A kimberlite field, represented by fertile and sterile kimberlite pipes (chimneys) is located in the region of Kenieba (West Mali, Kédougou-Kenieba inlier, West African Craton). Thirty pipes and kimberlite dykes ...A kimberlite field, represented by fertile and sterile kimberlite pipes (chimneys) is located in the region of Kenieba (West Mali, Kédougou-Kenieba inlier, West African Craton). Thirty pipes and kimberlite dykes have been identified in the birimian formations, composed mainly of metasediments and granitoids, covered by sedimentary formations (sandstones and conglomerates) of Neoproterozoic age. All these formations are injected with dykes and doleritic sills of Jurassic age. The study of kimberlite pipes is still stammering in Mali, and thus no previous study has allowed to characterize the structures controlling their implementation. The reinterpretation of aeromagnetic data validated by field work indicates that the major structures of the Kenieba region are oriented NNE-SSW, NE-SW, E-W and NW-SE. These structures (faults and kimberlite pipes) are often associated with dolerite dykes, which would imply an injection of dolerite magma into the other formations. The location of the known kimberlite pipes makes it possible to say that the direction NW-SE is the most favorable for the exploration of kimberlites in the region of Kenieba.展开更多
Recent petro-structural investigations on the Faboula gold deposit located in the Bougouni-Kékoro basin, in southern Mali, north-west of the Leo-Man Shield, have provided new data on the nature and spatial organi...Recent petro-structural investigations on the Faboula gold deposit located in the Bougouni-Kékoro basin, in southern Mali, north-west of the Leo-Man Shield, have provided new data on the nature and spatial organization of the lithostratigraphic units as well as their deformation style. The deposit is covered by a thick lateritic layer and is hosted by a metavolcano-sedimentary sequence of Paleoproterozoic age intersected by intrusive bodies and filled fractures of various shape</span></span><span><span><span style="font-family:"">s</span></span></span><span><span><span style="font-family:""> and type</span></span></span><span><span><span style="font-family:"">s</span></span></span><span><span><span style="font-family:"">. The lithostratigraphic units consist of metagreywackes, metasiltstones, meta-argillites, slates and schists. Metagreywackes and metasiltstones are generally feldspathic, both may contain biotite and locally amphibole, just as slates may contain andalusite which is locally stretched. Plutonic units most often occur as stocks or as dikes on the drill core, up to 1 m. The metavolcano-sedimentary rocks are schistose and deformed under greenschist facies conditions, </span></span></span><span><span><span style="font-family:"">and </span></span></span><span><span><span style="font-family:"">locally they reach the epidote-amphibolite facies. The structural study revealed that the deposit is affected by several stages of deformation evolving from a ductile type to a brittle type via a ductile-brittle type. The dominant ductile and brittle-ductile de<span>formations show a combination of isoclinal folding and strike-slip faults.</span> <span>Both the isoclinal folding and the strike-slip faults whose sigmoidal en-echelon</span> tension gashes indicate a dextral movement in the NNE-SSW direction are the result of the same ENE-WSW regional shortening. Consequently, they highlight a transpressive deformation. This deformation noted here D<sub>2Fb</sub>, could be equivalent to the regional D<sub>2</sub> or D<sub>3</sub> deformations identified at the scale of the Leo-Man Shield if we refer to the style of deformation. There is an abundance of quartz veins networks. Their relation within the structural features indicate</span></span></span><span><span><span style="font-family:"">s</span></span></span><span><span><span style="font-family:""> that the mineralization is structurally controlled during a hydrothermal event linked certainly to the circulations of fluids during the transpressive event D<sub>2Fb</sub>.展开更多
文摘A kimberlite field, represented by fertile and sterile kimberlite pipes (chimneys) is located in the region of Kenieba (West Mali, Kédougou-Kenieba inlier, West African Craton). Thirty pipes and kimberlite dykes have been identified in the birimian formations, composed mainly of metasediments and granitoids, covered by sedimentary formations (sandstones and conglomerates) of Neoproterozoic age. All these formations are injected with dykes and doleritic sills of Jurassic age. The study of kimberlite pipes is still stammering in Mali, and thus no previous study has allowed to characterize the structures controlling their implementation. The reinterpretation of aeromagnetic data validated by field work indicates that the major structures of the Kenieba region are oriented NNE-SSW, NE-SW, E-W and NW-SE. These structures (faults and kimberlite pipes) are often associated with dolerite dykes, which would imply an injection of dolerite magma into the other formations. The location of the known kimberlite pipes makes it possible to say that the direction NW-SE is the most favorable for the exploration of kimberlites in the region of Kenieba.
文摘Recent petro-structural investigations on the Faboula gold deposit located in the Bougouni-Kékoro basin, in southern Mali, north-west of the Leo-Man Shield, have provided new data on the nature and spatial organization of the lithostratigraphic units as well as their deformation style. The deposit is covered by a thick lateritic layer and is hosted by a metavolcano-sedimentary sequence of Paleoproterozoic age intersected by intrusive bodies and filled fractures of various shape</span></span><span><span><span style="font-family:"">s</span></span></span><span><span><span style="font-family:""> and type</span></span></span><span><span><span style="font-family:"">s</span></span></span><span><span><span style="font-family:"">. The lithostratigraphic units consist of metagreywackes, metasiltstones, meta-argillites, slates and schists. Metagreywackes and metasiltstones are generally feldspathic, both may contain biotite and locally amphibole, just as slates may contain andalusite which is locally stretched. Plutonic units most often occur as stocks or as dikes on the drill core, up to 1 m. The metavolcano-sedimentary rocks are schistose and deformed under greenschist facies conditions, </span></span></span><span><span><span style="font-family:"">and </span></span></span><span><span><span style="font-family:"">locally they reach the epidote-amphibolite facies. The structural study revealed that the deposit is affected by several stages of deformation evolving from a ductile type to a brittle type via a ductile-brittle type. The dominant ductile and brittle-ductile de<span>formations show a combination of isoclinal folding and strike-slip faults.</span> <span>Both the isoclinal folding and the strike-slip faults whose sigmoidal en-echelon</span> tension gashes indicate a dextral movement in the NNE-SSW direction are the result of the same ENE-WSW regional shortening. Consequently, they highlight a transpressive deformation. This deformation noted here D<sub>2Fb</sub>, could be equivalent to the regional D<sub>2</sub> or D<sub>3</sub> deformations identified at the scale of the Leo-Man Shield if we refer to the style of deformation. There is an abundance of quartz veins networks. Their relation within the structural features indicate</span></span></span><span><span><span style="font-family:"">s</span></span></span><span><span><span style="font-family:""> that the mineralization is structurally controlled during a hydrothermal event linked certainly to the circulations of fluids during the transpressive event D<sub>2Fb</sub>.