Contexte geologique de la mineralisation aurifere du prospect de Bobosso (region de Dabakala, centre-nord de la Cote d’Ivoire)

La lithologie du prospect de Bobosso (region de Dabakala, centre-nord de la Cote d’Ivoire) est constituee d’une roche hypovolcanique (microdiorite quartzique) et de roches volcaniques (basalte et/ou laves andesitique). Ces roches ont ete affectees par une importante activite hydrothermale marquee par des filons et filonnets de quartz, calcite, ± tourmaline, ± sulfures. La mineralisation aurifere de Bobosso a ete observee localement dans toutes les formations de la zone et ne presente donc pas de controle lithologique. Par contre, cette mineralisation apparait principalement liee aux filons de quartz et presente donc un controle structural. Ainsi, la mineralisation est principalement d’affiliation hydrothermale. La paragenese metallifere est essentiellement constituee de pyrite (sulfure principal), de chalcopyrite et d’arsenopyrite. On note souvent la presence de magnetite et d’hematite. L'or n’est pas visible a l’oeil nu meme dans les sections de forage presentant les plus fortes teneurs. Mots cles: Birimien, microdiorite, or, hydrothermal, Dabakala English Title: Geological context of the gold mineralization of Bobosso prospect (Dabakala region, north-central of Ivory Coast) English Abstract The rocks of the Bobosso gold prospect (Dabakala region, north-central of Ivory Coast) consists of subvolcanic rocks (quartz microdiorite) and volcanic rocks (basalt and/or andesitic lava). These rocks have been affected by a significant hydrothermal activity characterized by veins and veinlets filled by quartz, calcite, ± tourmaline, ± sulphides. The gold mineralization of Bobosso was observed locally all of the rocks of the area and therefore does not present a lithological control. On the contrary, this mineralization appears mainly related to quartz veins and thus presents a structural control. Thus, the mineralization is of hydrothermal affiliation. The ore paragenesis consists mainly of pyrite (main sulphide), chalcopyrite and arsenopyrite ± magnetite and ± hematite. Native gold has not been observed even in the drill sections with the highest gold contents. Keywords: Birimian, Microdiorite, Gold, Hydrothermal, Dabakala