GEOCHEMICAL AND MINERALOGICAL RELATIONSHIPS BETWEEN MANGANESE SILICATE MINERALS AND ZINC ORE MINERALIZATION AT GÜRECE CONTACT AUREOLE (BIGA PENINSULA, NW-TURKEY)

In this study, we show the diversity of bimetasomatic skarn mineralisation and associated zinc ore formation. At Bakirlik Tepe hill we observed in a roof pendant contact metamorphosed units of the Cetmi Melange bordering the monzonitic Gurece Pluton of Eocene age. Additionally, two types of endoskarn were identified in this zone; diopside- bearing monzonite along the garnet skarn and hedenbergite-bearing monzogabbro along the pyroxene skarn contacts. The ratio of garnet skarn/pyroxene skarn is about 201. The presence of manganiferous minerals (johannsenite, Mn- garnet, Mn-chlorite4 in the pyroxene skarn provides evidence for sphalerite mineralization at temperatures less than 400°C, under high oxygen fugacity and in the presence of water-enriched fluids.