TSK 11 Göttingen 2006 Zámolyi et al.
 Late stage evolution of the
 Serifos Metamrophic Core
 Complex (Cyclades, Greece)
 Poster
 András Zámolyi1 Bernhard
 Grasemann1 Erich Draganits2
 Konstantin Petrakakis3 Christoph
 Iglseder1 Christian Rambousek1
 Ulrike Exner1 Klaus Voit1 Monika
 Müller1
 Introduction
 The island of Serifos is located in
 the Western Cyclades within the Attic-
 Cycladic metamorphic belt. It repre-
 sents the westward continuation of an
 arcuate belt of Metamorphic Core Com-
 plexes with intrusions of late syn-post
 tectonic intrusions younging from East
 (e.g. Naxos main activity ca. 12Ma)
 to West (e.g. Serifos with 9–8Ma). In
 scientific discussions the dominance of
 probably continuous extension since ca.
 30Ma (e.g. Jolivet & Faccenna, 2000)
 and the presence of Metamorphic Core
 Complexes (Lister et al. 1984) is ac-
 cepted. The speculated roll-back of
 the subducting plate possibly started
 due to the slowing down of absolute
 plate convergence rate between Africa
 and Eurasia. This model is attrac-
 tive, because it would also explain the
 shift from a compressional Andean-type
 regime to an extensional Mariana-type
 regime (Jolivet & Faccenna 2000). Con-
 trary to the kinematic directions re-
 ported from the Central and Eastern
 Cyclades, the movement of the hanging
 1 Department of Geodynamics and Sedimen-
 tology, Structural Processes Group, University
 of Vienna, Austria 2 Institute for Engineer-
 ing Geology, Vienna University of Technology,
 Austria 3 Department of Geodynamics and
 Sedimentology, University of Vienna, Austria
 wall of the Serifos Metamorphic Core
 Complex is south directed. The island’s
 main part is occupied by an undeformed
 granodiorite. Early granitic intrusions
 intruded into low-grade M2-crystalline
 rocks that have been overprinted to as
 high as amphibolite facies conditions
 due to contact metamorphism. Parts of
 these rocks (gneisses and amphibolites)
 as well as the early intrusions are de-
 formed to mylonites (Grasemann et al.
 2004).
 Structural observations
 A striking feature is found in the south-
 western part of the Serifos Metamorphic
 Core Complex, where a SW-dipping
 brittle surface cuts through the gneiss-
 marble lithology forming a prominent
 morphological fault scarp. During
 higher greenschist facies metamorphic
 deformation, the marbles acted as a
 weak layer between deforming areas of
 more rigid gneisses. They show a fine-
 grained homogenous recrystallized mi-
 crostructure with crystal-preferred ori-
 entation. Structures indicating high
 strain like sheath folds are recorded
 within the marble with south dipping
 fold axes. In contrast to the marble-
 ultramylonites, centimeter to meter
 scale gneiss lenses act as boudins within
 the marble-ultramylonite. Deforma-
 tion is characterized by overall exten-
 sion (chocolate-tablet boudinage) with
 stretching directions NW–SE and NE–
 SW, respectively. Carbonatic meta-
 conglomerate layers with oblate com-
 ponents and pressure solutions indicate
 a considerable amount of pure shear.
 The shear sense of the main ductile
 shear zone is top to the SSW, also
 indicated by SCC′ fabrics and sigma
 clasts. Subsequent brittle deforma-
 tion overprinted certain layers of the
 1
Zámolyi et al. TSK 11 Göttingen 2006
 marble-ultramylonite, forming a contin-
 uous, decimeter to meter thick marble
 layer immediately below the prominent
 morphologic brittle fault scarp, show-
 ing a mature stage of cataclastic rework-
 ing and high content of mica and sil-
 ica. We find two generations of catacla-
 sites: subvertical and low angle catacla-
 sites. The subvertical generation grades
 into decameter thick non-cohesive cat-
 aclasites. In the hanging wall of the
 brittle surface block rotations can be
 observed, whereas in the footwall horst
 and graben structures occur.
 Conclusion
 Two main phases can be recognized
 from the above mentioned:
 1. a phase of ductile to brittle-ductile
 deformation represented by the de-
 cameter thick interlayered marble-
 gneiss shear zone and
 2. a purely brittle phase represented
 by thick cataclasite horizons and an
 ankeritic dolomite surface forming
 the prominent morphological scarp.
 This shear zone likely represents the fi-
 nal stage in the evolution of the Serifos
 Metamorphic Core Complex and is an
 excellent outcrop rarely found on the is-
 lands of the Cyclades.
 Literatur
 Grasemann B, Petrakakis K, Iglseder C, Ram-
 bousek C, Zámolyi A & Draganits E (2004)
 The Serifos Metamorphic Core Complex
 (Western Cyclades, Greece). 5th Interna-
 tional Symposium on Eastern Mediterranean
 Geology, Thessaloniki, Greece, 14–20 April
 2004
 Jolivet L & Faccenna C (2000) Mediterranean
 extension and the Africa–Eurasia collision,
 Tectonics, 19-6, 1095–1106
 Lister GS, Banga G & Feenstra A (1984) Meta-
 morphic core complex of Cordilleran type in
 the Cyclades, Aegean Sea, Greece, Geology,
 12, 221–225
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