首页|Thrust to transpression and transtension tectonics during the Paleoproterozoic evolution of the Birimian Greenstone Belt of Mako, Kedougou-Kenieba Inlier, Eastern Senegal
Thrust to transpression and transtension tectonics during the Paleoproterozoic evolution of the Birimian Greenstone Belt of Mako, Kedougou-Kenieba Inlier, Eastern Senegal
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NETL
NSTL
Elsevier
The structural cartography of the Birimian formations of the Mako area shows a polyphase deformation marked by variable structures such as imbricated shear zones, thrusts and reverse-shears, poly-folding, boudinage, normal faults. The multiscale analysis of the various mapped structures combined with the satellite images allowed us to distinguish three major phases of Eoeburnean and Eburnean deformation. The Eoeburnean D1deformation phase is preserved through ductile structures in some lithologies (metabasalts, quartzites). It is composed of early thrusting and late sinistral reverse-shearing due to a NW-SE principal shortening direction, which involved large overturned folds verging northwestward and associated with thrust faults. It is also associated with the emplacement of early granitoids (c. 2200 Ma) followed by andesitic to felsic volcanic rocks around c. 2160 Ma. The Eburnean event is divided into two phases of deformation namely D2and D3. The D2phase is the early Eburnean event which involves a sinistral transpressive deformation. It is characterized by a NNE-SSW shortening direction which creates major NNW-SSE (N160°-170°) and NNE-SSW (N20°-30°) sinistral reverse-shear zones associated with ENE-WSW (N60°-70°) dextral reverse-shear zones. Interference between both major NNE-SSW and NNW-SSE reverse-shear zones involves an anatomizing pattern of deformation. The D3phase is a transtensional deformation associated with a dextral movement which creates dextral shear zones and conjugate normal faults leading to graben depression. The D3principal maximum stress is ENE-WSW oriented. The granitoids were emplaced during these Eoeburnean and Eburnean orogenic events.
NETL
NSTL
Elsevier
