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Kinsenda |
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Katanga, Dem. Rep. Congo |
| Main commodities:
Cu
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Kinsenda sediment hosted copper deposit is located 18 km east of Kasumbalesa and 90 km by road southeast of Lubumbashi in the Katanga Province of the Democratic Republic of Congo within 5 km of the border with Zambia (#Location: 12°15' 9"S 27° 58' 4"E).
The Kinsenda deposit was discovered in 1930 by Union Miniére du Haut-Katanga, but remained undeveloped until the formation of Sodimico (80% Nippon Mining and 20% Congolese state) in 1969 to mine Kinsenda and Musoshi 20 km to the east. Following testing and development, mining operations commenced in 1977, with ore being shipped to Musoshi for treatment. Nippon Mining withdrew from the DRC in 1983 and their share was taken up by a Canadian company, Phillips Barratt Kaiser, who withdrew in 1987, when Sodimico was declared insolvent and became a subsidiary of the state owned Gécamines. Production dropped from around 1990, and in 1997 the operation was placed on care and maintenance due to flooding of the mine. Minor production continued in the early 2000s. Between 1977 and 2003, 4.2 Mt of ore at 5.12% Cu Total was extracted from the mine. Various dealings were undertaken from 2002 to 2008 when Metorex acquired 50.3% of the operating company, which increased to 87% in early 2009 when the mine was again placed on care and maintenance and a program to confirm resources and feasibility was commenced.
Geological Setting
The Kinsenda deposit is located on the southern edge of the Luina basement dome. It is hosted by a thick sequence of coarse to fine-grained sandstones, siltstones and shales of the Mindola Clastics Formation, the lowermost unit of the Lower Roan Subgroup, and occurs in the footwall of the Copperbelt Orebody Member. As such it is a "footwall deposit", similar to those at Chibuluma, further to the south in Zambia. It is one of the northern-most deposits of the Zambian Copperbelt.
For details of the regional setting and stratigraphy of the Kinsenda deposit and the Zambian Copperbelt, see the separate Central African Copperbelt - Zambian Copperbelt record.
The Mindola Clastics Formation host sequence at the Kinsenda deposit was apparently emplaced within a fault-controlled, active rift environment. It exhibits local thickness and facies variations corresponding to pulses of sedimentation progressing from conglomerates towards the base, to siltstones and dirty sandstones at the top of the host package. Sub parallel horsts and grabens in the basement are suggested by rapid variations in thickness of the basal units of the Lower Roan both along strike and down dip. There is also a strong correlation between the position of the Kinsenda mineralisation and resistant basement granite palaeotopography.
The host rocks occur as valley fill sediments in down-faulted graben structures adjacent to growth faults that were active during sedimentation. These growth faults are oriented roughly ENE, and have a well-defined magnetic signature that can be traced into the basement rocks of the Luina Dome to the north of the Kinsenda deposit.
The basement of the Luina Dome is composed of metaquartzites and mica schists, intruded by Palaeoproterozoic granites. This dome has undergone intense fracturing which is reflected by a dense network of joints, often filled by quartz veins. Dolerite dykes cut the quartzites and the granites. The unconformably overlying Neoproterozoic Katanga Supergroup comprises:
Roan Group
Lower Roan Subgroup
• Mindola Clastics Formation (classed as a Group in DRC literature), which is locally subdivided further into,
- Chimfusi Formation, which is >250 m thick and commences with a basal, fine, well stratified arkoses that gradually becomes coarser, containing clasts that are 2 to 5 cm across, with intercalations of arkose or clayey arkosic sandstone. These rocks are overlain by a very poorly sorted conglomerate with angular to subrounded clasts that vary from 1 to 120 cm across of granite and quartzite. Towards the top, the coarse material decreases in size and quantity.
- Kafufya Formation, which is ~65 m thick and consists primarily of bedded to cross-bedded, clear to light grey and beige quartzites. The crossbedding is at a high angle, with "soft-sand avalanche structures", which Lefebvre (1989) interprets to represent aeolian sand dunes. Iron-rich Feldspathic sandstones are intercalated with the quartzite towards the top of the unit, and are interpreted to be the host of the Kasumbalesa iron deposit 18 km to the west.
- Mutonda Formation, which is generally ~300 m thick, although elsewhere it varies from 70 to 450 m. It is essentially an arkose at the base, grading to an arkosic rudite to conglomerate with interbeds of fine arkoses or siltstones. These arkosic rocks vary from white to black or red and contain rounded and angular clasts up to 5 cm in diameter and are cross bedded. The upper section is composed of argillaceous to clayey sandstones with arkosic, argillite and carbonate lenses. The Mutonda Formation has been further subdivided, from the base to the top, into the Kawimba, Lubembe, Simbi, Kalemba and Kitotwe members, with the bulk of the mineralisation in the Lubembe Member. The lowermost Kawimba Member is locally absent, resulting in the Lubembe Member resting directly on basement.
The Chimfusi and Kafufya members are absent at the Kinsenda deposit, where the Mutonda Member rests directly on basement, although the two lower members are exposed in the core of the syncline separating the Konkola and Luina domes (Lefebvre, 1989).
• Musoshi 'Formation', which is classed as a Group in DRC literature and is directly equivalent to the Kitwe Formation in Zambia. It comprises:
- Laminar black shales to siltstones which contain copper mineralisation, define the base of the Musoshi 'Formation', and are the equivalents of the Copperbelt Orebody Member (RL6) in Zambia. These are overlain by
- Pelitic arkoses, of RL5, composed of a thin sequence of arkoses, and sandy to dolomitic argillites, and
- Chingola Dolomite, composed of white, talcose dolostones which is frequently brecciated, but where intact at Kinsenda, is mainly composed of black to grey dolomitic shales, dolostones and grey pelites, the latter capping the dolostones. The brecciated talcose carbonates are interpreted to have contained evaporite beds (SRK, 2013).
The Musoshi 'Formation' is up to 175 to 200 m thick in the Kinsenda area. It transgressively overlies the Mutonda Formations, with the Chingola Dolomite pinching out to the NE and thickening to the SW
Upper Roan Subgroup, which has been equated by Cailteux et al. (1994) with the Dipeta (R3) Subgroup in the DRC, and subdivided by Kampunzu (1993) and Cailteux et al. (1994) into the:
- Kibalongo Formation, which consist of grey-green siltstones with arkosic lenses at the base, followed by dolomitic sandstones and dolostones at the top.
- Kanwangungu Formation, which is predominantly composed of massive dolostones with a gradational contact, via dolomitic siltstones from the underlying Kibalongo Formation. These dolostones at the top of the sequence are strongly brecciated.
Mwashya Subgroup, which averages 50 m in thickness and contains a sequence that is dolomitic at the base, grading upwards into feldspathic sandstones and dolomites alternating with marly lenses and sandy-pelites at the top.
Nguba Group
Only the basal unit of the Nguba Group has been mapped at Kinsenda, the diamictites of the Grand Conglomerat, which is a grey-green pyritic rock containing a variety of very poorly sorted, grit to boulder sized, rounded to subangular clasts, including quartz, quartzites, arkoses, shales, granites and dolostone in a compact clay to sand-sized matrix.
There is a north-south oriented, steeply dipping ~80 m wide corridor of intense fracturing, cutting the deposit near its centre, in which the ore is strongly leached. The deposit is also cut by the east-west striking Kamukato fault, a normal fault that acts as relay ramp. It has little or no vertical displacement to the east, but increasingly downthrows the southern third of the orebody to the south as it progresses to the west. The north-south fracture corridor produces a dextral offset of the Kamukato fault.
Mineralisation
Kinsenda is a copper-only sulphide orebody, predominantly composed of chalcocite, bornite and chalcopyrite mineralisation hosted in detrital conglomerates, sandstones and argillaceous siltstones of the Musoshi 'Formation', part of the Lower Roan Subgroup Mindola Clastics Formation. It comprises a number of vertically stacked, subconcordant, lenticular to tabular mineralised zones that vary from 1 to 20 m in thickness, and generally occur in the more porous, conglomerate rich beds directly below thick, less permeable siltstone rich zones (SRK Consulting).
The mineralisation of the deposit occurs over a strike of ~2000 m, and dip at 25 to 30°SW. In plan view, the mineralised lenses occur as a series of partially overlapping, wedge shaped tabular bodies with a NW-SE strike orientation, forming five laterally continuous lenses, the i). upper upper ore zone (UUOZ), ii). upper ore zone (UOZ), iii). middle ore zone (MOZ), iv). lower ore zone (LOZ) and the v). basal lower lower ore zone (LLOZ).
Apart from the LLOZ, which is within the Kawimba Member of the Musoshi 'Formation', all of the others are hosted within the overlying Lubembe Member, with the uppermost UUOZ capped by the base of the overlying Simbi Member. The Kawimba Member is locally absent, resulting in the corresponding absence of the LLOZ and the Lubembe Member resting directly on basement granite. The UUOZ and UOZ are found shallower than 285 m below surface and have been largely mined out. The characteristics of these ore zones are as follows:
• The LLOZ usually comprises 4 layers (but can locally have as many as 6), 2 coarser, mineralised layers, OL1, OL2, separated by finer interlayers, ILl and IL2. However, in practice, the facies distribution is sometimes more complex with mineralisation irregular distributed within any of the layers. Locally, very thin (<5 cm) beds of apparently barren beige siltstone, are sandwiched between two thick (up to 12 m) layers of strongly mineralised coarse arkose.
• The LOZ has been divided into 4 coarser layers (OL0 to OL3) separated by 4 corresponding finer sublayers (IL0 to IL3). Mineralisation is laterally discontinuous, divided into multiple zones which can split and coalesce over relatively short distances, with two main permutations. In the first, most of zone is mineralised, although, the lower two (OL0 and IL0) and uppermost (IL3) are largely barren to poorly mineralised. In the second, it is divided into two mineralised sub-zones, the lower LOZB and upper LOZA, separated by a barren interval that corresponde to IL1 and the lower half of OL2.
• The MOZ, is divided into three coarse sublayers OL1 to 3, separated by finer interlayers IL1 to IL3. Mineralization distributed across all except OL1 at the base and OL3 at the top. This zone is the most extensively developed, with a maximum strike length of ~2000 m.
• The UOZ and MOZ are always separated by a relatively constant thickness interlayer of ~40 m of very weakly mineralised <2% Cu, regarded as barren.
• The UOZ is similarly composed of 3 coarse sublayers (OL0 to 2) and 3 finer interlayers (ILO to 2), with well developed mineralisation in IL1 and OL1 towards the base and OL2 higher, separated by weaker mineralisation in , and ILl OLL and is more sporadic in OL0, IL1 and IL2.
• The UUOZ is a thin layer of oxidised ore that sometimes occurs at the base of the Simbi Member. It is the least developed with a total length of ~250 m.
The distribution of the mineralisation within the main zones, and the coarser layers and finer interlayers is not homogeneous throughout the deposit. The barren to low grade interlayers (IL) separating the ore layers (OL) is generally in the order of only a few metres. Down dip, the maximum length of the individual orebodies can be up to 800 m, with ore thickness ranging from 1 m in peripheries, to 22 m in the core of the ore lens. At least 60% of the mineralisation occurs in zones of between 4 and 12 m in thickness, with an average width of all lenses of 5.9 m. The LOZA and LOZB zones have the highest grade and constitute 64% of total mineral resource tonnage.
In plan, the UUO, UO, MO and LO zones have a crudely concentric distribution, with each zone being laterally more extensive than the ore lense above.
Microscopic investigations by Ngoyi and Dejonghe (1995) show that the arkosic host is very heterogeneous and poorly sorted, and can be very fine to conglomeratic, black, red or light grey, and generally a gritstone. The conglomeratic clasts are moderately rounded to angular and are composed of microcline, plagioclase, quartz and rock debris, including granite, metaquartzite, gneiss, schist and dolerite. The clasts are cut by microcracks filled with sericite and associated copper sulphides. Accessories minerals include tourmaline, epidote, ilmenite, titanite, zircon and sometimes apatite. The matrix is either a detrital mineral assembly identical to that of the clasts, or clay minerals, quartz, microcline or sericite. Sulphides fill the interstices between the component grains, but also sometimes occur as overgrowth on authigenic growths on the peripheries of albite, quartz or feldspar grains.This implies that the introduction of copper post-dated early diagenetic authigenic overgrowths on the sedimentary grains of the host clastic rock. The red rocks contain abundant iron oxides, while sericitisation is greater in the grey rocks. Sericite is often associated with mineralisation and authigenic quartz in the black rocks.
Ngoyi and Dejonghe (1995) recognised a paragenetic sequence that involves early rutile and hematite, which are most likely detrital or diagentic in origin. These are followed by a phase of pyrite, followed by a generation of weak cattierite, cobaltite and carrolite. These cobalt minerals are rare, with much of the cobalt restricted to cobaltiferous pyrite. The cobalt minerals, where present, are overlapped by slightly younger chalcopyrite and bornite, which are in turn followed by chalcocite and digenite, temporally overlapped by late covellite. Subsequent oxidation produced more hematite, cuprite, malachite, azurite and native copper.
Ngoyi and Dejonghe (1995) observed the following occurrence and relationships between the minerals and hosts:
• Rutile (TiO2) occurs as anhedral grains, which in sometimes included in the copper sulphides, whilst other cases, it develops a structure mutual contact with some sulphides (pyrite, chalcopyrite and bornite). It is sometimes concentrated in lamination sheets and crossbedding foresets. It is also frequently disseminated in the gangue.
• Pyrite (FeS2) is frequently observed as anhedral grains intimately linked to the cattiérite, and as small idiomorphic grains. It is also observed as euhedral inclusions, more or less corroded, in all other sulphides and as framboidal inclusions in chalcopyrite. The microprobe analyses revealed that some pyrites are cobaltiferous, and that these are generally those that are in contact with the cattierite.
• Cattierite (CoS2) occurs in association with pyrite, in chalcopyrite and pyrite, and is generally anhedral, although small euhedral crystals are dispersed in the sedimentary matrix, or are included in rutile.
• Cobaltite ([CoFe]AsS) is often found in the sedimentary matrix as very small anhedral grains, but also occurs as rare euhedral inclusions in chalcopyrite.
• Carrollite (Cu[Co, Ni]2S4) occurs as small anhedral grains in the sedimentary matrix.
• Chalcopyrite (CuFeS2) occurs in the following forms in decreasing order of importance,
- in continuous bands containing fairly frequent inclusions of pyrite, cattierite, rutile and sometimes cobaltite,
- as disseminations, either isolated or in contact with other grains, or following fractures/cleavage that cut the bedding layers where they are associated with covellite,
- as exsolution blebs in bornite
- as inclusions in other sulphides.
• Bornite (Cu5FeS5) is mostly directly associated with chalcopyrite occurring as bands, but is also rarely rarely observed as small crystals in the sedimentary matrix. Bornite is frequently associated with rutile grains, while anhedral rutile has also been observed as inclusions in bornite.
• Galena (PbS) is only seen as minute grains detected by electron microscope.
• Digenite (Cu9S5) is found coating and cementing other sulphide minerals, and as isolated anhedral crystals. It often contains inclusions of pyrite, bornite and chalcopyrite, and sometimes occurs in association with chalcocite with intergrowth structures.
• Chalcocite (Cu2S) also surrounds other sulphide minerals, where it occurs as large bands, with frequent rutile inclusions.
• Covellite (CuS) is observed in irregular cracks cutting chalcopyrite and bornite, as coatings on chalcopyrite, bornite, chalcocite and digenite and as lamelIae penetrating these minerals along cleavage planes. It is sometimes also associated with rutile.
• Late hematite (Fe2O3) overprints the sulphides, sometimes with a myrmekitic chalcocite structure. Most frequently it was developed with iron hydroxides as a network of veinlets in fractured chalcocite bands, but also occurs as anhedral crystals in the sedimentary matrix or filling multiple cracks and laminations in the host rock.
• Malachite (Cu2[CO3][OH]2) is a late oxidation product, frequently seen as botryoidal layers surrounding a preceding oxidation phase. It is also developed around cuprite crystals.
• Azurite (Cu2[CO3]2[OH]2) occurs as a superficial impregnation of mineralised rocks.
• Cuprite (Cu2O) is rare and occurs as small anhedral crystals isolated in the sedimentary matrix.
• Native copper (Cu) is occassionally observed in the form of small irregular platelets in the host rock.
In addition to disseminated mineralisation, sulphides are also distributed along bedding planes. The sulphides are mainly digenite, covellite and chalcocite, with associated rutile and hematite which are found in basal, foresets and topsets of the cross bedded host. Macroscopically, they appear to form continuous bands along stratification and bedding controlled fractures. However, microscopically, these minerals are found to be either attached to each other or disseminated along the controlling fracture/stratification.
Massive sulphide mineralisation is observed, and is mainly composed of chalcocite, which under the microscope, generally appears relatively uniform over significant widths. It includes some euhedral inclusions, mainly of pyrite and cattierite, and anhedral grains of rutile. Massive sulphide mineralisation is sometimes surrounded by chalcocite veinlets invading the surrounding host rock in all directions.
Copper oxides represent a maximum of 20% of the mineralisation, with the proportion decreasing with depth.
Resources and reserves
Mineral resources and ore reserves at 31 December 2012 (SRK report to Metorex, 2013)
High grade resource (1.5% Cu cut-off),
Indicated - 13.4 Mt @ 5.30% Cu,
Inferred - 7.4 Mt @ 6.03% Cu,
Low grade resource,
Indicated - 0.2 Mt @ 1.66% Cu,
Inferred - 0.1 Mt @ 1.64% Cu,
TOTAL resources - 21.0 Mt @ 5.51% Cu,
Probable high grade reserves - 6.1 Mt @ 4.80% Cu (3.5% Cu cut-off).
This summary is drawn from "A competent person's report and valuation report on the mineral assets of Metorex (Pty) Ltd in the Democratic Republic of Congo and the Republic of Zambia", prepared for Metorex (Pty) Ltd in June 2013 by SRK Consulting (South Africa) (Pty) Ltd." and "Ngoyi, K. and Dejonghe, L., 1995 - Geologie et genese du gisement stratoide cuprifere de Kinsenda (se Du Shaba, Zaire); Bulletin de la Societe beige de Geologie, v. 104, pp. 245-281".
The most recent source geological information used to prepare this decription was dated: 2013.
Record last updated: 23/12/2015
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.
Kinsenda
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Ngoyi, K. and Dejonghe, L., 1995 - Geologie et genese du gisement stratoide cuprifere de Kinsenda (se Du Shaba, Zaire): in Bulletin de La Societe Belge de Geologie (in French, Abstract in English) v. 104, pp. 245-281
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