Whole-rock highly siderophile element geochemistry of eocene aged basic volcanics in the Samsun area

In this study, highly siderophile element (HSE: Os, Ir, Ru, Rh, Pd, Pt, Re) geochemical characteristics of Middle Eocene aged basic volcanics outcropping in Samsun and surrounding areas have been determined, and petrological processes (partial melting, fractional crystallization, crustal assimilation), which are important in their genesis, were evoluated. Basic volcanics in the study area are investigated as three groups; Tekkeköy, Kulacadağ and Bafra areas. The studied Tekkeköy volcanics are composed of basaltic lava samples, the Kulacadağ volcanics are consist of tephritic sil samples, and the Bafra volcanics contain basaltic and tephritic lava/dyke samples. When the highly siderophile element abundances of the the studied basic volcanics were considered, total PGE contents (0.13 to 11.6 ppb) are generally low and 187Os /188Os isotope ratios range from 0.15 to 1.20. The chondrite normalised HSE patterns of the studied volcanics exhibite PPGE enrichment compared to IPGE. Besides, low total PGE and Cu/Zr ratios, and high Cu/Pd ratios of the volcanics suggest that they may have derived from sulfur saturated magmas. In addition to silicate fractionation, it can be suggested that sulphide fractionation is also effective in evolution of the studied volcanics. Integrated HSE and Os isotope systematics as well as AFC modelling of the studied volcanics suggest that fractional crystallization with lesser crustal assimilation are effective in the evolution of the parental magmas.