Preliminary Geochemical Enrichment in Zirconium, Hafnium and Rare Earth Elements of Fine-Grained and Migmatitic Gneisses from the Garango–Tenkodogo Area, Burkina Faso, West African Craton

Background: Zirconium (Zr), hafnium (Hf) and rare earth elements (REE) are geochemically important elements whose distribution in felsic rocks is influenced by accessory mineral assemblages, magmatic differentiation and metamorphic processes. Although fine-grained and migmatitic gneisses are widespread in the Garango–Tenkodogo area of Burkina Faso, their Zr–Hf–REE concentrations and enrichment characteristics remain poorly documented. This study addresses this knowledge gap through preliminary petrographic and lithogeochemical investigations. Aims: To assess, for the first time, the zirconium (Zr), hafnium (Hf) and rare earth element (REE) contents of the fine-grained and migmatitic gneisses of the Garango–Tenkodogo area, to describe the distribution of these elements and to identify the samples that deserve further mineralogical investigation. Study Design: Exploratory field, petrographic and whole-rock lithogeochemical screening study. Place and Duration of Study: Garango–Tenkodogo area, Baoulé-Mossi domain, Burkina Faso (West African Craton). Fieldwork was carried out in March–April 2021; whole-rock analyses were performed by SGS Canada and zircon U–Th–Pb data were acquired at the GeOHeLiS platform, Université de Rennes (France). Methodology: Field observations at 32 sites, petrographic examination of 31 thin sections, optical cathodoluminescence imaging of zircon and apatite grains, and 15 whole-rock analyses (lithium metaborate fusion, ICP-AES and ICP-MS). Covariations were evaluated with Spearman rank correlations corrected for multiple testing, enrichment factors relative to the upper continental crust, and apparent zircon saturation temperatures. Results: The rocks are felsic (SiO2 = 70.25–79.53 wt.%) and mostly metaluminous to weakly peraluminous. Zr reaches 714 ppm, Hf 20.1 ppm and total REE 576.5 ppm, i.e. at most about four times the upper continental crust, whereas heavy REE reach 12.8 times this reference. Zr, Hf, Nb and heavy REE vary together (Zr–heavy REE: ρ = 0.75, P = .001; Zr–Hf: ρ = 0.99, P < .001), whereas light REE are decoupled from Zr and P2O5 (ρ = 0.28, P = .35), which suggests at least two mineralogical controls. Three samples (A08, A21 and A22) that are simultaneously enriched in Zr, heavy REE and total REE are proposed as priority targets. Conclusion: These moderate enrichments may reflect a felsic protolith rich in high field strength elements or redistribution during migmatisation. They do not constitute a mineralisation, but justify a quantitative study of the host minerals and an assessment of the regolith developed on these gneisses.