The Cycladic Basement (CB) and the overlying Cycladic Blueschist Unit (CBU) are part of the Paleogene Cycladic subduction complex exposed in Miocene metamorphic core complexes in the distended back‐arc of the retreating Hellenic subduction zone of the southern Aegean. While the Cenozoic tectono‐metamorphic evolutions of the CB and the CBU have been the foci of numerous studies, this study presents new laser ablation inductively coupled plasma mass spectrometry bedrock and detrital zircon (DZ) U‐Pb ages that place robust constraints on the presubduction tectonic, magmatic, and paleogeographic evolution of the CB. Zircon U‐Pb ages of crystalline CB are ~306‐330 Ma, demonstrating local plutonism associated with regional voluminous, protracted Carboniferous magmatism related to Paleo‐Tethys subduction. The plutons intruded the CB metasedimentary host‐rock sequence, characterized by distinct Gondwanan DZ U‐Pb provenance, Neoproterozoic to early Paleozoic maximum depositional ages, and synmagmatic, contact metamorphic zircon rims (~300‐330 Ma). DZ U‐Pb dating revealed postmagmatic Permian metasedimentary rocks (~270‐295 Ma) that unconformably overlie the CB and have unimodal DZ spectra that indicate exhumation of the CB prior to Permian deposition within extensional basins, as well as mark the onset of CBU deposition prior to formation of the Pindos rift domain. These U‐Pb results clarify the late Paleozoic‐early Mesozoic evolution of the CB as a peri‐Gondwanan terrane composed of Neoproterozoic and early Paleozoic metasedimentary rocks, intruded by voluminous Carboniferous arc magmatism, and exhumed in the Permian, prior to Triassic rifting and CBU deposition. Additionally, these data provide a chronostratigraphic framework and illuminate subduction‐related juxtaposition within the CB metasedimentary sequence.

Sikinos and Ios Islands, located in the Southern Cyclades, represent part of a Cenozoic metamorphic core complex system that exposes subduction-related metamorphic rocks in the highly extended back-arc region of the Hellenic subduction zone. These exhumed HP-LT metamorphic units are composed of Mesozoic metasedimentary rocks of the Cycladic Blueschist Unit (CBU) and the Paleozoic Cycladic Basement (CB). The magmatic and stratigraphic evolution of these units, as well as the nature of the contact between the CBU and CB, have remained poorly understood. We used zircon U-Pb dating to determine crystallization ages of the CB on Sikinos and the maximum deposition ages and detrital provenance of the metasedimentary units to reconstruct the Mesozoic to early Cenozoic stratigraphic and tectonic evolution of the CBU on both islands. The results reveal that the CB in Sikinos is composed of Cambrian-Silurian metasedimentary rocks intruded by Carboniferous granites and is overlain by metasedimentary rocks of the CBU with depositional ages spanning from Permo-Triassic to Late Cretaceous. The provenance data from the CBU records a long-lived tectonic evolution from Paleo-Tethys subduction and rifting, to passive margin formation, and to subduction of the Neo-Tethyan Pindos basin. The continuous stratigraphic record and provenance evolution from the CB into the CBU imply a para-autochthonous relationship. On NE Sikinos and Ios, stratigraphic constraints suggest older-over-younger relationships along cryptic-thrusts, supporting premetamorphic or synmetamorphic structural repetition of the CBU by imbrication, likely during subduction underplating.

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Since the early Cenozoic, the closure of the Alpine Tethys in the Western Mediterranean has been accomplished by protracted subduction, followed by collision and orogenic collapse. The internal zones of the Betic Cordillera (southern Spain) and Rif (northern Morocco) experienced subduction metamorphism and subsequent exhumation due to the westward migration of the orogenic system. The detrital provenance of these meta-sedimentary units contains crucial insights into their pre-subduction stratigraphic arrangement, which is essential to constrain the pre-Cenozoic paleogeography and tectonic evolution of the Western Mediterranean. This study focuses on the Nevado-Filábride Complex (NFC) and the Eastern Alpujárride Complex in the Internal Betic Cordillera. New depth-profile zircon U-Pb LA-ICP-MS data from the NFC (N = 72) and Alpujárride (N = 21) and in situ apatite U-Pb data from a metabasite within the NFC allow us to establish the pre-subduction stratigraphy, sedimentary provenance, and paleotectonic configuration of the Iberian rifted margin during the Paleozoic–Early Mesozoic. Our dataset demonstrates that the NFC represents an intact Devonian to Early Jurassic stratigraphic sequence that records the evolution of the Western Mediterranean from the Variscan orogeny to rifting and opening of the Alpine Tethys. Detrital zircon U-Pb age modes of the NFC remain remarkably similar for over 200 Myr with only the differences being the progressive addition of new zircon modes related to depositional ages. Additionally, a comparison between the provenance record of the NFC and Alpujárride reveals notably similar zircon signatures of Carboniferous and Permian strata. This study reports the first data from the Triassic–Jurassic strata that record the opening of the Alpine Tethys. Additional evidence for rifting is present in the metabasites from the Veleta unit yielding in situ apatite U-Pb ages of 197 Ma, recording CAMP magmatism and Early Jurassic rifting in the Alpine Tethys. The data demonstrate a palinspastic connection between the NFC and the Alpujárride. Based on these extensive new provenance data, we propose a pre-subduction tectonic configuration in which the NFC and Alpujárride both represent adjacent attenuated continental fragments that are separated from the southern Iberian rifted margin by a narrow oceanic domain of the Alpine Tethys in the early Mesozoic.

Detailed mapping and structural observations on the Cycladic Blueschist Unit (CBU) on Iraklia Island integrated with detrital zircon (DZ) U-Pb ages elucidate the Mesozoic pre-subduction and the Cenozoic orogenic evolution. Iraklia tectonostratigraphy includes a heterogeneous Lower Schist Fm., juxtaposed against a Marble Fm. and an overlying Upper Schist Fm. The contact is an extensional ductile-to-brittle-ductile, top-to-N shear zone, kinematically associated with the Oligo-Miocene exhumation. The DZ spectra of the Lower Schist have Gondwanan/peri-Gondwanan provenance signatures and point to Late Triassic Maximum Depositional Ages (MDAs). A quartz-rich schist lens yielded Precambrian DZ ages exclusively and is interpreted as part of the pre-Variscan metasedimentary Cycladic Basement, equivalent to schists of the Ios Island core. The Upper Schist represents a distinctly different stratigraphic package with late Cretaceous MDAs and dominance of Late Paleozoic DZ ages, suggestive of a more internal Pelagonian source. The contrast in the DZ U-Pb record between Lower and Upper Schist likely reflects the difference between a Paleotethyan and Neotethyan geodynamic imprint. The Triassic DZ input from eroded volcanic material is related to the final Paleotethys closure and Pindos/CBU rift basin opening, while late Cretaceous metamorphic/magmatic zircons and ~48–56 Ma zircon rims constrain the onset of Neotethyan convergence and high-pressure subduction metamorphism.