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Central African Copperbelt - Zambian Copperbelt

Zambia

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Deposit Description

The Zambian Copperbelt is part of the larger Central African Copperbelt, and extends north into the neighbouring Democratic Republic of Congo (DRC), to continue as the Congolese Copperbelt. It closely coincides with a complex, arcuate structural zone, the Lufilian Arc, which trends from east-west in the west, to NW-SE to NNW-SSE in the SE. This arcuate structure is developed normal to, and near the northeastern extremity of the elongate, 2000 km long, NE-SW trending, Damaran-Katangan belt of Meso- to Neoproterozoic sedimentary rocks that extends across the continent to the Atlantic Ocean in the SW.


Regional Setting

The ~800 km long Lufilian Arc is a structural element imposed upon the rocks of the Katangan fold belt in western Zambia and southern DRC during the ~600 to 510 Ma Lufilian Orogeny. It substantially reactivated and reflects earlier syn-depositional structures, and extends from the edge of the Archaean Congo/Kasai craton in the NW, to the major trans-continental WSW-ENE trending, sinistral, Mwembeshi shear zone to the SE, separating it from the Zambezi Belt to the south. The Zambezi Belt trends east-west, normal to the Lufilian Arc, and is a zone of shearing and metamorphism that rims the northeastern margins of the Kalahari craton to the south. Porada and Berhorst (2000) suggest the Mwembeshi shear zone marks a suture between the predecessors of the Kalahari and Angolan/Congo cratons that were welded during the Ubendian-Eburnian cycle in the Palaeoproterozoic, and has focussed subsequent tectonic activity from the Palaeo- to late Neoproterozoic.
   The Kalahari and Congo cratons are composites of earlier Archaean nuclei (e.g., the Kaapvaal and Zimbabwe cratons within the former) and Palaeo- to Mesoproterozoic elements that were amalgamated and cratonised by ~1.05 Ga as part of the Rodinia supercontinent.
   The oldest orogenic basement rocks between the cratons are exposed as inliers within, and marginal to the Lufilian Arc, particularly in the core of the Zambian Copperbelt and the Bangweulu Block to the NE. They dominantly comprise a Palaeoproterozoic, Eburnian-Ubendian (~2.05 to 1.82 Ga) calc-alkaline magmatic arc sequence of metasedimentary, metavolcanic and intrusive granitoid rocks of the Lufubu Metamorphic Complex (Rainaud et al., 2005; Selley et al., 2005). These rocks are interpreted to be part of a broader, regionally extensive, Palaeoproterozoic magmatic arc terrane, stretching from northern Namibia to northern Zambia, and into the DRC, separating the Kalahari and Angola/Congo craton, then to the north and NNW, where they separate the Congo and Tanzanian cratons (Rainaud et al., 2005; Petters, 1986). In the east, this basement includes a reworked Neoarchaen component (2.73 Ga; in the Bangweulu Block only), a Palaeoproterozoic granitic phase (2.05 to 1.93 Ga) and a Palaeoproterozoic plutono-volcanic magmatic arc complex (1.87 to 1.82 Ga; De Waele and Fitzsimons, 2007 and sources cited therein). This orogenic terrane is inferred to have been related to the Ubendian-Eburnian collision mentioned above, and was accreted onto the southern and eastern margins of the Congo Craton during the ~1.4 to 1.0 Kibaran orogeny, represented by a broad SW-NE trending string of 'Eburnian basement inliers' (Porada and Berhorst, 2000).
   To the south of the Zambezi belt, a partially coeval sequence of 2.16 to 2.10 Ga continental to shelf clastic and lesser carbonate sedimentary rocks, with a mafic volcanic component, the Magondi Supergroup, was deposited over the margins of the Archaean Zimbabwe craton (Master,1991). This sequence hosts the Magondi Copperbelt deposits in Zimbabwe, ~400 km south of the Zambian Copperbelt (see the separate Magondi Belt record).
   Within the Zambian Copperbelt, Lufubu Metamorphic Complex rocks are unconformably overlain by a ~1.3 to 1.1 Ga supracrustal sequence of quartzite and metapelite, the Muva Group (1982) (Selley et al., 2005).
   The Archaean to early Palaeoproterozoic basement rocks of the Congo and Kalahari craton are separated from the Neoproterozoic sequence of the Katangan supergeroup by the Palaeo- to Mesoproterozoic Kibaran and Irumide successions respectively. These rocks represent the extensive, generally northeast-trending, Kibaran-Irumide mobile belt, a precursor rift basin to the Neoproterozoic Katangan sequence.
   The Irumide sequence comprises a thick (>8 km) sequence of variously metamorphosed conglomerates, sandstones and shales with lesser dolerite flows, and thin overlying graphitic shales, evaporites, stromatolitic limestones and dolostones. It occurs as a condensed succession over the Bangweulu Block, passing into a thick marine sequence to the south. Deposition in an rift-setting commenced at ~1.4 Ga (Selley et al., 2005), in response to extension caused by the impending breakup of the Nuna/Columbia supercontinent. However, dating by De Waele and Fitzsimons (2007) suggest the Irumide rocks were deposited in two episodes, the first in the Palaeoproterozoic at ~1.8 Ga (from interlayered 1815 Ma volcanic rocks), and a second at ~1.4 Ga. Peak metamorphism in the Irumide sequence was at 1.05 to 1.02 Ga (Rainaud et al., 2005).
   To the NW of the Katangan rocks, the >10 km thick, 1.4 to 1.0 Ga Kibaran sequence can be subdivided into four lithostratigraphic units, from the base: i). Kiaora Group - dominantly phyllites and schists with quartzite horizons, and rhyolites at the top; ii).  Nzilo group - predominantly quartzite, with local (quartzo-)phyllitic interbeds; iii). Mount Hakanssson Group - dark slates and quartzites, with basal conglomerates; iv). Lubudi Group - dark arkoses with conglomerate lenses, black graphitic shale, some sandstone, and an upper limestones and dolostone unit, often with silicified stromatolites (Laghmouch et al., 2012). Rainaud et al. (2005) and references cited therein, suggest there is evidence that over 1000 km to the north in Rwanda and Burundi, the belt underwent rifting, oceanic opening and then closure, accompanied by subduction and collisional overthrusting between the Congo and Tanzanian cratons. Over the 1500 km extent of the Kibaran belt, it tapers from a width of ~200 km in the north, narrowing to wedge out and disappear to the south in western Zambia, with only the rift facies described above mapped in its southern section below the Lufilian Arc.
   Two main styles of granitoid intrusion are recognised in the Kibaran Belt, syn- and post-orogenic phases at ~1.3 to 1.25 and 1.2 to 0.95 Ga respectively. The syn-orogenic gneissic to un-metamorphosed granitoids accompanied compression and basin inversion, while those of post-orogenic origin are alkaline and include the Kibaran tin granites (Petters, 1986 and sources quoted therein).
Location    The Neoproterozoic Katanga Supergroup of the Katangan fold belt separates, and laps onto, both the Kalahari and Congo Palaeoproterozoic cratons of southern and central Africa respectively, both north and south of the Mwembeshi shear zone. It is one of a number of similar Neoproterozoic Pan-African fold belt sequences (including the West Congo and Damaran) that fringe and/or separate these two cratons, and which may be interconnected below intervening Phanerozoic cover.
   In each of the Pan-African mobile belts of southern Africa, a ~200 m.y. period of tectonic quiescence followed the assembly of Rodinia, before extension and Neoproterozoic sedimentation heralded the commencement of its breakup.

In the Zambian section of the Lufilian Arc, the resultant 4 to 10 km thick, Katanga Supergroup (~880 to ~530 Ma) comprises an initial sequence of coarse grained, fluvial conglomerates and sandstones, dominantly siliciclastics, devoid of volcanic activity, deposited within relatively restricted, fault controlled intracontinental rift basins. These rift basins flanked a NW-SE trending basement high, now reflected by the younger Kafue Anticline, and are represented by the Mindola Clastics Formation, a variable sequence from 0 to 1300 m thick, most commonly up to ~150 to 240 m, composed of an oxidised suite of interbedded conglomerates, arenites, quartzites and lesser argillites. At the main deposits of the Zambian Copperbelt, it represents the footwall sequence, and contains basal conglomerate that varies from thin developments a few tens of metres, up to ~240 to 300 m thick, to near 1200 m on the northern margin of the Kafue Antilcine, east of Konkola and Nchanga (although the latter may in part be due to structural repetition). This conglomerate is overlain by an arenite/quartzite unit, with rare argillites, and some conglomerate interbeds, particularly near the upper transitional contact, that similarly varies from a few tens of metres to as much as 300 m in thickness. These are followed by another conglomerate that is a few to a few tens of metres thick, then a further arenite/quartzite of similar thickness, and a final footwall conglomerate that is only a few metres thick. Locally at Nchanga, the upper two conglomerates and intervening arenite are absent. On the eastern margin of the Kafue Anticline, the Mindola Clastics Formation equivalent primarily comprises a 0 to 150 m thick sequence, commencing with a thin basal conglomerate, overlain by a succession of quartzite and grits.
   These depositional centres were subsequently linked along master faults, marking a transgression, reflected by the deposition of local finer facies of the Copperbelt Orebody Member, the basal unit of the Kitwe Formation. The Copperbelt Orebody Member (or "Ore Shale") represents the culmination of early rift-stage extension and the first marine incursion within the Katangan basin in the Zambian Copperbelt. It comprises coarse and fine siliciclastic sedimentary rocks, representing fluctuating emergent and subaqueous conditions. The unit varies from 0 to as much as 60 m, more commonly 15 to 35 m thick, and frequently commences with a basal band of dolomitic schist, representing a décollement. It comprises carbonaceous and/or dolomitic siltstones, argillites, thin dolostones and fine sandstones, and hosts the bulk of the ore in the main large deposits of the Zambian Copperbelt (e.g., Luanshaya, Nkana, Mindola, Chambishi and Konkola), although a number of smaller deposits (e.g., Chibuluma, Fitula and Mimbula) are hosted by the Mindola Clastics Formation. To the east of the Kafue anticline (e.g., at Mufulira), the stratigraphically equivalent unit of the Copperbelt Orebody Member is the 1 to 2 m thick dolomitic bed known as the "Mudseam" (Binda, 1994).
   The remainder of the Kitwe Formation varies from <100 to >300 m in thickness, and at most localities commences with a quartzite to arkose unit, which may be locally absent (e.g., Nkana). It is followed by a finer unit that varies from argillite to dolomitic argillite or sandstone, to dolostone and dolomitic schist, that varies from a few to 160 m thick, culminating in a generally 10 to 30 m dolostone band. These are succeeded by a thick (up to 160 m) of feldspathic and dolomitic sandstones, interbedded with coarse grained calcareous sandstones to grit. At Nchanga, the ore extends upward into the sequence above the Copperbelt Orebody Member, with much of the ore within feldspathic quartzite of the "hanging wall", capped by a shale interbed.
   The Mindola Clastics and Kitwe Formations, together, comprise the Lower Roan Subgroup. The upper two units of the Kitwe Formation (dolostone and calcareous sandstones to grit) were included into the Upper Roan Subgroup by earlier authors (e.g., Mendelsohn, 1961), although the Lower to Upper Roan Subgroup boundary has been shifted to the base of the Upper Roan Dolomite unit in more recent papers (e.g., Binda and Mulgrew, 1974).
   Significant authigenic anhydrite is found in the Lower Roan Subgroup, in particular within the upper Mindola Clastics and lower Kitwe formations. Narrow evaporite units are also indicated by local breccias and porous units in both formations (e.g., within the Basal Quartzite at Nkana, and the Hangingwall Aquifer at Kirila Bombwe/Konkola).
   See the separate Luanshya, Mufulira, Nkana-Mindola, Chambishi, Nchanga-Chingola and Konkola-Lubambe records for the detailed stratigraphy through the Zambian Copperbelt.

The succeeding post-rift, thermal sag phase, produced the laterally more extensive platformal sequence of the Upper Roan Subgroup, comprising laterally extensive mixed shallow marine to lagoonal carbonate rocks and generally finer grained siliciclastic rocks with abundant evaporitic textures and mainly stratabound chaotic breccia (interpreted to represent the dissolution of evaporites). The sequence varies considerably in thickness, from <30 to 800 m, and is characterised by metre-scale, laterally extensive cycles of upward-fining, sandstone, siltstone, dolomite, algal dolomite and local anhydrite. Thickness variations can be abrupt and commonly are associated with breccias. The breccias are usually composed of rounded to angular, mm to metre sized polylithic intraformational clasts, set in a crystalline matrix of carbonate, albite, quartz, anhydrite and or magnesian chlorite. The breccias may be single cm to metre thick bands, to stacked complexes, up to several hundred metres thick. In general they are stratabound, but on a larger scale, step down through the sequence to the south and west (Selley et al., 2005).

The Upper Roan Subgroup in Zambia is overlain across either a conformable transition, or an evaporite-facilitated breccia-detachment, by the (150 to 650 m thick Mwashya (or Mwashia) Subgroup, emplaced within a deepening marine setting. This sequence comprises a lower suite of reefal to intertidal clastic carbonate rocks, mainly arenitic dolostone with lesser argillaceous dolostone containing pseudomorph after anhydrite nodules, overlain by an upper succession of mainly carbonaceous shales, siltstones and lesser clastic carbonate rocks. The lower Mwashya is only poorly developed in Zambia, but in the DRC, where it is thicker, it is included in the upper Dipeta Subgroup as the Kansuki Formation (Cailteux et al., 2007). The Dipeta Subgroup is equivalent to the upper half of the Upper Roan Subgroup of Zambia (Cailteux et al., 2005; 2007; Hitzman et al., 2012).

second period of rift extension is reflected by the local intrusion of large ~765 to 736 Ma gabbroic sills in Zambia (commonly within the Upper Roan Subgroup dolostones) and equivalent pyroclastic and extrusive rocks within Kansuki Formation rocks of the equivalent upper Dipeta Subgroup in the northern part of the Arc in the DRC (and possibly some A-type granitoids). This extension commenced during the deposition of late Upper Roan Subgroup, and continued through into the Mwashya and lower Nguba groups (~765-735 Ma).

The base of the overlying Nguba Group (previously Lower Kundelungu) is defined by the 10 to 1300 m thick Grand Conglomérat, a regional sequence of debris flows, glacial diamictites, some mafic flows and numerous iron formations, correlated with the world wide ~740 Ma Sturtian glacial event. The Grand Conglomérat is overlain by massive carbonate rocks of the Kakontwe Limestone represented by 350 to 500 m of massive dolostones and limestones in Zambia, and by a thinner sequence of carbonate-bearing to carbonate-poor siltstones and sandstones northward into the DRC, and appear to represent shallow marine to fluvial sediments. The remainder of the Nguba Group is composed of dolomitic sandstones and siltstones, also becoming progressively carbonate-poor and coarser to the north (Cailteux et al., 2007; Batumike et al., 2006, 2007).

To the north, mostly in the DRC, this succession is overlain by the Kundelungu Group, the base of which is defined by the Petit Conglomérat, a glacial diamictite, believed to be the time-equivalent to the global ~635 Ma Marinoan glacial event (Hoffmann et al., 2004; Master and Wendorff, 2011). The Petit Conglomérat is overlain by a weakly metamorphosed and deformed sequence that passes upwards from limestones and dolomitic sandstones (the 'Calcaire Rose', capping the diamictite), through dolomitic siltstones and argillites, to sandstones with lesser carbonate rocks. This sequence is, in turn, overlain by the extensive, flat lying, continental clastic molasse succession of the Plateaux Subgroup, composed of argillaceous and arkosic sandstones, and conglomerates (Cailteux et al., 2005; Batumike et al., 2006, 2007).

The equivalent Katanga Supergroup sequence in the Zambezi Belt to the south (hosting the Nampundwe Cu-pyrite deposit), includes a thick syn-rift, 879±19 Ma bimodal volcanic suite, which is earlier than the commencement of sedimentation in the Lufilian Arc, which is limited by the basement ~880 Ma Nchanga Red Granite. Small, but widespread developments of ~765 to 735 Ma mafic to intermediate magmatism, brackets the basal units of the Nguba Group, suggesting the main deposition may have ceased before 700 Ma (Selley et al., 2005, and sources cited therein).


Tectonic, Tectono-stratigraphic and Structural Setting

The main (late-Katangan) Lufilian Orogenesis appears to span a period of >100 m.y., with the oldest metamorphic ages of ~590 Ma, the main stage orogenesis from 560 to 530 Ma and widespread dates of 510 to 465 Ma possibly recording post-orogenic cooling (Selley et al., 2005, and sources cited therein). The Lufilian event culminated in peak greenschist-grade metamorphism at ~530 Ma. This orogenesis was the result of compressive basin inversion, which occurred throughout the Katangan and Damaran systems from southern DRC to the Atlantic Ocean. The late-tectonic composite Hook Granite, which cuts the Nguba Group, comprises an older, magnetically flat set of medium-grained biotite-hornblende granitoid intrusions, dated at 559±18 and 566±5 Ma in two samples. These are cut by numerous, younger microcline-biotite-hornblende megacrystic phases, reflected by donut-shaped magnetic anomalies with diameters of from <10 to 50 km, interpreted to represent anorogenic ring complex intrusions. Samples of these intrusions have been dated at 533±3 Ma (Hanson et al., 1993; Nisbet et al., 2000; Lobo-Guerrero, 2010).
Location The Lufilian Arc comprises four distinct, north-convex, arcuate tectonic subdivisions, the:
i). External Fold and Thrust Belt to the northeast, mainly in the DRC (where it hosts the Congolese Copperbelt), characterised by thin-skinned thrust/nappe-dominated deformation, absence of exposed basement, low-grade metamorphism and structural repetition of the Katangan stratigraphy;
ii). Domes Region, which includes the Zambian Copperbelt in its outer margins, comprises a series of exposed basement domes, characterised by upper-greenschist facies metamorphism in the east, increasing in intensity to upper-amphibolite in the west.
  The belt is also characterised by a corridor of gabbroic intrusions, cutting both the basement in the domes, Upper Roan Subgroup and Nguba Group country rocks.
  The individual domes west of the Kafue Anticline, coincide with magnetic highs within a well defined arcuate belt of greater magnetic relief than the neighbouring Synclinorial Belt.
  Unconformable relationships between Katangan Supergroup rocks and older basement are preserved on the flanks of the Kafue Anticline, where upright to inclined, high-amplitude folds dominate. However, tectonic decoupling has been described at the same contact with basement domes further west, which are cored by recumbent folds and nappes, and juxtaposed thrust sheets of contrasting metamorphic grade (Cosi et al., 1992; Binda and Porada, 1995; Key et al., 2001).
  Daly et al. (1984) interpret the basement inliers in the Domes region to represent antiformal stacks above mid- to lower crustal ramps.
  These domes resemble metamorphic core complexes, capped by domal, radially outward-dipping detachments/décollements. The rocks above the décollements are usually metamorphosed to greenschist facies and comprise Katanga Supergroup lithologies, while those below are strongly metamorphosed Palaeo- and Mesoproterozoic gneisses and schists, with interpreted interleaved metamorphosed Neoproterozoic slices, and include quartz-feldspar-biotite±magnetite gneisses, garnet-bearing granite gneisses, etc., with a strong mylonite texture in the upper parts of the dome (cf., at Lumwana in the Mwonbezhi Dome). Talc-kyanite white-schists occur within the décollements between the basement and the Katangan Supergroup sedimentary sequence in the Domes (Hitzman et al., 2012), dated at ~530 Ma (John et al., 2004).
  The core of the more extensive Kafue Anticline on the southeastern margin of this region, was a basement high during deposition of the Katanga Supergroup, although it also shares some of the extensional and subsequent compressional features seen in the domes to the west, and is locally fringed by décollement structures (e.g., in the Nchanga-Mindola district);
iii). Synclinorial Belt, where sedimentary rocks were subjected to large scale folding during at least two deformation events, and low grade metamorphism and is reflected by a more subdued pattern in magnetic data, contrasting with its neighbouring regions. It has been suggested this sequence, reflects a change from a marginal shelf in the north in what is now the External Fold and Thrust Belt, to a deeper basin SW of the Domes region (Cosi et al., 1992; Porada and Berhorst, 2000). However, Selley et al. (2005) suggested that they could find no evidence for a deeper marine sequence in the Synclinorial Belt; and
iv). Katanga Core (or Katanga High) to the southwest, in which only the upper parts of the Katanga Supergroup and almost all of the outcropping granitic intrusions of the Lufilian Arc are exposed (Petters, 1986; Selley et al., 2005). It is reflected by a more complex and variable pattern in aeromagnetic data, with a well defined margin.
  The Katanga High was first proposed by De Swardt and Drysdall (1964), who considered that it represented a central core of uplift (for unknown reasons), which induced gravitational sliding of the Katangan cover sequence to both the north and the south. To the NE, Roan (Nguba) and Kundelungu group rocks were folded, imbricated and thrust northwards to form the Lufilian Arc. As a mirror image, the Zambezi Belt developed from similar processes to the SW, with late-stage transcurrent movements on the Mwembeshi Shear Zone juxtaposing low-grade rocks of the Lufilian Belt and high-grade rocks of the Zambezi Belt. Porada (1989) and Porada and Berhorst (2000) argued against this interpretation, and suggested instead, the Katanga High was composed of late Katangan rocks over shallow basement, over-thrust to the NE onto the Synclinorial Belt during the Lufilian orogeny.
  The exact nature of the Katanga High remains unclear. Hitzman et al. (2012) do not differentiate it from the core of the broader Katangan basin. It may well occupy the central core of a wide, NE-SW elongated, shallow basin of marine-shelf facies rocks that extended from the Kasai/Congo craton in the NW, to south of the Mwembeshi Shear Zone to the Kalahari Craton to the SE, and from the Foreland and Bangweulu Block to the NE, into Angola, Namibia and Botswana to the SW. The current geophysical expression of the Katanga High may be no more than a reflection of the superimposed late-Lufilian magmatic event intrusions represented by the late-tectonic composite Hook Granite complex.

The northeastern margin of the Lufilian Arc is represented by exposures of the relatively undeformed upper units of the Upper Kundelungu Group within the Kundelungu Gulf Foreland. The eastern margin of the arc, to the east of the Zambian Copperbelt, passes into a similar prong of Nguba Group overlying Irumide rocks, separated from the Kundelungu Gulf by the triangular Bangweula Block. This embayment represents transgression onto Irumide basement during the renewed extension that accompanied the onset of Nguba group deposition. The southern limit is defined by the major, WSW-ENE trending, sinistral Mwembeshi shear zone which separates it from the Zambezi Belt.

Following the two extensional events and deposition of the majority of the Katangan Supergroup, Late Neoproterozoic to Lower Cambrian basin inversion was initiated. Kinematics suggest NW to NE directed thrusting during this orogenesis, with displacement vectors radiating perpendicular to the arcuate trend of the fold belt (Selley et al., 2005). However, Porada and Berhorst (2000) and Kapunzu and Cailteux (1999) suggest the arcuate shape is the result of oblique compression during this event, between the northern margin of the Kalahari craton and the southwestern edge of the Congo craton. The stress field was complicated by the east-west compression that formed the major Mozambique Belt collision zone to the east, and resultant sinistral movement on the Mwembeshi shear zone, to produce 'oroclinal bending' and form the Lufilian Arc.

  See the Congolese/Katangan Copperbelt record for a more detailed summary of the deformation stages that formed the Lufilian Arc.

  In Zambia, these phases of deformation are expressed as follows:
• Early Extension, which followed an ~200 Ma period of quiescence, and marks the early onset of the break-up of the Rodinia Supercontinent. This resulted in the commencement of deposition of the Katanga Supergroup, initially in narrow grabens, which became interconnected and grew into the larger rift basin, as described above. The earliest deposition in the region, was south of the Mwembeshi shear zone (and the Lufilian Arc), in the Zambezi Belt, where it was accompanied by rift volcanic rocks (mainly dolerites) which yielded zircon ages of ~880 Ma (Frimmel et al., 2011). Within the main Lufilian Arc, the coeval Nchanga Red Granite (877±11 Ma; U-Pb SHRIMP zircon; Rainaud et al., 2000) is overlain by the basal Katanga Supergroup above an erosional contact, without any volcanic component. This phase of extension corresponded to the deposition of the Lower and Upper Roan subgroups.
  During this phase, a NNW-SSE trending structural high occupied what was to become the core of the D2 Kafue Anticline (see below), influencing the distribution and thickness of facies. This structure also included the basement exposed in the Konkola and Luina domes, now separated by D2 and D3 synforms. It was partially emergent during deposition of the Lower Roan subgroup Mindola Clastics Formation, which on the rims of, and in remnant structural basins in the core of the anticline, contain basal conglomerates, channel sediments incised into basement, and aeolian sandstones. Away from the anticline, the sequence grades into finer and deeper water facies.
  The same basement high was largely submerged during the deposition of the overlying Kitwe Formation, which grades from arenites over the crest of the basement high in the east, to a well defined shale corridor, before passing into deeper water turbiditic sedimentary rocks in the Synclinorial Zone to the west. Similarly, the structure is subsequently largely submerged, overlain by the shelf/carbonate-rich to lagoonal Upper Roan subgroup sequence (Porada and Berhorst, 2000);
  Breccias, interpreted to be after mobilised evaporitic units, are found within the Upper Roan subgroup over and adjacent to the Kafue Anticline. These breccias and interpreted evaporitic layers are less developed than in the similar lithologies and halokinetic megabreccias of the mineralised sequence in the DRC.
Roan cross section • Renewed Extension, from ~765 to 735 Ma (Hitzman et al., 2012), corresponding to the D1 Kolwezian tectonic event, of François (1974) and Kampunza and Cailteux (1999) in the DRC. It is suggested here, that during this event, extension resulted in the development of a corridor of metamorphic core complexes in the Domes Region, including the Solwezi, Mwonbezhi and Kabompo domes, possibly in part the Luswishi Dome, but not the Kafue Anticline. The latter, had formed as a faulted basement high during or prior to the Early extension, as is probably also true of the Luswishi Dome, although it was also most likely uplifted during this extension. During the uplift of the metamorphic core complex domes, and coincident widening and deepening of the rift basin, the evaporite rich Upper Roan subgroup rocks were tectonically dismembered and attenuated over the domes, and slumped to the north above a salt-lubricated gravity glide décollement, to be imbricated into a stack of north-vergent thrust sheets and nappes in the deeper section of the rift basin on the outer half of the External Fold and Thrust Belt (Kampunzu and Cailteux, 1999 and references cited therein; see also the diagram in the separate Congolese/Katangan Copperbelt record). This represents extension of this unit in the Domes Region of northern Zambia, and contraction/shortening in the External Fold and Thrust Belt of the DRC.
  This extension accompanied, and post-dated deposition of the Mwashya subgroup and Nguba Group. Both units are found over and flanking the Kafue Anticline and associated Konkola and Luina domes, the Solwezi dome and the External Fold and Thrust Belt. The dominantly shale facies of the Mwashya subgroup are developed in the deeper section of the rift basin in the outer half of this belt in the DRC, grading into sandy facies on the margin with the Kundelungu Gulf Foreland to the north, and to the south towards the Domes Region (Cailteux et al., 2007). At the same time, deposition extended to the west and east over the marginal Kibaran and Irumide basement respectively, and into the Kundelungu Gulf Foreland. These rocks are not mapped around or to the south of the domes to the west, in the Synclinorial Belt or over the Katanga High, although they may have not been differentiated in these areas.
  A ~30 to 100 km wide by ~500 km long, linear ESE-WNW trending corridor of gabbroic to dioritic intrusions follows the Domes region from the Luanshya Structural Basin through the Chambishi Structural Basin, the southern margin of the Nkana Dome, the Luswishi, Solwezi, Mwombezhi and Kabompo domes. These rocks vary from mafic to ultramafic in composition, mainly amphibolites, ophitic gabbros and olivine gabbros, but also basaltic lavas, norites, picrites, peridotites, Iherzolites, troctolites and a few eclogites and serpentinites. They are often lensoid and discontinuous, with structural margins accompanied by brecciation (Porada and Berhorst, 2000), although large masses up to 10 km across have also been mapped. Based on limited dating, and stratigraphic relationships, these intrusions are interpreted to be associated with the ~765 to ~735 Ma extensional event, and coeval with the mafic to intermediate volcanic rocks in the Dipeta and Mwashia subgroups and lower Nguba group in the DRC. Mwashia Group rocks have not been differentiated to the south of this corridor. The geochemical evolution of these mafic rocks ranges from earliest continental tholeiite to alkaline and tholeiitic magmas, and finally in the DRC, to lavas with E-MORB affinities, suggesting a progression from continental to a possible embryonic oceanic rift (Kampunza et al., 2000). Stratigraphic relationships at Kansanshi suggest some of these intrusions may be late Lufilian, <600 Ma in age. These mafic rocks are observed to have a wide variation in metamorphic overprint (Porada and Berhorst, 2000), which may be explained by their presence within and outside of the metamorphic core complexes of the Domes and two different ages.
• Main Stage Lufilian Orogenesis, commencing at ~600 Ma, but spread over the interval from 600 to 512 Ma (Armstrong et al., 2005). The earliest greenschist facies metamorphism has been dated at 592±22 Ma (U-Pb monazite from zircon) and 585±0.8 Ma (Ar-Ar biotite; Rainaud et al., 2002), with peak metamorphism at ~530 Ma for white schist metamorphism in the western Domes region (John et al., 2004). Post orogenic cooling is represented by widespread 510 to 465 Ma Ar-Ar biotite and Rb-Sr muscovite ages (Cosi et al., 1992; Torrealday et al. 2000; Rainaud et al., 2002; John et al., 2004).
  This, generally NE-SW directed compressional stage, corresponds to the structural inversion of the Katangan rift basin, and is characterised by complex polyphase deformation and superimposed thrust terranes, curved folds and sinistral strike-slip shear/fault zones. Kipata (2013) regards this D2 phase as the second major deformation in the Lufilian Arc, compatible with an overall NE-SW transpression, reactivating D1 structures.
  D1 décollements appear to have been reactivated in the domes to the west of the Kafue Anticline, and post-D1 rocks of the Mwashia and Nguba groups have been isoclinally, folded as interpreted at the Kansanshi deposit (see the separate Kansanshi record).
  The structure over and adjacent to the Kafue Anticline is characterised by thrusting within the basement, passing up to be expressed as folding within the overlying Roan Group rocks. This is evident across the anticline from Chingola-Nchanga eastward to Mufulira. In the west of this section, ENE verging thrusts follow the basement-Roan Group contact, passing upwards to emplace imbricated and interleaved wedges of basement gneiss and granite with Roan Group rocks. Further east, the basement thrust climbs into the Roan Group, and follows the Copperbelt Orebody Member of the basal Kitwe Formation as a décollement. This structure separates basement, granite and overlying Mindola Clastics Formation siliciclastic rocks, all of which are poorly deformed, from overlying, strongly folded, Kitwe Formation lithologies. Similar décollements and decoupling are common at this stratigraphic position elsewhere, e.g., at the Luanshya, Nkana and Chambishi deposits, exploiting the more fissile lithologies of this member. Eastward, towards the centre and eastern margin of the Kafue Anticline, WSW facing folds and east dipping reverse faulting, thrusting and banded mylonite zones are evident. On the eastern margin of the Kafue Anticline, at Mufulira, ENE verging folds are evident although, these face downwards. Similar structures are mapped elsewhere on the same margin (Daly et al., 1984).
  Daly et al. (1984) interpret this structural pattern to reflect ENE vergent thrusting above a deep décollement within the basement of the Kafue Anticline, with associated branching subsidiary thrusts that climbed up through the sequence. The back thrusts to the east are interpreted to be compensatory structures, while the downward facing folds are taken to be equivalents of the structures on the western flank that have been subsequently tilted as the Kafue Anticline rose as a thrust culmination.
Cross section
  The Kafue Anticline is also characterised by a series of basinal and domal structures e.g., the Luanshya and Chambishi structural basins and the Konkola and Luina domes and the basin between the Luina, Konkola domes and northern Kafue Anticline. These structures appear to be the result of interference between an earlier NE-SW and a later NNE-SSW compressional event. It is suggested that during the three separate D2 pulses recognised by Croaker (2011), the direction of compression may have rotated to produce this interference pattern. Croaker (2011) also suggests the pattern of folding may be partly influenced by the orientation of the original rift/graben depositional basins and inhomogeneity of facies distribution. Annels (1984) suggest the interference pattern is due to the overprinting of initial ESE-WNW trending rift phase depositional basins and the NE-SW D2 compression, although this is at odds with the through-going NNW-SSE trend of the shale-facies corridor from Luanshya to Musoshi.
• Late Orogenic Extensional Collapse, a brittle event, probably post ~530 Ma, only recorded in the Lufilian Arc (Kipata, 2013). It caused NW-SE directed extension across the whole arc, and reactivation of earlier compressional and strike-slip structures. This protracted period of post-orogenic uplift and cooling extended to 483 Ma (Porada and Berhorst, 2000; John et al., 2004; Rainaud et al., 2005 in Master and Wendorff, 2011).
• Post-orogenic Transpressional Inversion, a NW-SE brittle transpressional inversion recorded in the Lufilian Arc also affects the Kundelungu Foreland and the fringing Irumide and Ubendian basement. It corresponds to the Lufilian D3 Chilatembo stage of Kampunzu and Cailteux (1999) and took place after the Lufilian extensional collapse. François (1993) suggested an age of ~305 Ma for this event, which Kipata (2013) similarly regards to be post-Lufilian, most likely Palaeozoic in age. It produced large, gentle, open, upright folds with axes varying from NNE-SSW to ENE-WSW (e.g., the ENE-WSW oriented syncline that separates the Luina and Konkola domes from the main Kafue anticline), and north-south and east-west faults, low-angle thrusting of Nguba and Kundelungu group units, possibly accompanied by late salt diapirism (Kampunzu and Cailteux, 1999; Schuh et al., 2012; Kipata, 2013). This phase is responsible for much of the interference folding seen in the DRC section of the Lufilian Arc.
• Uplift, Peneplanation and Cratonisation and extension related to the Cenozoic African Rift.

Zambian Copperbelt



Distribution of Mineralisation

Traditionally, the ore deposits of the Zambian Copperbelt have been interpreted to lie within the Neoproterozoic Lower Roan Subgroup, composed principally of coarse siliciclastics (conglomerate to arkose and siltstone, with lesser carbonate rocks). The main deposits define two NW-SE trending parallel lines of Cu mineralisation some 20 km apart, separated by the Palaeoproterozoic basement gneisses, granitoids and schists, and Mesoproterozoic conglomerates, quartzites and granitoids that make up the Kafue Anticline, in the eastern Domes Region of the Lufilian Arc. Each of these two belts is 5 to 20 km wide and up to 150 km long. Ore grade mineralisation, however, tends to occupy linear, often more structurally complex, semicontinuous bands, up to 2 to 3 km wide, and as much as 17 km long, particularly on the SW line, interrupted by narrow barren gaps and cross folded anticlinal basement ridges (e.g., the Nkana-Mindola, Nchanga and Konkola strings of deposits). The majority of the deposits are on the SW of the two lines of mineralisation, which coincides with a corridor of shale facies developed at the base of the Kitwe Formation, and lapping onto basement to the east.
   Within these two belts of deposits, there are some 6 major and >25 minor stratabound deposits. The major deposits are Luanshya-Baluba, Mufulira, Nkana-Mindola, Nchanga-Chingola, Chambishi and Konkola-Lubambe. The larger orebodies had production + resources that range from 90 to 1000 Mt @ 2.4 to 3.6% Cu. Between 1930 and 1987 some 24 Mt of copper metal was produced from 1.07 Gt of ore averaging 2.71% Cu. The total mined ore plus reserves/resources has been calculated at 3.28 Gt @ 2.68% Cu containing ~88 Mt of Cu (Selley et al., 2005 and references cited therein).

The Lower Roan Subgroup is conformably overlain by Neoproterozoic carbonate rocks of the Upper Roan Subgroup which is equivalent to the R.A.T., Mines and Dipeta subgroups in the External Fold and Thrust Belt of the neighbouring Democratic Republic of Congo (DRC). These rocks are mostly barren in the Zambian Copperbelt, but host most of the significant Cu-Co deposits of the Katangan section of the Central African Copperbelt in the DRC.

More recently, the Lumwana and Kansanshi operations, located in the central to western Domes Region to the west of the established Copperbelt, were brought into production. In 2013 they were the biggest copper producers in Africa, each with large, lower graded resources of 800 to 1000 Mt @ 0.5 to 0.7% Cu. These deposits have differences in the apparent mode of occurrence compared to the main copperbelt deposits fringing the Kafue Anticline. See the two overlapping images below for a geological summary of the Domes Regions and distribution of units described above. For more details of the local geology and the mineralisation styles, see the records for the Lumwana (Chimiwungo and Malundwe), Kansanshi, Enterprise and Sentinel deposits. Eastern Domes Region Western Domes Region


Mineralisation

Mineralisation within the major deposits 'flanking' and overlying the Kafue Anticline has the following characteristics:

i). Fault-controls - The geometry, size and distribution of orebodies is closely linked to early fault-controlled sub-basin architecture during deposition of the Lower Roan Subgroup. Basement faulting affected facies distribution on basement margins, the formation of structural and stratigraphic culminations influencing fluid flow and entrapment, and may also have provided pathways for fluid ingress, e.g., most argillite hosted orebodies overlie anomalously condensed wedges of Mindola Clastics Formation, where the overlying Copperbelt Orebody Member is transgressive onto basement, coincident with fault related trough margins/basement highs. Many orebodies are also located at the intersection of basin bounding faults. In addition, footwall and hanging wall arenite hosted orebodies are also frequently aligned along basin margin faults (Selley et al., 2005 and references cited therein).
   Many of the early basin controlling faults appear to have been reactivated during Mwashya to lower Nguba extension, reflected by changes in stratal thickness of Roan Group rocks and by increased folding and deformation that was commonly focused by these structures during Lufilian deformation (Hitzman et al., 2012).

ii). Mafic magmatism - Many of the largest deposits in the Central African Copperbelt, have a spatial association with mafic magmatism, e.g., Kamoa and Kolwezi in the DRC and Konkola and Kansanshi in Zambia, which are spatially associated with abundant mafic sills or flows or aeromagnetic anomalies that may represent buried mafic intrusions (M. Hitzman, unpub. data, 2010). The line of deposits of the Domes Region in Zambia (Sentinel, Enterprise, Lumwana and Kansanshi) fall within and are aligned along the major corridor of gabbroic intrusions that occupy that structural feature. In addition, the same gabbroic corridor obliquely intersects the Kafue Anticline from Luanshya in the south to Nchanga in the north, although mafic dykes are also found at Konkola. The flanks of the Kafue Anticline over this interval hosts virtually all of the large Cu-Co deposits of the Zambian Copperbelt.

iii). Stratigraphic control - Mineralisation and major Cu-Co ore deposits, are found in association with the following carbonaceous units within the Central African Copperbelt, including those that only host ore in the DRC:
• A package of rocks, up to ~150 m thick, straddling the Copperbelt Orebody Member, incorporating sections of the upper Mindola Clastics and lower Kitwe formations of the Lower Roan Subgroup. The Copperbelt Orebody Member largely comprises a finer 0 to 100 m thick unit of generally carbonaceous argillites, carbonatic argillites and interbedded arenites, underlain and overlain by the coarser, oxidised, clastic successions of the Mindola Clastics and Kitwe formations respectively, on the SW fringe of the Kafue Anticline. The 30 to 80 m thick Mufulira ore-bearing sandstones to the NE of the same basement high, are an inferred equivalent of the Copperbelt Orebody Member, and comprises three "Orebody Quartzites", each capped by a mudseam, dolomitic bed or argillaceous quartzite. Some 65% of the mineralisation of the Zambian Copperbelt lies within the Copperbelt Orebody Member (e.g., Luanshya-Baluba, Mufulira, Nkana-Mindola, Nchanga-Chingola, Chambishi and Konkola-Lubambe) and Mufulira ore-bearing sandstones (e.g., Mufulira).
   A further 25% of the Zambian Copperbelt ore lies within coarser footwall clastics of the underlying Mindola Clastics Formation (e.g., at the Chibuluma deposits, where ore is capped by sandy argillites within the Mindola Clastics, whilst the Copperbelt Orebody Member and Kitwe Formation are absent, and the Mindola Clastics formation is directly overlain by the Upper Roan Subgroup; at Fitula, Mimbula and Chingola in the Nchanga district, where the ore steps upwards to the north, from the "footwall" Mindola Clastics formation, in the south, to the Copperbelt Orebody Member at Chingola-Nchanga and then into the "hanging wall" at Nchanga; and the Footwall ore below the Southern Ore Body at Nkana).
   The remaining 10% of the ore within the Zambian Copperbelt lies within the coarse "Hanging Wall" arenites of the Kitwe Formation, above the main mineralised Copperbelt Orebody Member (e.g., the large deposit within The Feldspahic Quartzite at Nchanga, where it is 15 to 40 m thick, and is capped by the Upper Banded Shale);
   Lithologically, 60% of the ore in this package is hosted by argillites, and 40% in arkose, quartzites and conglomerates. Ore within this package is largely restricted to the eastern Domes Region in Zambia and southern DRC.
• The 'Lower' and 'Upper' orebody packages in the Mines Subgroup, only found in the DRC (e.g., at the Kolwezi and Tenke-Fungurume deposits), and sometimes the overlying 'Third orebody' position (e.g., Kambove-Ouest), also in the same subgroup. The Lower and Upper orebody packages overlie the red to lilac R.A.T. Subgroup and comprise two 5 to 15 m thick units of grey, laminated, fine-grained, argillaceous and chloritic dolostone to dolomitic siltstones, sandwiching a strongly silica-dolomite altered unit that is 10 to 30 m thick, originally composed of massive, porous reefal stromatolitic dolostones. The Third orebody position is 60 to 100 m above the the Upper orebody package, within carbonaceous massive to laminated dolostones. Where ore occurs in this latter position, the mineralised intervals lower in the sequence are often poor (Pelletier,1964). These rocks were deposited in the post-Lower Roan Subgroup sag phase facies of the Roan Group that transgressed northward from the main rift in Zambia, onto its margins in the DRC. For detail, see the Congolese/Katangan Copperbelt record;
• The Kansuki Formation of the Dipeta Subgroup, also restricted to hosting ore in the DRC (e.g., Mutanda and Deziwa), are part of the Roan Group sag phase facies, deposited at the transition to renewed extension. It comprises a generally >80 m thick sequence, mostly separated from the underlying Dipeta sequence by a structural contact, marked by an evaporite-facilitated breccia-detachment. It is characterised by alternating reefal to intertidal deposition, comprising laminated and massive stromatolitic or arenaceous dolostones, oolitic dolostone, erosional surfaces, intraformational conglomerates and pseudomorphs after anhydrite near the top of the formation. The Kansuki Formation also contains ~765 Ma (Key et al., 2001) mafic lavas, and extensive, 2 to 12 m thick beds of associated pyroclastic flows and volcaniclastic rocks interbedded with dolostones, defining a regional 'volcanic belt'. This sequence is underlain by the R.G.S. Formation, at the base of the Dipeta Subgroup, containing oxidised clastic rocks, similar to those of the R.A.T. Subgroup. Where this unit hosts major deposits, it is uncertain if the Mines Subgroup is developed below, although it may only be represented by the normally barren Menda facies. For detail, see the Congolese/Katangan Copperbelt record;
• The Mwashya Subgroup in Zambia (e.g., Kansanshi) and DRC (e.g., Frontier), deposited in the deepening Katangan basin during the main episode of renewed extension and northward migration of the depocentre. The main prospective unit is the central, ~75 to 140 m thick Kafubu Formation, a sequence of finely bedded, grey to dark grey or black, pyritic carbonaceous shales with local sandy, silty and dolomitic interbeds. At Frontier, the normally underlying Lower Roan hosts are absent, and the Mwashya Subgroup represents the first reduced unit overlying an oxidised arenite sequence separating it from the basement. At Kansanshi, the underlying Lower and Upper Roan subgroups are exposed on the margins of the Solwezi Dome, 12 km to the south;
• The Grand Conglomérat of the basal Nguba Group (e.g., Kamoa in the DRC, Fishtie in Zambia, and to a lesser extent at Frontier in the DRC), deposited in a similar setting to the Mwashya Subgroup. During this renewed extension, the Katangan Basin deepened and spread outward onto the Kibaran and Irumide basement to the NW and SE respectively, without any underlying Roan Group, other than a thin oxidised conglomeratic wedge of Mwashya Subgroup at Kamoa.
   At Kamoa, the Grand Conglomérat comprises a 'basal diamictite package', commencing with 0 to 30 m thick, clast-rich, sandy diamictite, overlain by 0 to 5 m of sandstone-siltstone to lithic greywacke and by 0 to 15 m of clast-poor, silty/muddy and weakly carbonaceous diamictite. This package hosts the bulk of the resource, and it is uncertain how much original pyrite was in the rock, prior to the introduction of the copper sulphides. It is overlain by a 15 to 45 m thick, dark, pyritic, siltstone-sandstone unit, which is predominantly well stratified and laminated, with bedded pyrite and little Cu sulphide. These are overlain by 0 to 900 m of diamictites and pyritic siltstones, and then by the Kakontwe Limestone (For detail, see the Congolese/Katangan Copperbelt, Kamoa and Fishtie records).
  No major stratabound Cu-Co deposits have yet been found (to 2015) higher than the Grand Conglomérat, although late stage pitchblende and uraninite veins penetrate overlying Nguba and Kundelungu group rocks at Shinkolobwe and related deposits both in the DRC and Zambian Copperbelt, while late stage Pb-Zn ore at Kipushi and similar occurrences are also hosted by rocks at higher stratigraphic positions.

iv). Redox boundaries - Mineralisation within the Zambian Copperbelt is closely associated with stratigraphic or structural redox boundaries in the host units described above, related to rocks that may have contained reductants and that overlie coarse, permeable, oxidised arenites. The redox boundaries are related to reductants that may be either i). in situ largely occurring relatively dark and locally carbonaceous siltstones and argillites, often with fine arenite interbeds; or ii). mobile e.g., sites that are geometrically favourable to the entrapment of liquid hydrocarbons or sour gas. These rocks acted both as a cap to fluid flow within the coarse clastic sediments, and as a redox boundary and reductant, catalysing the release of Cu from oxidised fluids. Pyritic, carbonaceous rocks, with few exceptions, form a barren cap and or mark the lateral margins to ore, as well as in some cases, a barren footwall.
   Of the major deposits, Luanshya, Nkana-Mindola, Chambishi, Konkola-Lubambe and in part Nchanga are hosted by the Copperbelt Orebody member which is taken to represent a unit that contained in situ hydrocarbons. Deposits of this type are laterally extensive with strike lengths up to 17 km. The deposits hosted by Mwashya Subgroup (e.g., Frontier and Kansanshi) and Nguba Group (Fishtie in Zambia and Kamoa in DRC) are also most likely associated with in situ hydrocarbons.
   Deposits interpreted to be related to accumulation of mobile hydrocarbons are usually arenite-hosted deposits which occur in both the footwall, hanging wall and equivalents of the Copperbelt Orebody member, and have maximum strike lengths of 5 km. Deposits of this type include Mufulira and much of the Fitula-Mimbula-Chingola-Nchanga string of deposits, as well as Mwambashi B and the Chibulumu deposits.
   On the eastern margin of the Kafue Anticline, a thick carbonaceous arenite unit, occurs at the same stratigraphic position as the Mufulira arenite hosted ore deposit, and forms the lateral gradational margin to mineralisation. The carbonaceous matter, which is finely disseminated throughout this sandstone suite, is interpreted to have originated as mobile hydrocarbons based on δ13C and δ18O values (see below; Annels, 1979; 1989). It transgresses bedding and is continuous over a strike length of >16 km, capped by less permeable shale and dolomite interbeds. Similarly, the string of deposits from Fitula, through Chingola and Nchanga gradually climbs through the sequence from the Mindola Clastics Formation in the south, to the hangingwall of the Copperbelt Orebody member of the Kitwe Formation 18 km to the north, much of which is hosted by arenites, capped by argillite bands.
   The location, geometry and size of deposits, particularly those related to mobile hydrocarbons are fundamentally controlled by early subbasin fault architecture and the supply of the reductants, which are also linked to basin architecture (Selley et al., 2005). The most common interpreted trap sites for mobile hydrocarbons include: i). where the argillites of the Copperbelt Orebody member lap onto basement up-dip, over a pinchout wedge of Mindola Clastics formation rocks; ii). early Lufilian antiformal culminations, as postulated at Nchanga, and iii). culminations resulting from differential compaction of sediments over basement highs that do not penetrate to the capping 'shale', as at Mufulira, due to a lesser decrease in thickness of thinner sections over underlying basement hills (usually of granite), compared to the greater cumulative reduction in thickness over intervening basement lows (usually over Lufubu schists).
   Where mobile hydrocarbons are the indicated redox agent, mineralisation would have occurred after the hydrocarbon source rocks of the basin had been buried to several thousand metres depth in order to maturate and generate gaseous and liquid hydrocarbons. This burial would take place in the deeper core of the basin, and hydrocarbons migrated up dip to shallower structural and stratigraphic traps on the basin margin, to combine with oxidised Cu-bearing fluids. This would require ore deposition took place during late- or post-diagenesis.
   Throughout the Zambian Copperbelt, the most carbonaceous rocks within an ore horizon are commonly not economically mineralised, i.e., there is an antithetic relationship between carbonaceous rocks and ore. This implies the carbonaceous reductant is 'consumed' during the ore forming process, as explained below. Also, where deposits occur in the stratigraphically lowermost reduced rocks (e.g., the Copperbelt Orebody Member), overlying reduced or favourable rocks (e.g., the Mwashya Subgroup) generally were not mineralised. Conversely, deposits within higher stratigraphic level reduced rocks (e.g., the Mwashya Subgroup) are found where no underlying reduced unit has been developed.
   The antithetic relationships described previously, between both carbonaceous material and anhydrite with copper sulphide mineralisation, suggests both were an integral part of the formation of ore. Mobile hydrocarbons within a hydrocarbon reservoir react with authigenic anhydrite cements (using methane as generic hydrocarbon), to produce H
2S (sour gas) in the first instance: CaSO4 + CH4 → CaCO3 + H2S + H2O. The second step involves interaction with a Cu-bearing brine, with a most likely chloride ligand, as follows: H2S + 2 CuCl → Cu2S + 2 HCl.
   In the event of a Cu-bearing brine reacting with in situ carbonaceous material and entrained authigenic anhydrite cements, the process becomes: CaSO
4 + CH4 + 2 CuCl → Cu2S + 2 HCl + CaCO3 + H2S + H2O.
   However, in both cases, the HCl produced breaks down the CaCO
3 and reverses the process. But, where excess Fe, Mg or Mn ions are present within the brine, the HCl is neutralised and the process becomes: CaCO3 + (Mg/Fe/Mn) + HCl → CaCl + (Mg/Fe/Mn)CO3 + H2O (Orr 1974 and Irwin, et al., 1977). This process destroys both the anhydrite and carbonaceous matter, where ore is formed, and produces a gangue of dolomite, ankerite, siderite, etc., deficient in free carbon and anhydrite, as is observed.
   Annels (1989) recognised that light δ
13C and δ18O values can be the result of temperature effects during hydrothermal alteration, from the incorporation of isotopically light C and O, produced by oxidation of organic matter (in situ or mobile hydrocarbons), into secondary carbonates during low-temperature (~60 to 80°C) bacterial sulphate reduction, or from high temperature (>100°C) thermochemical sulphate reduction as in the processes outlined above.
   Selley et al. (2005) collected δ
13C and δ18O data from 369 carbonate samples (whole rock, veins and evaporite nodules) from 10 deposits and one regional drill hole, spanning the stratigraphic interval from rocks of the Mindola Clastics Formation to those of the Mwashya Group. These data revealed that samples from both ore zones and the immediate hanging walls to ore zones have consistently light isotopic signatures compared with normal sedimentary values found in primary carbonate and clastic rocks. Carbonates from the argillaceous rocks of the Copperbelt Orebody Member, and Mindola Clastics Formation contain a broad range of isotopic values (δ13C ~ -26 to +3‰ and δ18O ~ +7 to +23‰). However, strongly depleted isotopic values (δ13C < -14‰ and δ18O <+13‰) are entirely restricted to ore zones. There are a number of possible ways to produce this result, which Selley et al. (2005) discuss, but conclude that the most plausible is oxidation of organic matter to CO2 which then becomes incorporated in diagenetic or hydrothermal carbonates (e.g., Rollinson, 1993; Ohmoto and Goldhaber, 1997; Wilson et al., 2003).

v). Ore fluids - Salinities of fluid inclusions (Selley et al., 2005 and references cited therein) increase from:
• 11 to 21 wt.% NaCl
equiv. and homogenisation temperatures of 110 to 170°C, from diagenetic early mineralisation (chalcopyrite-bearing carbonate nodules and subconcordant veins at the Chambishi and Chambishi South East deposits; Annels, 1989), to
• 21 to 38 wt.% NaCl
equiv. and homogenisation temperatures of 155 to 185°C, from folded veins cutting stratabound ore (unmineralised, high-angle and deformed quartz±carbonate-K-feldspar-pyrite veins cutting the Lower and Upper orebodies, at the Nchanga deposit; McGowan, 2003), to
• ~39 wt.% NaCl
equiv. and homogenisation temperatures of ~400°C for late ~500 Ma veins interpreted to be related to mineralisation at Musoshi, interpreted to represent feeders for copper mineralising fluids (Richards et al., 1988).
This trend indicates an increase in salinity and temperature with time.

vi). Mineralisation styles and textures - Deposits have a range of differing mineralisation styles and textures that may occur together or alone. The chief of these are:
• Disseminated, generally fine-grained (<0.1 to 3 mm) sulphides within interstitial sites between detrital or authigenic grains, randomly distributed or aggregated to form bedding-parallel streaks and lenses of blebs. There is a correlation between the size of detrital and sulphide grains in this style of dissemination (Selley et al., 2005 and references cited therein). Sulphides may also occur replacing detrital grains and authigenic cements, including anhydrite, carbonate, quartz and feldspar, as well as diagenetic pyrite, anhydrite, carbonate, quartz, feldspar or heavy minerals such as rutile (Binda, 1975; Fleischer et al., 1976). Disseminated ores predominate in porous and permeable host rocks such as sandstones, coarse silts or shales with sandy interbeds (Hitzman et al., 2012);
• Vein-hosted, which may occur as prefolding, layer-parallel and discordant veins or veinlets of sulphide, which have sharp contacts with argillaceous strata, and diffuse margins in arenites (Annels, 1989). Prefolding vein-dominated deposits occur within strongly carbonaceous host rocks which lack economic disseminated mineralisation, and may consist entirely of sulphides or be accompanied by other minerals, particularly quartz and dolomite, with lesser K feldspar, albite, chlorite, sericite, phlogopite and anhydrite (Hitzman et al., 2012).
   Veining also occurs as late-tectonic, generally coarse-grained sulphide grains (commonly >0.5 to 3 cm) in quartz-carbonate (dolomite, calcite) veinlets and subordinate veins, which may also contain K-feldspar, chlorite, sericite, biotite, and, very locally, albite, tremolite, and below the zone of supergene dissolution, anhydrite. Veinlets are typically ~0.5 to 2 cm wide, but may locally be up to several tens of cm thick and extend for distances of several tens of metres or more, with densities of 1 to 5 per metre, following and stepping up through the stratigraphy. Veins also occupy tension gashes on a small scale and other structures at a high angle to bedding. Veins and veinlets can be particularly abundant at the tops and/or bottoms of the stratabound orebodies, commonly coinciding with rheologic contrasts and occupying shear zones and décollements at the boundaries between more argillaceous and siliciclastic rocks. Veinlets often penetrate upwards from arenite hosted disseminated mineralisation into otherwise unmineralised, impermeable carbonaceous shales. Mineralised veins are restricted to zones of disseminated mineralisation, and contain the identical sulphide assemblages found within the enclosing disseminated mineralisation throughout the zoned sulphide assemblages (Hitzman et al., 2012, and references cited therein; Sillitoe et al., 2010).
   In addition to these Cu±Co vein systems, the Zambian Copperbelt contains volumetrically minor Cu-U-Mo-(Au)-(Ni) sulphide assemblages in post-folding veins with associated albite haloes, e.g., Mindola, which is the only known economic accumulation (Darnley et al., 1961). Generally sub-economic uranium occurs as late veins and local disseminations of pitchblende, uraninite, brannerite, coffinite and secondary oxide minerals below or adjacent to copper mineralisation (Selley et al., 2005).
•  oxide ores, usually gradationally overlying the hypogene mineralisation, through a progression from primary sulphide (chalcopyrite-bornite-carrollite), through mixed oxide-sulphide (chalcocite-copper carbonate/sulphate-cuprite-native copper) to leached capping (usually ~30 m thick). The transition usually takes place over an interval of 30 to 70 m below the surface, although in some areas of deep faulting, malachite and chalcocite have been found to persist to depths of as much as 1 km at Konkola and >600 m at Nchanga Lower. As chalcocite generally occurs closest to the surface in the primary sulphide zonation, it is often difficult to differentiate between primary and supergene populations of the mineral (Selley et al., 2005).
•  cupriferous mica mineralisation, which occurs at a number of deposits as an upper and/or lower fringe to sulphide orebodies, but never laterally. At the Mimbula-Fitula deposits, cupriferous micas persist to a depth of up to 150 m, although the bulk is in the zone from near surface to a depth of 60 m. The cupriferous micas are brown to dark brown in colour, and are visually indistinguishable from unmineralised mica. Stockpiles of as much as 150 Mt @ 1.2% Cu have been accumulated at Chingola, and resources of in situ mineralisation and stockpiles at Nchanga are >275 Mt @ 1 to 1.4% Cu. The mineralisation is refractory. Copper is held in the mica lattices in the exchange position, tied largely to hydroxyl groups in interstratified phlogopite-cupriferous chlorite micas. Some copper is also absorbed on the surfaces of layered mineral structures. Under tropical or sub-tropical conditions of weathering, it has been shown that copper may be dissolved out of primary minerals, and where the adjacent rock is micaceous, Cu is 'soaked up' by the micas as it passes through the rock. Weathering of primary phlogopite causes exchanges of K ions by hydrated Cu and Mg ions, followed by chloritisation. The Cu content of this mineralisation ranges from 1 to 8% Cu (Diederix 1977).

vii). Alteration - Prolonged, repeated, multiple stages of alteration are evident within the Zambian Copperbelt, ranging from diagenetic overgrowths, to post-metamorphic vein selvedges, reflecting the similarly prolonged history of Cu mineralisation. Three dominant alteration types are widespread throughout the Copperbelt, controlled partly by lithology and indicative of the large scale passage of basinal brines. These are (after Selley et al., 2005 and references cited therein):
•  Calcic-magnesian - an early diagenetic to early lithification, dominantly pre-ore, alteration suite, characterised by anhydrite, dolomite, calcite and later development of phlogopite. Anhydrite, dolomite and calcite are common throughout the Roan Group, occurring as coarsely crystalline anhydrite-dolomite beds, patchy to pervasive authigenic cements, replacive grains, nodules (up to several cm diameter) and as veins. These are most abundant within the Kitwe Formation and Upper Roan Subgroup, where they are probably of evaporitic origin. Widespread discordant and semiconcordant breccias within the Upper Roan Subgroup have been interpreted to have resulted from the dissolution of extensive halokinetic remobilised evaporites.
  However, anhydrite, dolomite and calcite are also present, mainly as authigenic cements, within non-evaporitic deltaic and shallow marine lithologies of the Lower Roan Subgroup, e.g., i). ±30% anhydrite filling pores within the Porous Conglomerate member and other arenites of the Mindola Clastics Formation; ii). quartz-dolomite-anhydrite veinlets in the lower Copperbelt Orebody Member argillites of the basal Kitwe Formation; and iii). 20 to 30% anhydrite in the Mufulira ore-bearing sandstones. The presence of this assemblage in these non-evaporitic lower units of the Lower Roan Subgroup, suggests diagenetic brine reflux, whereby dense Mg-Ca-SO
4 brines, sourced from the overlying evaporitic Upper Roan Subgroup, sink to displace lighter fresh pore waters. There is a marked antithetic relationship between anhydrite and ore, which is taken to indicate that anhydrite may represent an in situ source of sulphur in ore minerals and was 'consumed' in the process of ore formation, to produce sulphides and a dolomite gangue, as described above. Authigenic anhydrite nodules show progressive to total replacement by ore sulphides and gangue dolomite/carbonates at the lateral transition to ore (Hitzman et al., 2012; Selley et al., 2005; Sweeney and Binda, 1989; Annels, 1974).
  The widespread development of phlogopite (KMg
3AlSi3O10(F,OH)2), particularly in argillites, is suggested by Selley et al. (2005) to represent later isochemical metamorphism of previously pervasively magnesian metasomatised rocks throughout the succession. Within the Upper Roan and Mwashya subgroups, and the lower Nguba Group, above the main evaporite horizons, local significant albitisation and silicification accompanies the calcic-magnesian phase.
•  Potassic - characterised by K feldspar and sericite-muscovite. The feldspar content of detrital rocks within the Lower Roan Subgroup is virtually 100% potassic, at variance with the high sodic feldspar content of the source basement rocks. This and textural features of the rocks (e.g., the partial to total replacement of plagioclase detrital grains), are interpreted to be the result of intense K metasomatism of the Lower Roan Subgroup. Textures indicate multistage K feldspar replacement which took place from diagenesis (as pre-anhydrite-carbonate overgrowths) to orogenesis (vein-hosted K feldspar). Secondary K feldspar is a major gangue mineral in many Zambian Copperbelt deposits, typically intergrown with Cu-Co sulphides, particularly in argillite hosted deposits where sulphides and K feldspar are intergrown in coarse clots throughout the detrital network. In addition, there is a concomitant increase of the the K
2O:Al2O3 ratio and Cu within rocks of the Copperbelt Orebody Member. However, elevated K2O:Al2O3 ratios persist for hundreds of metres into the hanging wall of mineralisation and for kilometres laterally beyond the margins of ore (Selley et al., 2005). The formation of sericite, in close association with Cu-Co mineralisation, at the expense of K feldspar (and Ca-Mg-bearing minerals), is evident at a number of (but not all) deposits, particularly those hosted by arenites (e.g., Mufulira. This has been taken to reflect evolving conditions in the potassic environment, resulting from a more acid phase, possibly associated with H2S in sour gas within the sandstones, and/or generated from the reaction between Cu-bearing fluids and anhydrite. In these deposits, the sericite alteration is much more closely associated with the ore mineralisation. Sericite is also localised along faults and shear zones at a number of deposits (Selley et al., 2005).
•  Sodic - late-stage, structurally controlled alteration, usually as structurally controlled, vein-associated, albite and/or scapolite. Secondary albite alteration dominates in rocks above the evaporite horizons in the Upper Roan and Mwashya subgroups and the lower Nguba Group, but is relatively rare in the Lower Roan Subgroup, where it mainly occurs where the Upper Roan has stepped down to be juxtaposed with the Mindola Clastics Formation, in some 'footwall' arenite-hosted deposits, e.g., Chibuluma. Within the Zambian Copperbelt, sodic alteration is associated with late events, e.g., as a halo to discordant, post-folding, barren to sub-economic vein-fracture zones superimposed on the stratabound ore, as at Chambishi and Musoshi, but also as albite associated with an increase in economic mineralisation elsewhere in the same deposits, associated with shearing at the base of the Copperbelt Orebody Member. Albite is developed as a partial replacement of secondary K feldspar and sericite, and occurs both in equilibrium with, and overprinting, Cu-Co sulphides at different deposits. Some albite-sulphide veins are post-peak metamorphic, e.g., albite associated with quartz-dolomite-chalcopyrite veining at Kansanshi, dated at ~510 Ma (Selley et al., 2005; Torrealday et al. 2000).
   This sodic alteration may be part of a regional 'IOCG' associated alteration system that also includes numerous and widespread magnetite, copper and uranium occurrences that extend north from the 560 Ma Hook Granite in the Katanga High to the Domes Region and envelope the Mumbwa IOCG and Kasempa magnetite-breccia deposits.

viii). There is a zonation of minerals on both a deposit and local scale. At the deposit scale, there is a gross mineral zonation from hematite in oxidised footwall rocks to a chalcocite-bornite assemblage in immediately adjacent or overlying reduced rocks, particularly those adjacent to syn-sedimentary faults. The chalcocite-bornite assemblage than grades stratigraphically upward and/or laterally away from the footwall or syn-sedimentary structures to a bornite-chalcopyrite assemblage, then a chalcopyrite-rich assemblage, a chalcopyrite-pyrite assemblage and, finally to pyrite (Hitzman et al., 2012). This zonation reflects the flow of Cu-bearing ore fluids, from chalcocite-bornite proximal to pyrite distal.
  On a finer scale, zonation may occur between individual beds, being relatively simple where host rocks lack significant compositional layering, to complex and overlapping where bedding is well developed (e.g., the Mines Subgroup orebodies), and fluids are contemporaneously penetrating along and outwards from closely spaced layers.
  Individual grains of sulphide may also display sequential, concentric replacement textures, mimicking the observed broader scale mineral zonation. Similarly, the transition from early to late-formed sulphides is reflected by identical zoning in disseminated sulphides, veins and nodules (Brummer, 1955; Mendelsohn, 1961; Richards et al., 1988; Selley et al., 2005; Sillitoe et al., 2010). The complex and overlapping mineral zonation observed in some deposits, particularly those of the Mines Subgroup in the DRC, could reflect either multiple fluid ingress events, controls on sulphide speciation by local host-rock variability, or both (Hitzman et al., 2012).

ix). Paragenesis - Croaker (2011) determined the following paragenesis for the Nkana deposit in Zambia:
• Pyrite - the earliest sulphides are a disseminated pyrite phase, which is interpreted to be of late diagenetic origin, typically replacing earlier diagenetic anhydrite and/or dolomite (Annels, 1989).
  Croaker (2011) identified a number of pyrite types. These included pyrite grains hosted within black carbonaceous argillite, with 'spongy' cores, and the isotopically lightest sulphur signatures, at the poorly deformed Chambishi SE deposit, 10 km to the north, interpreted as typical of early diagenetic origin. At the more heavily metamorphosed Nkana deposit, fine grained (~0.1 mm or less) disseminated pyrite is observed in low strain zones, interpreted to be late diagenetic. This is suggested by the rotation of some equivalent, but coarser (0.2 to 10 mm), inclusion free pyrite porphyroblasts, with quartz-calcite strain shadows, in high strain domains, suggesting they are pre-tectonic. In addition, a further variety of disseminated pyrite with inclusions of mica laths aligned parallel to the regional structural foliation is taken to be syn-tectonic.
  Similarly, late diagenetic, (pre-kinematic), syn-tectonic and late-tectonic (or recrystallised) pyrite veins were identified, based on their structural relationships. These later generations may not represent introduction of new pyrite, but recrystallisation and the localised deformation and remobilisation of the sulphides on the scale of centimetres to mnetres within the confines of the stratabound copper ore envelope. Locally pyrrhotite dissolves and partially replaces pyrite along cleavage and fracture planes in the high strain domain.
• Copper sulphides - predominantly chalcopyrite, with lesser bornite and carrollite. An early phase of chalcopyrite and carrollite overgrows and/or replaces pyrite, whilst chalcopyrite locally displays myrymekitic, vesicular and exsolution textures with bornite. A second generation of chalcopyrite-bornite frequently overgrows carrollite, or encloses fractured carrollite. A volumetrically minor late stage of carrollite, confined to the high strain domain, overgrows both chalcopyrite and bornite. A minor bornite phase may have exsolved or pseudomorphic intergrowths of chalcocite. Chalcopyrite and bornite have been recrystalised and locally remobilised during peak deformation and metamorphism and are commonly aligned parallel to cleavage and intergrown with, or overprinted by, silicate minerals.
  These generations are represented in both disseminations and veins of late diagenetic, syn-tectonic and late-tectonic origin. Croaker (2011) notes that whilst these relationships may be interpreted to indicate syn-orogenic introduction of metals, the existence of disseminated sulphides in more poorly deformed parts of the orebody that are truncated/overprinted by cleavage, is considered to be evidence of at least some pre-existing sulphide assemblages prior to deformation which was remobilised.
• Accessory sulphides - sphalerite occurs as anhedral grains within balck carbonaceous shales, commonly on the margins of cjhalcopyrite grains aligned parallel to cleavage. Molybdenite occurs as rare 10 to 30µm subhedral grains, associated with veins parallel to and crosscutting cleavage, commonly intergrown with chalcopyrite and bornite.
• All mineralised veins are confined to the stratabound, folded copper orebody envelope and regardless of their generation, contain a similar sulphide and gangue assemblage to the host lithology.

x). Geochronology of ore - Most datings of sulphides and ore-related minerals in the Zambian Copperbelt give Lufilian ages of 670 to 550 Ma. Available data from Selley et al. (2005) includes the following:
• Nchanga - 576±41 Ma (Re-Os Co sulphide; Barra and Broughton, unpub. data);
• Chibuluma West - 576±41 Ma (Re-Os Cu sulphide; Barra and Broughton, unpub. data);
• Nkana-Mindola - 520±20 Ma (U-Pb uraninite; Cahen et al.,1971 and references therein); 522±15 Ma (U-Pb uraninite; Darnley et al., 1961);
   576±41 Ma (Re-Os Cu sulphide; Barra and Broughton, unpub. data); 525±3.4 Ma (Re-Os molybdenite; Barra et al., 2004);
• Musoshi - 514±3 Ma (U-Pb uraninite; Richards et al., 1988); 514±2 Ma (U-Pb rutile; Richards et al., 1988); 496±1 Ma (U-Pb rutile; Richards
    et al., 1988); 645±15 Ma (Pb-Pb Cu sulphide; Richards et al., 1988);
• Kansanshi - 503±15 Ma (U-Pb uraninite; Darnley et al., 1961); 512.4±1.2 Ma (Re-Os molybdenite; Torrealday et al., 2000); 502.4±1.2 Ma
    (Re-Os molybdenite; Torrealday et al., 2000); 511±11Ma (U-Pb monazite; Torrealday et al., 2000).
However, an Re-Os isochron age for chalcopyrite in diagenetic evaporitic nodules in the hanging wall (not ore) of the Konkola deposit (Barra et al., 2004), yielded an age of 816±62 Ma presumed to be close to the post 877±11 Ma (basement Nchanga Red Granite age) depositional age. The minimum age of 645±15 Ma determined for copper-sulphides in little deformed disseminated ores from the Musoshi deposit, DRC (Richards et al., 1988) would be consistent with a late diagenetic emplacement. The range of dates, styles of mineralisation, textural evidence and the presence of ore in rocks younger than this earliest age, suggest mineralisation took place over a protracted period from late diagenesis to post orogenesis.

xi). Basement mineralisation, is found in numerous locations within the Lufubu Complex gneisses, schists and granitoids, both in close association with, and distal to, Roan Group hosted deposits. Mineralisation occurs in a number of forms, specifically:
• within palaeosols/palaeoregolith formed at the Katangan unconformity, where Roan Group hosted orebodies rest directly onto basement topographic highs. This is interpreted to represent mineralising fluids that have penetrated into the weathered regolith during the main ore formation. In some localities this mineralisation persists below the regolith, e.g., at Mufulira, where deep fissures filled with Roan Group sands, pebbles and boulders contain disseminated pyrite and chalcopyrite. Similar mineralised palaeosols have been outlined at Nkana and Nchanga (Pienaar, in Mendelsohn, 1961).
• mineralised veins within basement below orebodies, e.g., at Luanshya, where the main orebody in the lower Roan Subgroup rests directly on basement, chalcopyrite and minor pyrite occurs in sporadic, short, discontinuous quartz-calcite veins and as disseminations within schist (mainly biotite schist). The overall average grade in the zone is ~1% Cu, over a thickness of 10 to 15 m below the unconformity. Similar mineralisation has been outlined at Nchanga in both the palaeosol and as dissemination and veins in the underlying granite to depths of ~8 m, carrying an average of 0.77% Cu. At Mufulira, pyrite and chalcopyrite occur in short, erratic and discontinuous quartz-carbonate veins which contain some anhydrite. The more persistent veins strike NE and dip to the NW. At the Selkirk shaft (Mufulira), mineralised veins up to 2 cm thick occur in swarms up to 400 m below the unconformity, hosted by both schists and granites (more abundant near granite contacts), with maximum grades of up to 3% Cu over 2 m intervals (Pienaar, in Mendelsohn, 1961).
• basement host deposits removed from Roan Group ores, the most significant of which is the Samba deposit, hosted in 1.9 Ga (Rainaud et al., 2005) basement metavolcanic rocks on the western edge of the Zambian Copperbelt, 21 km south of Chingola and 24 km west if Chambishi. Mineralisation is hosted by quartz-sericite to quartz-biotite and chloritic schists, which have gradational contacts with sandwiching granodioritic to quartz-monzonitic gneisses (Wakefield, 1978; Freeman, 1988). It occurs as disseminations, stringers and veinlets of pyrite, chalcopyrite and bornite, with minor shallow malachite development. The mineralisation forms lenses that dip at 45 to 80°S and vary from a few mm to ~10 m in thickness, usually decreasing in width with depth. Grades vary from trace to 2.16% Cu over 8.15 m widths, the best being 1.68 m of 4.11% Cu. Two or three, locally up to eight, bands are present at any one interval, each separated by waste bands that are from 2 to 140 m thick. Samba has been interpreted to be a Palaeoproterozoic porphyry Cu deposit with a resource of ~50 Mt @ 0.5% Cu (Wakefield 1978). Freeman (1988) quotes a resource of 14 Mt @ 1.1% Cu with a higher cut-off, based on the tabular bands of ore. However, Hitzman 2012, quotes unpublished data (M. Hitzman, unpub. data, 2006), which has demonstrated that mineralization took place between 490 and 460 Ma, during late to post Lufilian orogenesis.
   Another of the basement accumulations (undated) is the Fimpimpa Prospect, on the NE tip of the Kafue Anticline, 20 km NE of Nchanga and <10 km west of Lubembe, where copper mineralisation occurs along a massive quartz vein cutting basement garnetiferous quartz-mica schists and biotite gneisses, and in an adjacent, vermiculite-rich lamprophyre dyke (Freeman, 1988) or feldspathised quartz diorite (Pienaar, in Mendelsohn, 1961). The lamprophyre dyke is continuous for 20 km south to the Nchanga River Lode. The quartz vein is ~8 m thick with sporadic malachite, chalcopyrite and bornite and is largely < 0.4% Cu (Pienaar, in Mendelsohn, 1961). The lamprophyre dyke is host to fracture, quartz-calcite vein to veinlet hosted and disseminated malachite, chalcopyrite and bornite mineralisation over widths of up to 14 m. The known resource over a 1000 m interval tested was estimated at 1.2 Mt @ 1.23% Cu to a depth of 100 m, including 0.2 Mt @ 1.19% Cu as cupriferous mica to a depth of 15 m (Freeman, 1988).
   Most of the basement hosted occurrences below the palaeoweathering zone have been assumed to represent pre-Katangan mineralisation and illustrate the fertility of the basement as a source of metals. However, the dating of Samba questions this latter assumption. If other occurrences are shown to be Lufilian in age, they may instead reflect the passage of mineralised fluids upward into the Katangan sequence.


Timing, Origin and Discussion        This section is currently being amended

The most recent source geological information used to prepare this summary was dated: 2012.     Record last updated: 13/1/2015
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.


  References & Additional Information
 References to this deposit in the PGC Literature Service Collection: Want any of these papers ? Click Here
Annels A E  1989 - Ore Genesis in the Zambian Copperbelt, with Particular Reference to the Northern Sector of the Chambishi Basin: in Boyle R W, Brown A C, Jefferson C W, Jowett E C, Kirkham R V, (eds),  Sediment-hosted Stratiform Copper Deposits:  Geological Association of Canada   Special paper 36 pp 427-452
Annels A E  1984 - The Geotectonic Environment of Zambian Copper-cobalt Mineralization: in    Journal of the Geological Society of London   v141 pp 279-289
Annels A E  1974 - Some Aspects of the Stratiform Ore Deposits of the Zambian Copperbelt and their Genetic Significance: in Bartholome P (Ed),  Gisements Stratiformes et Provinces Cupriferes: Societe Geologique de Belgique, Liege    pp 235-254
Annels A E,  1979 - Mufulira Greywackes and Their Associated Sulphides: in    Trans. IMM, Section B   v.88 pp B15-B23
Annels A E, Vaughan D J, Craig J R  1983 - Conditions of Ore Mineral Formation in Certain Zambian Copperbelt deposits with Special Reference to the Role of Cobalt: in    Mineralium Deposita   v18 pp 71-88
Armstrong R A, Master S and Robb L J,  2005 - Geochronology of the Nchanga Granite, and constraints on the maximum age of the Katanga Supergroup, Zambian Copperbelt: in    J. of African Earth Sciences   v42 pp 32-40
Armstrong R A, Robb L J, Master S, Kruger F J, Mumba P A C C  1999 - New U-Pb age constraints on the Katangan Sequence, Central African Copperbelt: in    Journal of African Earth Sciences, Elsevier, Amsterdam   v28, no.4A pp 6-7
Brandt R T, Burton C C J, Maree S C, Woakes M E  1961 - Mufulira: in Mendelsohn F (ed),  Geology of the Northern Rhodesian Copperbelt McDonald, London    pp 411-461
Cailteux J L H, Kampunzu A B and Lerouge C,  2007 - The Neoproterozoic Mwashya-Kansuki sedimentary rock succession in the central African Copperbelt, its Cu-Co mineralisation, and regional correlations: in    Gondwana Research   v.11 pp. 414-431
Cailteux J L H, Kampunzu A B, Lerouge C, Kaputo A K and Milesi J P,  2005 - Genesis of sediment-hosted stratiform copper-cobalt deposits, Central African Copperbelt: in    J. of African Earth Sciences   v42 pp 134-158
Daly M C, Chakraborty S K, Kasolo P, Musiwa M, Mumba P. Naidu B, Namateba C, Ngambi O, Coward M P  1984 - The Lufilian Arc and Irumide Belt of Zambia, Results of a Geotraverse across their Intersection: in    Journal of African Earth Sciences, Elsevier, Amsterdam   v2, no.4 pp 311-318
Darnley A G  1960 - Petrology of Some Rhodesian Copperbelt Orebodies and Associated Rocks: in    Transactions of the Institution of Mining and Metallurgy   v69 pp 137-173
Ellis M W, Austen A L, Garlick W G, Gane P G, Cornwall F W  1961 - Exploration: in Mendelsohn F (ed),   Geology of the Northern Rhodesian Copperbelt McDonald, London    pp 166-212
Fleischer V D  1984 - Discovery, Geology and Genesis of Copper-cobalt Mineralisation at Chambishi Southeast Prospect, Zambia: in    Precambrian Research    v25, no.1-3 pp 119-133
Fleischer V D, Garlick W G, Haldane R  1976 - Geology of the Zambian Copperbelt - (Excerpt on Genesis): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 323-352
Fleischer V D, Garlick W G, Haldane R  1976 - Geology of the Zambian Copperbelt (Exerpt covering Roan Antelope and Baluba): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 285-297
Fleischer V D, Garlick W G, Haldane R  1976 - Geology of the Zambian Copperbelt - Mufulira Mine, Zambia (Exerpt on Mufulira only): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 304-323
Fleischer V D, Garlick W G, Haldane R  1976 - Geology of the Zambian Copperbelt (Exerpt covering Nkana): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 275-285
Fleischer V D, Garlick W G, Haldane R  1976 - Geology of the Zambian Copperbelt (Excerpt covering Konkola and Musoshi): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 244-249
Fleischer V D, Garlick W G, Haldane R  1976 - Geology of the Zambian Copperbelt (Exerpt covering Chibuluma and Chibuluma West): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 298-304
Fleischer V D, Garlick W G, Haldane R  1976 - Geology of the Zambian Copperbelt (Excerpt covering the geology only): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 223-243
Fleischer V D, Garlick W G, Haldane R  1976 - Geology of the Zambian Copperbelt (Exerpt covering Chambishi): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 249-256
Fleischer V D, Garlick W G,and Haldane R  1976 - Geology of the Zambian Copperbelt (Exerpt by Garlick and Haldane covering Nchanga): in Wolf K H, (ed),  Handbook of Strata-bound and Stratiform Deposits; II. Regional Studies and Specific Deposits Elsevier, Amsterdam   v6, Cu, Zn, Pb and Ag Deposits pp 256-274
Garlick W G  1961 - Chambishi: in Mendelsohn F (ed),  Geology of the Northern Rhodesian Copperbelt McDonald, London    pp 281-297
Greyling L N, Robb L J, Master S, Boiron M C and Yao Y,  2005 - The nature of early basinal fluids in the Zambian Copperbelt: A case study from the Chambishi deposit: in    J. of African Earth Sciences   v42 pp 159-172
Gunning H C  1961 - The Early Years: in Mendelsohn F (ed),  Geology of the Northern Rhodesian Copperbelt McDonald, London    pp 3-10
Haynes D W  1986 - Stratiform Copper deposits hosted by low-energy sediments: II. Nature of source rocks and composition of metal-transporting water: in    Econ. Geol.   v81 pp 266-280
Haynes D W  1986 - Stratiform Copper deposits hosted by low-energy sediments: I. Timing of Sulfide precipitation - an hypothesis: in    Econ. Geol.   v81 pp 250-265
Hitzman M W  1998 - Petrographic Studies of Ore Shale from the Zambian Copperbelt, Implications for Models of Ore Formation: in   Geological Society of America, 1998 Annual Meeting Geological Society of America - Abstracts with Programs   v30, No.7 pp 19-20
Hitzman M W, Selley D and Bull S,  2010 - Formation of Sedimentary Rock-Hosted Stratiform Copper Deposits through Earth History : in    Econ. Geol.   v105 pp 627639
Hitzman M W, Broughton D, Selley D, Woodhead J, Wood D and Bull S,  2012 - The Central African Copperbelt: Diverse Stratigraphic, Structural, and Temporal Settings in the Worlds Largest Sedimentary Copper District: in Hedenquist J W, Harris M and Camus F, 2012 Geology and Genesis of Major Copper Deposits and Districts of the World - A tribute to Richard H Sillitoe Society of Economic Geologists   Special Publication 16, pp. 487514
Hitzman M W, Kirkham R, Broughton D, Thorson J and Selley D,  2005 - The sediment-hosted stratiform copper ore system: in Hedenquist J W, Thompson J F H, Goldfarb R J and Richards J P (Eds.), 2005 Economic Geology 100th Anniversary Volume, Society of Economic Geologists, Denver,     pp. 609-642
Jordaan J  1961 - Nkana: in Mendelsohn F (ed),  Geology of the Northern Rhodesian Copperbelt McDonald, London    pp 297-328
Kampunzu A B and Cailteux J L H,  1999 - Tectonic Evolution of the Lufilian Arc (Central Africa Copper Belt) During Neoproterozoic Pan African Orogenesis: in    Gondwana Research   v.2 pp. 401-421
Key R M, Liyungu A K, Njamu F M, Somwe V, Banda J, Mosley P N and Armstrong R A,  2001 - The western arm of the Lufilian Arc in NW Zambia and its potential for copper mineralization: in    J. of African Earth Sciences   v.33 pp. 503528
Master S, Rainaud C, Armstrong R A, Phillips D and Robb L J,  2005 - Provenance ages of the Neoproterozoic Katanga Supergroup (Central African Copperbelt), with implications for basin evolution: in    J. of African Earth Sciences   v42 pp 41-60
Master S, Rainaud C, Armstrong R A, Philips D and Robb L J,  2005 - Provenance ages of the Neoproterozoic Katanga Supergroup (Central African Copperbelt), with implications for basin evolution: in    J. of African Earth Sciences   v.42 pp. 41-60
McGowan R  2001 - Towards a New Genetic Model for Precambrian Sediment-hosted Copper Deposits: in   A brief overview of the Zambian Copperbelt  - Web page extract, from: www.soc.soton.ac.uk/SOES/STAFF/sr1/Ross/RMcGowan_HP.htm    5p
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Mendelsohn F  1961 - Roan Antelope: in Mendelsohn F (ed),  Geology of the Northern Rhodesian Copperbelt McDonald, London    pp 351-405
Mendelsohn F  1989 - Central/Southern African Ore Shale Deposits: in Boyle R W, Brown A C, Jefferson C W, Jowett E C, Kirkham R V, (eds),  Sediment-hosted Stratiform Copper Deposits Geological Association of Canada   Special paper 36 pp 453-469
Mendelsohn F, Garlick W G, Pienaar P J, Demesmaeker G  1961 - General Geology (Extract): in Mendelsohn F (Ed.),  Geology of the Northern Rhodesian Copperbelt McDonald, London    pp 17-56
Porada H and Berhorst V,  2000 - Towards a new understanding of the Neoproterozoic-Early Palaeozoic Lufilian and northern Zambezi Belts in Zambia and the Democratic Republic of Congo: in    J. of African Earth Sciences   v.30 pp. 727-771
Porada H and Druschel G,  2010 - Evidence for participation of microbial mats in the deposition of the siliciclastic ore formation in the Copperbelt of Zambia: in    J. of African Earth Sciences   v.58 pp. 427-444
Rainaud C, Master S, Armstrong R A and Robb L J,  2003 - A cryptic Mesoarchaean terrane in the basement to the Central African Copperbelt: in    Journal of the Geological Society, London   v.160 pp 11-14
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Rainaud C, Master S, Armstrong R A, Phillips D and Robb L J,  2005 - Monazite U-Pb dating and 40Ar-39Ar thermochronology of metamorphic events in the Central African Copperbelt during the Pan-African Lufilian Orogeny: in    J. of African Earth Sciences   v.42 pp. 183-199
Richards J P, Cumming G L, Krstic D, Wagner P A, Spooner E T C  1988 - Pb isotope constraints on the age of Sulfide ore deposition and U-Pb age of late Uraninite veining at the Musoshi stratiform Copper deposit, central African Copper belt, Zaire: in    Econ. Geol.   v83 pp 724-741
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Sillitoe R H, Perello J and Garcia A,  2010 - Sulfide-Bearing Veinlets Throughout the Stratiform Mineralization of the Central African Copperbelt: Temporal and Genetic Implications : in    Econ. Geol.   v105 pp 1361-1368
Sutton S J and Maynard J B,  2005 - A fluid mixing model for copper mineralization at Konkola North, Zambian Copperbelt: in    J. of African Earth Sciences   v42 pp 95-118
Sweeney M A, Binda P L  1989 - The Role of Diagenesis in the Formation of the Konkola Cu-Co Orebody of the Zambian Copperbelt: in Boyle R W, Brown A C, Jefferson C W, Jowett E C, Kirkham R V, (eds),  Sediment-hosted Stratiform Copper Deposits Geological Association of Canada   Special paper 36 pp 499-518
Sweeney M A, Binda P L  1994 - Some Constraints on the Formation of the Zambian Copperbelt Deposits: in    J. of African Earth Sciences   v19 pp 303-313
Sweeney M A, Binda P L, Vaughan D J  1991 - Genesis of the Ores of the Zambian Copperbelt: in    Ore Geology Reviews   v6 pp 51-76
Sweeney M, Turner P, Vaughan D J  1986 - Stable isotope and geochemical studies of the role of early diagenesis in ore formation, Konkola Basin, Zambian Copper belt: in    Econ. Geol.   v81 pp 1838-1852
Unrug R  1988 - Mineralization Controls and Source of Metals in the Lufilian Fold Belt, Shaba (Zaire), Zambia and Angola: in    Econ. Geol.   v83 pp 1247-1258
Unrug R  1989 - LANDSAT-based Structural Map of the Lufilian Fold Belt and the Kundelungu Aulacogen, Shaba (Zaire), Zambia and Angola, and the Regional Position of Cu, Co, U, Au, Zn and Pb Mineralisation: in Boyle R W, Brown A C, Jefferson C W, Jowett E C, Kirkham R V, (eds),  Sediment-hosted Stratiform Copper Deposits Geological Association of Canada   Special paper 36 pp 519-524
Unrug R  1988 - Mineralization controls and source of metals in the Lufilian Fold Belt, Shaba (Zaire), Zambia, and Angola: in    Econ. Geol.   v83 pp 1247-1258
van Eden J G  1974 - Deposition and Diagenetic Environment Related to Sulfide Mineralization, Mufulira, Zambia: in    Econ. Geol.   v69 pp 59-79
Wendorff M,  2005 - Sedimentary genesis and lithostratigraphy of Neoproterozoic megabreccia from Mufulira, Copperbelt of Zambia: in    J. of African Earth Sciences   v42 pp 61-81
Winfield O  1961 - Chibuluma: in Mendelsohn F (ed),  Geology of the Northern Rhodesian Copperbelt McDonald, London    pp 328-342
Zientek M L, Hayes T S and Hammarstrom J M  2013 - Overview of a New Descriptive Model for Sediment- Hosted Stratabound Copper Deposits: in Zientek M L, Hammarstrom J M and Johnson K M, 2013 Descriptive Models, Grade-Tonnage Relations, and Databases for the Assessment of Sediment-Hosted Copper DepositsWith Emphasis on Deposits in the Central African Copperbelt, Democratic Republic of the Congo and Zambia USGS Scientific Investigations,   Report 20105090J pp. 2-16

 PGC Literature Compilations containing papers referring to this deposit: Browse & Buy collection papers
Africa-B 2001: Volume 1 - The Zambian Copper Belt


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