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

Abstract

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.