Lithological and Structural Control of the Gold Mineralization of the Souwa Prospect (Doropo), Northeastern Côte d’Ivoire

Abstract

Birimian rocks host a wide range of mineralizations, of which gold is a major metal. These mineralizations are sometimes described as disseminated systems related to the circulation of mineralizing fluids in fractures generating quartz veins and veinlets, and sometimes as strongly controlled by structures (shear zones, intrusions, associated veins). These discrepancies highlight the need for detailed studies in still poorly documented areas, such as the Souwa prospect, located in the Birimian formations at the northeastern end of Côte d’Ivoire, in the Doropo department. This study aims to identify the main factors responsible for the gold mineralization at Souwa. For this purpose, macro- and microscopic petrographic analysis allowed characterization of the main lithological units, while a structural study, based on interpretation of geophysical data and examination of drill cores, identified the deformation structures and tectonics affecting the study area. Finally, the relationship between gold mineralization, host formations, and structures was established using gold grades, to better constrain lithostructural controls and guide future exploration work. The results show that the study area is dominated by granodioritic granitoids, crosscut by late dolerite dykes, affected by widespread greenschist facies metamorphism and intense hydrothermal alteration marked by sericite, silica, chlorite, epidote, and carbonate addition, as well as quartz, calcite, hematite, epidote, and ± sulfide veins and veinlets. Structurally, the Souwa prospect records polyphase ductile-brittle deformation, generating several generations of structures (quartz veins and veinlets, joints, fractures, shear zones) mainly oriented NNE-SSW, NE-SW, NW-SE, N-S, and E-W, with a predominance of NE and NW structures; these fracture networks constitute preferred pathways for the circulation and accumulation of mineralizing fluids. Gold mineralization is locally observed within the granodiorite, reflecting lithological control, and the highest grades are associated with lenses, veinlets, stockworks, and more or less brecciated quartz veins; located in intensely fractured and highly altered zones. The Souwa gold mineralization is thus interpreted as a hydrothermal mineralization controlled by both lithology and tectonics.