Petrographic and Geochemical Characters of the Metasediments and Granitoids in the Dimbokro Region (Centre-East Côte d’Ivoire)

This study examines the petrographic and geochemical characteristics of the metasediments and granitoids in the Dimbokro region. Petrographic characterisation reveals that the study area is dominated by two major lithological units: metasedimentary rocks (mica schists, metagrauwackes and quartzites) and a suite of intrusive granitoids (biotite granites, granodiorites and tonalites). Chemical analysis indicates that these granitoids are of type I, and the chemical weathering index (CWI) values for the metasediments range from 54.3 to 79.1, indicating moderate weathering of the parent rocks, suggesting protoliths of intermediate to felsic igneous composition. Rare earth element patterns show marked LREE enrichment over HREE, with (La/Yb) N ratios ranging from 7.2 to 18.6 in the metasediments and from approximately 15 to 110 in the granitoids, reflecting varying degrees of crustal fractionation. Negative Nb-Ta anomalies in multi-element spectra indicate that both lithological units were formed in a subduction-related tectonic setting. These two lithological units form part of the Palaeoproterozoic Birimian evolution of the West African Craton.