Reactive transport modelling of ore mineral zoning and the paragenesis of copper sulfides in sediment-hosted stratiform ore deposits, the Katanga Copperbelt (DRC)

1. Introduction and geological settingSediment-hosted stratiform copper deposits are characterized by including several types of sulfide and oxide minerals that exhibit different zoning and paragenesis. Stratiform copper mineralization in the Katanga Copperbelt (Democratic Republic of Congo; Fig. 1) took place in the Neoproterozoic Katanga Supergroup, mainly in the Roan Group, but also in the Nguba and Kundelungu Groups. The Nguba Group overlies the Roan Group and consists at its base of the Grand Conglomerat, a glacial deposit. The Nguba Group is overlain by the Kundelungu Group, with the Petit Conglomerat at its base. The latter is also a diamictite deposit (Cailteux et al., 2005). Two main ore bodies are present in the Mines Subgroup in the lower part of the Roan Group, i.e. the Lower and Upper Orebody. Between both ore bodies, a barren or weakly mineralized member, the Roches Siliceuses Cellulaire (RSC), occurs. The host rock of the two ore bodies is formed by dolomitic shales, siltstones and stromatolitic dolomites (Cailteux et al., 2005). The latter shales and siltstones contain lenticular layers and nodules of pseudomorphs after anhydrite and very early diagenetic pyrite (Cailteux et al., 2005). The RSC is interpreted to originally represent massive stromatolitic dolomites with some interbedded dolomitic siltstone, and thus biogenic carbonates. Figure 1. Location of the Central African Copperbelt and of the most important ore deposits (after Cailteux et al. 2005).Numer