ORIGINAL FINDINGS ON THE ORE-BEARING FACIES OF VOLCANOGENIC MASSIVE SULPHIDE DEPOSITS IN THE EASTERN BLACK SEA REGION (NE TURKEY)

In the massive sulphide deposits of the eastern Black Sea region, there are ore facies and ore-bearing sedimentary facies. The former are subdivided into hydrothermal-metasomatic, seafloor hydrothermal, and biological facies. Hydrothermal-metasomatic facies refer to sub-seafloor processes and include network-disseminated, massive vein, and massive lens facies. The precipitation of sulphide minerals within pre-existing volcano-sedimentary rocks occurs largely beneath the seafloor, and these ores form an important component of some deposits. The term seafloor hydrothermal facies refers to sulphide accumulation on the seafloor and is characterised by hydrothermal chimneys and clastic sulphide ores. Clastic sulphide ores can be subdivided into proximal and distal facies. Ore-bearing sedimentary facies are characterised by relatively thin ferruginous chert (exhalite?) beds that occur along the uppermost part of the ore horizon. The biological facies is represented by fossil vent fauna, which are diagnostic for seafloor sulphide formation. The VMS ores of the eastern Black Sea region have well-preserved facies characteristics, especially in terms of texture and components. Some massive sulphide deposits accumulated via molasse/mass flow on the seafloor, whereas others formed via sub-seafloor replacement processes. Clastic sulphide textures and some sedimentary structures indicate that these deposits formed in a highly active setting. Clastic sulphide textures, sulphide chimney fragments, ferruginous cherts and fossil vent fauna (tube worms) recognised in the Pontide deposits are diagnostic and support the seafloor origin of VMS deposits.