Peri-Amazonian provenance of the Euxinic Craton components in Dobrogea and of the North Dobrogean Orogen components (Romania): A detrital zircon study

Abstract

The Romanian South Carpathians foreland is located southwards of the East European Craton (EEC) and consists of three major tectonic units: the Scythian Platform, the North Dobrogean Orogen and the Euxinic Craton. The Euxinic Craton is represented in the Dobrogea area by two components: (i) Central Dobrogean Shield and (ii) East Moesia. In central-northern Dobrogea, the Trans European Suture Zone (TESZ), including the Teisseyre–Tornquist Zone, presumably strikes below the surface. Because the paleogeographic provenance of the above tectonic units was poorly documented until present, a systematic sampling for detrital zircon has been conducted in all tectonic units except for the Scythian Platform basement which is entirely covered by the Danube Delta. In all, this totals 26 samples and around 1833 analyzed zircon grains. The distribution of zircon grains dates along the time scale for all the sampled terranes suggests that the sampled components of the Euxinic Craton in Dobrogea and the constitutive terranes of the North Dobrogean Orogen have a peri-Gondwanan, peri-Amazonian provenance. Their ages are Neoproterozoic or younger. In addition, the Euxinic Craton can be depicted as a paleo-Amazonian crustal fragment that was marginally affected by the Avalonian–Cadomian orogenic events. Along with its margin, the Avalonian type terranes accreted or Ganderian type terranes have evolved. Primary relationships between the Amazonian derived terranes and EEC are obscured due to an intricate geologic history exhibited by the North Dobrogean Orogen involving Caledonian, Variscan and Cimmerian orogenic events, while the geologic history of the Scythian Platform is also poorly established. The general distribution diagram of U–Pb detrital zircon ages shows some major zircon sources, shared with those detected at a global scale. They are episodic and coincident along with the time scale, such as those at the end of Archean or those from the Pan-African orogens. Finally, among these discussed tectonic components, only the Scythian Platform can possibly have an EEC provenance.