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Structural evolution of the Paleoproterozoic formations of the Kédougou-Kéniéba Inlier, Eastern Senegal

Abstract : Our lithologic and structural field data are combined with image data from air borne geophysics and Landsat and Aster satelliteas well as with geochemical and geochronological data from the literature to better constrain the geodynamic evolution of the Birimian for mations of the Kédougou-Kéniéba Inlier (KKI). Thelithological analysis to get her with the available geochronological and geochemical data indicates adiachronic evolution from west (Mako Super group) to east (Dialé-Daléma Super group). This evolution started by the emplacement westward of atholeiitic ophiolitic sequencein a deep oceanic environment. It is followedbyan intermediate to felsiccalc-alkaline volcanism very developed in the eastern part and emplaced ina shallow environment. The structural results show a polyphase Eoeburnean to Eburnean deformation. The first deformation phase istangential tectonics associated to large over turned folds (P1) and localized thrusts. It affects the ophiolitic sequence of the Mako Green beltas well assome Dialé- Dalémavolcano-sediments and sediments. This phaseis Eoeburnean and would have occurred between 2170 Ma and 2140 Ma. It mainly affects the for mations of the green belt rocks of the Mako Super group which constitutes the oldest segment of the KKI (2220-2060Ma).The Eoeburnean D1 deformation phase is accompanied by the emplacement of granitoid sπ1 (2213-2160 Ma) characterized by syntectonic ductile structures (folds, planarand linear fabrics).The Eburnean D2 deformation phase isa transpressive tectonics broad lysinistral which would have occurred between 2130 Ma and 2080 Ma. It involved wide thrust sheared corridors (MTZ,FSM) and a P2 folding with tilted and curved axis. The D3 phaseis a dextral transtension which reactivates the former structures and creates extensional zones to various scales associated with normal faults. The Eburnean granitoid sπ2 (2150-2100 Ma) and π3 (2090-2040 Ma) emplaced during and after the set wo Eburnean orogenic phases.
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Submitted on : Tuesday, February 19, 2019 - 1:53:35 PM
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  • HAL Id : insu-02024869, version 1



Moussa Dabo, Tahar Aïfa, Emmanuel Tama Samoura, Ibrahima Gassama, Ibrahima Guingne, et al.. Structural evolution of the Paleoproterozoic formations of the Kédougou-Kéniéba Inlier, Eastern Senegal. 3rd IGCP 638 International Conference, Oct 2018, Abidjan, Côte d’Ivoire. pp.18. ⟨insu-02024869⟩