Geological Information
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Deposit Type
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Vein
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Geological Setting
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As for the Shinkolobwe, the deposit is in the median part of the Katanga synclinorium, an arcuate fold belt ca. 3OO km long extending from Zambia into Zaire. Regional stratigraphic units are the Kibara Group (Precambrian III) overlain by the Upper Proterozoic Katanga Group (Precambrian IV). The sediments were deposited 1300 to 620 My ago, and folded and faulted during three phases of the Lufillian Orogeny dated at 840 to 710 and 670 to 620 My. The Katanga Group includes in descending order, the Kundelungu, Grand Conglomerate Shale-Dolomite (Roan Group) Systems. The latter includes Mwashya Series and the ore hosting Mine Series (Série des Mines), 600 to 1000m thick.
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Age of Mineralization
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Age dating of uraninite : 992, 710, 697 and 682 My. The youngest age is considered to be that of the main mineralisation.
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Mineralization
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Mineralisation corresponds to dolomitic breccia zones developping along an irregular steeply dipping fault zone.
The main primary mineral is uraninite. From surface to around 60m, it is replaced by gummites, curite, uranophane, soddyite, kasolite, and more rarely sklodowskite and metatorbernite. Disseminated pyrite is common, associated to siegenite, monazite, chalcopyrite, covellite, vaesite, digenite, gold.
Brecia zones are made of heterogeneous fragments from the different horizons of the Mines Series. Large fragments of white, red or grey siliceous dolomites, greenish fragments of dolomitic schists and small fragments of chloritic schists are cemented by crystalline dolomite associated to green chlorite.
Apparent succession of events :
- uraninite,
-recrystallisation of dolomite and hematisation,
- microcrystalline silicification and chloritisation,
- sulfides,
- white dolomite, quartz
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MetallogenicAspects
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All of the uranium deposits in Shaba are closely linked to the two Cu-Co stratabound ore-formations located at the lower part of the R.2 Group. This Group belongs to the Roan Supergroup, i.e. To the lower part of the Ktanga System, dated late Proterozoic.
The R.2. Group occurs as huge fragments of dolomitico-psammitic rocks included in a silty brecciated matrix. The whole forms a kind of megabreccia, possibly formed by creeping and dissolution of evaporitic thick beds during important tectonic movements.
A stratiform poor proto-ore, probably syngenetic, is observed at the bottom of the lower Cu-Co ore formation, linked to a marked redox contact, the first observed in the Katanga system. Locally, in some R.2 fragments, this proto-ore was remobilized in veinlets of uraninite. Superficial weathering resulted in hexavalent uranium minerals.
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Age of Mineralization
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Age dating of uraninite : 992, 710, 697 and 682 My. The youngest age is considered to be that of the main mineralisation.
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DepositShape
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Irregular steeply dipping large veins
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DepositDimensions
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Open to a depth of 125m, length of 60-100m, thickness of 1 to 15m.
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GeologicalRemarks
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Metallogenic Aspects
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All of the uranium deposits in Shaba are closely linked to the two Cu-Co stratabound ore-formations located at the lower part of the R.2 Group. This Group belongs to the Roan Supergroup, i.e. To the lower part of the Ktanga System, dated late Proterozoic.
The R.2. Group occurs as huge fragments of dolomitico-psammitic rocks included in a silty brecciated matrix. The whole forms a kind of megabreccia, possibly formed by creeping and dissolution of evaporitic thick beds during important tectonic movements.
A stratiform poor proto-ore, probably syngenetic, is observed at the bottom of the lower Cu-Co ore formation, linked to a marked redox contact, the first observed in the Katanga system. Locally, in some R.2 fragments, this proto-ore was remobilized in veinlets of uraninite. Superficial weathering resulted in hexavalent uranium minerals.
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