Oblique collision and evolution of large-scale transcurrent shear zones in the Kaoko belt,NW Namibia |
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| Institution: | 1. Institut für Geowissenschaften – Tektonophysik, Universität Mainz, 55099 Mainz, Germany;2. Geological Survey of Namibia, P.O. Box 2168, Windhoek, Namibia;1. Departamento de Geología, Universidad Nacional de Río Cuarto, Ruta Nac. Nº 36, Km 601, X5804BYA, Río Cuarto, Córdoba, Argentina;2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina;1. School of Geosciences, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein 2000, Johannesburg, South Africa;2. Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, Johannesburg, South Africa;3. Department of Geosciences and CEED, University of Oslo, Postbox 1047 Blindern, N-0316 Oslo, Norway;1. Department of Geology & Geological Engineering, Colorado School of Mines, 1516 Illinois Street, Golden, CO 80401, USA;2. LASS Petrochronology Facility, Department of Earth Science, University of California, Santa Barbara, CA 93106, USA;3. U.S. Geological Survey, MS 963, Denver Federal Center, Denver, CO 80225, USA;4. Cupric Africa, Corner Van der Linde and Smith Roads, 2nd Floor, Bedford Square Office Suite, Bedford Gardens, Bedfordview 2008, South Africa;1. Instituto de Geociências, Universidade Estadual de Campinas (UNICAMP), Campinas-SP, Brazil;2. Instituto de Geociências, Universidade de Brasília (UnB), Brasília-DF, Brazil;1. Depto. de Geologia – IGEO – UFRJ, Cidade Universitária, CEP 21949-900, Ilha do Fundão, Rio de Janeiro-RJ, Brazil;2. Institut für Geowissenschaften – Goethe Universität Frankfurt am Main, Altenhöferallee 1, D-60438 Frankfurt am Main, Germany;3. Depto. de Geologia – UFES – CCA Alto Universitário, s/n – Guararema – CEP 29500-000, Alegre-ES, Brazil |
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| Abstract: | Early structures in the central part of the Kaoko orogenic belt of NW Namibia suggest that the initial stage of collision was governed by underthrusting of the medium-grade Central Kaoko zone below the high-grade Western Kaoko zone, resulting in the development of an inverted metamorphic gradient. In the Western zone, early structures were overprinted by a second phase of deformation, which is associated with localization of the transcurrent Puros shear zone along the contact between the Western and Central zones. During this second phase, extensive partial melting and intrusion of ～550 Ma granitic bodies occurred in the high-grade Western zone. In the Central zone, the second phase of deformation led to complete overprinting of the early foliation in the zone adjacent to the Puros shear zone, and to the development of kilometre-scale folds in the more distal parts. Strain partitioning into transcurrent deformation along the Puros shear zone and NE–SW oriented shortening in the Central zone is consistent with a sinistral transpressional regime during the second phase of deformation. Transcurrent deformation continued during cooling of the entire belt, giving rise to the localized low-temperature Village Mylonite Zone that separates a segment of elevated Mesoproterozoic basement from the rest of the Western zone in which only Pan-African ages have so far been observed. The data suggest that the boundary between the Western and Central Kaoko zones represents a modified thrust zone controlling the tectonic evolution of the Pan-African Kaoko belt. |
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