Mise En Evidence De Nouvelles Cibles De Forages A Partir De L’analyse De La Fracturation Du Prospect Aurifère De Dougbafla-OUME (Centre-Ouest De La Côte d’Ivoire)

The mining research license of Oume (PR105) is located in the Centerwest forestry of Côte d’Ivoire on Fettekro greenstone belt. This furrow belongs to the Proterozoic Birimian series of West Africa. This concession which is our study area, is sheltered by the Bonikro gold deposit, which was discovered by sampling the geochemical gold soil anomaly. All around the latter within a radius of about 15 km, ten prospects or targets were highlighted by the method of soil geochemistry. These targets or potential anomalies are currently undergoing intensive drilling to identify potential resources that could feed into Bonikro mine processing unit. It is in this perspective that the aim of this work is to locate new targets likely to contain gold indices from the use of synthetic opening radar satellite imagery. The fracturing map was obtained by applying directional filters from Sobel on the radar images (N-S, E-W, NESW and NW-SE) and Yesou gradient filter. The enhanced lineaments were extracted manually. The report of the lineament direction on the specific tools called “Rosace” showed five (5) preferential direction classes [N00 - N10], [N20 - N30], [N40 - N80], [N90 - N100] and [N120 - N140]. The analysis of the relationship between the lineaments map and geochemical signature map of the study area shows that the area is intensely fractured and describes an anomaly that overlap with coarsely elongated gold content along the Birimian formations direction. The study permitted to identify four (4) potential targets within Oume license

Potentiel de productivité des aquifères de la région de Man (Côte d’Ivoire) par analyse spatiale et krigeage

Les taux d’échec répétés dans les différents projets d’adduction en eau potable en région de socle, poussent à mener des études préliminaires sur la productivité des aquifères. La région de Man à l’Ouest de la Côte d’Ivoire présente un relief accentué. Approvisionné à 85% par des eaux souterraines, l’étude du potentiel de productivité des aquifères de fractures demeure primordiale. Les données d’étude sont constituées en 155 débits de forages, le MNT de la région et les données linéamentaires. Le rôle de chacun de ces paramètres (fracture, relief) dans la productivité des forages est évalué et exprimé sous le terme d’indice de productivité. Celui-ci est une valeur numérique simulée selon le poids exercé par le paramètre dans la productivité des aquifères. Une sommation des différentes valeurs d’indice de productivité a été effectuée et spatialisée par la méthode géostatistique. D’une manière générale, la région de Man présente des potentialités en eau souterraine importante, avec environ 90% de la région à potentiel de productivité élevé

APPLICATION DU MODELE INVERSE AUX INTERACTIONS EAU-ROCHE DANS LES EAUX SOUTERRAINES DES METAGRANODIORITES, SUD-EST COTE D’IVOIRE

In Ivory Cost, few studies have been performed on the process of water-rock interactions in aquifers of basement. The study aim is to provide, from an inverse model by usgs program “phreeqci”, orders of magnitude of the mass transfer from each mineral during the process of water mineralization in the aquifer of metagranodiorites. We use mineralogy and geochemistry of water and rocks. The mineralogical study indicated paragenesis of plagioclase-feldspar-chlorite-biotite and amphibole. Kaolinite is assumed to be the clay product of silicate minerals hydrolysis in the study area. The simulation provided dissolution rate of 8.3 10-4 mol l-1 for plagioclase, 1.7 10-4 mol l-1 for chlorite, 9.4 10-5 mol l-1 for biotite and 2.3 10- 5 mol l-1 for amphibole during water-rock interaction process occurred 15,000 years ago

Impact of Climate Variabilty on Water Resources And Population Health in the South Eastern Coastal Area of Côte d’Ivoire

The present study evaluates the impact of climate variability on water resources and population health in the coastal area of Cote d’Ivoire between Abidjan and Aboisso. First, hydroclimatic methods (Nicholson index) and statistical tests (Pettitt test, Hubert segmentation) were used for variability characterisation. Then, Thornthwaite Water balance method was used to evaluate water availability for aquifers recharge. Coefficient depletion method was also used to assess the impact of climate variability on surface water resources. The relationship between diseases occurence (AhigbeKoffikro and Samo) and rainfall pattern was evaluated through descriptive method. The results revealed important fluctuations of water resources levels at that time. The relationship rainfall-runoff showed with synchron trend that rivers flows regime was linked to rainfall. The impact on groundwater resources was explained by deficit of infiltrated water of about 35.49% and 22.61% after 1982 break at Abidjan airport and Bingerville stations respectively. Concerning health, 63% of malaria cases was observed against 2.85% for diarrhoea and 2.35% for helminthiasis. There was a strong relationship between rainfall and the diseases (malaria and diarrhoea)

Cartographie De La Vulnérabilité À La Pollution Des Aquifères Du Socle Précambrien : Cas De La Région D’oumé (Centre-Ouest De La Côte D’ivoire)

Development of agricultural and mining activities and the rapid growth of the population (3.8%) in Oumé’s area, constitute a potential risk of groundwater’s pollutions. This study interested Oumé’s area and aims to elaborate a map of vulnerability to pollution for a better management of groundwaters. The database is constituted by various data in particular, geological, hydrogeological, geomorphological, pluviometric data and satellite image. Methods DRASTIC and GOD were used in this study. Results of DRASTIC method indicated that 31.86% of study area have a very low vulnerability, 68.12% a low vulnerability and 0.02% a moderate vulnerability. With GOD method, 12.8% of study area have a very low vulnerability, 86.46% a low vulnerability and 0.74% a moderate vulnerability. The chemical analysis of groundwater showed that weaker rates of nitrates (0-14mg/l) registered inside the surely well protected zones. These observations have led to validate some various maps obtained. Result of the test of Kappa revealed that coefficient K is reliable and gave moderate agreement (K=0.43) between both methods. This agreement is confirmed by the surface analysis (79.01%). In this study, the DRASTIC method supplied better results and is thus better adapted for the evaluation of vulnerability in the pollution of groundwater of this area

APPLICATION DU MODELE INVERSE AUX INTERACTIONS EAU-ROCHE DANS LES EAUX SOUTERRAINES DES METAGRANODIORITES, SUD-EST COTE D’IVOIRE

In Ivory Cost, few studies have been performed on the process of water-rock interactions in aquifers of basement. The study aim is to provide, from an inverse model by usgs program “phreeqci”, orders of magnitude of the mass transfer from each mineral during the process of water mineralization in the aquifer of metagranodiorites. We use mineralogy and geochemistry of water and rocks. The mineralogical study indicated paragenesis of plagioclase-feldspar-chlorite-biotite and amphibole. Kaolinite is assumed to be the clay product of silicate minerals hydrolysis in the study area. The simulation provided dissolution rate of 8.3 10-4 mol l-1 for plagioclase, 1.7 10-4 mol l-1 for chlorite, 9.4 10-5 mol l-1 for biotite and 2.3 10- 5 mol l-1 for amphibole during water-rock interaction process occurred 15,000 years ago

Apport Du SIG Et De L’analyse Multicritère Dans La Prospection Hydrogéologique Du Socle Précambrien De Gagnoa (Centre-Ouest De La Côte d’Ivoire)

Côte d’Ivoire is constituted in more than 97.5% of crystalline basement which contains the main part of groundwater resources of the country. These resources are contained in the weathering material and fissured aquifers. Gagnoa area located at the Central West of Côte d'Ivoire, on crystalline and metamorphic basement. In this area, surface water and groundwater are exploited for the water supply of the populations. However surface water are often doubtful quality and can affect the health of these populations. Thus find water resources in sufficient and good quality amount is a necessity in this area. The study aims to identify favourable areas for the archievement of drillings with important discharge using geomorphologic, hydrogeological data and remote sensing. Multi-criteria analisys methods were used in this study. The database is constituted by various data in particular, data sheets of drillings, hydroclimatic statements and satellite image. This database was stored, analyzed, treated and managed using ARCGIS 10.2. software. Various treatments allowed to establish various thematic maps (accessibility, exploitability, availability). The synthesis of all information inside a SIG allowed to establish the maps of favourable areas to achieve drillings with large discharges. The classes of good and excellent sensibility cover 26% of the study area. These favourable areas for the achievement of drillings with important discharge are located at the center and south of the study area. Validation of this map showed that 66% of the water points (drillings) with discharge superior to 5 m3/h overlap on the good and excellent classes of sensibility. The various zones of productivity of Gagnoa area were able to be characterized. These results are very interesting and useful for the hydrogeological prospecting. They contribute to a better knowledge and a groundwater resource management

Analyse du réseau de fractures extrait des images radar du socle précambrien de la région d'Oumé (Centre-Ouest de la Côte d'Ivoire)

article publié en français, avec un résumé étendu en anglais, et des planches couleur hors-texteInternational audienceThe aim of the study is the analysis of the fractures network in the OUmé region of Ivory Coast, using statistical and geostatistical methods. Lineaments identification is performed from; a SAR image of Radarsat-1, recorded in January 2001. Results have shown a high intensity of fracturation, with a complex spatial pattern. Such results could be used for a better understanding of underground water flows.Cette étude a pour objectif d'analyser à partir de méthodes statistiques et géostatistiques le réseau de fractures de la région d'Oumé. L'extraction des linéaments de la zone d'étude a été faite à partir d'une scène RSO de Radarsat-1, prise en janvier 2001. Les résultats ont mis en évidence une structuration importante et une géométrie complexe du réseau de fractures. Ces résultats pourraient être utilisés pour la compréhension et la modélisation des écoulements souterrains

Analyse du réseau de fractures extrait des images radar du socle précambrien de la région d'Oumé (Centre-Ouest de la Côte d'Ivoire)

article publié en français, avec un résumé étendu en anglais, et des planches couleur hors-texteInternational audienceThe aim of the study is the analysis of the fractures network in the OUmé region of Ivory Coast, using statistical and geostatistical methods. Lineaments identification is performed from; a SAR image of Radarsat-1, recorded in January 2001. Results have shown a high intensity of fracturation, with a complex spatial pattern. Such results could be used for a better understanding of underground water flows.Cette étude a pour objectif d'analyser à partir de méthodes statistiques et géostatistiques le réseau de fractures de la région d'Oumé. L'extraction des linéaments de la zone d'étude a été faite à partir d'une scène RSO de Radarsat-1, prise en janvier 2001. Les résultats ont mis en évidence une structuration importante et une géométrie complexe du réseau de fractures. Ces résultats pourraient être utilisés pour la compréhension et la modélisation des écoulements souterrains

Agro-climatic Update of Favorable Areas to the Cultivation of Robusta and Arabusta Coffee in Côte d'Ivoire

Following a drastic fall in coffee production, Côte d'Ivoire has made it a priority to revive its coffee-growing industry. This requires the development of regionalized technical itineraries adapted to climate change. To this end, agro-climatic analyzes were carried out using data from 55 rain gauge stations covering the period from 1985 to 2019. This involved cross-referencing the climatic parameters calculated, taking into account the climatic requirements of coffee trees (Robusta and Arabusta) to define homogeneous agro-climatic zones in the forest and pre-forest zones bounded by the 8th parallel north. The results show that 70.47% of the area is suitable for growing Robusta coffee, compared with 11.37% for Arabusta. The mountainous west remains generally favorable to growing both varieties of coffee. The study also updated information on the agro-climatic suitability of coffee-growing areas