1. The geology, petrography, geochemistry and uranium ore mineralogy of the Namibplaas sheeted leucogranites, Damaran orogen, Namibia
- Author
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Shilongo, Emmanuel and Shilongo, Emmanuel
- Abstract
This research study focused on the previously unknown uranium mineralisation hosted in garnet and magnetite bearing sheeted leucogranites (SLG's) I alaskites at Namibplaas. The various SLG's were distinguished and characterised by means of field, petrographic and geochemical studies into B, C and D-types based on the classification scheme ofNex and Kinnaird (1995) in the Goanikontes area. In addition, the stratigraphic positions of the SLG' s were established. The research techniques applied in the study included review of historical data, ground mapping, diamond drill core logging and sample preparation, thin section preparation, geochemical analyses and uranium ore mineralogical investigation. At Namibplaas, the Damaran sequence is most complete; the B-types are least abundant and are localised to the Kuiseb Formation, the C-types are most abundant and intrude the whole stratigraphic sequence. The D-types are emplaced within the Karibib, Chuos, Rossing and Khan Formations and at the Khan-Rossing-Chuos-Karibib Formation boundaries. The B and C- types are post D1- D2 but pre D3 deformation and are barren in uranium. D-types are post D1- D2- D3 deformation, these are uranium enriched and cross-cut the B and C-types making them the youngest of the intrusives. The sheeted leucogranites at both Goanik:ontes and at N arnibplaas have undergone similar structural events. But there is however a difference in accessory mineralogy and U & Th geochemistry. The D-types at Namibplaas bear garnet and magnetite. The occurrence of these accessory minerals can be explained as a result of host stratigraphic - assimilation. Individual sheeted leucogranite types are discemable from each other by a number of major, trace and rare earth element discrimination plots. Uranium and thorium and U/Th ratio distinguishes and characterises the Namibplaas sheeted leucogranites very well. The D-type contain the highest concentrations of uranium (22.5ppm to 1020ppm) with a U/Th ratio > 1. The C-typ
- Published
- 2017