Detrital zircon study of Triassic metasediments from the Cycladic Islands (Cyclades, Greece): Insights into the transition from Paleotethyan subduction to Neotethyan rifting.

During the late Paleozoic late Triassic, a significant change in the paleogeographic configuration and geodynamic evolution occurred in the Eastern Mediterranean, related to the closure of the Paleo-Tethys and the opening of the Neotethys oceans. Subduction and rifting were responsible for the development of different depositional paleo-environments that correspond to fore-arc, volcanic-arc, back-arc, and eventually rift-related basins. All these basins received eroded material from basement rocks that have been involved in different orogenic cycles, preserving the records of pre-Alpine imprints. During the Cenozoic, these basins were subducted and subsequently exhumed in the Aegean domain forming metamorphic core complexes (including the Cycladic core complexes) obscuring the original configuration and making plate reconstructions hard to unravel. Therefore, understanding the depositional environments depends significantly on describing the provenance areas of the siliciclastic metasediments observed in the Aegean domain and record the Triassic rifting. In this study, we present new detrital zircon (DZ) U-Pb analyses from the Cycladic Blueschist Unit (CBU) on the Iraklia and Amorgos islands part of the Cycladic core complexes. Triassic metasedimentary rocks from these islands coupled with published DZ ages obtained from the neighboring areas of the Attic-Cycladic complex suggest that the clastic sequences between the CBU and Amorgos Unit have a distinct paleogeographic origin. Maximum Depositional Ages constraints and provenance data suggest different paleotectonic positions in isolated back-arc basins, receiving clastic material from the exhumed rocks of Gondwanan, peri-Gondwanan, and Variscan affinities with the contribution of the Triassic magmatism during the transition from Paleotethyan fore-arc basins to the Neotethyan rifting. This study demonstrates the importance of DZ analyses in these distractive tectonic settings to elucidate the transition from the Paleotethys to Neotethys and the current configuration.