GSA Connects 2021 in Portland, Oregon

Paper No. 7-4
Presentation Time: 8:50 AM


ROCHE, Vincent, Institut des Sciences de la Terre de Paris, UMR 7193 CNRS-UPMC, Sorbonne Université, Paris, 75005, France, JOLIVET, Laurent, Institut des Sciences de la Terre de Paris, UMR 7193 CNRS-UPMC, Sorbonne Université, 4 place Jussieu, Paris, 75005, France, GRASEMANN, Bernhard, Institute of Geology, Univ of Vienna, Althanstrasse 14, Vienna, A-1090, Austria, PAPANIKOLAOU, Dimitrios, Department of Geology and Geoenvironment, National & Kapodistrian University of Athens, Zografou 15784, Athens, Greece and BOZKURT, Erdin, Center for Global Tectonics & State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, 388 Lumo Road, Hongshan District, Wuhan, 430074, China; Department of Geological Engineering, Middle East Technical University, Ankara, TR–06531, Turkey

Slab dynamics in the Eastern Mediterranean realm is the main control on tectonic and magmatic evolution through time. Although there is an agreement on the localization of a major transfer zone accommodating differential retreat in back-arc region below the Aegean Sea, there is no consensus about the time-space evolution, the deformation and thermal consequences of such dynamics in the overriding plate of the subduction zone. Here, we present a global vision of the area, investigating the correlation with the Aegean and western Anatolian, focusing mainly on the poorly studied Dodecanese islands and on the Menderes Massif. Results show that post-orogenic extension in the overriding plate around the slab tear keeps a constant NNE-SSW direction accommodating the difference in finite rates of extension. Deformation is mainly accommodated by crustal-scale low-angle normal faults since the Oligo-Miocene. Extension in the northern Cyclades, Dodecanese and Menderes Massif records top-to-NNE shear sense whereas the southern regions show top-to-SSW kinematics, suggesting that back-arc extension in the whole Eastern Mediterranean realm is bivergent. Extension induced by slab dynamics is also often associated with high-temperature low-pressure metamorphic events. In that sense, geochronological investigations reveal the formation of a large Miocene thermal pulse contemporaneous with the exhumation of the Menderes MCC and other MCCs in Cyclades. In addition, despite the complexity involved in the Aegean-Anatolian orogenic wedge, we demonstrate the existence of a similar regional tectono-metamorphic evolution before post-orogenic extension through the entire region. From top to bottom, we found that several nappes have recorded different high-pressure and low-temperature conditions. We recognized (i) the Lycian Nappes, which were exhumed earlier in the Late Cretaceous, (ii) the Upper Cycladic Blueschist Nappe characterized by eclogite parageneses and finally (iii) the colder units such as Amorgos unit, the cover of the Menderes Massif and the Lower Cycladic Blueschist Nappe (e.g. Folegandros, a part of the Dodecanese and Fourni islands). Nonetheless, a major difference is the presence of the Eocene Barrovian-type metamorphism in the Menderes Massif that partly obliterated the high-pressure parageneses, implying a larger amount of basement units in the Menderes Massif compared to the Cyclades. To sum-up, the Eastern Mediterranean realm is an ideal natural laboratory to study subduction dynamics since the last 60 Ma.