The Pelagonian terrane in Greece is one of the easternmost Avalonian fragments, as attested by the peri-Amazonian affinity of its lowermost (>700 Ma) metasedimentary unit. In the present study, we obtained zircon ages and U-Pb-Hf data for consecutive rock units comprising the Pelagonian basement. These include newly discovered Ediacaran (ca. 600 Ma) orthogneisses and overstepping Late Ediacaran to earliest-Cambrian metasedimentary rocks. The former can be correlated to the Avalonian “main arc phase” the latter, deposited between 560 and 530 Ma, yield zircon ages mainly of 750–570 Ma, with Hf-TDM of 1.0–1.4 Ga. When the Pelagonian zircon record is combined with that of other Avalonian provinces, the following stages in the geological evolution of Avalonia are revealed: (1) Early Neoproterozoic siliciclastic deposition in a continental basin on the northwestern Amazonian margin, (2) Cryogenian (750–670 Ma) subduction magmatism on this continental margin, (3) rifting from Amazonia, accompanied by voluminous bimodal magmatism in the Ediacaran (peaking at 620–600 Ma), (4) drifting of an insular Avalonian microcontinent, (5) docking to NW Africa in the Early Cambrian (∼530 Ma), prior to Early Ordovician (ca. 480 Ma) rifting from Gondwana towards the region of Caledonian convergence (450–400 Ma). In the NE Mediterranean, Caledonian accretion to Baltica, or magmatism of a comparable age (ca. 450 Ma), is recorded in several peri-Gondwanan terranes, including those of Cadomian-type. However, no Caledonian imprint is recognized in syn- to post-Caledonian rocks of the Pelagonian terrane. This implies that the geological history of the Pelagonian terrane diverged from that of Avalonia since the Early Ordovician. The data from the NE Mediterranean suggest that, when the Avalonian-Cadomian continental ribbon rifted from Gondwana to open the Rheic Ocean in the Early Ordovician, some Avalonian vestiges, now preserved in southeastern Europe, remained attached to Gondwana.
Bibliographical noteFunding Information:
This research was supported by the Israel Science Foundation – Israel (ISF grant no. 426/11 to DA). We wish to thank Annie Rassios and Nikos Skarpelis for their kind help on various aspects of the Greek geology. We thank Omri Dvir, Ofir Tirosh and Linda Marko for their support during the analytical sessions. We thank Z. Garfunkel, S. Pisarevsky, D. van Hinsbergen and M. Domeier for helpful discussions. Reviews by Damian Nance and Andreas Gärtner helped to improve this manuscript and are gratefully acknowledged.
© 2017 Elsevier B.V.