LITHO-STRUCTURAL CHARACTERIZATION OF THE GEOLOGICAL FORMATIONS OF THE KOURONDOUGOU-LINGUESSO AREA (ODIENNÉ DEPARTMENT, NORTHWEST CÔTE D'IVOIRE)

The study area is located in the Odienné region, situated in the northwestern part of Côte d’Ivoire. This study contributes to increasing knowledge of the geology of the Kourondougou-Linguesso sector. The methodological approach began with a remote sensing study and concluded with macroscopic observations (petrography and structural analysis, with the naked eye and/or a hand lens) of outcrops in the field. Subsequently, thin sections were prepared in the laboratory for study under a polarizing and metallographic microscope. The lithologies of the study area consist of igneous rocks (granites, pink granites, granodiorites, pegmatites, microdiorites, and lapilli tuff) and metamorphic rocks (biotite metagranites, orthogneisses, and amphibolites-schists). These rocks are affected by a general metamorphism of amphibolite to green schist facies and hydrothermal alteration (both pervasive and vein-related) marked by the presence of chlorite, epidote, sericite, sulfides (pyrite, chalcopyrite, and pyrrhotite), and oxides such as magnetite. Three deformation phases (D1, D2, and D3) have been identified. The D1 phase corresponds to a N-S shortening marked by mineral stretching lineations and E-W trending foliations, with subvertical dips. The D2 phase, resulting from NNW-SSE to NW-SE shortening, is manifested by veins, dikes, faults, and fractures generally oriented NNE-SSW to NE-SW. It generates shear zones oriented NNE-SSW to NE-SW. The D3 phase is marked by fractures, veins, and late mineral veins secondarily oriented NW-SE.