Archean Tonalite-Trondhjemite-Granodiorite Suites Bearing Orthopyroxene Mineral of the Bounta Region and Their Sulfide and Oxide Iron Mineralization (Western Ivory Coast)

The mining company Sama Nickel-CI during its exploration activities in the Bounta area (Biankouma department, western Côte d’Ivoire) identified rocks with magmatic and metamorphic characteristics of felsic to mafic compositions mineralized in sulfide but unknown in the region. Thus, the petrographic characterization of these rocks of Bounta as well as the sulfides they contain, was carried out from macroscopic to microscopic observations. Petrographic analysis of these rocks has shown that these rocks are trondhjemite, tonalite and granodiorite (TTG) suites, composed of the main minerals (quartz, plagioclase, orthopyroxene, amphibole, feldspar) and accessory minerals (biotite, garnet) with magmatic textures supplanted by metamorphic textures. They were set up by fractional crystallization and would be products of Archean crustal anatexis formed from the partial melting of basaltic protocrust during the Liberian orogeny. The Bounta’s series of trondhjemite, tonalite and granodiorite (TTG) contain speckles of sulfide (pyrite and pyrrhotite) which are disseminated in places and are relatively abundant, as well as iron oxides (magnetite) which are of low proportion.

Assessment of Meteorological Drought in Climate Variability Context within the Comoe River Transboundary Watershed

In the context of climate variability resulting in a decrease in rainfall with a severe drought, a spatio-temporal study of this phenomenon remains imperative for the efficient management of water resources. This paper aims to assess the long-term rainfall drought trend and breakpoints within the Comoe River watershed. From monthly rainfall data series (1960-2000), Standardized Precipitation Index (SPI) values were calculated for a time scale of 3 months (SPI.3). Statistical tests for breaks (CUSUM, and t-Student) and trends (Man-Kendall and Linear Regression) as well as the Sen’ slope method for estimating the magnitude of trends was applied. The breaks dates observed are mostly located after the 1970s. Based on SPI.3 values below the threshold of 0.84 chosen as an indicator of drought, rarely has more than half of the catchment area been affected by drought. The average watershed affected is about 20% over the study period (1960-2000). The most representative years, in terms of spatial expansion of the drought, in decreasing order of importance are: 1983, 1992, 1972 and 1982. The years 1982 and 1983 stand out for their exceptional condition, as the drought-affected 50% to 90% of the total catchment area. SPI.3 series from 1960 to the various break dates recorded slopes between -0.01 and 0.00 with a slight drought trend for most of the catchment. After the break periods, almost the entire northern part of the basin is characterized by slight moisture with Sen’s slopes between 0.000 and 0.005. The southern part will remain slightly subject to normal rainfall conditions.