Structural and cooling history of the Eastern Pelagonian metamorphic core complex (northern Greece)

Schenker, Filippo and Fellin, Maria Giuditta and Burg, Jean-Pierre (2010) Structural and cooling history of the Eastern Pelagonian metamorphic core complex (northern Greece). In: Abstract Volume, 8th Swiss Geoscience Meeting 8th Swiss Geoscience Meeting, Fribourg, Switzerland.

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Abstract

The Pelagonian Zone in continental Greece is the westernmost unit of the Internal Hellenides and is characterized by a structural and topographic high trending approximately NNW-SSE. We present mapping, petrographic, structural and thermochronologic data that are evidence of a metamorphic core complex in the eastern part of the Pelagonian. The area lies north and east of the Aliakmon River artificial lake (between the village of Servia in the west and the village of Kolindros in the east). The denuded metamorphic dome is about 20 x 15 km with the long axis striking NNW-SSE. The main lithologies (gneiss, marbles and amphibolites) show a shallow-dipping foliation whose bending defines the dome. On the foliation plane aligned micas and amphiboles, and elongated quartz and feldspar form a pervasive lineation that trends SW-NE. The systematic record of asymmetric structures in the XZ-plane of finite strain ellipsoid indicates two senses of shear: (i) a regional top-to-the-SW sense of shear (Direction: 243°±25; Plunge: 8°±15) characterized by a strain gradient from protomylonite to ultramylonite, and related to recumbent, isoclinal and occasional sheath folds; (ii) a top-to-the-E sense of shear (Direction: 88°±20; Plunge: 11°±16) found in narrow (20 to 100 m) low angle shear zones located on the eastern flank of subdomes. In the footwall of the top-to-the-E detachments, migmatitic orthogneisses and amphibolites vary from metatexite, with partial melting associated with folding, to diatexite. Leucosomes cut the main foliation. Thus, the metamorphic peak and the main fabric-forming event are coeval. Zircon fission-track ages of about 24 Ma on both sides of the top-to-the-E shear zones show that the ductile fabric is older than the late Oligocene. Fission-track data on apatites indicate cooling at <110°C during the early to middle Miocene. These cooling ages show that extensional tectonics in the Pelagonian were contemporaneous with the Aegean extension (Mykonos, Naxos, etc.).

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