Tectonometamorphic evolution of blueschist-facies rocks in the Phyllite-Quartzite Unit of the External Hellenides (Mani, Greece)

Abstract

The Phyllite-Quartzite Unit of the southern Peloponnese (Mani, Greece) experienced HP-LT metamorphism as result of northeastwarddirected subduction of the Adriatic plate beneath the Eurasian plate during the Late Oligocene to Early Miocene. On the basis of macroand microstructures and quartz textures the Phyllite-Quartzite Unit experienced four deformation stages that have been linked with an already proposed age range from literature: D1-uniaxial stretching at about 29-24 Ma, D2-rotational shearing and folding at ca. Ma, D3-folding at ca. 19 Ma and D4-extension at 19-15 Ma. D2-related shear folds F2 and subsequent open folds F3 (D3) form a largescale fold interference pattern including relics of F1-constriction folds. Blueschist-facies micaschists contain chloritoid 1 porphyroblasts including an earliest foliation S1 which was overprinted by SSW directed shearing (D2). Blueschists show syngenetic chloritoid 1 and glaucophane, both rotated parallel to the dominant foliation S2 defined by mica and graphite. Fluid inclusion microthermometry was performed on concordant quartz layers (Qtz1) as well as discordant D4-related extensional quartz veins (Qtz2). Fluid data combined with rheological characteristics have been used to constrain conditions for deformation stages along a published P-T path representative for the southern Peloponnese. Fluid density isochores related to Qtz1 indicate density loss from peak conditions down to ca. 6 kbars along non-isochoric exhumation (isothermal decompression between 450-500°C) and deformation stages D1-D3. Conditions

Tectonic units of the Alpine collision zone between Eastern Alps and western Turkey

“…Non-to low-grade metamorphic carbonates of Triassic to Eocene age with Oligocene flysch are commonly referred to as the Tripolitza unit (e.g., Rahl et al, 2005), whilst HP/LT metamorphosed clastic rocks known as the Phyllite-Quartzite unit with Carboniferous to Triassic ages originally likely formed the stratigraphic underpinnings of the Tripolitza unit ( van Hinsbergen et al, 2005b). These overlie the metamorphics of the Ionian unit (Plattenkalk) and are known as Phyllite-Quartzite unit, exposed in the Mani Peninsula (Micheuz et al, 2015) and in Crete (Dornsiepen and Manutsoglu, 1994). Together, these occurrences form a South Aegean window that formed in the Miocene (Jolivet et al, 1996;van Hinsbergen et al, 2005b).…”