XLIII, No 1 – 368 PATTERNS OF DUCTILE DEFORMATION IN ATTICO-CYCLADIC MASSIF Spanos D., Koukouvelas I., Kokkalas S. and Xypolias P. University of Patras, Department of Geology, Laboratory of Structural Geology, 26500 Patras, Greece, spanos@upatras.gr Abstract The area of Lavrion constitutes the westernmost part of the Attico-Cycladic massif where the al- lochthonous Cycladic Greenschist-Blueschist unit overthrusts the para-authochthonous Basal unit. The tectonic contact of these units forms a crustal scale thrust zone which is the continuation of the Evia thrust. Our research was focused on quartz-rich schists of the overlying allochthonous unit. Combination of microstructural, finite strain data and quartz and calcite c-axis fabrics analysis was used to characterize the kinematics of rock flow within the thrust zone. The latter was formed under conditions of progressive exhumation and decompression of the high-pressure schists of the Attico- Cycladic massif. A dominant top-to-the-ENE sense of shearing along the thrust zone is inferred by several shear sense criteria. The analysis of several specimens collected from various structural depths manifest that the deformation close to the thrust zone occurred under approximately plane strain conditions and was characterized by an Rxz strain ratio which fluctuates between 3 and 6.5. Key words: finite strain, quartz c-axis fabrics, calcite c-axis fabrics, exhumation, Attico-Cycladic massif, Lavrion. 1. Introduction Over the last decades, there is a strong debate in the Attico-Cycladic massif (ACM) about the di- rection of nappes movement that led to the upsurge of the HP/LT rocks from deeper floors of the crust as well as about the prevalent exhumation mechanism. Although numerous studies were done in Evia and the islands of Cyclades, the region of Attica didn’t receive similar attention. In the southern part of Attica (Lavrion area) we implemented a combined analysis consisting of cal- cite and quartz c-axis fabrics and the evaluation of finite strain data in order to examine the kine- matics of rock flow in a crustal scale ductile shear zone. Crystallographic preferred orientation (CPO) of minerals constitutes a widely used criterion for evaluating shear sense in ductile thrust zones (Law, 1990). Identification of kinematic indicators can confirm the results of petrofabric analysis or imply individual deformation events. On the other hand, strain analysis can decipher the conditions that predominate within the deformed rocks of the area. Furthermore, we present first results of cal- cite c-axis analysis from three representative samples collected from strongly deformed marbles from the thrust zone. 2. Geological setting The area of Attica comprises the westernmost extension of the Attico-Cycladic Massif (ACM). The Δελτίο της Ελληνικής Γεωλογικής Εταιρίας, 2010 Bulletin of the Geological Society of Greece, 2010 Πρακτικά 12ου Διεθνούς Συνεδρίου Proceedings of the 12th International Congress Πάτρα, Μάιος 2010 Patras, May, 2010