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Accueil du site → Doctorat → Allemagne → 2013 → Geodynamic evolution of the central-eastern Bayuda Desert Basement, Sudan : structural, petrological, geochemical and geochronological investigations

Technische Universität Berlin (2013)

Geodynamic evolution of the central-eastern Bayuda Desert Basement, Sudan : structural, petrological, geochemical and geochronological investigations

Evuk David

Titre : Geodynamic evolution of the central-eastern Bayuda Desert Basement, Sudan : structural, petrological, geochemical and geochronological investigations

Geodynamische Entwicklung des Basements in der zentral-östlichen Bayuda Wüste, Sudan : strukturelle, petrologische, geochemische und geochronologische Untersuchungen

Auteur : Evuk David

Université de soutenance : Technische Universität Berlin

Grade : Doctoral Thesis 2013

Résumé
Integrated remote sensing and GIS, field, petrographical, geochemical, geochronological, structural and geodynamic studies were conducted at the central-eastern Bayuda Desert along and west of southern Keraf Shear Zone, part of the collisional zone between east and west Gondwana. The location of the boundary between east and west Gondwana and the structural and geodynamic evolution of this boundary and adjacent terranes during the Neoproterozoic in NE Africa have been controversial for a long time. Techniques of band combination, band ratios, principal component analysis on satellite Landsat 7 ETM+ images and band combination of ASTER images, arial photo interpretation, archival maps digitization in ArcMap were employed for lithological differentiation and creation of a database model. Field mapping, directional filters and RADAR images were used for structural analysis. Petrological, whole-rock geochemistry, Pb-Sr isotope and U-Pb zircon laser ablation techniques were performed on rock samples from the study area. These studies confirmed that the boundary between the Saharan Metacraton and the Nubian Shield lies between Rahaba-Absol and the Abu Harik-Kurmut Terranes in the central-eastern Bayuda Desert. The Rahaba-Absol terrane comprised of calc-alkaline to high-K calc-alkaline porphyroblastic metagranites, meta-monzodiorite and undifferentiated Rahaba Series rocks that have isotopic signatures of a craton that evolved during an extended Bayudian Event from 1000 to 900 Ma through magmatic and metamorphic activities at 969±5 Ma, 914±6 Ma, 912±4 Ma, 909±9 Ma, and pan-African rejuvenation registered by the meta-monzodiorite at 818±19 Ma and 669±13 Ma. However details of these activities still require a better understanding. Meanwhile, the latter terranes are made of calc-alkaline island-arc intrusives and volcanics, metasediments and dismembered ophiolites with metagranitoids having a juvenile isotopic signature of the Arabian-Nubian Shield. Moreover, it is proposed that the southern Keraf Shear Zone is an arc-arc suture between Abu Harik-Kurmut Terranes and Gabgaba Terrane. These terranes evolved through extension at 900-850 Ma, convergence between 850 to 750 with peak subduction related magmatism at 825 to 800 Ma, collision between 750 to 630 Ma, horizontal displacement between 630 to 590 Ma and post-collision plutonism and later cooling from 590 to 550 Ma. This geodynamic activity resulted in the development of structures associated with three deformation phases. The Pre-Dam ElTor deformation due to NE-SW shortening formed F1 and F2 co-axial NW trending folds with NE vergence and thrusting at Absol area. Dam ElTor deformation from NW-SE shortening superposed NE trending F3 folds with SE vergence on earlier folds forming the Azuma fold interference pattern with thrusting and dextral movement at Dam ElTor Fold and Thrust Belt. Post-Dam ElTor deformation from N-S compression formed E-W upright fold and NNW, NS and NNE trending upright folds by E-W extension that was translated to compression at the Fifth Cataract. This compression probably formed Fifth Cataract Thrust Fold with vergence to the west. Final N-S compression formed a sinistral movement along the Fith Cataract Stretch. Vertical collapse and intrusion of post-collision granites was probably aided by shear zones along NW, NE and NS with most of the Phanerozoic magmatism controlled by NW trending lower lithopheric mantle structures

Mots clés : panafrikanisch ; in-situ Datierung ; Deformationphasen Metacraton ; pan-African ; in-situ dating ; deformation phases ; Bayuda

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Page publiée le 23 octobre 2014, mise à jour le 29 décembre 2018