Evaluation of Water Resources Quality in Sabodala Gold Mining Region and Its Surrounding Area (Senegal)

peer reviewedGeochemical and Geostatistical tools were used to assess: 1) the chemical quality and, geochemical processes in crystalline rock aquifers in Sabodala (Eastern Senegal) and its surroundings and 2) the impact of mining activities on their quality. A total of 26 water samples collected at boreholes, dug wells and stream, were analyzed to determine major and trace elements concentration focused on elements that represent more threats on human health. Boxplots define chemical characteristics of water for each aquifer formation compared to surface waters. Geostatistical analysis show two sources of water mineralization with regard to major elements: a first natural source characterized by Ca-Mg-HCO3 water type from boreholes and unpolluted surface water and a second group characterized by polluted water by nitrates with Na-NO3-Cl type mainly observed in upper weathered aquifers. However, considering trace element, geostatistical analysis showed three water groups: water with very low trace element concentrations encountered in boreholes and unpolluted surface waters, and waters with relatively high trace element concentrations such as Al observed in areas affected by gold mining activities and finally, polluted waters by Ni, Co, Mn and Cr observed at Sabodala. Results show that in eastern Senegal well waters are vulnerable and often affected by pollution

Thrust to braiding transpression and transtension tectonics during the Paleoproterozoic evolution of the Birimian Greenstone Belt of Mako, Kédougou-Kéniéba Inlier, Eastern Senegal

International audienceThe 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-foldings, “boudinages”, normal faults. The multiscale analysis of the various mapped structures combined with the satellite images allowed to distinguish three major phases of Eburnean deformations D1, D2 and D3. The D1 phase is compressive to thrust deformation due to SSE-NNW principal shortening direction which involves large overturned folds verging to the NW associated with minor thrust fault which are preserved in some lithologies (metabasalts, quartzites). The D2 phase is a sinistral transpressive deformation which comprises an early (D2a) stage followed by a late (D2b) stage. The early D2a stage is characterized by major NE-SW reverse-shears verging to the NW associated with NW-SE minor dextral shear zones. It is followed by D2b stage characterized by ENE-WSW shortening direction which creates major NNW-SSE sinistral reverse-shear zones. Interference between NE-SW and NNW-SSE major reverse-shear zone of D2a and D2b respectively creates an anatomizing pattern of the deformation. Shearing along D2 shear zone is associated with development of minor extensional zone which filled by varied magmatic products (mafic, intermediate and felsic). D3 phase is a transtension deformation associated with a dextral movement which creates conjugate normal faults with locally negative flower structures. D3 principal maximum stress is ENE-WSW oriented. The orientation of the main shortening direction of Eburnean phases D1, D3 and D3 is NNW-SSE, NW-SE and ENE-WSW, respectively. Such a pattern could be induced by an anticlockwise rotation of principal maximum stress in the Mako sector. The Eburnean granitoids emplaced before and during these three Eburnean orogenic phases

Thrust to braiding transpression and transtension tectonics during the Paleoproterozoic evolution of the Birimian Greenstone Belt of Mako, Kédougou-Kéniéba Inlier, Eastern Senegal

International audienceThe 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-foldings, “boudinages”, normal faults. The multiscale analysis of the various mapped structures combined with the satellite images allowed to distinguish three major phases of Eburnean deformations D1, D2 and D3. The D1 phase is compressive to thrust deformation due to SSE-NNW principal shortening direction which involves large overturned folds verging to the NW associated with minor thrust fault which are preserved in some lithologies (metabasalts, quartzites). The D2 phase is a sinistral transpressive deformation which comprises an early (D2a) stage followed by a late (D2b) stage. The early D2a stage is characterized by major NE-SW reverse-shears verging to the NW associated with NW-SE minor dextral shear zones. It is followed by D2b stage characterized by ENE-WSW shortening direction which creates major NNW-SSE sinistral reverse-shear zones. Interference between NE-SW and NNW-SSE major reverse-shear zone of D2a and D2b respectively creates an anatomizing pattern of the deformation. Shearing along D2 shear zone is associated with development of minor extensional zone which filled by varied magmatic products (mafic, intermediate and felsic). D3 phase is a transtension deformation associated with a dextral movement which creates conjugate normal faults with locally negative flower structures. D3 principal maximum stress is ENE-WSW oriented. The orientation of the main shortening direction of Eburnean phases D1, D3 and D3 is NNW-SSE, NW-SE and ENE-WSW, respectively. Such a pattern could be induced by an anticlockwise rotation of principal maximum stress in the Mako sector. The Eburnean granitoids emplaced before and during these three Eburnean orogenic phases

Thrust to braiding transpression and transtension tectonics during the Paleoproterozoic evolution of the Birimian Greenstone Belt of Mako, Kédougou-Kéniéba Inlier, Eastern Senegal

International audienceThe 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-foldings, “boudinages”, normal faults. The multiscale analysis of the various mapped structures combined with the satellite images allowed to distinguish three major phases of Eburnean deformations D1, D2 and D3. The D1 phase is compressive to thrust deformation due to SSE-NNW principal shortening direction which involves large overturned folds verging to the NW associated with minor thrust fault which are preserved in some lithologies (metabasalts, quartzites). The D2 phase is a sinistral transpressive deformation which comprises an early (D2a) stage followed by a late (D2b) stage. The early D2a stage is characterized by major NE-SW reverse-shears verging to the NW associated with NW-SE minor dextral shear zones. It is followed by D2b stage characterized by ENE-WSW shortening direction which creates major NNW-SSE sinistral reverse-shear zones. Interference between NE-SW and NNW-SSE major reverse-shear zone of D2a and D2b respectively creates an anatomizing pattern of the deformation. Shearing along D2 shear zone is associated with development of minor extensional zone which filled by varied magmatic products (mafic, intermediate and felsic). D3 phase is a transtension deformation associated with a dextral movement which creates conjugate normal faults with locally negative flower structures. D3 principal maximum stress is ENE-WSW oriented. The orientation of the main shortening direction of Eburnean phases D1, D3 and D3 is NNW-SSE, NW-SE and ENE-WSW, respectively. Such a pattern could be induced by an anticlockwise rotation of principal maximum stress in the Mako sector. The Eburnean granitoids emplaced before and during these three Eburnean orogenic phases