The Zircon Isotope Dating of the Jurassic Basalts from the Ghoithsk Volcanic Area of the Western Greater Caucasus (Russia)

The paper presents the results of the U-Th-Pb isotope system study of the accessory zircon from the basalts of the Ghoithsk volcanic region (GVO) of the Western Caucasus. The sample for isotope dating was taken from basalt porphyrites of the Chataltapa volcanic complex, in the Tuapse River basin. It was shown by using of the ion microprobe isotope dating method of the zircon, that the effusion of basalts of the Chataltapa volcanic complex of the GVO occurred in the Jurassic at the boundary of the Aalenian and Bajocian age (169 Ma), during the tectonic transformation of the Greater Caucasus riftogenic basin. A low Th/U ratio was obtained for zircons from basalts, which is more typical for rocks of acidic composition. This fact indirectly confirms that the evolution of the Jurassic rift magmatism in the Caucasus occurred due to the assimilation of the continental type crust.