Geological Information
|
Deposit Type
|
Vein
|
Geological Setting
|
The deposit consists of a vein stockwork in sediments distant of any know granite and is therefore classified as sediment-hosted, not granite-related vein uranium deposit.
Shinkolobwe 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.
Principal host rocks at Shinkolobwe are siliceous dolomites and dolomitic and carbonaceous shales of the RSF, RSC and SD units of the Mines Series.
The deposit is located in a structurally complex deformed area due to folding, overturning, faulting and overthrusting. The dominant structure is the Shinkolobwe fault zone trending between east and north-east, dipping 60°S. Thrusting pushed Kundelungu strata over each other, sqeezing beds of the Mines Series into an irregular NE-SW -oriented fold-fault wedge 150 to 250m wide and several km long on the surface.
|
Age of Mineralization
|
Age dating of uraninite : 706, 670±20, 620±10 My (Cahen et al., 1971).
|
Mineralization
|
Principal ore minerals are uraninite present in cubes up to 1 cm, occasionally 4 cm long, and, in oxidised sections, a large variety of hexavalent U-minerals. Remarkably, no pitchblende has been formed. Associated minerals are chiefly Co-Ni-sulfides and selenides, minor pyrite, molybdenite, galena, Cu-sulfides (vaesite and sigenite), monazite, and traces of Au, AG, Pd and other elements. Gangue minerals include abundant magnesite, chlorite, quartz, dolomite and rare aragonite.
Uraninite forms massive aggregates ans associations with Co-Ni minerals. Co-Ni mineralisation extends beyond uranium zones but Ni values drop rapidly.
The ore and associated minerals occur as discontinuous veins, veinlets, or stringers along fissures, joits , bedding planes and minor faults, as breccia matrix, replacement masses and nodules and as disseminated particles and aggregates in the host rocks. Major faults are never mineralised but filled with clay-talc breccias.
Mineralisation occurs in the three blocks within the nappe. Ore as accumulated particularly in the numerous fissures, shears, and joints developped in dolomitic shales beneath the dome like structure form by the impermeable front of the RAT nappe.
|
MetallogenicAspects
|
|
Age of Mineralization
|
Age dating of uraninite : 706, 670±20, 620±10 My (Cahen et al., 1971).
|
DepositShape
|
|
DepositDimensions
|
Uranium ore within the main ore zone extends for more than 200m in E-W direction, 100m wide and at least 255m deep. More ore is drill-indicated at depth in a easterly extension, 300 to 450m deep.
Dimensions of individual veins vary between a few centimeters to a meter thick. They commonly lack continuity, being only a meter or two, less often as much as 10m long. Locally, veins and veinlets are numerous enough to form stockworks.
|
GeologicalRemarks
|
|
Metallogenic Aspects
|
|
