New Detrital Zircon Geochronology From the Cycladic Basement (Greece): Implications for the Paleozoic Accretion of Peri‐Gondwanan Terranes to Laurussia

Abstract

AbstractBetween the eastern Mediterranean basin in the South and the East European (Baltica) Craton to the north, we distinguish two fundamental pre‐Variscan geological domains: an Internal domain, which hosts Ordovician‐Devonian (450–400 Ma) igneous rocks and detrital zircon populations, and an External domain, which contains no 450‐ to 400‐Ma zircon ages. From the Balkan Peninsula to the Turkish plate, the aforementioned Internal domain includes the Serbo‐Macedonian Massif, the Istanbul and Sakarya terranes, whereas the External domain, holding a more distal position relative to Baltica, includes the Pelagonian terrane and the External Hellenides. The two domains are interpreted as two consecutive (i.e., Caledonian and Variscan) Paleozoic accretionary belts, attached to the southern margin of Baltica. The Cycladic and Pelagonian terranes are currently juxtaposed along strike of the central Hellenides in Northern Greece. The Cycladic Massif is a Cadomian‐type terrane, while the Pelagonian displays an Avalonian‐type affinity. Despite its Avalonian affinity, the Pelagonian lacks Ordovician‐Devonian (450–400‐Ma) zircon ages. In contrast, detrital zircon grains of such ages are abundant in the Cycladic Massif. In this study, the Ordovician‐Devonian detrital zircon population is recognized also in pre‐Variscan (>310‐Ma) Cycladic Basement from Ios and Naxos Islands, affiliating the Cycladic Massif with the Internal (Caledonian) domain. This indicates that the Caledonian accretion incorporated some Cadomian‐type terranes. It also suggests that the protolith of the Cycladic blueschists was deposited within the Internal domain, that is, northeast of the Pelagonian terrane. This recognition helps to reconstruct the Paleozoic and Mesozoic paleogeography of the peri‐Gondwanan terranes.