Regional aeromagnetic and stratigraphic correlations of the Kalahari Copperbelt in Namibia and Botswana |
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| Institution: | 1. EGRI, School of Geosciences, University of the Witwatersrand, PVT Bag 3, Wits 2050, South Africa;2. Geological Institute, BAS, 24 Acad. G. Bonchev str, 1113 Sofia, Bulgaria;3. Geological Survey of Norway (NGU), Postboks 6315 Sluppen, 7491 Trondheim, Norway;4. Rio Tinto Mining and Exploration, 1 Harries Rod, Illovo 2196, South Africa;1. Centre for Exploration Targeting and Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS), School of Earth and Environment, The University of Western Australia, Crawley, WA 6009, Australia;2. Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran;3. Centre of Studies in Resources Engineering, Indian Institute of Technology Bombay, Powai, India;4. Department of Mining Engineering, University of Tehran, Tehran, Iran;1. KU Leuven, Department of Earth and Environmental Sciences, Celestijnenlaan 200E, 3001 Leuven, Belgium;2. University of Johannesburg, Department of Geology, Auckland Park 2006, Johannesburg, South Africa;3. Ghent University, Department of Analytical Chemistry, Krijgslaan 281-S12, 9000 Ghent, Belgium;1. School of Geosciences, University of the Witwatersrand, PVT Bag 3, Wits, 2050 Johannesburg, South Africa;2. Norges geologiske undersøkelse (NGU), Postboks 6315 Sluppen, 7491 Trondheim, Norway;3. Department of Earth Sciences, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa;4. Institut für Geowissenschaften, Mineralogie, Goethe-University Frankfurt (GUF), Altenhöferallee 1, D-60438 Frankfurt am Main, Germany |
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| Abstract: | The late Mesoproterozoic to Neoproterozoic Kalahari Copperbelt (KCB) in Namibia and Botswana is widely covered by Kalahari sand, which precludes direct correlations between known stratabound sediment-hosted Cu–Ag districts. We use a combination of review of literature data, and newly processed and interpreted high-resolution aeromagnetic maps in both countries to provide a new correlative cross-border interpretation. Lithostratigraphic control on the aeromagnetic response allows detailed indirect mapping of the Kalahari Copperbelt lithotectonic domains below the sand cover. This enabled us to redefine the width and lateral extent of the KCB as two continuous magnetic domains (the Rehoboth and Ghanzi–Chobe domains) extending from central Namibia to northern Botswana, and helped in resolving problems of stratigraphic correlations across the international border.The Rehoboth magnetic domain, in the western part of the KCB in Namibia, records continental arc magmatism at ~ 1200 Ma during orogenic events along the northwestern edge of the Kalahari Craton. This was followed at 1110–1090 Ma by widespread magmatism, identified within the entire KCB, and related to the 1112–1106 Ma Umkondo Large Igneous Province. The basal parts of the Tsumis Group in Namibia and Ghanzi Group in Botswana were deposited in shallow-water environments after a period of erosion and peneplanation. Subsequently, and prior to the Sturtian glaciation, the host-rocks of the Cu–Ag deposits formed by the deposition of chemically reduced shales and siltstones that formed in deeper water and overlie chemically oxidised shallow-water sandstones. This regional interface, which is both a permeability barrier and redox boundary, played a critical role in the formation of the stratabound sediment-hosted Cu–Ag deposits of the Kalahari Copperbelt, and the interface, with its strong magnetic contrast, can be followed through the entire Ghanzi–Chobe magnetic domain of the copperbelt. The whole KCB was affected by the Damara Orogeny during early Cambrian times, which resulted in the formation of a NE–SW trending ~ 250 km-wide fold-and-thrust belt. |
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