The Tasiast deposit,Mauritania |
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| Institution: | 1. Department of Geology, School of Natural Sciences, Trinity College, Dublin 2, Ireland;2. Laboratoire GET, Université Toulouse 3 Paul Sabatier, IRD, CNRS UMR 5563, Observatoire Midi-Pyrénées, 31400 Toulouse, France;3. Centre for Exploration Targeting, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;4. Terracognita Geological Consulting Inc., P.O. Box 100, 4874 St. Clair Parkway, Port Lambton, ON N0P 2B0, Canada;5. Mineral Exploration Consultant, 96 Marlow St, Wembley, WA 6014, Australia;6. Department of Geology, School of Natural Sciences, Trinity College Dublin 2, Ireland;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. Centre for Exploration Targeting, School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;1. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;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. Université Sidi Mohamed Ben Abdellah, Faculté des Sciences Dhar El Mahraz, Département de Géologie, BP 1796 Fès, Morocco;3. Iamgold Exploration, 3503 Av. Al Qods Hippodrome, BP 2699 Bamako, Mali;4. Avnel Gold Mining Limited, 39 Cheval Place, London SW7 1EW, UK;1. U.S. Geological Survey, Spokane, WA 99201, USA;2. School of the Environment, Washington State University, Pullman, WA 99164, USA;3. U.S. Geological Survey, Denver, CO 80225, USA |
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| Abstract: | The Tasiast gold deposits are hosted within Mesoarchean rocks of the Aouéouat greenstone belt, Mauritania. The Tasiast Mine consists of two deposits hosted within distinctly different rock types, both situated within the hanging wall of the west-vergent Tasiast thrust. The Piment deposits are hosted within metasedimentary rocks including metaturbidites and banded iron formation where the main mineral association consists of magnetite-quartz-pyrrhotite ± actinolite ± garnet ± biotite. Gold is associated with silica flooding and sulphide replacement of magnetite in the turbidites and in the banded iron formation units. The West Branch deposit is hosted within meta-igneous rocks, mainly diorites and quartz diorites that lie stratigraphically below host rocks of the Piment deposits. Most of the gold mineralisation at West Branch is hosted by quartz–carbonate veins within the sheared and hydrothermally altered meta-diorites that constitute the Greenschist Zone. At Tasiast, gold mineralisation has been defined over a strike length > 10 km and to vertical depths of 740 m. All of the significant mineralised bodies defined to date dip moderately to steeply (45° to 70°) to the east and have a south–southeasterly plunge. Gold deposits on the Tasiast trend are associated with second order shear zones that are splays cutting the hanging wall block of the Tasiast thrust. An age of 2839 ± 36 Ma obtained from the hydrothermal overgrowth on zircons from a quartz vein is interpreted to represent the age of mineralisation. |
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