A new magmatic crystallization age constraint for the Petrota gabbroic complex from the Jurassic Evros ophiolite, eastern Circum-Rhodope Belt, NE Greece

Abstract

The Circum-Rhodope Belt is a major tectonic unit that frames both the Rhodope and the Serbo-Macedonian zones of the Alpine orogen in the northern Aegean region. In the eastern part of the Circum-Rhodope Belt, the supra-subduction zone Evros ophiolite is an important crustal component that spans 176 Ma to 169 Ma magmatic activity, which cooled down to 550 °C around 164 Ma according to published radiometric dating. This incomplete ophiolite contains in its upper crustal section gabbroic complexes, to- gether with massive and pillow lavas and dykes. In this contribution, in one of these gabbroic complexes, namely the Petrota gabbroic complex, a cross-cutting basalt dyke was dated to refine the timing of the gabbro crystallization and the temporal spread of the magmatic evolution for the whole complex. The basalt dyke yielded magmatic crystallization age at 164.5±0.93 Ma as derived from U-Pb zircon geochronology. This new crystallization age confirms the previous age for the Petrota gabbro crystallization at 169±2 Ma, but extends the span of the magmatic evolution within 7–8 Myr-lasting time interval (including the analytical errors) for the complex. The latter time interval is comparable in span to the magmatic evolution of another Evros ophi- olite gabbro occurrence at the town of Didymotycho in northeastern Greece.