Laboratory of Geology, Mineral and Energy Resources, Training and Research Unit in Earth Sciences and Mineral Resources, University Felix HOUPHOUËT-BOIGNY, Abidjan, Côte d’Ivoire
The study area is located in the southeastern part of the Comoé basin (southeast of Côte d’Ivoire, north of the town of Alépé). The geology of this study area is marked by granitoids (two-mica bearing granites, granodiorites, microgranites and pegmatites) and metamorphic rocks (gneiss, micaschists, metawackes and schists) which are crossed by several quartz veins. The aim of this study is to identify the petro-structural and metallogenic features of the quartz veins in this part of the Ivorian birimian. The methodology used focused on geological surveys, petrographic descriptions (macroscopic and microscopic), structural analysis and metallogenic analyzed. The petro-structural study revealed the presence of saccharoid quartz veins, tourmaline bearing quartz veins, banded tourmaline quartz veins, biotite bearing quartz vein, translucent quartz veins, smoky quartz veins, white to milky white quartz vein. The morphology of the veins is variable: rectilinear or fusiform with a main NE-SW orientation and secondary orientations NNW-SSE and E-W. In addition, these veins are generally deformed in the form of folds, tension slots, sigmoidal figures. These structures demonstrate the existence of shear corridors. The presence of rolling extinction and quartz subgrains were highlighted by microscopic observations, confirming the dislocation creep mechanism. This mechanism indicates high temperature and differential stress conditions. Observations with metallographic microscopes coupled with geochemical analysis data show that sulphides and gold are present in the fracture planes and quartz subgrains and generally associated with the quartz-tourmaline veins. Hence, the interest in taking into account the quartz-tourmaline association in gold prospecting in the Birimian rocks.