Petrography, 40Ar-39Ar geochronology, petrochemistry, Sr-Nd-Pb isotope geochemistry, and petrology of tertiary volcanic rocks between Trabzon and Giresun areas

Tertiary volcanic rocks between Trabzon and Giresun areas were investigated by using petrography, mineral chemistry, 40Ar-39Ar geochronology, whole-rock and Sr-Nd-Pb isotope geochemistry data. Mildly alkaline Eocene volcanic rocks (42.4-44.7 Ma) comprise of basalt, trachybasalt and basaltic trachyandesite (BTB) and trachyte, trachyandesite (TT) suites, and medium alkaline Miocene volcanic rocks (5.8-6.0 My) consist of basanite-tephrite (BT) suite. N-MORB normalized trace element distributions of the all suites are characterized by enrichment in LILEs, Th and Ce, and depletion in HFSEs, implying a subduction fingerprint. Chondrite normalized REE patterns of the rocks display slight enrichment with LaN/LuN=4.65-11.64 for the Eocene aged suites whereas high enrichment patterns with LaN/LuN=36.43-69.0 for the Miocene aged suites. (87Sr/86Sr)i, (143Nd/144Nd)i, ?7/4Pb and ?8/4Pb values are (0.703893-0.704479), (0.512680-0.512794), (10.68-14.69) and (52.53-63.30) in the Eocene suites whereas (0.705178-0.705362), (0.512666-0.512689), (11.81-13.53) and (46.94-52.53) values in the Miocene suites, respectively. The studied volcanic rocks have evolved a post-collisional extension geodynamic setting, and were differentiated via complex magmatic processes from parental magmas derived from spinel-garnet(?) bearing lithospheric mantle source which were enriched by subduction related fluids ± melts.