Artisanal gold mining is gaining momentum in western Côte d'Ivoire. However, little information is available on the mineralized horizons and primary source of gold. The objective of our study is thus to investigate the artisanal mining sites of Doumbiadougou near Duékoué in order to characterize the gold horizons then the primary source of gold and to propose exploration guides. We carried out fieldwork in Doumbiadougou followed by lithostratigraphic correlations and interpretations at the University of Man. In Doumbiadougou, we observed saprolite derived from a felsic intrusive affected by sheared quartz veins of orientation ranging from N035 to N060°. On the lithostratigraphic level, two quarries served as a basis for study. Thus, in the quarry on eluvial, three horizons are observed from the bottom to the top: fine saprolite, ferruginous shell and ferruginous cuirass. The geological substratum is dominated by quartzites and micaschists. Then, the quarry on alluvium presents four horizons from the bottom to the top: clay, gravelly, clay-sandy, and sandy. Gold mineralization is primarily related to eluvial wells whose elements percolate and enrich alluvium in the surrounding shallows. This resulted in concentrating the gold in the gravelly horizon. The abundance of quartz in the gravelly mineralized horizon and in the veins as well as the substratum made of quartzite and micaschist gives an epigenic origin to the gold of Doumbiadougou. These veins and felsic intrusive that hosts them appear as guides to be sought for the mineral exploration project.
The southern part of the Toumodi-Fètêkro greenstone belt is located in central-southeastern Côte d'Ivoire. The lithologies encountered in the felsic rocks can be subdivided in to three units corresponding to volcanic lavas (dacites, rhyodacites and rhyolites), pyroclastics rocks (ignimbrites) and granitoids (granodiorites and granites). All of these lithologies have been generally foliated and metamorphosed in to greenschist facies. Geochemical data show that these felsic rocks are metaluminous to peraluminous, calc-alkaline and have characteristics of magmatic arc rocks (TiO2 < 2 %). The dacites are sodic and the granitoids are “I” Type. Geochemical trends show a possibility of mixing due to the existence of a small Archean legacy component.
This study was carried out with the aim of clarifying the lithostratigraphy of the Dougbafla –Bandama area located in the southern part of the Birimian belt of Fettékro, in the center-West of Côte d’Ivoire. The vertical succession of these formations can be summarized at the base by volcanic rocks (basaltic and andesitic) mainly basalts, with in intermediate positions several successive volcaniclastic flows of autobrechic type and at the top by Various sedimentary lithologies usually composed of black schists or a more modest volume of sericite or chlorite schists capped with quartzites. These various shales sometimes play an important role of transition between lithologies. This complex is intersected by intrusions (granites, granophyres, granodiorites, tonalites, epidiorites, microgranodiorites, microdiorites, lamprophyres) and several generations of veins and quartz veinlets.
Fractured aquifers of gneiss are the main drinking water sources for population living in the north area of Alépé. Neglecting geochemical monitoring of such groundwater is able to deliver water consumers taking unacceptable risks. The quality of water from bedrock in terms of taste can lead people to drink surface water whose chemical quality is lower in comparison with the reference quality. The aim of this study is to estimate the major cations concentration of gneiss groundwater in which mineralization was almost due to silicate hydrolysis. To achieve the aim in view, a study of main mineral of the gneiss aquifer was carried out and a geochemical simulation through inverse modeling by PHREEQCI code was applied on water rock process. The study showed that the main silicate minerals of gneiss that contained major cations were albite, K feldspar, plagioclases and amphibole. The dissolution mean rates of minerals able to increase groundwater mineralization by hydrolysis were 1.3 x 10-5 mol L-1 for K-feldspar, 3.8 x 10-4 mol L-1 and 1.0 x 10-4 mol L-1 for oligoclase and amphibole (ferro-tshermakite), respectively. Through these results, it shown that oligoclase would be the mineral more favourable for hydrolysis among feldspars studied in the gneiss. In gneiss groundwater, sodium was mainly supplied by oligoclase, potassium was supplied by K-feldspar and ferro-tshermakite, magnesium was supplied by ferro-tshermakite only and calcium was supplied by oligoclase and ferro-tshermakite.