The Geological Formations of Koun Fao (East of C?te d'Ivoire): Petrographic Characterization and Associated Deformations

摘要

This study aims to contribute to improve knowledge on geological formations of Comoé basin. The petrographic study of the geological formations of Koun Fao has highlighted two major lithological families: magmatic rocks consisting of monzonites, monzogranites, diorites, biotite granodiorites, syenites, porphyritic micromonzonites and porphyritic dacite and metamorphic rocks from sedimentary origin (quartz schists, meta-greywackes, schists, andalusite chloritoschist and paragneiss). These formations are affected by amphibolite to greenschist facies metamorphism and hydrothermal alteration (pervasive and vein) marked by the presence of quartz, epidotes, chlorites and sericite. Minerals such as andalusite, muscovite and chlorite characterize a local low pressure contact metamorphism in the andalusite chloritoschist. Remote sensing data (Landsat 8 image) coupled with field data allowed the production of a geological map of the area. The study of the structures and microstructures highlighted two deformation mechanisms. These are flattening and simple shear (ductile and brittle). The study area is affected by four deformation phases: D1 marked by a N-S to NNE-SSW elongation, D2 marked by a NW-SE to NNW-SSE compression phase, D3 which is a NE-SW to NNE-SSW transpression phase and D4, responsible for late structures, marked by a NW-SE to NNW-SSE transpression phase.