Geological Information
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Deposit Type
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Intrusive
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Geological Setting
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It is located within the north-east trending Central Zone of the Neoproterozoic Pan-African Damara Orogenic Belt. The belt, which is divided into a number of parallel zones, is interpreted to have resulted from a « Wilson cycle » which has culminated in the collision of the Congo and Kalahari cratons around 500 Ma. Peak metamorphism and D2 deformation has been constrained between 550 and 510 Ma. Primary mineralisation within the orogen is associated with igneous activity during this period and includes Cu, Au, Li, Sn and U.Rocks of the Damara sequence are divided into two major groups, the lower Nosib Group and the upper pelitic and calcareous Swakop Group.
At Goanikontes, uranium occurrences are located along the western flank of the Goanikontes dome which consists of pre-Damara basement, with a core of reddish leucocratic gneiss that is referred to as the « red granite gneiss ». The central gneiss is surrounded by migmatites and other basement rock types.
The uraniferous intrusive alaskites are a late stage leucocratic granite that often has a pegmatitic texture. Six types of alaskites (types A to F) classified according to their field apparence and ralationships, mineralogy and petrology, are recognized in the Goanikontes area. Economic uranium mineralisation occurs in types D and E, peaking in the D-type alaskotes.
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Age of Mineralization
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The alaskites are associated with the regional F4 tectonic event and have intruded the Nosib and Swakop Group metasedimentary sequences. Near Rossing, they have been dated at 458+/-8Ma.
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Mineralization
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Uranium mineralisation is associated with intrusive alaskite granitoids that comprise stock-like dykes of varying thickness (a few cm to 100m) and have intruded into the surrounding Damara sequence metasedimentary host rocks.
The dominant primary uranium mineral is uraninite, but minor betafite is also present. The primary uranium mineralisation occurs as disseminations within rock fractures, at crystal interfaces and as inclusion within other minerals. Secondary uranium minerals such as autunite and uranophane occur as replacement of the primary minerals or as coatings along fractures. The uraninite is commonly associated with chloritised biotite in the alaskites within the Lower Khan Formation and within ilmenite and magnetite within foliated alaskites.
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MetallogenicAspects
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This type of primary uranium mineralisation is commonly referred to as « Rossing type » mineralisation. Other near-by examples of this type of mineralisation includes the Rossing mine and the Valencia deposit.
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Age of Mineralization
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The alaskites are associated with the regional F4 tectonic event and have intruded the Nosib and Swakop Group metasedimentary sequences. Near Rossing, they have been dated at 458+/-8Ma.
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DepositShape
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Alaskites generally occur as bodies parallel to, but can sometime transgress the main S3 foliation and vary in thickness from a few cm to 100m. The alaskite bodies can have a strike continuity of up to several hundreds of meters, although along dip t
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DepositDimensions
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GeologicalRemarks
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Metallogenic Aspects
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This type of primary uranium mineralisation is commonly referred to as « Rossing type » mineralisation. Other near-by examples of this type of mineralisation includes the Rossing mine and the Valencia deposit.
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