In the Lower Palaeozoic Anglo–Brabant fold belt in Belgium, a detailed study of the geochemistry of different generations of pyrite has been carried out by electron microprobe analysis. The occurrence of pyrite is related to different episodes in the evolution of this fold belt. Pyrite occurs either as a pre- or as a syn-deformation phase in the metamorphosed sedimentary and igneous rocks. Pre-cleavage pyrite in greenschist metamorphosed sedimentary rocks has a relative higher Ni-content. As illustrated in the Kupferschiefer, this could be due to the release of Ni from organic matter during diagenesis. Pre-cleavage pyrite in the igneous rocks has higher Cu, Pb, Cd and Zn contents, which could be caused by the incorporation of these elements in the sulphide phase during the final stage of the crystallisation of the magma. Syn-deformation pyrite along cleavage planes and in quartz/carbonate veins is characterised by higher As, Sb, Se and Au contents, typical for hydrothermal mineralisation in a greenschist facies fold belt. [ABSTRACT FROM AUTHOR]