The Dialafara area is part of the highly endowed Kédougou-Kéniéba Inlier (KKI), West-Malian gold belt, which corresponds to a Paleoproterozoic window through the West African Craton (WAC). This study pr...The Dialafara area is part of the highly endowed Kédougou-Kéniéba Inlier (KKI), West-Malian gold belt, which corresponds to a Paleoproterozoic window through the West African Craton (WAC). This study presents, first of all, an integration of geophysical data interpretation with litho-structural field reconnaissance and then proposes a new litho-structural map of the Dialafara area. The Dialafara area shows a variety of lithology characterized by volcanic and volcano-sedimentary units, metasediments and plutonic intrusion. These lithologies were affected by a complex superposition of structures of unequal importance defining three deformation phases (D<sub>D1</sub> to D<sub>D3</sub>) under ductile to brittle regimes. These features permit to portray a new litho-structural map, which shows that the Dialafara area presents a more complex lithological and structural context than the one presented in regional map of the KKI. This leads to the evidence that this area could be a potential site for exploration as it is situated between two world-class gold districts.展开更多
The present study focuses on the analysis and description of lineaments interpreted as secondary structures to describe the nature of Senegalo Malian Discontinuity. These lineaments cross-cut the large north-south ori...The present study focuses on the analysis and description of lineaments interpreted as secondary structures to describe the nature of Senegalo Malian Discontinuity. These lineaments cross-cut the large north-south oriented transcurrent lithospheric structure known as the Senegalo Malian Discontinuity (SMD). Two lineaments were selected oriented NNE (N15˚ to N25˚), one at Dialafara and one at Sadiola. Four profiles on each lineament of these 2 zones, so that there were 2 on each side of the SMD. The ground data collected were processed using proper parameter and software. Some filters were applied to enhance the signal level. These ground data were later compared to the existing airborne magnetic data for consistency and accuracy using the upward continuation filter. The results show that the quality of ground data is good. In addition, the ground magnetic data show the presence of certain local anomalies that are not visible in the regional data. The analytical signal was also used to determine domain boundaries or possible contact zones. The contact zone can be highlighted on certain profiles such as L300 and L600. The study showed that the west and east sides of the SMD are not the same. Secondary structures become wide when approaching the SMD on both sides. They are also duplicated to the east of the SMD when we move progressively away. In the Dialafara area, the ground magnetic data intersect an interpreted fold. The results of this work confirm the presence of the secondary structures and their evolution in relation to the SMD. The relationships between the secondary structures in the Dailafara and Sadiola zones and their relations with the SMD are highlighted. The technique used in this study, is an important approach to better description and interpreting of regional structures using the secondary structures and proposing a structural model.展开更多
The Douta permit of African Star Resources/Thor Explorations, located in the southeast of Senegal, in the Kédougou-Kéniéba Inlier (western part of the West African Craton), is dominated to the East by m...The Douta permit of African Star Resources/Thor Explorations, located in the southeast of Senegal, in the Kédougou-Kéniéba Inlier (western part of the West African Craton), is dominated to the East by metasedimentary formations such as greywackes, shales, graphitic shales, quartzites, cherts, claystones and breccias characteristic of the Dialé-Daléma basin. To the West, the mafic formations of the Mako volcanic belt are the most common. Metasedimentary rocks are associated with metavolcanosedimentary terms found at the contact zones between the two (2) Birimian groups. These different geological formations are cut by mafic dolerite and gabbro sills and/or dykes, as well as quartz and microgranite veins. The Douta gold project is crossed from North to South by the MTZ (Main Transcurrent Zone), generally oriented NE-SW and becoming N-S towards the North. The permit is characterized by several shear corridors. The rocks are affected by brittle, brittle-ductile to ductile deformations. The gold mineralization is hosted by a NE-trending shear corridor called the Makosa corridor (Makosa shear zone), therefore sub-parallel to the MTZ. It has a subvertical dip (75˚ to 85˚ to the NW). It is associated with a hydrothermal phase characterized by quartz-sericite-epidote-fine, disseminated pyrite and arsenopyrite ± albite ± chlorite paragenesis. These minerals testify to the existence of a low degree of metamorphism (greenschist facies, epizonal domain) in the area. However, metamorphism reaches amphibolite facies in some places, particularly in the vicinity of intrusive bodies, with the presence of hornblende (amphiboles) and plagioclase. The gold mineralization is mainly hosted by two (2) metasedimentary lithological units: meta-greywackes and shales.展开更多
Landsat 8 Oli,ASTER,and Sentinel 2A satellite images processing was used to map geological formations,lineaments and hydrothermal alteration minerals in the Aouli inlier,as a case study to illustrate the application o...Landsat 8 Oli,ASTER,and Sentinel 2A satellite images processing was used to map geological formations,lineaments and hydrothermal alteration minerals in the Aouli inlier,as a case study to illustrate the application of digital images processing and Geographic Information System(GIS)in geological mapping and mining prospecting.Principal Component Analysis(PCA)applied to the Landsat images allowed good lithological discrimination and contributed to the updating of available geological maps.The Automatic lineament extraction from Sentinel images revealed the main tectonic structures affecting Aouli inlier.The ratio bands(b5+b7)/b6 and the false color composite(b4/b6,b2/b1,b3/b2)allowed the hydrothermal alteration minerals mapping from Aster images.Combined with available geological data and field observations,the satellite derived data were integrated and analyzed in a GIS software to establish mining prospecting guides.The results showed that the anomaly zones are intimately linked to NNE-SSW and NW-SE oriented faults and to highly fractured areas developing argillic and Fe rich alterations.Verified via field survey,this approach was successfully applied to the Aouli inlier to rapidly target potential areas to be explored in the tactical phase.This provides a model for future prospecting efforts for similar mineral deposits in other areas.展开更多
The calc-alkaline volcanic formations in the western part of the Kedougou-Kenieba inlier crop out in three complexes: the Foulde in the North and the areas of Mako and Baniomba in the South. These complexes which eith...The calc-alkaline volcanic formations in the western part of the Kedougou-Kenieba inlier crop out in three complexes: the Foulde in the North and the areas of Mako and Baniomba in the South. These complexes which either combine with the tholeiites or cut across the sedimentary formations are composed of thin veins and massive lava flows. They have many petrographic similarities and show chemical characteristics that resemble those of island-arc rocks. At the tectonic level, the D1 deformation phase preceding the formation of the basins and the transpressive tectonics including an oblique convergence may account for the structural evolution of the Mako volcanic belt. Its occurrence in different basins may be evidenced by the composition of some lithophilic components like the Sr, Ba, U, Rb and the composition of clinopyroxenes enriched in TiO2, FeO, Na2O in the Foulde calc-alkaline volcanic rocks that developed in a sedimentary environment.展开更多
Precambrian carbonate sequence of Riasi Inlier hosts epigenetic lead-zinc mineralization in the form of pockets, lenses and veins. The mineralization is having variable Pb:Zn ratio and shows lithological preferences. ...Precambrian carbonate sequence of Riasi Inlier hosts epigenetic lead-zinc mineralization in the form of pockets, lenses and veins. The mineralization is having variable Pb:Zn ratio and shows lithological preferences. The sphalerite rich pockets are concentrated within the dolostone of older Trikuta Formation while galena rich mineralization occurs in form of veins, lenses and pockets hosted within siliceous varieties of dolostone and quartzite belonging to younger Khairikot Formation. Sulphur isotope geochemistry is reported in the present paper for the sphalerire and galena from the area for first time. Overall?δ34S of sulphides varies from (+9.67‰ to +34.42‰). Sphalerite ores hosted within older Trikuta Formation and younger Khairikot Formation, however, show different?δ34S values. It ranged from +9.67‰ to +10.59‰ for the sphalarite hosted in Trikuta Formation and from +18.38‰ to +34.42‰ for sphalerite hosted within Khairikot Formation. Sulphur isotopic data and ore petrographic data suggest that there is two-generation of sphalerite present in the area.展开更多
The Anti-Atlas belt of southern Morocco is situated on the northern edge of the West African craton(WAC).It corresponds to a broad anticlinorium some 800 km long and 200 km wide,trending ENE-WSW,parallel to the
The late Neoproterozoïc Toubkal inlier (Ancient Massif of the High-Atlas, Morocco) contains two igneous basaltic series (Tircht and Sidi Chamharouch). Investigated rocks display characteristics of within-plate...The late Neoproterozoïc Toubkal inlier (Ancient Massif of the High-Atlas, Morocco) contains two igneous basaltic series (Tircht and Sidi Chamharouch). Investigated rocks display characteristics of within-plate continental tholeiitic and are similar to rocks originated in orogenic contexts. The geochemical results allow the assumption that subduction active processes are indirectly responsible for the genesis of theses rocks. The orogenic signature is linked probably to a Pan-African magmatic source previously metasomatized in the northern margin of the West African Craton.展开更多
长期以来,孤立点的检测一直聚焦于簇边缘的离散点,当聚类后簇的数目低于实际数目,或孤立点被伪装在簇内的情况下,簇内孤立点的判定则会更加困难.为判定簇内孤立点,提出一种基于密度聚类DBSCAN (Density based spatial clustering of app...长期以来,孤立点的检测一直聚焦于簇边缘的离散点,当聚类后簇的数目低于实际数目,或孤立点被伪装在簇内的情况下,簇内孤立点的判定则会更加困难.为判定簇内孤立点,提出一种基于密度聚类DBSCAN (Density based spatial clustering of application with noise)的簇内孤立点检测方法 ODIC-DBSCAN (Outlier detection of inner-cluster based on DBSCAN).首先在建立距离矩阵的基础上,通过半径获取策略得到针对该点集的k个有效半径Radius集合,并据此构造密度矩阵;然后建立点集覆盖模型,提出了相邻有效半径构造的覆盖多维体能够覆盖点集的思想,并通过拉格朗日乘子法求取最优的覆盖多维体数目之比,输出点比阈值组;最后重建ODIC-DBSCAN的孤立点检测方法,以簇发生融合现象作为算法终止的判定条件.实验通过模拟数据集,公开benchmark与UCI数据集共同验证了ODIC-DBSCAN算法,展示了聚类过程;分析了算法性能;并通过与其他聚类、孤立点判定方法的对比,验证了算法对簇内孤立点的判定效果.展开更多
The western part of the Kedougou Kenieba Inlier is located in the West African Craton. It consists of paleoproterozoic NE-trending elongate belts (subprovinces) of metavolcanic and granitic rocks that alternate with m...The western part of the Kedougou Kenieba Inlier is located in the West African Craton. It consists of paleoproterozoic NE-trending elongate belts (subprovinces) of metavolcanic and granitic rocks that alternate with metasedimentary belts. Major linear fault such as the MTZ which also approximate a north-easterly trend form the eastern boundaries. The field observations and geophysics analyses were completed by a microscopic study. Based on these data we define across this region four lithostructural domains from east to west. The western domain is structurally complex. The rocks of this domain have been subjected to a complex history of polyphase deformation and metamorphism. The structural analyse allow us to distinguished three deformation events. The deformation results in the formation of D1 thrust tectonic and D2 and D3 transcurrent tectonic. The structural evolution of the Mako Belt is characterized by deformation dominated by the intrusion of large TTG batholiths (D1) followed by basins formation and transpression accommodating oblique convergence and collision (D2 and D3). The change from thrusting (D1 deformation to transcurrent motion (D2 and D3) is recorded in the marginal basin of the central domain and in Tinkoto pull apart basin. The timing of these basins indicates a diachronous evolution. Deformation styles within the basin are compatible with a dextral transpression which terminated at ca 2090 Ma. Small extensional basins formed over the rocks of the Mako Belt are filled with continental detrital sedimentary rocks that show weak foliation and active felsic volcanism. We suggest that the sinistral transpressive tectonic associated with oblique subduction may have generated the pull-apart basin and subaqueous volcanism. In part these features are now related to terrain accretion, thrusting and strike slip movement during oblique convergence. The inversion of the large scale structural evolution from thrusting to strike slip is common to modern orogenies.展开更多
文摘The Dialafara area is part of the highly endowed Kédougou-Kéniéba Inlier (KKI), West-Malian gold belt, which corresponds to a Paleoproterozoic window through the West African Craton (WAC). This study presents, first of all, an integration of geophysical data interpretation with litho-structural field reconnaissance and then proposes a new litho-structural map of the Dialafara area. The Dialafara area shows a variety of lithology characterized by volcanic and volcano-sedimentary units, metasediments and plutonic intrusion. These lithologies were affected by a complex superposition of structures of unequal importance defining three deformation phases (D<sub>D1</sub> to D<sub>D3</sub>) under ductile to brittle regimes. These features permit to portray a new litho-structural map, which shows that the Dialafara area presents a more complex lithological and structural context than the one presented in regional map of the KKI. This leads to the evidence that this area could be a potential site for exploration as it is situated between two world-class gold districts.
文摘The present study focuses on the analysis and description of lineaments interpreted as secondary structures to describe the nature of Senegalo Malian Discontinuity. These lineaments cross-cut the large north-south oriented transcurrent lithospheric structure known as the Senegalo Malian Discontinuity (SMD). Two lineaments were selected oriented NNE (N15˚ to N25˚), one at Dialafara and one at Sadiola. Four profiles on each lineament of these 2 zones, so that there were 2 on each side of the SMD. The ground data collected were processed using proper parameter and software. Some filters were applied to enhance the signal level. These ground data were later compared to the existing airborne magnetic data for consistency and accuracy using the upward continuation filter. The results show that the quality of ground data is good. In addition, the ground magnetic data show the presence of certain local anomalies that are not visible in the regional data. The analytical signal was also used to determine domain boundaries or possible contact zones. The contact zone can be highlighted on certain profiles such as L300 and L600. The study showed that the west and east sides of the SMD are not the same. Secondary structures become wide when approaching the SMD on both sides. They are also duplicated to the east of the SMD when we move progressively away. In the Dialafara area, the ground magnetic data intersect an interpreted fold. The results of this work confirm the presence of the secondary structures and their evolution in relation to the SMD. The relationships between the secondary structures in the Dailafara and Sadiola zones and their relations with the SMD are highlighted. The technique used in this study, is an important approach to better description and interpreting of regional structures using the secondary structures and proposing a structural model.
文摘The Douta permit of African Star Resources/Thor Explorations, located in the southeast of Senegal, in the Kédougou-Kéniéba Inlier (western part of the West African Craton), is dominated to the East by metasedimentary formations such as greywackes, shales, graphitic shales, quartzites, cherts, claystones and breccias characteristic of the Dialé-Daléma basin. To the West, the mafic formations of the Mako volcanic belt are the most common. Metasedimentary rocks are associated with metavolcanosedimentary terms found at the contact zones between the two (2) Birimian groups. These different geological formations are cut by mafic dolerite and gabbro sills and/or dykes, as well as quartz and microgranite veins. The Douta gold project is crossed from North to South by the MTZ (Main Transcurrent Zone), generally oriented NE-SW and becoming N-S towards the North. The permit is characterized by several shear corridors. The rocks are affected by brittle, brittle-ductile to ductile deformations. The gold mineralization is hosted by a NE-trending shear corridor called the Makosa corridor (Makosa shear zone), therefore sub-parallel to the MTZ. It has a subvertical dip (75˚ to 85˚ to the NW). It is associated with a hydrothermal phase characterized by quartz-sericite-epidote-fine, disseminated pyrite and arsenopyrite ± albite ± chlorite paragenesis. These minerals testify to the existence of a low degree of metamorphism (greenschist facies, epizonal domain) in the area. However, metamorphism reaches amphibolite facies in some places, particularly in the vicinity of intrusive bodies, with the presence of hornblende (amphiboles) and plagioclase. The gold mineralization is mainly hosted by two (2) metasedimentary lithological units: meta-greywackes and shales.
文摘Landsat 8 Oli,ASTER,and Sentinel 2A satellite images processing was used to map geological formations,lineaments and hydrothermal alteration minerals in the Aouli inlier,as a case study to illustrate the application of digital images processing and Geographic Information System(GIS)in geological mapping and mining prospecting.Principal Component Analysis(PCA)applied to the Landsat images allowed good lithological discrimination and contributed to the updating of available geological maps.The Automatic lineament extraction from Sentinel images revealed the main tectonic structures affecting Aouli inlier.The ratio bands(b5+b7)/b6 and the false color composite(b4/b6,b2/b1,b3/b2)allowed the hydrothermal alteration minerals mapping from Aster images.Combined with available geological data and field observations,the satellite derived data were integrated and analyzed in a GIS software to establish mining prospecting guides.The results showed that the anomaly zones are intimately linked to NNE-SSW and NW-SE oriented faults and to highly fractured areas developing argillic and Fe rich alterations.Verified via field survey,this approach was successfully applied to the Aouli inlier to rapidly target potential areas to be explored in the tactical phase.This provides a model for future prospecting efforts for similar mineral deposits in other areas.
文摘The calc-alkaline volcanic formations in the western part of the Kedougou-Kenieba inlier crop out in three complexes: the Foulde in the North and the areas of Mako and Baniomba in the South. These complexes which either combine with the tholeiites or cut across the sedimentary formations are composed of thin veins and massive lava flows. They have many petrographic similarities and show chemical characteristics that resemble those of island-arc rocks. At the tectonic level, the D1 deformation phase preceding the formation of the basins and the transpressive tectonics including an oblique convergence may account for the structural evolution of the Mako volcanic belt. Its occurrence in different basins may be evidenced by the composition of some lithophilic components like the Sr, Ba, U, Rb and the composition of clinopyroxenes enriched in TiO2, FeO, Na2O in the Foulde calc-alkaline volcanic rocks that developed in a sedimentary environment.
文摘Precambrian carbonate sequence of Riasi Inlier hosts epigenetic lead-zinc mineralization in the form of pockets, lenses and veins. The mineralization is having variable Pb:Zn ratio and shows lithological preferences. The sphalerite rich pockets are concentrated within the dolostone of older Trikuta Formation while galena rich mineralization occurs in form of veins, lenses and pockets hosted within siliceous varieties of dolostone and quartzite belonging to younger Khairikot Formation. Sulphur isotope geochemistry is reported in the present paper for the sphalerire and galena from the area for first time. Overall?δ34S of sulphides varies from (+9.67‰ to +34.42‰). Sphalerite ores hosted within older Trikuta Formation and younger Khairikot Formation, however, show different?δ34S values. It ranged from +9.67‰ to +10.59‰ for the sphalarite hosted in Trikuta Formation and from +18.38‰ to +34.42‰ for sphalerite hosted within Khairikot Formation. Sulphur isotopic data and ore petrographic data suggest that there is two-generation of sphalerite present in the area.
文摘The Anti-Atlas belt of southern Morocco is situated on the northern edge of the West African craton(WAC).It corresponds to a broad anticlinorium some 800 km long and 200 km wide,trending ENE-WSW,parallel to the
文摘The late Neoproterozoïc Toubkal inlier (Ancient Massif of the High-Atlas, Morocco) contains two igneous basaltic series (Tircht and Sidi Chamharouch). Investigated rocks display characteristics of within-plate continental tholeiitic and are similar to rocks originated in orogenic contexts. The geochemical results allow the assumption that subduction active processes are indirectly responsible for the genesis of theses rocks. The orogenic signature is linked probably to a Pan-African magmatic source previously metasomatized in the northern margin of the West African Craton.
文摘长期以来,孤立点的检测一直聚焦于簇边缘的离散点,当聚类后簇的数目低于实际数目,或孤立点被伪装在簇内的情况下,簇内孤立点的判定则会更加困难.为判定簇内孤立点,提出一种基于密度聚类DBSCAN (Density based spatial clustering of application with noise)的簇内孤立点检测方法 ODIC-DBSCAN (Outlier detection of inner-cluster based on DBSCAN).首先在建立距离矩阵的基础上,通过半径获取策略得到针对该点集的k个有效半径Radius集合,并据此构造密度矩阵;然后建立点集覆盖模型,提出了相邻有效半径构造的覆盖多维体能够覆盖点集的思想,并通过拉格朗日乘子法求取最优的覆盖多维体数目之比,输出点比阈值组;最后重建ODIC-DBSCAN的孤立点检测方法,以簇发生融合现象作为算法终止的判定条件.实验通过模拟数据集,公开benchmark与UCI数据集共同验证了ODIC-DBSCAN算法,展示了聚类过程;分析了算法性能;并通过与其他聚类、孤立点判定方法的对比,验证了算法对簇内孤立点的判定效果.
文摘The western part of the Kedougou Kenieba Inlier is located in the West African Craton. It consists of paleoproterozoic NE-trending elongate belts (subprovinces) of metavolcanic and granitic rocks that alternate with metasedimentary belts. Major linear fault such as the MTZ which also approximate a north-easterly trend form the eastern boundaries. The field observations and geophysics analyses were completed by a microscopic study. Based on these data we define across this region four lithostructural domains from east to west. The western domain is structurally complex. The rocks of this domain have been subjected to a complex history of polyphase deformation and metamorphism. The structural analyse allow us to distinguished three deformation events. The deformation results in the formation of D1 thrust tectonic and D2 and D3 transcurrent tectonic. The structural evolution of the Mako Belt is characterized by deformation dominated by the intrusion of large TTG batholiths (D1) followed by basins formation and transpression accommodating oblique convergence and collision (D2 and D3). The change from thrusting (D1 deformation to transcurrent motion (D2 and D3) is recorded in the marginal basin of the central domain and in Tinkoto pull apart basin. The timing of these basins indicates a diachronous evolution. Deformation styles within the basin are compatible with a dextral transpression which terminated at ca 2090 Ma. Small extensional basins formed over the rocks of the Mako Belt are filled with continental detrital sedimentary rocks that show weak foliation and active felsic volcanism. We suggest that the sinistral transpressive tectonic associated with oblique subduction may have generated the pull-apart basin and subaqueous volcanism. In part these features are now related to terrain accretion, thrusting and strike slip movement during oblique convergence. The inversion of the large scale structural evolution from thrusting to strike slip is common to modern orogenies.
