Depositional ages and provenance of the Neoproterozoic Damara Supergroup (northwest Namibia): Implications for the Angola-Congo and Kalahari cratons connection |
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| Institution: | 1. Programa de Pós–graduação em Geologia, Universidade Federal do Rio de Janeiro (PPGL/UFRJ), CEP 21941-916 Rio de Janeiro, Brazil;2. Instituto de Geociências, Universidade Federal do Rio de Janeiro (IGEO/UFRJ), CEP 21941-916 Rio de Janeiro, Brazil;3. Institut für Geowissenschaften, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany;4. Instituto de Geociências, Universidade de São Paulo, CEP 05508-080 São Paulo, Brazil;1. Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611, USA;2. School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing 100083, PR China;3. Department of Earth Sciences, The University of Adelaide, Adelaide, SA 5005, Australia;4. Department of Earth System Sciences, Yonsei University, Seoul 03722, Republic of Korea;1. School of Geosciences, University of the Witwatersrand, PVT Bag 3, Wits, 2050, South Africa;2. PRISE, Australian National University, Research School of Earth Sciences, Building 61, Mills Road, Acton 0200, Australia;1. Universidade Federal de Minas Gerais, Programa de Pós-Graduação em Geologia, CPMTC-IGC-UFMG, Av. Antônio Carlos 6627, Pampulha, 31270-901 Belo Horizonte, MG, Brazil;2. Universidade do Estado do Rio de Janeiro, Faculdade de Geologia, MULTILAB, Rua Francisco Xavier, 524, Maracanã, 20550-900 Rio de Janeiro, RJ, Brazil;3. Departamento de Geologia, Escola de Minas, Universidade Federal de Ouro, Morro do Cruzeiro, 35400-000 Ouro Preto, MG, Brazil;4. TU Bergakademie Freiberg, Institute of Mineralogy, 09596 Freiberg, Saxony, Germany |
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| Abstract: | The Damara Orogen is composed of the Damara, Kaoko and Gariep belts developed during the Neoproterozoic Pan-African Orogeny. The Damara Belt contains Neoproterozoic siliciclastic and carbonate successions of the Damara Supergroup that record rift to proto-ocean depositional phases during the Rodinia supercontinent break up. There are two conflicting interpretations of the geotectonic framework of the Damara Supergroup basin: i) as one major basin, composed of the Outjo and Khomas basins, related to rifting in the Angola-Congo-Kalahari paleocontinent or, ii) as two independent passive margin basins, one related to the Angola-Congo and the other to the Kalahari proto-cratons. Detrital zircon provenance studies linked to field geology were used to solve this controversy. U-Pb zircon age data were analyzed in order to characterize depositional ages and provenance of the sediments and evolution of the succession in the northern part of the Outjo Basin. The basal Nabis Formation (Nosib Group) and the base of the Chuos Formation were deposited between ca. 870 Ma and 760 Ma. The upper Chuos, Berg Aukas, Gauss, Auros and lower Brak River formations formed between ca. 760 Ma and 635 Ma. It also includes the time span recorded by the unconformity between the Auros and lower Brak River formations. The Ghaub, upper Brak River, Karibib and Kuiseb formations were deposited between 663 Ma and 590 Ma. The geochronological data indicate that the main source areas are related to: i) the Angola-Congo Craton, ii) rift-related intrabasinal igneous rocks of the Naauwpoort Formation, iii) an intrabasinal basement structural high (Abbabis High), and iv) the Coastal Terrane of the Kaoko Belt. The Kalahari Craton units apparently did not constitute a main source area for the studied succession. This is possibly due to the position of the succession in the northern part of the Outjo Basin, at the southern margin of the Congo Craton. Comparison of the obtained geochronological data with those from the literature shows that the Abbabis High forms part of the Kalahari proto-craton and that Angola-Congo and Kalahari cratons were part of the same paleocontinent in Rodinia times. |
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