Slab fragmentation beneath the Aegean/Anatolia transition zone: Insights from the tectonic and metamorphic evolution of the Eastern Aegean region

摘要

Slab tearing below western Turkey had first-order tectonic and magmatic consequences by inducing a lateral gradient of extension in the upper plate and toroidal flow of asthenosphere that affected the typology and distribution of melts at the surface. But the coupling mechanisms between the 3D mantle flow at depth and deformation in the upper plate above a slab tear have received little attention so far. This paper is focused on the description of the distribution and kinematics of deformation in the eastern part of the Aegean Sea, within the transition zone between the Cyclades and the Menderes Massif, which have been little studied. By investigating the Dodecanese and Eastern Aegean islands, we thus complete the description of the extensional strain field in the overriding plate around the slab tear. There, extension related to slab retreat and tearing keeps a constant NNE-SSW direction accommodating the difference in finite rates of extension, without localized crustal-scale strike-slip faults and block rotations above the tear. In addition, despite the complexity involved in the Aegean Anatolian orogenic wedge, a similar structural position is recognized through the entire region. From top to bottom, we found that (i) the Lycian units which were exhumed earlier, in the Late Cretaceous, (ii) the higher pressure and higher-temperature units (i.e. the Upper Cycladic Blueschist Nappe), with exception of the Vourliotes nappe in Samos, and finally (iii) the colder units such as Amorgos unit, the Menderes and its cover before the Main Menderes Metamorphism overprint and the Lower Cycladic Blueschist Nappe (e.g. Milos, Folegandros, a part of the Dodecanese and Fourni islands).