This study aims to uses paleomagnetic and anisotropy of magnetic susceptibility(AMS)methods to recognize the initial deposit position and to track the paleoflow at the origin of an iron skarn-related deposit.The Yaman...This study aims to uses paleomagnetic and anisotropy of magnetic susceptibility(AMS)methods to recognize the initial deposit position and to track the paleoflow at the origin of an iron skarn-related deposit.The Yamansu deposit is located in eastern Tianshan(Charvet,2007).This province has a substantial mining potential for Fe–(Cu)skarn,Cu–Ni and V–Ti orthomagmatic deposits,and orogenic Au lodes(Branquet et al.,2012;Zhang et a.,2005;Mao et al.,2005).Recent publication dates the Yamansu deposit at 323 Ma,and uses this deposit to define a model of Submarine Volcanogenic Iron Oxide(SVIO)deposits(Hou et al.,展开更多
The objective of this project is the valorization of Mako andesitic volcanic tuffs for use in social housing in the Kedougou region. To achieve these objectives, a geotechnical characterization of the tuff samples was...The objective of this project is the valorization of Mako andesitic volcanic tuffs for use in social housing in the Kedougou region. To achieve these objectives, a geotechnical characterization of the tuff samples was carried out and the geopolymerization stabilization was adopted for the manufacture of bricks. These bricks stabilized by an alkaline activation offer compressive strengths that exceed the threshold value (2.9 MPa) set by the standard (NF P14-304). The best compressive strengths (12.14 MPa) and flexural tensile strengths (5.43 MPa) are obtained in the series of bricks made with 35% of the mass of a solution of caustic soda at 12 molars concentration with a curing temperature cooking of 185°C and an average absorbance of 13.21%.展开更多
This study is carried out to appreciate the coarse elements influence of the gravel lateritic soils on the pavement behavior. The material involves not only the 0/20 mm granular particles considered in the specificati...This study is carried out to appreciate the coarse elements influence of the gravel lateritic soils on the pavement behavior. The material involves not only the 0/20 mm granular particles considered in the specifications and on the laboratory tests, but also all of the material that is actually used in the construction sites. Geotechnical characterization was leaned on five differentiated granular classes of 0/20;0/25;0/31.5;0/40 and 0/63 mm diameters. The sample of 0/40 mm gets the best compaction aptitude, while that of 0/31.5 mm reaches the greatest bearing strength and a good Optimum Moisture Content. According to the requirements and its bearing strengths, the material is usable up to subbase layer and its behavior depends on the grain size.展开更多
The “mainstream” climatology (MSC)—i.e. which includes the Intergovernmental Panel on Climate Change (IPCC) community—considers the present day massive release of greenhouse gases into the atmosphere as the main c...The “mainstream” climatology (MSC)—i.e. which includes the Intergovernmental Panel on Climate Change (IPCC) community—considers the present day massive release of greenhouse gases into the atmosphere as the main cause of the current global warming trend. The main inference from this stance is that the increase in temperature must occur after the release of greenhouse gases originating from the anthropic activities. However, no scientific evidence has been provided for this basic notion. Earth paleoclimatic records document the antecedence of temperature over CO<sub>2</sub> levels. For the past 65 Ma, the temperature parameter has controlled the subsequent increase in CO<sub>2</sub>. This includes the three rapid aberrant shifts and extreme climate transients at 55 Ma, 34 Ma, and 23 Ma REF _Ref159913672 \r \h \* MERGEFORMAT [1]. The simple fact of their existence points to the potential for highly nonlinear responses in climate forcing. Whatever these shifts and transients are, CO<sub>2</sub> remains a second order parameter in their evolution through time. Confronted with the past, a suitable response must therefore be given to the unresolved question of whether the CO<sub>2</sub> trends precede the temperature trends in the current period, or not. The assertion that the current global warming is anthropogenic in origin implicitly presupposes a change of paradigm, with the consequence (the increase in CO<sub>2</sub> levels) that occurred in Earth’s past being positioned as the cause of the warming for its present day climatic evolution. The compulsory assumption regarding the antecedence of CO<sub>2</sub> levels over the temperature trends is associated with the haziness of the methodological framework—i.e. the paradigm—and tightens the research fields on the likely origins of global warming. The possible involvement of an “aberrant” natural event, hidden behind the massive release of greenhouse gases, has not been considered by the MSC.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
This study aims to determine the optimal quantity of fillers to add to hydraulic concrete and to assess the influence of these fillers on its rheological characteristics and mechanical properties. The characterization...This study aims to determine the optimal quantity of fillers to add to hydraulic concrete and to assess the influence of these fillers on its rheological characteristics and mechanical properties. The characterization of the aggregates shows that they meet the specifications for the formulation of hydraulic concrete according to the Dreux-Gorisse method. Normalizing the formula to the cubic meter enables to define the standard concrete. The cement content is 350 kg/m<sup>3</sup>. The mineral materials added to the concrete to increase its characteristics and properties are limestone, basalt, and sandstone fillers with a weight percent of 4%, 5%, and 3% respectively. Changes in concrete properties with the addition of fillers were determined through geotechnical tests. The results obtained show a decrease in the workability measured by slump test which returned 7.8 cm for the standard concrete sample, 7.2 cm with 5% of basalt, 7.3 cm with 4% of limestone, and 6.1 cm with 3% of sandstone. Regarding the bleeding, the results show that it decreases leading to a substantial improvement in stabilization reaching 26% with 5% of basalt fillers, 29% with 4% of limestone fillers, and 31% with 3% of sandstone fillers. The compressive strengths noted R<sub>c28</sub> at 28 days increases compared to that of the standard concrete, which is 31.5 MPa. They increase to 34.3 MPa with 5% of basalt fillers being 8.9%, 36.2 MPa with 4% of limestone fillers being 14.9%, and 36.8 MPa with 3% of sandstone fillers being 16.8%. Finally, the addition of fillers increases the degree of compaction values to 83.62% with 5% of basalt fillers, 84.2% with 4% of limestone fillers, and 84.34% with 3% of sandstone fillers.展开更多
Machine learning is becoming increasingly important in scientific and technological progress,due to its ability to create models that describe complex data and generalize well.The wealth of publicly-available seismic ...Machine learning is becoming increasingly important in scientific and technological progress,due to its ability to create models that describe complex data and generalize well.The wealth of publicly-available seismic data nowadays requires automated,fast,and reliable tools to carry out a multitude of tasks,such as the detection of small,local earthquakes in areas characterized by sparsity of receivers.A similar application of machine learning,however,should be built on a large amount of labeled seismograms,which is neither immediate to obtain nor to compile.In this study we present a large dataset of seismograms recorded along the vertical,north,and east components of 1487 broad-band or very broad-band receivers distributed worldwide;this includes 629,0953-component seismograms generated by 304,878 local earthquakes and labeled as EQ,and 615,847 ones labeled as noise(AN).Application of machine learning to this dataset shows that a simple Convolutional Neural Network of 67,939 parameters allows discriminating between earthquakes and noise single-station recordings,even if applied in regions not represented in the training set.Achieving an accuracy of 96.7,95.3,and 93.2% on training,validation,and test set,respectively,we prove that the large variety of geological and tectonic settings covered by our data supports the generalization capabilities of the algorithm,and makes it applicable to real-time detection of local events.We make the database publicly available,intending to provide the seismological and broader scientific community with a benchmark for time-series to be used as a testing ground in signal processing.展开更多
Pozzolans from the Tombel Plain,Bamileke Plateau,and Noun Plain,3 monogenetic volcanic fields in the central part of the Cameroon Volcanic Line(the Tombel Plain,Bamileke Plateau,and Noun Plain),were explored in order ...Pozzolans from the Tombel Plain,Bamileke Plateau,and Noun Plain,3 monogenetic volcanic fields in the central part of the Cameroon Volcanic Line(the Tombel Plain,Bamileke Plateau,and Noun Plain),were explored in order to constrain their petrology and make some predictions on their pozzolanicity.The rocks in this study include alkaline and subalkaline basalts,trachybasalts,and basanites.Most of these rocks present an overall composition that overlaps with primitive mantle,suggesting rapid ascent of magmas,limited crustal contamination and crystal fractionation of olivine,clinopyroxene,and feldspar.The pozzolans present enrichment of LREE relative to HREE and high chondrite normalized ratios of La/Yb and Tb/Yb.ranging between 7 and 20 and>1.9 respectively,similar to those of Ocean Island Basalts.Like other nearby volcanoes,partial melting in a dominantly garnet-bearing mantle zone can be assumed.Quantitative mineralogy by X-ray diffraction revealed various mineral phases with dominantly plagioclase,augite,olivine,and Fe-Ti oxides.The samples contains important amorphous phase up to 23,51,and 69 wt%in the Tombel Plain,Noun Plain,and Bamileke Plateau,respectively.This elevated amount of amorphous phases together with the sum of SiO2,Al2O3 and total Fe2O3(SAI=68.50-83.50>70 wt%)according to ASTM C618 standard and the sum of CaO,FeO,and MgO(CIM=14.5-30.52 wt%and 23.58-31.08 wt%)suggest interesting pozzolanicity character for the studied pozzolans.展开更多
Remote sensing analysis is an efficient tool for updating geological maps. The regional scale map obtained in this project from compilation of the pre-existing maps and of a number of space images is somewhat more com...Remote sensing analysis is an efficient tool for updating geological maps. The regional scale map obtained in this project from compilation of the pre-existing maps and of a number of space images is somewhat more complete. It takes into account the usual field and laboratory parameters of the rock units, through the previous geologic maps, together with remote sensing parameters such as spectral signatures, textures, roughness, morphology that are observed from optical, microwave and DEM imagery. With more rock characteristics, the old maps are obligatory improved. The Cenozoic faulting in the Al Hamra al Hamadah plateau is largely influenced by the tectonics affecting the Paleozoic oil bearing structures that are hidden by the late Cretaceous-Paleocene layers. The tectonic style is that of reactivation of the Paleozoic faults under effects of the NNE-trending regional tension. Then the faults on the surface of the plateau would indicate location of the hidden Paleozoic faults in depth. A flat plateau, in the arid environment, appears to be a very favorable environment for mapping of gentle folds, faults and tectonic sinkholes. Remote sensing is a fruitful approach in this case study. The gentle anticlines for instance are undetectable in the field, but computer assisted shadowing with a low elevation angle of illumination is the key processing for evidencing these features. Problems of drillings in the area are well known for example to Waha, AGOCO and PB Companies during their exploration activities in the concessions in Ghadames Basin. According to them several incidents of losing drilling Pits have occurred and drilling came into a hole. Because this paper is aimed to know the exact location of sinkholes in the Ghadames basin, I would recommend all the oil companies to review this work and try to trace the sinkholes indicated to minimize the risk of drilling problems.展开更多
Gravimetric and geologic data show that the reactivation of the Neogene Interandean depression and/or the ~75 - 65 Ma ophiolite suture into the modern dynamic of the Andes controlled the Gulf of Guayaquil Tumbes basin...Gravimetric and geologic data show that the reactivation of the Neogene Interandean depression and/or the ~75 - 65 Ma ophiolite suture into the modern dynamic of the Andes controlled the Gulf of Guayaquil Tumbes basin (GGTB) location and evolution during the past 1.8 - 1.6 Myr at least. Depending on whether the remobilization occurred along the interandean depression or the ophiolite suture, the GGTB evolved trough pure or simple shear mechanisms, respectively. Because the GGTB exhibits an along strike tectonic asymmetry associated with a pervasive seismic gap, the simple shear solution is more likely. Tectonic inversion occurred along a mid-crust detachment (the Mid-Crust detachment hereafter) matching the ophiolite suture that accommodates the North Andean Block (NAB) northward drift. The so-called Decoupling Strip located at the shelf slope break accommodated the tensional stress rotation from N-S along the shelf area i.e. NAB-drift induced to E-W along the continental margin i.e. subduction-erosion-induced. The landward dipping Woollard detachment system located at the Upper-Lower slope boundary connects the subduction channel at depth, allowing the Upper slope to evolve independently from the Lower slope wedge. The long-term recurrence interval between earthquakes, the strong interplate coupling, and the aseismic creeping deformation acting along the main low-angle detachments i.e. the Woollard and the Mid-Crust detachments may account for the pervasive seismic gap at the GGTB area. Because the subduction channel exhibits no record of significant seismic activity, no evidence exists to establish a link between the GGTB sustained subsidence and a basin-centered asperity. Because the GGTB is a promising site of hydrocarbon resources, to understand processes at the origin of this escape-induced forearc basin has a major economic interest.展开更多
The Sabodala gold mine tailings were stabilised using geopolymerization technics in order to improve their mechanical properties in general for a reuse as building materials for local communities. The effect of severa...The Sabodala gold mine tailings were stabilised using geopolymerization technics in order to improve their mechanical properties in general for a reuse as building materials for local communities. The effect of several preparation parameters on the compressive and tensile strength of the stabilised tailings has been studied to define their optimums. For each formulation, all parameters are kept constant and only one is variable. The prepared samples are then tested for compressive and tensile strength to see how the variable parameter impact on these properties. The same work was carried out for the fresh tailings and for the weathered one to see whether they behave differently and if they need different treatment. The results show that for most of parameters, there is an optimal value on either side of which compressive and tensile strength decrease. Except for few parameters, the fresh and the weathered tailings have a similar behaviour with regards to trends of their mechanical properties with changing preparation conditions. In addition to the similarity of weathered and fresh tailings mechanical characteristics following their stabilization by geopolymerization, this work has proved the considerable effects of the preparation’s parameters.展开更多
During this research work we developed another approach to digital mapping using the pixelation technic. This unprecedented digital mapping of the basin MSGBC in Senegal required the compilation of numerous geological...During this research work we developed another approach to digital mapping using the pixelation technic. This unprecedented digital mapping of the basin MSGBC in Senegal required the compilation of numerous geological data consisting of seismic lines and oil and hydraulic log reports. These spatial reference data include geological information from the surface to the top of the Campanian. The mapped terrains are composed of the Post-Paleocene Complex (PPC), the Paleocene, the Maastrichtian, and the Campanian. The nearest neighbor method has been used to establish the spatial distribution of the different geological formations. Histograms of values were used to determine the confidence intervals of the mapping. They were used to locate areas of low relative error and to apply the 3D digital mapping technique. For instance, Diender Guedj has been mapped at 1:25,000. The result of this mapping is extracted and processed using the DBMS (MySQL) software. The latter allowed both to determine Paleocene gab and update data. And then the database is processed. The programming languages PHP and Javascript have been used to simulate a website.展开更多
Urban areas house vegetation cover in several forms, fulfilling several ecological functions like thermal regulator, biodiversity, air quality, etc. However, their extent is often not very well known, especially in Af...Urban areas house vegetation cover in several forms, fulfilling several ecological functions like thermal regulator, biodiversity, air quality, etc. However, their extent is often not very well known, especially in African cities, making it sometimes difficult to assess their real impact on the urban ecosystem functioning. This work aims to analyse the capacity of satellite sensors for mapping vegetation and wetlands in urban areas. The data produced by the MSI sensors of Sentinel 2 and OLI of Landsat-8 are used to identify and map the vegetation cover in the Dakar region through a supervised classification with the Support Vector Machine (SVM) algorithm. The results show that it is sometimes not very easy to analyse urban vegetation with high spatial resolution images (HRS) resulting from the configuration of the vegetation in an urban environment, sometimes characterized by isolated trees or small green spaces. This explains why Sentinel-2 data which spatial resolution of 10 meters gives a better result compared to Landsat-8 data which is 30 meters. However, a good rendering is noted for the vegetation around the wetlands area for the two sensors resulting from the high density and the size of the vegetated perimeters in this part of the capital. Overall, there is an underestimation of urban vegetation cover, particularly for Landsat-8. The use of very high spatial resolution images could be necessary to better assess the potential of satellite data for monitoring urban vegetation in Sahelian context.展开更多
An old erg covers the northern part of the Lake Chad basin. This dune landform allowed the formation of many interdune ponds of various sizes. Still present in certain zones where the groundwater level is high (e.g. K...An old erg covers the northern part of the Lake Chad basin. This dune landform allowed the formation of many interdune ponds of various sizes. Still present in certain zones where the groundwater level is high (e.g. Kanem, southern Manga), these ponds formed in the past a vast network of lacustrine microsystems, as shown by the nature and the distribution of their deposits. In the Manga, these interdune deposits represent the main sedimentary records of the Holocene environmental succession. Their paleobiological (pollens, diatoms, ostracods) and geochemical (δ18O, δ13C, Sr/Ca) contents are often the basis for paleoenvironmental reconstruction. On the other hand, their sedimentological characters are rarely exploited. This study of palustro-lacustrine deposits of the Holocene N’Guigmi lake (northern bank of the Lake Chad;Niger) is based on the relationships between the sedimentological features and the climato-hydrological fluctuations. The mineralogical parameters (e.g. calcium carbonate content, clay mineralogy) and the nature of autochthonous mineralization (i.e. amorphous silica, clays, calcium carbonates) can be interpreted using a straightforward hydro-sedimentary model. Established to explain the geochemical dynamics of Lake Chad, this model is based on a biogeochemical cycle of the main elements (i.e. silicium, calcium) directly controlled by the local hydrological balance (i.e. rainfall/evaporation ratio). All these results show that a detailed study of sedimentological features can provide important paleohydrological informations about the regional aridification since ca 6500 14C BP.展开更多
The analytical technique PIXE experiment for measuring light and heavy elements concentration inside different samples of soil and residual water collected in the region of Safi-El Jadida, where an industrial complex ...The analytical technique PIXE experiment for measuring light and heavy elements concentration inside different samples of soil and residual water collected in the region of Safi-El Jadida, where an industrial complex resided, was performed. The same method was used to investigate the presence of elements ranging from silicon to lead in different soils samples and seaweed collected upstream from the site of Safi-El Jadida industrial zone, inside lands and downstream of it, in the entrance of the Casablanca region. This study allows us to highlight the influence of activities of this industrial zone on the neighbouring areas the site.展开更多
Numerous scientific fields are facing a replication crisis,where the results of a study often cannot be replicated when a new study uses independent data.This issue has been particularly emphasized in psychology,healt...Numerous scientific fields are facing a replication crisis,where the results of a study often cannot be replicated when a new study uses independent data.This issue has been particularly emphasized in psychology,health,and medicine,as incorrect results in these fields could have serious consequences,where lives might be at stake.While other fields have also highlighted significant replication problems,the Earth Sciences seem to be an exception.The paucity of Earth Science research aimed at understanding the replication crisis prompted this study.Specifically,this work aims to fill that gap by seeking to replicate geological results involving various types of time-series.We identify and discuss 11 key variables for replicating U-Pb age distributions:independent data,global sampling,proxy data,data quality,disproportionate non-random sampling,stratigraphic bias,potential filtering bias,accuracy and precision,correlating time-series segments,testing assumptions and divergent analytical methods,and analytical transparency.Even while this work primarily focuses on U-Pb age distributions,most of these factors(or variations of them)also apply to other geoscience disciplines.Thus,some of the discussions involve time-series consisting ofεHf,δ18O-zircon,14C,10Be,marineδ13C,and marineδ18O.We then provide specific recommendations for minimizing adverse effects related to these factors,and in the process enhancing prospects for replicating geological results.展开更多
文摘This study aims to uses paleomagnetic and anisotropy of magnetic susceptibility(AMS)methods to recognize the initial deposit position and to track the paleoflow at the origin of an iron skarn-related deposit.The Yamansu deposit is located in eastern Tianshan(Charvet,2007).This province has a substantial mining potential for Fe–(Cu)skarn,Cu–Ni and V–Ti orthomagmatic deposits,and orogenic Au lodes(Branquet et al.,2012;Zhang et a.,2005;Mao et al.,2005).Recent publication dates the Yamansu deposit at 323 Ma,and uses this deposit to define a model of Submarine Volcanogenic Iron Oxide(SVIO)deposits(Hou et al.,
文摘The objective of this project is the valorization of Mako andesitic volcanic tuffs for use in social housing in the Kedougou region. To achieve these objectives, a geotechnical characterization of the tuff samples was carried out and the geopolymerization stabilization was adopted for the manufacture of bricks. These bricks stabilized by an alkaline activation offer compressive strengths that exceed the threshold value (2.9 MPa) set by the standard (NF P14-304). The best compressive strengths (12.14 MPa) and flexural tensile strengths (5.43 MPa) are obtained in the series of bricks made with 35% of the mass of a solution of caustic soda at 12 molars concentration with a curing temperature cooking of 185°C and an average absorbance of 13.21%.
文摘This study is carried out to appreciate the coarse elements influence of the gravel lateritic soils on the pavement behavior. The material involves not only the 0/20 mm granular particles considered in the specifications and on the laboratory tests, but also all of the material that is actually used in the construction sites. Geotechnical characterization was leaned on five differentiated granular classes of 0/20;0/25;0/31.5;0/40 and 0/63 mm diameters. The sample of 0/40 mm gets the best compaction aptitude, while that of 0/31.5 mm reaches the greatest bearing strength and a good Optimum Moisture Content. According to the requirements and its bearing strengths, the material is usable up to subbase layer and its behavior depends on the grain size.
文摘The “mainstream” climatology (MSC)—i.e. which includes the Intergovernmental Panel on Climate Change (IPCC) community—considers the present day massive release of greenhouse gases into the atmosphere as the main cause of the current global warming trend. The main inference from this stance is that the increase in temperature must occur after the release of greenhouse gases originating from the anthropic activities. However, no scientific evidence has been provided for this basic notion. Earth paleoclimatic records document the antecedence of temperature over CO<sub>2</sub> levels. For the past 65 Ma, the temperature parameter has controlled the subsequent increase in CO<sub>2</sub>. This includes the three rapid aberrant shifts and extreme climate transients at 55 Ma, 34 Ma, and 23 Ma REF _Ref159913672 \r \h \* MERGEFORMAT [1]. The simple fact of their existence points to the potential for highly nonlinear responses in climate forcing. Whatever these shifts and transients are, CO<sub>2</sub> remains a second order parameter in their evolution through time. Confronted with the past, a suitable response must therefore be given to the unresolved question of whether the CO<sub>2</sub> trends precede the temperature trends in the current period, or not. The assertion that the current global warming is anthropogenic in origin implicitly presupposes a change of paradigm, with the consequence (the increase in CO<sub>2</sub> levels) that occurred in Earth’s past being positioned as the cause of the warming for its present day climatic evolution. The compulsory assumption regarding the antecedence of CO<sub>2</sub> levels over the temperature trends is associated with the haziness of the methodological framework—i.e. the paradigm—and tightens the research fields on the likely origins of global warming. The possible involvement of an “aberrant” natural event, hidden behind the massive release of greenhouse gases, has not been considered by the MSC.
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This study aims to determine the optimal quantity of fillers to add to hydraulic concrete and to assess the influence of these fillers on its rheological characteristics and mechanical properties. The characterization of the aggregates shows that they meet the specifications for the formulation of hydraulic concrete according to the Dreux-Gorisse method. Normalizing the formula to the cubic meter enables to define the standard concrete. The cement content is 350 kg/m<sup>3</sup>. The mineral materials added to the concrete to increase its characteristics and properties are limestone, basalt, and sandstone fillers with a weight percent of 4%, 5%, and 3% respectively. Changes in concrete properties with the addition of fillers were determined through geotechnical tests. The results obtained show a decrease in the workability measured by slump test which returned 7.8 cm for the standard concrete sample, 7.2 cm with 5% of basalt, 7.3 cm with 4% of limestone, and 6.1 cm with 3% of sandstone. Regarding the bleeding, the results show that it decreases leading to a substantial improvement in stabilization reaching 26% with 5% of basalt fillers, 29% with 4% of limestone fillers, and 31% with 3% of sandstone fillers. The compressive strengths noted R<sub>c28</sub> at 28 days increases compared to that of the standard concrete, which is 31.5 MPa. They increase to 34.3 MPa with 5% of basalt fillers being 8.9%, 36.2 MPa with 4% of limestone fillers being 14.9%, and 36.8 MPa with 3% of sandstone fillers being 16.8%. Finally, the addition of fillers increases the degree of compaction values to 83.62% with 5% of basalt fillers, 84.2% with 4% of limestone fillers, and 84.34% with 3% of sandstone fillers.
文摘Machine learning is becoming increasingly important in scientific and technological progress,due to its ability to create models that describe complex data and generalize well.The wealth of publicly-available seismic data nowadays requires automated,fast,and reliable tools to carry out a multitude of tasks,such as the detection of small,local earthquakes in areas characterized by sparsity of receivers.A similar application of machine learning,however,should be built on a large amount of labeled seismograms,which is neither immediate to obtain nor to compile.In this study we present a large dataset of seismograms recorded along the vertical,north,and east components of 1487 broad-band or very broad-band receivers distributed worldwide;this includes 629,0953-component seismograms generated by 304,878 local earthquakes and labeled as EQ,and 615,847 ones labeled as noise(AN).Application of machine learning to this dataset shows that a simple Convolutional Neural Network of 67,939 parameters allows discriminating between earthquakes and noise single-station recordings,even if applied in regions not represented in the training set.Achieving an accuracy of 96.7,95.3,and 93.2% on training,validation,and test set,respectively,we prove that the large variety of geological and tectonic settings covered by our data supports the generalization capabilities of the algorithm,and makes it applicable to real-time detection of local events.We make the database publicly available,intending to provide the seismological and broader scientific community with a benchmark for time-series to be used as a testing ground in signal processing.
基金Authors are thankful to the ISTerre of Grenoble(France)and Nathaniel Findling for hosting and training the first author on the XRD technique and Rietveld method interpretation as part of his Ph.D.research work.The authors are also thankful to the Ministry of Higher Education of Cameroon for providing Research Modernization Allowance(RMA)that has been very helpful to support part of the field trip and Geochemical analysis expenses.
文摘Pozzolans from the Tombel Plain,Bamileke Plateau,and Noun Plain,3 monogenetic volcanic fields in the central part of the Cameroon Volcanic Line(the Tombel Plain,Bamileke Plateau,and Noun Plain),were explored in order to constrain their petrology and make some predictions on their pozzolanicity.The rocks in this study include alkaline and subalkaline basalts,trachybasalts,and basanites.Most of these rocks present an overall composition that overlaps with primitive mantle,suggesting rapid ascent of magmas,limited crustal contamination and crystal fractionation of olivine,clinopyroxene,and feldspar.The pozzolans present enrichment of LREE relative to HREE and high chondrite normalized ratios of La/Yb and Tb/Yb.ranging between 7 and 20 and>1.9 respectively,similar to those of Ocean Island Basalts.Like other nearby volcanoes,partial melting in a dominantly garnet-bearing mantle zone can be assumed.Quantitative mineralogy by X-ray diffraction revealed various mineral phases with dominantly plagioclase,augite,olivine,and Fe-Ti oxides.The samples contains important amorphous phase up to 23,51,and 69 wt%in the Tombel Plain,Noun Plain,and Bamileke Plateau,respectively.This elevated amount of amorphous phases together with the sum of SiO2,Al2O3 and total Fe2O3(SAI=68.50-83.50>70 wt%)according to ASTM C618 standard and the sum of CaO,FeO,and MgO(CIM=14.5-30.52 wt%and 23.58-31.08 wt%)suggest interesting pozzolanicity character for the studied pozzolans.
文摘Remote sensing analysis is an efficient tool for updating geological maps. The regional scale map obtained in this project from compilation of the pre-existing maps and of a number of space images is somewhat more complete. It takes into account the usual field and laboratory parameters of the rock units, through the previous geologic maps, together with remote sensing parameters such as spectral signatures, textures, roughness, morphology that are observed from optical, microwave and DEM imagery. With more rock characteristics, the old maps are obligatory improved. The Cenozoic faulting in the Al Hamra al Hamadah plateau is largely influenced by the tectonics affecting the Paleozoic oil bearing structures that are hidden by the late Cretaceous-Paleocene layers. The tectonic style is that of reactivation of the Paleozoic faults under effects of the NNE-trending regional tension. Then the faults on the surface of the plateau would indicate location of the hidden Paleozoic faults in depth. A flat plateau, in the arid environment, appears to be a very favorable environment for mapping of gentle folds, faults and tectonic sinkholes. Remote sensing is a fruitful approach in this case study. The gentle anticlines for instance are undetectable in the field, but computer assisted shadowing with a low elevation angle of illumination is the key processing for evidencing these features. Problems of drillings in the area are well known for example to Waha, AGOCO and PB Companies during their exploration activities in the concessions in Ghadames Basin. According to them several incidents of losing drilling Pits have occurred and drilling came into a hole. Because this paper is aimed to know the exact location of sinkholes in the Ghadames basin, I would recommend all the oil companies to review this work and try to trace the sinkholes indicated to minimize the risk of drilling problems.
文摘Gravimetric and geologic data show that the reactivation of the Neogene Interandean depression and/or the ~75 - 65 Ma ophiolite suture into the modern dynamic of the Andes controlled the Gulf of Guayaquil Tumbes basin (GGTB) location and evolution during the past 1.8 - 1.6 Myr at least. Depending on whether the remobilization occurred along the interandean depression or the ophiolite suture, the GGTB evolved trough pure or simple shear mechanisms, respectively. Because the GGTB exhibits an along strike tectonic asymmetry associated with a pervasive seismic gap, the simple shear solution is more likely. Tectonic inversion occurred along a mid-crust detachment (the Mid-Crust detachment hereafter) matching the ophiolite suture that accommodates the North Andean Block (NAB) northward drift. The so-called Decoupling Strip located at the shelf slope break accommodated the tensional stress rotation from N-S along the shelf area i.e. NAB-drift induced to E-W along the continental margin i.e. subduction-erosion-induced. The landward dipping Woollard detachment system located at the Upper-Lower slope boundary connects the subduction channel at depth, allowing the Upper slope to evolve independently from the Lower slope wedge. The long-term recurrence interval between earthquakes, the strong interplate coupling, and the aseismic creeping deformation acting along the main low-angle detachments i.e. the Woollard and the Mid-Crust detachments may account for the pervasive seismic gap at the GGTB area. Because the subduction channel exhibits no record of significant seismic activity, no evidence exists to establish a link between the GGTB sustained subsidence and a basin-centered asperity. Because the GGTB is a promising site of hydrocarbon resources, to understand processes at the origin of this escape-induced forearc basin has a major economic interest.
文摘The Sabodala gold mine tailings were stabilised using geopolymerization technics in order to improve their mechanical properties in general for a reuse as building materials for local communities. The effect of several preparation parameters on the compressive and tensile strength of the stabilised tailings has been studied to define their optimums. For each formulation, all parameters are kept constant and only one is variable. The prepared samples are then tested for compressive and tensile strength to see how the variable parameter impact on these properties. The same work was carried out for the fresh tailings and for the weathered one to see whether they behave differently and if they need different treatment. The results show that for most of parameters, there is an optimal value on either side of which compressive and tensile strength decrease. Except for few parameters, the fresh and the weathered tailings have a similar behaviour with regards to trends of their mechanical properties with changing preparation conditions. In addition to the similarity of weathered and fresh tailings mechanical characteristics following their stabilization by geopolymerization, this work has proved the considerable effects of the preparation’s parameters.
文摘During this research work we developed another approach to digital mapping using the pixelation technic. This unprecedented digital mapping of the basin MSGBC in Senegal required the compilation of numerous geological data consisting of seismic lines and oil and hydraulic log reports. These spatial reference data include geological information from the surface to the top of the Campanian. The mapped terrains are composed of the Post-Paleocene Complex (PPC), the Paleocene, the Maastrichtian, and the Campanian. The nearest neighbor method has been used to establish the spatial distribution of the different geological formations. Histograms of values were used to determine the confidence intervals of the mapping. They were used to locate areas of low relative error and to apply the 3D digital mapping technique. For instance, Diender Guedj has been mapped at 1:25,000. The result of this mapping is extracted and processed using the DBMS (MySQL) software. The latter allowed both to determine Paleocene gab and update data. And then the database is processed. The programming languages PHP and Javascript have been used to simulate a website.
文摘Urban areas house vegetation cover in several forms, fulfilling several ecological functions like thermal regulator, biodiversity, air quality, etc. However, their extent is often not very well known, especially in African cities, making it sometimes difficult to assess their real impact on the urban ecosystem functioning. This work aims to analyse the capacity of satellite sensors for mapping vegetation and wetlands in urban areas. The data produced by the MSI sensors of Sentinel 2 and OLI of Landsat-8 are used to identify and map the vegetation cover in the Dakar region through a supervised classification with the Support Vector Machine (SVM) algorithm. The results show that it is sometimes not very easy to analyse urban vegetation with high spatial resolution images (HRS) resulting from the configuration of the vegetation in an urban environment, sometimes characterized by isolated trees or small green spaces. This explains why Sentinel-2 data which spatial resolution of 10 meters gives a better result compared to Landsat-8 data which is 30 meters. However, a good rendering is noted for the vegetation around the wetlands area for the two sensors resulting from the high density and the size of the vegetated perimeters in this part of the capital. Overall, there is an underestimation of urban vegetation cover, particularly for Landsat-8. The use of very high spatial resolution images could be necessary to better assess the potential of satellite data for monitoring urban vegetation in Sahelian context.
基金supported by the AIRD(Agence Inter-établissements de Recherche pour le Développement)through the CORUS2 project entitled“Impact de la pression anthropique et du Changement Global sur les flux sédimentaires en zone sahélienne”(Grant No.6116).
文摘An old erg covers the northern part of the Lake Chad basin. This dune landform allowed the formation of many interdune ponds of various sizes. Still present in certain zones where the groundwater level is high (e.g. Kanem, southern Manga), these ponds formed in the past a vast network of lacustrine microsystems, as shown by the nature and the distribution of their deposits. In the Manga, these interdune deposits represent the main sedimentary records of the Holocene environmental succession. Their paleobiological (pollens, diatoms, ostracods) and geochemical (δ18O, δ13C, Sr/Ca) contents are often the basis for paleoenvironmental reconstruction. On the other hand, their sedimentological characters are rarely exploited. This study of palustro-lacustrine deposits of the Holocene N’Guigmi lake (northern bank of the Lake Chad;Niger) is based on the relationships between the sedimentological features and the climato-hydrological fluctuations. The mineralogical parameters (e.g. calcium carbonate content, clay mineralogy) and the nature of autochthonous mineralization (i.e. amorphous silica, clays, calcium carbonates) can be interpreted using a straightforward hydro-sedimentary model. Established to explain the geochemical dynamics of Lake Chad, this model is based on a biogeochemical cycle of the main elements (i.e. silicium, calcium) directly controlled by the local hydrological balance (i.e. rainfall/evaporation ratio). All these results show that a detailed study of sedimentological features can provide important paleohydrological informations about the regional aridification since ca 6500 14C BP.
文摘The analytical technique PIXE experiment for measuring light and heavy elements concentration inside different samples of soil and residual water collected in the region of Safi-El Jadida, where an industrial complex resided, was performed. The same method was used to investigate the presence of elements ranging from silicon to lead in different soils samples and seaweed collected upstream from the site of Safi-El Jadida industrial zone, inside lands and downstream of it, in the entrance of the Casablanca region. This study allows us to highlight the influence of activities of this industrial zone on the neighbouring areas the site.
文摘Numerous scientific fields are facing a replication crisis,where the results of a study often cannot be replicated when a new study uses independent data.This issue has been particularly emphasized in psychology,health,and medicine,as incorrect results in these fields could have serious consequences,where lives might be at stake.While other fields have also highlighted significant replication problems,the Earth Sciences seem to be an exception.The paucity of Earth Science research aimed at understanding the replication crisis prompted this study.Specifically,this work aims to fill that gap by seeking to replicate geological results involving various types of time-series.We identify and discuss 11 key variables for replicating U-Pb age distributions:independent data,global sampling,proxy data,data quality,disproportionate non-random sampling,stratigraphic bias,potential filtering bias,accuracy and precision,correlating time-series segments,testing assumptions and divergent analytical methods,and analytical transparency.Even while this work primarily focuses on U-Pb age distributions,most of these factors(or variations of them)also apply to other geoscience disciplines.Thus,some of the discussions involve time-series consisting ofεHf,δ18O-zircon,14C,10Be,marineδ13C,and marineδ18O.We then provide specific recommendations for minimizing adverse effects related to these factors,and in the process enhancing prospects for replicating geological results.