XRF and EDX analyses were carried out on 18 batches of representative raw samples to determine the distribution of major chemical elements in the petroleum source rocks of Donga and Yogou formations of Termit sediment...XRF and EDX analyses were carried out on 18 batches of representative raw samples to determine the distribution of major chemical elements in the petroleum source rocks of Donga and Yogou formations of Termit sedimentary basin. The chemical composition of these formations is dominated by silicon (Si), aluminum (Al) and iron (Fe). This is consistent with the oxide composition, which is also dominated by silicon oxide (SiO2), aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) and iron monoxide (FeO). No less important chemical elements are calcium (Ca), potassium (K), sulfur (S), titanium (Ti), magnesium (Mg), manganese (Mn) and barium (Ba), as well as some of their oxides. All these major chemical elements are carried by silicate detrital minerals associated with pyrite and goethite and/or clay minerals such as kaolinite and interstratified illite, smectite and chlorite. This trend is illustrated by the values of the Si/Al and SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratios.展开更多
The Agadez city is built on the faulted and fractured sandstones formation of the“Agadez Sandstones”,which deposit in unconformity on the Precambrian basement of the Aïr Mountain.The present study focuses on th...The Agadez city is built on the faulted and fractured sandstones formation of the“Agadez Sandstones”,which deposit in unconformity on the Precambrian basement of the Aïr Mountain.The present study focuses on the geotechnical risk assessment and geological origin of building fracturation in Agadez city.A methodological approach integrating measurement of fractures planes affecting the buildings and their statistical analysis has been implemented.Statistical analysis of obtained data showed that in 100 fractured buildings,about 3%buildings are at risk of collapse(very high risk),64%buildings are fractured(medium risk of collapse),and 34%buildings are cracked(lower risk of collapse).These results showed as well that the nature of the material(rheology)influences the buildings fracturation.Indeed,the buildings made from cement are more easily fractured than buildings made from clay materials.Statistical analysis of fracture planes reveals that the geotechnical risk associated with buildings fracturation propagates in NW-SE,corresponding to the major directions of risk propagation,mainly dipping in northwest sectors(zones)of the Agadez city.The interpretation of geological and geophysical data combined to those obtained in the case of this study,reveals that the risk associated with buildings fracturation in Agadez city is caused by geological seismic events and or anthropogenic activities(explosive firing on the uranium mining sites like Somaïr and Cominak).展开更多
文摘XRF and EDX analyses were carried out on 18 batches of representative raw samples to determine the distribution of major chemical elements in the petroleum source rocks of Donga and Yogou formations of Termit sedimentary basin. The chemical composition of these formations is dominated by silicon (Si), aluminum (Al) and iron (Fe). This is consistent with the oxide composition, which is also dominated by silicon oxide (SiO2), aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) and iron monoxide (FeO). No less important chemical elements are calcium (Ca), potassium (K), sulfur (S), titanium (Ti), magnesium (Mg), manganese (Mn) and barium (Ba), as well as some of their oxides. All these major chemical elements are carried by silicate detrital minerals associated with pyrite and goethite and/or clay minerals such as kaolinite and interstratified illite, smectite and chlorite. This trend is illustrated by the values of the Si/Al and SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratios.
文摘The Agadez city is built on the faulted and fractured sandstones formation of the“Agadez Sandstones”,which deposit in unconformity on the Precambrian basement of the Aïr Mountain.The present study focuses on the geotechnical risk assessment and geological origin of building fracturation in Agadez city.A methodological approach integrating measurement of fractures planes affecting the buildings and their statistical analysis has been implemented.Statistical analysis of obtained data showed that in 100 fractured buildings,about 3%buildings are at risk of collapse(very high risk),64%buildings are fractured(medium risk of collapse),and 34%buildings are cracked(lower risk of collapse).These results showed as well that the nature of the material(rheology)influences the buildings fracturation.Indeed,the buildings made from cement are more easily fractured than buildings made from clay materials.Statistical analysis of fracture planes reveals that the geotechnical risk associated with buildings fracturation propagates in NW-SE,corresponding to the major directions of risk propagation,mainly dipping in northwest sectors(zones)of the Agadez city.The interpretation of geological and geophysical data combined to those obtained in the case of this study,reveals that the risk associated with buildings fracturation in Agadez city is caused by geological seismic events and or anthropogenic activities(explosive firing on the uranium mining sites like Somaïr and Cominak).
