Unit:
Department of Geology and GeoenvirommentLibrary of the School of Science
Dissertation committee:
Κωνσταντίνος Σούκης, Επ. Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Στυλιανός Λόζιος, Αν. Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Daniel Fritz Stockli, Professor, Jackson Scholl of Geosiences, Austin Texas, USA
Μαρία Τριανταφύλλου, Καθηγήτρια, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Παρασκευάς Ξυπολιάς, Καθηγητής, Τμήμα Γεωλογίας Πάτρα
Χαράλαμπος Κράνης, Αν. Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Εμμανουήλ Σκούρτσος, Επ. Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Original Title:
Tectonometamorphic evolution and exhumation of the metamorphic rocks of Amorgos Island. A study on the architecture and evolution of the Late Eocene-Oligocene Hellenic subduction zone
Translated title:
Tectonometamorphic evolution and exhumation of the metamorphic rocks of Amorgos Island A study on the architecture and evolution of the Late Eocene-Oligocene Hellenic subduction zone
Summary:
The Hellenides constitute an integral part of the Alpine mountain chain in the eastern Mediterranean. They were shaped during the Cretaceous to Tertiary Africa-Eurasia convergence-collision and subsequent overprinting by extensional tectonics forming the Aegean domain. Exhumed HP rocks have been affected by extensional processes, concealing their syn-orogenic history that is essential for understanding the regional configuration of the Attic-Cycladic during the subduction-related stage.
This dissertation concentrates on the southeastern Cyclades of the Aegean domain. Field-based observations and structural measurements combined with novel lab techniques are used to investigate the deformation and exhumation of the low-grade HP rocks of Amorgos Island. The new findings are further compared to the neighboring Iraklia island to understand better the exhumation mechanisms and the different tectonometamorphic records of the exhumed subduction-type rocks.
In Chapter II, a new lithostratigraphic configuration for the Amorgos Unit is presented, and a new paleogeographic position is proposed. Based on along-strike variations in the sedimentary facies, the Amorgos Unit is subdivided into three stratigraphic columns representative of the island's northeast, central and southwest parts, respectively. Furthermore, the structural evolution is briefly discussed, and a retro-wedge setting is proposed for the top-NW kinematics of the early syn-HP deformation. The detrital zircon U-Pb geochronology and zircon (U-Th)/He dating results are described in detail, providing fundamental knowledge for the provenance signatures and the timing of exhumation processes. Our results show that the Amorgos Unit was paleogeographically located at the southern Pelagonian margin and structurally above the CBU.
In Chapter III, we present new structural data and integrate our results with those of Chapter IΙ. A multi-stage deformation is described as evolving from a consistent syn-orogenic compressional phase during the Late Eocene-Oligocene to a post-orogenic extensional phase in the early-mid Miocene. An alternative tectonic model for the Amorgos structural evolution is proposed that includes a short-lived SE-directed subduction zone that was eventually developed at the retrowedge side of the late Eocene-Oligocene subduction zone. Based on our results, a composite double-verging orogen is proposed for the Late Eocene-Oligocene collisional phase. Detachment faulting has affected the Amorgos Unit by top-SE kinematics during the Early-mid Miocene extensional phase, associated with the Santorini Detachment System.
Chapter IV presents a structural analysis of the Iraklia Island CBU rocks combined with detrital zircon U-Pb geochronology. Based on the provenance signatures of the schists, the stratigraphy of Iraklia is reviewed and the record of distinct geodynamic environments is discussed. The structural evolution of Iraklia revealed the retrogression/decompression stage during exhumation. An intra-CBU shear zone with top- N kinematics is recorded associated with the Paros-Naxos Detachment System. Relics of the prograde path is preserved as blue amphibole inclusions in feldspars. Zircon rim U-Pb ages indicate an early Eocene subduction-related HP event, typical for the CBU rocks documented in the neighboring islands.
Main subject category:
Science
Keywords:
Amorgos unit, detrital zircon U-Pb, U-Th/Ηe thermochronology, retro-wedge, backthrusting
Number of references:
300
