Geological, geochemical and geochronological characteristics of the Buyuk Hill bimodal-mafic type volcanogenic massive sulfide deposit (Central Pontides, Turkiye): Implications for an island arc tectonic setting

The Pontides are located to the north of the Anatolian segment of the Alpine-Himalayan orogeny. The Central Pontides are distinguished from the Western and Eastern Pontides with a large turbiditic fan in the north, and an area composed of thrust-accretion complex which is defined as Central Pontide Structural Complex (CPSC) hosting volcanogenic massive sulfide (VMS) deposits in the south. VMS deposits discovered in the CPSC recently have been classified into three types: Mafic-type, mafic-siliciclastic type and bimodal-mafic type. The Buyuk Hill deposit is a Cu-Zn-dominated VMS with a well-developed gossan zone, and has ores showing semi-massive to massive textures constituting of clastic sulfide minerals. The ore mineral paragenesis is predominantly composed of pyrite, chalcopyrite and lesser amounts of sphalerite and magnetite. The volcanic units in a wide region comprise of dacite (69 -73.3 SiO2 wt%) hosting the mineralization, and basaltic andesite, both of which have undergone metamorphism at greenschist facies conditions. The zircon U-Pb geochronology of the dacite (Th/U: 0.2 - 0.6; U/Yb: 0.1- 0.2) indicates presence of an oceanic island arc during the Early Jurassic (182 & PLUSMN; 8 Ma). The structure-texture and geochemical data of the Buyuk Hill deposit, together with the petrogenetic properties of the wall-rocks, imply that the mineralization is a bimodal-mafic type VMS. Correlation of the Buyuk Hill deposit with other VMS deposits discovered in the Central Pontides suggest temporal and spatial association within an Early Jurassic arc-back arc rift system developed over the same oceanic crust.