Geochronology, geochemistry and isotope systematics of a mafic-intermediate dyke complex in the Istanbul Zone. New constraints on the evolution of the Black Sea in NW Turkey

Abstract

We report new U-Pb zircon ages, major and trace element data, mineral chemistry, and Sr-Nd isotopic analyses of the mafic-intermediate dykes and intrusions in the Istanbul Zone. Mafic dykes are represented by calc-alkaline to alkaline lamprophyre and diabase. Intermediate dykes and subvolcanics are andesitic to dacitic in composition and calc-alkaline in character, while intrusive rocks (stocks and small plutons) are granodioritic and dioritic in composition. New zircon U-Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) dating yielded ages from 72.49 +/- 0.79 (Upper Cretaceous-Campanian) to 65.44 +/- 0.93 Ma (Lower Paleocene-Danian) for the intermediate dykes, and 58.9 +/- 1.8 Ma (Upper Paleocene-Thanetian) for a small granodiorite stock. Sr-87/Sr-86(i) values of the mafic and intermediate dykes and small stocks span a range from 0.703508 to 0.706311, while their Nd-143/Nd-144(i) values vary from 0.512614 to 0.512812 and eNd((i)) values from 5.09 to 1.24. Nd-TDM model ages range between 0.46 and 0.77 Ga.