The North Cycladic Detachment System |
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| Authors: | Laurent Jolivet Emmanuel Lecomte Benjamin Huet Yoann Denèle Olivier Lacombe Loïc Labrousse Laetitia Le Pourhiet Caroline Mehl |
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| Institution: | 1. Institut für Mineralogie, Westfälische-Wilhelms Universität Münster, Corrensstr. 24, 48149 Münster, Germany;2. A.P. Karpinsky Russian Geological Research Institute (VSEGEI), Centre of Isotopic Research, Sredny Prospect 74, 199106 St. Petersburg, Russia;1. Dipartimento di Scienze Mineralogiche e Petrologiche, Università di Torino, Via Valperga Caluso 35, 10125 Torino, Italy;2. IPGS-EOST, Université de Strasbourg, CNRS UMR 7516; 1 rue Blessig, F-67084 Strasbourg, France;3. Department of Geosciences and Environmental Sciences, Université de Cergy-Pontoise, France;4. Accademia delle Scienze di Torino, Via Maria Vittoria 3, 10123 Torino, Italy;5. Institut de Minéralogie et Physique des milieu Condensés (IMPMC) 4, Place Jussieu, 75005 Paris, France;1. Bogazici University, Kandilli Observatory and Earthquake Research Institute, Geodesy Department, 34680 Cengelkoy, Istanbul, Turkey;2. Ankara University, Geophysics Department, 06830 Golba??, Ankara, Turkey;3. Istanbul Technical University, Faculty of Mines, Department of Geological Engineering, Ayazaga, Istanbul 34426, Turkey |
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| Abstract: | Low-angle normal faults accommodate a large part of continental post-orogenic extension. Besides the intrinsic rheological characteristics of the continental crust that may lead to the formation of shallow-dipping shear zones at the brittle–ductile transition, the role of pre-existing low-angle structures such as large thrusts has been proposed by several authors. We explore this question with the example of the North Cycladic Detachment System (NCDS) that is composed of a series of distinct detachments cropping out on the islands of Andros, Tinos and Mykonos, separating the Cycladic Blueschists in the footwall from the Upper Cycladic Nappe in the hanging wall. We show that these extensional structures are part of a single large-scale structure (more than 200 km along strike) that reactivates the Vardar suture zone. It extends eastward on Ikaria and westward offshore Evia and Thessalia where it probably connects to recent shallow-dipping normal faults evidenced on published seismic reflection profiles. The NCDS started its activity in the Oligocene concommitantly with the Aegean extension, and was still active in the Late Miocene. It has exhumed a series of metamorphic domes from southern Evia to Mykonos below low-angle detachment systems, made of low-angle normal faults and low-angle ductile shear zones. The ductile shear zones and the faults were created with a low dip and they kept the same attitude throughout their exhumation. We identify three main detachments that are part of a continuum of extension on the NCDS : Tinos detachment, Livada detachment and Mykonos detachment. A fourth detachment (Vari detachment) is the reactivation of an Eocene exhumation-related structure. Deformation in the footwall is characterized by intense stretching and flattening. Using the spatial evolution observed along strike from Andros to Mykonos we construct a history of formation of the NCDS starting with the reactivation of former thrusts leading to the exhumation of high-temperature metamorphic domes. The Aegean example shows that reactivation of earlier shallow-dipping discontinuities can play a fundamental role in continental post-orogenic extension. |
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