Mineral chemistry of sulphide minerals in concentrates of the Kassandra mines (Chalkidiki, Greece)

The Kassandra mining district contains porphyry Au-Cu and Au-Ag-Pb-Zn-Cu carbonate replacement deposits that are associated with Oligocene-Miocene intrusions emplaced into polydeformed metamorphic basement rocks belonging to the Permo-Carboniferous to Late Jurassic Kerdilion unit and the Ordovician-Silurian Vertiskos unit. Regional extensional tectonics active since the middle Eocene resulted in the development of widespread normal and transtensional faults, including the Stratoni fault zone that hosts carbonate replacement sulfide ore bodies (Siron et al., 2018). More particularly, Stratoni (Madem Lakkos, Mavres Petres) and Olympias are the two main carbonate-replacement massive sulphide Pb-Zn (Ag-Au) deposits of the district; they are located on the footwall of the Tertiary Stratoni-Varvara fault. Both deposits are interpreted to form the proximal and distal part of a fault-controlled exoskarn-type ore system triggered by nearby small-scale intrusions close to the fault system (Hahn et al., 2012). The mineral chemistry of basic sulfide minerals (major phases) into concentrates from the flotation plants of Stratoni and Olympias mines was investigated by EPMA using a JEOL 8200 SEM equipped with WDS. The chemical formulae of the minerals in their relevant concentrates were calculated as following: Galena (Stratoni Mine): Pb0.975-0.990Zn0.000-0.004Mn0.000-0.002As0.000-0.001S Sphalerite (Stratoni Mine): Zn0.788-0.845Fe0.118-0.167Mn0.006-0.010Pb0.000-0.001S Pyrite (Olympias Mine): Fe1.019-1.051As0.000-0.033Pb0.000-0.001Zn0.000-0.001S2 Arsenopyrite (Olympias Mine): FeAs0.848-0.878S1.065-1.131 In addition, the presence of boulangerite was detected in the pyrite/arsenopyrite concentrate, with microprobe analyses revealing the following chemical formula: Pb5.182-5.253Sb4.214-4.449As0.058-0.154Fe0.040-0.154Zn0.000-0.063Mn0.010-0.020S11 All sulphide minerals studied were found having typical/expected chemical compositions in major elements. Ongoing research on these samples is also targeting the determination of their trace element concentrations, focusing on noble metals (Godelitsas et al., 2015; Kasama et al., 2018) and elements considered as Critical Raw Materials (CRM) for the EU. Aknowledgments. This research is implemented through IKY scholarships programme and co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the action entitled ”Reinforcement of Postdoctoral Researchers”, in the framework of the Operational Programme ”Human Resources Development Program, Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) 2014 – 2020.