TITLE:
Evidence of Volcanic Collapse and Mass-Wasting Events in the Paleoproterozoic Toumodi Region (Côte d’Ivoire)
AUTHORS:
Alphonse K. Yao, Eudes S. N. Tegan, Barthelemy Gnamytchey Koffi, Alain N. Kouamelan
KEYWORDS:
Toumodi, Volcanic Instability, Debris Avalanches
JOURNAL NAME:
Open Journal of Geology,
Vol.15 No.10,
October
11,
2025
ABSTRACT: The Toumodi-Fetêkro region, located in the heart of the Ivorian Paleoproterozoic domain, has been the subject of numerous petrographic, structural, and geochemical studies aimed at understanding its geological evolution. These studies, mainly conducted in the central part of the Fetêkro greenstone belt, around the Toumodi region, have focused on localities such as Lomo Nord, Akakro N’zipri, Anikro-Kadjokro, Angoda, Gbonti, Loukou-Yaokro, Konan-Kokorékro, and Zaakro. The main goal of this study is to broaden the understanding of the mafic volcaniclastic deposits found in the central part of the Toumodi-Fetêkro greenstone belt, with a specific focus on their depositional context while providing detailed volcanological insights. To achieve this, we conducted comprehensive fieldwork, including geological mapping, petrographic analysis, and sedimentological studies, complemented by thin-section analyses in the laboratory. The results obtained were carefully analyzed and interpreted from a volcanological perspective. Petrographic observations revealed the presence of various volcaniclastic deposits, including breccias (both monolithological and polylithological), lapilli tuffs, and cinerites. Detailed sedimentological analysis uncovered several key structures, including cross-laminations at tight angles, large amplitude parallel laminations, and depositional features based on the Bouma and Lowe classification systems. These sedimentary structures allowed us to construct three stratigraphic logs at the Lomo Nord, Akakro N’zipri, and Anikro localities. Volcanological interpretations of these deposits suggest that they are the result of pyroclastic fallout, debris avalanche deposits, hyperconcentrated debris flow deposits, and riverine deposits. These are all secondary deposits formed in a hydrovolcanic environment, reflecting the complex interactions between volcanic activity and water. The deposits are interpreted as originating from an avalanche phase during a sectoral collapse of an unstable volcanic edifice, likely triggered by significant hydromagmatic events. This study highlights the role of volcanic instability and hydromagmatic processes in the formation of mafic volcaniclastic deposits in the central Toumodi-Fetêkro region, offering new insights into the volcanic history and geological processes of the Birimian greenstone belt.