Petrography, Mineralogy, and Compositional Characteristics of Rare-Metal-Bearing Pegmatite of Côte d’Ivoire: A Review

Abstract

Côte d’Ivoire’s pegmatite occurrences have been the subject of limited studies. Fifteen areas of interest have been identified, including the Issia, Boundiali, and Comoé Basin regions. Only those in the Issia region, associated with the Issia peraluminous granites, have undergone rigorous studies. The Issia pegmatites are columbite-tantaliferous deposits, interpreted as deriving petrogenetically from differentiated residual fluids of the granite systems. Research in the Comoé Basin region has identified several pegmatite outcrops with significant potential for rare metals, including lithium, tantalum, niobium, and beryllium-bearing minerals. Four groups of pegmatites are categorized based on their mineralogy: spodumene-albite-tourmaline pegmatite, beryl-muscovite pegmatite, green-micas-tourmaline pegmatite, and muscovite-garnet pegmatite. These pegmatites exhibit traits that indicate a para-derivative origin and closely resemble the lithium-cesium-tantalum type, which features beryl and spodumene mineralization (similar to Ewoyaa pegmatites in Ghana). The Boundiali region pegmatites appear to be the most interesting regarding rare metal enrichment. These pegmatites are intrusive into the Birimian Supergroup (Palaeoproterozoic), either in metamorphic formations (mainly micaschist) or in granites. This region is characterized by five main types of pegmatites: the lepidolite-muscovite-spodumene-colombo-tantalite type, the green micas and colombo-tantalite type, the green beryl type, the muscovite-beryl type, and the biotite-magnetite type, grouped into two main families, including a lithium-bearing family and a non-lithium-bearing type (similar to the Bougouni-Goulamina pegmatites in Mali). They are primarily peraluminous, though it is not uncommon to find some of metaluminous origin, highlighting the pegmatitic diversity of this region. A recent investigation classified the Boundiali pegmatites as Lithium-Cesium-Tantalum pegmatites due to the discovery of lithium-bearing minerals (spodumene and lepidolite) in outcrops and the detection of lithium anomalies through soil sampling analyses. The exposures of the Boundiali and Comoé Basin pegmatites present valuable opportunities for further research, including lithium exploration and assessment of potential resources through detailed mineralogical and geochemical studies; geochronological analysis to determine timelines and genetic connections between the pegmatites and their potential parent rocks; refining petrogenetic and metallogenic models; analysis of alteration, metamorphic, and tectonic influences on pegmatite emplacement; and comparison of data with emerging LCT pegmatite fields worldwide.