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Pan-African shear zones in the Kaoko Belt (Namibia) and links across Southwestern Gondwana: Neoproterozoic evolution and Phanerozoic reactivation

Grant number: 19/06838-2
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): June 01, 2019
Effective date (End): May 31, 2022
Field of knowledge:Physical Sciences and Mathematics - Geosciences - Geology
Principal researcher:Mario da Costa Campos Neto
Grantee:Mathias Hueck
Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:15/03737-0 - The Rio de La Plata Craton and the Western Gondwana Assembly, AP.TEM

Abstract

This project aims to contribute to the understanding of the tectonic and geodynamic evolution of southwestern Gondwana, from its amalgamation in the Neoproterozoic to its break-up in the Cretaceous. For this, the research will focus on the long-term tectonic activity of the network of shear zones of the Kaoko Belt in northwestern Namibia. The deformation history of these structures during the Pan-African orogenic cycle will be reconstructed using a multi-method geochronological investigation including U-Th-Pb analyses in zircon and monazite, and K-Ar and Ar/Ar geochronology in amphibole, muscovite, biotite and illite fine fractions. The geochronological research will be grounded on detailed structural observations in the field and in microscale, aiming to compare the evolution history of these Shear Zones with the main regional events of the orogeny. The resulting evolution will then be compared with that of equivalent tectonic features in southern Africa and South America, leading to the construction of a tectonic model of the amalgamation of southwestern Gondwana. In addition, this project aims to evaluate the impact of the reactivation of these structures on the regional exhumation during the Phanerozoic, particularly during the period of ca. 400 Myr between the Neoproterozoic orogeny and the Cretaceous continental break-up. In order to do so, different thermochronological methods in the temperature range of 300-100 °C will be combined, focusing both on the direct dating of brittle activity in fault zones (K-Ar in illite fine fractions in fault gouges) and in the reconstruction of the thermal histories of adjacent blocks (Ar/Ar in K-feldspar and (U-Th)/He in zircon, titanite, rutile and apatite). By combining both approaches, the impact of fault activity in exhumation and surface processes will be robustly evaluated. The resulting long-term tectonothermal history of the shear zones and their influence in the regional exhumation will be contextualized and compared with adjacent units in Africa and its South American counterparts, enabling the establishment of correlations across southwestern Gondwana.

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