Multistage Mineralization of the Inata Gold Deposit, Burkina Faso: Insights from Sulphide and Fluid Inclusion Geochemistry

Abstract

International audienceThe Inata gold deposit formed during the Eburnean orogenesis and is hosted in meta-volcano-sedimentary rocks. Gold mineralization is directly linked to disseminated arsenopyrite and pyrite assemblages which are associated to a quartz-ankerite-albite-tourmaline vein system that formed inside a N-NNE-striking, steeply dipping, D2 deformation zone. LA-ICP-MS analyses reveal that early sulphides, which formed parallel to the metamorphic D1 foliations, have low Au/Ag ratios of 40) in contrast to late D2 sulphide overgrowths which show more or less equal Au/Ag ratios. These assemblages are locally crosscut by narrow D3 fault corridors, where visible gold is observed within fractured sulphides and is interpreted being the result of late stage remobilization during D3. Extraction of fluids indicates that veins associated to D1 and D3 are characterized by high CO2 content whereas especially early D2 veins are dominated by H2O-rich fluids. δD values of fluid inclusions versus δ 18 O isotopic compositions of hosting quartz veins indicate two distinct sources, one of metamorphic/magmatic origin, rich in H2O, and the other one being the result of extensive fluid-rock interactions with C-rich volcano-sediments