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Musoshi

Katanga, Dem. Rep. Congo

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The Musoshi copper deposit is the continuation of the Konkola mineralised zone in Zambia across the international border border into the Democratic Republic of the Congo.

The Konkola mineralisation is developed around the margin of the Konkola Dome, which comprises an east-west elongated, 12 x 5 km core of biotite gneisses and schists, intruded by granitic rocks. Ore is hosted by the Copperbelt Orebody Member of Lower Roan Group. The Musoshi deposit is on the eastern half of the northern margin of the dome, over a strike length of 5.25 km and dips north at 48 to 65°.

For the regional setting, see the Zambian Copper Belt record, and for a description of the host sequence, including a geological map, and distribution of mineralisation, see the Konkola, Konkola Deeps, Lubambe record.

Locally the host sequence is described as follows (Richards et al., 1988):
Konkola Granite basement
Unconformity
Chimfusi Conglomerate - granite clast conglomerate;
Kafufya Quartzite - dune bedded quartzite;
Mutonda Formation - ~400 m thick, commencing with a coarse cross-bedded arkose, overlain by interbedded arkose and argillaceous sandstone, cross-bedded coarse arkosic conglomerate and sandstone, argillaceous arkosic sandstone and the 40 to 50 m thick footwall conglomerate and coarse arkose;
Ore Shale, which is 15 to 20 m thick, composed of reduced laminated shale and siltstone, passing up into micaceous siltstone to sandstone;
Musoshi Formation - ~300 m thick, comprising coarse arkoses, pyritic sandy dolomite, coarse arkose, laminated and feldspathic siltstone and gritty siltstone;
Kanwangungu Dolomite, which is 100 to 700 m thick.

The Chimfusi Conglomerate, Kafufya Quartzite and Mutonda Formation represent the Mindola Clastic Formation of the Zambian Copperbelt, while the overlying local 'Ore Shale' and Musoshi Formation make up the regional Kitwe Formation. The Kanwangungu Dolomite represents the Upper Roan Subgroup.

According to Cailteux (2007), the Kanwangungu Dolomite is overlain by the following:

Tectonic breccia, composed of lithologies from both the immediate overlying and underlying units.
Dipeta Subgroup, Kansuki Formation equivalents, comprising 29 m of massive to bedded, grey to white, arenitic dolomite, which includes some dolomitic shaly beds or layers containing pseudomorph after anhydrite nodules at the top of the sequence.
Mwashya Subgroup, commencing with a 131 m this succession of mm to cm thick alternations of white to grey coarse dolomitic sandstone and grey-green shaly to silty phlogopitic layers, equated with the Kamoya Formation. These are followed by 7 m of finely bedded, grey to black, carbonaceous, silty, phlogopite-bearing, dolomitic shale, the Kafubu Formation equivalent, overlain, in turn, by the Kanzadi Formation equivalent which is represented by 24 m of massive to bedded, white to grey, feldspathic, carbonate-poor sandstones (0.1 to 0.5 mm grain size). The sandstones are marked by micro-conglomeratic beds.
Grand Conglomérat, diamictite.
Musoshi section

Copper sulphides (mainly chalcopyrite and bornite) occur as heavy disseminations in a 15 to 20 m thick, black, laminated, biotite-rich siltstone unit, within a sequence of hematitic arkosic sandstone and conglomerate. This shale comprises the first reduced unit above the basement, which is ~1 km stratigraphically below.

The basal 1 to 2 m interval of the reduced shale is entirely barren, overlain by a thin (2 to 5 mm) subconcordant red line, composed of fine dissemination of iron oxide, which immediately precedes the first appearance of sulphide mineralisation. Above this line, grades may be as high as 5% Cu or more, over the first ~1 m and may persist at >3% over thicknesses of 3 to 4 m. Grades are commonly >1% Cu for up to 10 m above the barren zone, although sulphides do not extend into the hanging-wall arkoses.

Bornite is found in the highest grade sections, although the bulk of the ore is chalcopyritic. Pyrite dominates at higher stratigraphic levels in the reduced shale. Carrolite (Co2CuS4), common in many of the copper belt deposits, is rare at Musoshi.

Sulphides are concentrated in the coarser grained laminae of the siltstone, suggesting a permeability control on the detailed distribution of mineralisation. At the base of the mineralised section the ore is texturally mature, and sulphides tend to coalesce around detrital and authigenic grains in the richer laminae. The host rock has been partially recrystallised, with the growth of biotite, muscovite, and rutile, although sedimentary textures (bedding, ripple marks etc.) are well preserved (Richards et al., 1988).

Hydrothermal quartz veining, with sulphides (the same as in the enclosing shale) where the veins cut the reduced shale, and hematite (with minor calcite, microcline, biotite, barite, and accessory rutile, but no copper minerals) where they occur in the footwall and hanging-wall sediments, are abundant at Musoshi. Locally, veining reaches stockwork proportions, with an interconnected network of veins forming a three-dimensional array. In such cases, argillic alteration of the arkosic wall rocks is so intense that the sediments are reduced to clay and recrystallised quartz. These zones of intense alteration form linear sub-vertical trends, typically 50 to 200 m wide, in the footwall and along the base of the ore shale, and appear to follow the loci of small monoclines in the ore shale, with a few metres maximum displacement, possibly localised by minor faults (Richards et al., 1988).

The Musoshi deposit is estimated to have contained ~30 Mt of ore @ 3.3% Cu (Noma et al., 1972).

For more detail consult the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 1993.     Record last updated: 22/11/2012
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information
 References to this deposit in the PGC Literature Collection:
LeFebvre, J.J. and Tshauka, T.,  1986 - Alterations associees a la minerausation uranifere de musoshi (Shaba, Zaire) [Alteration associated with the uraniferous mineralisation of Musoshi (Shaba, Zaire)]: in   Koninklijk Museum Voor Midden-Afrika - Tervuren, Belgie Annalen - Reek [Annals of the Royal Museum for Central Africa - Tervuren, Belgium], Geologische Wetenschappen   v.8, No. 92, pp. 1-63.
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
Richards J P, Krogh T E, Spooner E T C  1988 - Fluid inclusion characteristics and U-Pb Rutile age of late hydrothermal alteration and veining at the Musoshi stratiform copper deposit, central African Copper belt, Zaire: in    Econ. Geol.   v83 pp 118-139


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