Geochemical mobility associated to gold and base metal mineralization of Mangodara sector, in southern Burkina Faso, Banfora greenstone belt (West Africa Craton)

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Résumé

In the Mangodara sector within the Banfora greenstones belt our study focus on geochemical assessment of major and multielement and implying analysis and interpretation of
principal component. Gold and base metal mineralization is hosted in highly metamorphic altered felsic (metarhyolite) and intermediate (metadacite and metaandesite) volcanic formations. Mineralogy reveals aluminous assemblage made up of staurolitekyanite -pyrophyllite that are interpreted to represent the metamorphosed equivalent of aluminous hydrothermal alteration. Associated felsic and intermediate volcanic rocks are respectively enriched in Fe2O3 and K2O; Fe2O3, K2O, MgO, Al2O3, CaO, P2O5 and Fe2O3, MgO, CaO and depleted in MgO, Al2O3, CaO, P2O5, SiO2, Na2O, TiO2; SiO2, Na2O, TiO2 and SiO2, Na2O, K2O. Al2O3 and TiO2 are immobile in metadacites. Mineralized metaandesites show Fe2O3 and K2O enrichment and MgO, Al2O3, CaO, SiO2 depletion. Al2O3 depletion in mineralized kyanite-staurotide bearing metarhyolites suggest the minerals are corroded. Mineralized metarhyolites show enrichment in Au, Ag, Ba, Bi, Cr, Cu, Eu, La, Mo, Ni, Pb, S, Sc, V and depletion in As Sb Co, Sn, Zn while mineralized metaandesites show enrichment in Au, Ag, As, Mo, S, Sb and depletion in Co, Sn, Zn, Bi, Cr, Cu, Eu, Ni, Pb, Sc. Ba, La, V are immobile in metaandesites. finally Ag, As, Sb, Bi, Sn appear as geochemical vector for gold exploration in the study area since gold mineralization is characterized by Au+Ba+Cu+Eu+La+Mo+Ni+S association in metarhyolites and Au+S+Sb+As+Ag+Bi in metaandesites.

Mots-clés

Geochemistry, Mobility elements, Banfora Belt