Mt @ 2.6% Cu Total, 0.7% Cu Acid Sol.
TOTAL measured + indicated + inferred resources - 52.2 Mt @ 3.0% Cu Total, 1.8% Cu Acid Sol.
TOTAL proved + probable ore reserves - 25.8 Mt @ 3.5% Cu Total, 2.9% Cu Acid Sol. (incuded in resource).
Information in this summary is taken from Booth et al., 2010, "Anvil Mining Limited, NI 43-101 Technical Report, Kinsevere Copper Project, Katanga Province, Democratic Republic of Congo" and reports with similar titles by Fahey et al., 2007; Hillbeck et al., 2007; Lawlor et al., 2008. -and- Kazadi Banza, 2012 "Structural geology of the Kinsevere copper deposit, DRC", M.Sc. Geology thesis, University of Pretoria.
The most recent source geological information used to prepare this summary was dated: 2012.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Booth G, Cameron A, Fahey G and Lawler M, 2010 - Kinsevere Copper Project, Katanga Province, Democratic Republic of Congo (selected excerpts): in NI 43-101 Technical Report prepared for Anvil Mining Limited, www.sedar.com, 18p.|
Kazadi-Banza S B, 2012 - Structural geology of the Kinsevere Copper Deposit, DRC (selected excerpts): in MSc Geology Thesis, Faculty of Natural and Agricultural Sciences, University of Pretoria 47p.|
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