The Paleoproterozoic domain of the Ivory Coast lies in the central part of the West African Craton (WAC) and is mainly constituted by TTG, greenstones, supracrustal rocks and leucogranites. A compilation of metamorphic and radiometric data highlights that: i) metamorphic conditions are rather homogeneous through the domain, without important metamorphic jumps, ii) HP-LT assemblages are absent and iii) important volumes of magmas emplaced during the overall Paleoproterozoic orogeny suggesting the occurrence of longlived rather hot geotherms. Results of the structural analysis, focused on three areas within the Ivory Coast, suggest that the deformation is homogeneous and distributed through the Paleoproterozoic domain. In details, results of this study point out the long-lived character of vertical movements during the Eburnean orogeny with a two folds evolution. The first stage is characterized by the development of "domes and basins" geometries without any boundary tectonic forces and the second stage is marked by coeval diapiric movements and horizontal regional-scale shortening. These features suggest that the crust is affected by vertical movements during the overall orogeny. The Eburnean orogen can then be considered as an example of long-lived Paleoproterozoic "weak-type" orogen.

Ivory Coast is a country rich in base metals and precious minerals: gold, manganese, diamond, iron, bauxite, cobalt and nickel. These natural resources are exposed to destruction and fragmentation by mining activities. The artisanal and small-scale exploitation of gold are increasingly practiced in our rural areas. These activities escape often in the control and monitoring of the mining administration. In order to better constrain these activities on the environment, the present work used remote sensing imageries to see its spatio-temporal impacts in the rural world in central Ivory Coast. The results show that gold artisanal activities have been practiced since 2013 and are experiencing an increasingly important growth. We note a devastation of forests and savannahs, a pollution of surface water, as well as an increase in poverty in rural areas. These activities are practiced near habited areas (villages). This creates a reduction of cultivatable soil. Remote sensing imageries make it possible to quickly map areas at large-scale gold mining in time and space.

La présente étude évalue les connaissances gîtologiques ainsi que les impacts environnementaux liés aux activités aurifères artisanales pour l’or de Doumbiadougou en Côte d’Ivoire. L’étude s’appuie sur des données issues de la description in situ des puits de prospection, des carrières ainsi que des méthodes de récupération de l’or. La typologie des gîtes indique deux ensembles à Doumbiadougou : d’une part les gîtes alluvionnaires dans les bas-fonds et d’autre part les gîtes filoniens sur les collines environnantes. Leur prospection s’effectue par le fonçage de puits tests de 1m3 jusqu’à 16m3 dans les bas-fonds, également sur les pentes et autour des veines de quartz sur les collines. L’exploitation des gîtes alluvionnaires se fait par l’ouverture de carrières de 5 m x 2 m x 2 m soit 20 m3 tandis que ceux filoniens se fait par l’ouverture de puits de 80 cm de diamètre et de profondeur allant jusqu’à 25 m. Le minerai alluvionnaire est traité par les lavages à la batée ou au sluice tandis que celui des filons est pulvérisé avant de subir le même traitement. La production aurifère se termine par la récupération de l’or après amalgamation au mercure. Sur le volet environnemental, ces méthodes laissent des puits béants, détruisent les cultures tout en réduisant les espaces cultivables, accélèrent le drainage minier acide, réactivent les conflits fonciers et exposent les communautés locales à l’inhalation du mercure.

This paper is a synthesis of the evolution on the use of remote sensing imagery for geological and mining mapping in

The study area is located in the Ferkessédougou belt in northern Côte d'Ivoire, precisely 30 km east of the city of Ferkessédougou. The aim of this study is to understand the tectonic which control gold mineralization. A combination of remote analysis and field mapping work, trenching, reverse circulation drilling hole, core drilling hole was carried out and finally laboratory work (microscopy). Different processing such as ACP, adaptive filters have been applied to Landsat 8 and Radarsat satellite images, in order to enhance information for better lineament extraction. Also, different complementary techniques (horizontal gradient, Euler deconvolution) were applied to the areomagnetic map in order to highlight the different lineaments.Four sets of lineaments have been producted by these images: N080-N100, N030-050, N000-N020, N120-N135.The validation of these different linear structures was made with field data. Thus, in the field, the metasediments show a strong S1 schistosity, stirikes NNE, with and dips towards the South-East, compatible with a D1 shortening episode. The emplacement of leucogranitic batholith and tonalite induces deformation (D2) which is shearing foliation S2. ). Later, diorite dykes induces the S3 shearing foliation. The earliest form of gold mineralization is located in quartz veins and fractures filled by sulphide ( pyrite). The second form of gold mineralization is disseminated and hosted in the sheared contacts betwween intrusive units with the metasediments. Studies show that quartz veins control the highest gold grades in tonalite unit. The mineralization of our study area is an IRGS type.