Abstract
The Neo-Archean Dominion Reefs (~3.06 Ga) are thin meta-conglomerate layers with concentrations of U- and Th-bearing heavy minerals higher than in the overlying Witwatersrand Reefs. Ore samples from Uranium One Africa’s Rietkuil and Dominion exploration areas near Klerksdorp, South Africa, were investigated for their mineral paragenesis, texture and mineral chemical composition. The ore and heavy mineral assemblages consist of uraninite, other uraniferous minerals, Fe sulphides, Ni–Co sulfarsenides, garnet, pyrite, pyrrhotite, monazite, zircon, chromite, magnetite and minor gold. Sub-rounded uraninite grains occur associated with the primary detrital heavy mineral paragenesis. U–Ti, U–Th minerals, pitchblende (colloform uraninite) and coffinite are of secondary, re-mobilised origin as evidenced by crystal shape and texture. Most of the uranium mineralisation is represented by detrital uraninite with up to 70.2 wt.% UO2 and up to 9.3 wt.% ThO2. Re-crystallised phases such as secondary pitchblende (without Th), coffinite, U–Ti and U–Th phases are related to hydrothermal overprint during low-grade metamorphism and are of minor abundance.
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Acknowledgements
We thank the Department of Geology, UFS, Bloemfontein for instrumental and financial support and also the Institute of Mineralogy, Crystallography and Materials Science of the Leipzig University, Germany, for scientific support. We are grateful to the geology staff of Uranium One Africa, especially to Richard Stewart and Stephan Stander for initiating this near-industry research project and for financial support, provision of logistics and data. The management of Uranium One Africa Pty Ltd. is acknowledged for allowing access to their lease areas and for their permission to carry out this research. Finally, we are grateful for analytical support by the Faculté des Sciences, Université Henri Poincaré Nancy, France as well as their scientific input.
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Rantzsch, U., Gauert, C.D.K., Van der Westhuizen, W.A. et al. Mineral chemical study of U-bearing minerals from the Dominion Reefs, South Africa. Miner Deposita 46, 187–196 (2011). https://doi.org/10.1007/s00126-010-0317-4
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DOI: https://doi.org/10.1007/s00126-010-0317-4