The Bepkong gold deposit,Northwestern Ghana |
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| Institution: | 1. Université de Toulouse, CNRS, Géosciences Environnement Toulouse, Institut de Recherche pour le Développement, Observatoire Midi-Pyrénées, 14 Av. Edouard Belin, F-31400 Toulouse, France;2. Azumah Resources Ghana Limited, PMB CT452, Cantonments, Accra, Ghana;3. IFAN Cheikh Anta Diop, Dakar, Senegal;4. ONG-D “Le Soleil dans la Main” asbl, 48, Duerfstrooss, L-9696 Winseler, Luxembourg;5. University of Ghana, Department of Earth Sciences, P.O. Box LG 58, Legon, Accra, Ghana;6. Centre for Exploration Targeting, School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;1. University for Development Studies, Earth and Environmental Sciences, P.O. Box 24, Navrongo, Ghana;2. Department of Geology, University of Leicester, UK;3. Department of Earth and Environmental Science, Eastern Connecticut State University, USA;4. Department of Earth Science, University of Ghana, Legon, Ghana;1. School of Geography, Geology and the Environment, Kingston University London, Kingston upon Thames KT1 2EE, UK;2. Randgold Resources Ltd, Unity Chambers, Halkett Street, St Helier JE2 4WJ, Jersey;3. Scottish Universities Environmental Research Centre, East Kilbride, Glasgow, G75 0QF, Scotland |
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| Abstract: | The Bepkong gold deposit is located in the Wa–Lawra belt of the Paleoproterozoic Baoulé-Mossi domain of the West African Craton, in NW Ghana. It occurs in pelitic and volcano-sedimentary rocks, metamorphosed to greenschist facies, in genetic association with zones of shear interpreted to form during the regional D3 deformational event, denominated DB1 at the deposit scale. The ore zone forms a corridor-like body composed of multiple quartz ± carbonate veins surrounded by an alteration envelope, characterized by the presence of chlorite, calcite, sericite, quartz and disseminated pyrite, arsenopyrite plus subordinate pyrrhotite and chalcopyrite. The veins contain only small proportions of pyrite, whereas most of the sulphides, particularly arsenopyrite, occur in the altered host rock, next to the veins. Pyrite is also common outside of the ore zone. Gold is found in arsenopyrite, where it occurs as invisible gold and as visible – albeit micron-size – grains in its rims, and as free gold within fractures cross-cutting this sulphide. More rarely, free gold also occurs in the veins, in fractured quartz. In the ore zone, pyrite forms euhedral crystals surrounding arsenopyrite, but does not contain gold, suggesting that it formed at a late stage, from a gold-free hydrothermal fluid. |
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