Petro-structural characteristics of the Tarkwaian and associated formations in the Bondoukou area (Northeastern Côte d'Ivoire): Implications for the Paleoproterozoic evolution of the West African craton

The Tarkwaian formations, well known in Ghana for their gold-bearing potential, also outcrop in northeastern Côte d'Ivoire, particularly in the Bondoukou area. This study aims to characterize the petrographic and structural features of these formations and their associated volcanic and intrusive rocks, in order to contribute to the understanding of the Paleoproterozoic evolution of the West African craton. Fieldwork, macroscopic and microscopic petrographic analyses (seven thin sections), and structural measurements were carried out. The results show that the Bondoukou Tarkwaian consists of polygenic meta conglomerates (quartz, basalt, andesite, rhyolite, dolerite, schist pebbles) in a greywacke matrix, meta-arkoses, and greywackes with oxide laminations. Associated formations include volcanics (tuffs, deformed cinerites) and intrusive rocks (tonalite, oriented porphyritic granodiorite with mineralized metabasite enclaves). Structurally, these rocks record multiple brittle (N98° to N166° fractures, faults) and ductile (chevron isoclinal folds, cleavage, mineral lineations) deformation phases. The main orientations (NW-SE to NNE-SSW) are interpreted as resulting from Eburnean and post-Eburnean shortenings. The occurrence of mineralized metabasite enclaves and pebbles suggests a metallogenic potential similar to Ghanaian paleoplacers. This study confirms that the Ivorian Tarkwaian was emplaced in a shortening (tightening) context and represents a lateral equivalent of the Ghanaian series.