The Attic-Cycladic metamorphic-core complex province was formed during Miocene to recent regional back-arc extension in response to slab-rollback and gravitational collapse. The development of several metamorphic-core complexes along extensional low-angle detachment faults resulted in the exhumation of lower-plate rocks and the tectonic denudation of the upper plate that is only sparsely exposed throughout the Aegean Sea. One of these areas is in southern Syros where the tectonic configuration includes three tectonometamorphic units separated by two detachment faults. The lower-plate Cycladic Blueschist Unit underwent late Cretaceous-Eocene HP/LT metamorphism and subsequent greenschist-facies overprint during Oligo-Miocene times. The tectonically overlying greenschist-facies Upper Unit is a tectonic sliver between the Cycladic Blueschist Unit and the structurally highest unit, the Vari Unit, which is dominated by quartzofeldspathic gneisses that are affected by four distinct deformation events (D1-D4). The late Cretaceous upper greenschist-facies D1 episode is related to late Cretaceous-Eocene subduction while D2-D4 fabrics were formed in response to late Cenozoic extension and exhumation. Field relations and structural data suggest that the late Miocene brittle Vari Detachment juxtaposes both Vari Unit and Upper Unit against the Cycladic Blueschist Unit. Mylonitic rocks observed at the base of Vari Unit along the contact with Upper Unit and zircon and apatite (U-Th)/He thermochronometry corroborate this scenario with lower-plate Cycladic Blueschist Unit rocks recording rapid cooling at $\sim$. 8-10. Ma. In contrast, cooling ages from the Vari Unit cluster at $\sim$. 13-15. Ma, indicating rapid exhumation coeval with activity along the Livadi Detachment on the neighboring island of Tinos. These data document new evidence that Vari Unit was affected by a major middle Miocene phase of exhumation and an older semi-brittle episode, both unrelated to late Miocene detachment faulting, revealing that crustal extension occurred in multiple stages and in a protracted episodic fashion similar to other parts of the Cyclades. © 2012 Elsevier B.V.

The Aegean region of Greece hosts a series of crustal-scale extensional detachment systems that have accommodated the southward retreating Hellenic subduction zone. Extension has overprinted and dissected the Alpine nappe pile and locally exhumed Cordilleran-type metamorphic core complexes. On the island of Paros, a low-angle extensional detachment fault separates metamorphic footwall rocks from an unmetamorphosed sedimentary succession of the hanging wall. Basement orthogneisses were extensionally sheared in the footwall of the detachment until after 16. Ma (zircon U-Pb age of a slightly deformed granite), but pervasive ductile deformation had ceased by 7. Ma (zircon U-Pb age of an undeformed rhyolite dike that intrudes gneisses). Apatite and zircon (U-Th)/He ages from the gneisses confirm a period of cooling at rates >. 100. °C/Ma from 16 to 7. Ma. In the upper-plate, the basal sedimentary unit yields reset detrital apatite (U-Th)/He (DAHe) ages from 17 to 7. Ma and detrital zircon (U-Th)/He (DZHe) ages ranging from 270 to 18. Ma. DAHe ages from the stratigraphically higher fanglomerate units are reset to 10-7. Ma. The DZHe data have a primary thermal signature of 12-7. Ma, but preserve ages up to 113. Ma. The uppermost conglomerates exhibit completely reset DAHe ages of 15-9. Ma and reset DZHe ages from 10 to 8. Ma, with DZHe ages up to 104. Ma. Reset DAHe ages indicate late exposure of the footwall and constrain the depositional age of most sedimentary rocks on Paros to be from 14 to 7. Ma. Unreset DZHe ages preserve thermal signatures from the major Mesozoic-Tertiary tectonic events in the Aegean Region: [1] Cretaceous Pelagonian-type metamorphism; [2] Eocene peak HP metamorphism; and [3] Miocene Barrovian overprinting. Preservation of these signatures indicates long-term upper-plate recycling prior to syn-extensional deposition. The Paros supradetachment basin represents a classic inverted unroofing sequence deposited during progressive core complex exhumation in the Middle to Late Miocene. © 2012 Elsevier B.V.