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
南疆地区近四千年来气候与环境演化的研究表明 ,本地区气候环境的干旱状况持续未变 ,但期间仍有若干次相对凉湿与暖干旱时期的波动 ,且揭示出 3 .0 ka B.P.、2 .0 ka B.P.、1.5 ka B.P.、1.0 ka B.P.、0 .2 ka B.P.五个气候突变转干时...南疆地区近四千年来气候与环境演化的研究表明 ,本地区气候环境的干旱状况持续未变 ,但期间仍有若干次相对凉湿与暖干旱时期的波动 ,且揭示出 3 .0 ka B.P.、2 .0 ka B.P.、1.5 ka B.P.、1.0 ka B.P.、0 .2 ka B.P.五个气候突变转干时间界线。本研究揭示了近四千年来本地区持续干旱化的特征 ,并有后期加剧的趋势 ,并指出历史时期南疆地区若干人文事件的发生如近两千年以来丝绸之路的兴衰、南疆古城镇的废弃等与气候环境演化之间存在着良好的准对应关系 ,表明气候环境的自然演化是影响人地关系类型与内容的重要因素之一。展开更多
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>.
文摘南疆地区近四千年来气候与环境演化的研究表明 ,本地区气候环境的干旱状况持续未变 ,但期间仍有若干次相对凉湿与暖干旱时期的波动 ,且揭示出 3 .0 ka B.P.、2 .0 ka B.P.、1.5 ka B.P.、1.0 ka B.P.、0 .2 ka B.P.五个气候突变转干时间界线。本研究揭示了近四千年来本地区持续干旱化的特征 ,并有后期加剧的趋势 ,并指出历史时期南疆地区若干人文事件的发生如近两千年以来丝绸之路的兴衰、南疆古城镇的废弃等与气候环境演化之间存在着良好的准对应关系 ,表明气候环境的自然演化是影响人地关系类型与内容的重要因素之一。
