Structural analysis and implicit 3D modelling of high-grade host rocks to the Venetia kimberlite diatremes,Central Zone,Limpopo Belt,South Africa |
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| Affiliation: | 1. Tect Geological Consulting, Unit 8, AMDEC House, Steenberg Office Park, Tokai, South Africa;2. De Beers Consolidated Mines, Private Bag X01, Southdale 2193, Johannesburg, South Africa;3. Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa;1. GET, OMP, Université de Toulouse, 14 Avenue Edouard-Belin, 31400, Toulouse, France;2. UFBA, Instituto de Geociências, rua Barão de Geremoabo, 40170-020, Salvador BA, Brazil;1. GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, 14473, Germany;2. Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA;3. CERMES – Laboratoire Navier Ecole des Ponts Paros Teche, 6-8 Av. Blaise Pascal, Cite Descartes Champs sur Marne, 77455, Marne la Vallee Cedex 2, France;1. Geological Survey of NSW, Division of Resources and Energy, NSW Trade and Investment, Maitland, NSW, 2320, Australia;2. National Key Centre Geochemical Evolution and Metallogeny of Continents, Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW, 2109, Australia;3. School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia;1. Dipartimento di Scienze della Terra, Università di Napoli Federico II, Naples, Italy;2. Dipartimento di Scienze della Terra e dell''Ambiente, Università di Pavia, Via Ferrata, 1, Pavia, Italy |
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| Abstract: | The Beit Bridge Complex of the Central Zone (CZ) of the Limpopo Belt hosts the 519 ± 6 Ma Venetia kimberlite diatremes. Deformed shelf- or platform-type supracrustal sequences include the Mount Dowe, Malala Drift and Gumbu Groups, comprising quartzofeldspathic units, biotite-bearing gneiss, quartzite, metapelite, metacalcsilicate and ortho- and para-amphibolite. Previous studies define tectonometamorphic events at 3.3–3.1 Ga, 2.7–2.5 Ga and 2.04 Ga. Detailed structural mapping over 10 years highlights four deformation events at Venetia. Rules-based implicit 3D modelling in Leapfrog Geo™ provides an unprecedented insight into CZ ductile deformation and sheath folding. D1 juxtaposed gneisses against metasediments. D2 produced a pervasive axial planar foliation (S2) to isoclinal F2 folds. Sheared lithological contacts and S2 were refolded into regional, open, predominantly southward-verging, E–W trending F3 folds. Intrusion of a hornblendite protolith occurred at high angles to incipient S2. Constrictional-prolate D4 shows moderately NE-plunging azimuths defined by elongated hornblendite lenses, andalusite crystals in metapelite, crenulations in fuchsitic quartzite and sheath folding. D4 overlaps with a: 1) 2.03–2.01 Ga regional M3 metamorphic overprint; b) transpressional deformation at 2.2–1.9 Ga and c) 2.03 Ga transpressional, dextral shearing and thrusting around the CZ and d) formation of the Avoca, Bellavue and Baklykraal sheath folds and parallel lineations. |
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| Keywords: | Venetia Mine Limpopo Belt Central Zone High grade Implicit 3D modelling |
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