TECTONO-METAMORPHIC EVOLUTION OF BLUESCHIST FORMATIONS IN THE PELOPONNESUS (PARNON AND TAYGETOS MASSIFS, GREECE) - A MODEL OF NAPPE STACKING DURING TERTIARY OROGENESIS

Metamorphism in the Taygetos (western Peloponnesus) and Parnon (eastern Peloponnesus) tectonic windows shows two distinct styles of evolution. The metamorphism in the Taygetos window shows at least two conventional clockwise P-T-t evolutionary paths characteristic of collision of subduction settings. Metamorphism in the Parnon window, however, is characterized by a counter-clockwise P-T-t evolution followed by a later clockwise P-T-t path. The early evolution in the Parnon window implies that extension (lithospheric thinning) induced deep local shearing and local thickening of the Phyllite Series prior to collision. We propose that this extension was related to a major low-angle normal fault that appeared below the Ionian basin and the Tripolitza platform. This hypothesis implies a late Eocene or older age for the beginning of the metamorphism that affected the precursors of the Phyllite Series. It also implies that the closure of Tethys at this time was controlled by a complex system of converging as well as diverging boundaries. During collision, the Phyllite Series of Parnon began retrograde metamorphic evolution moving westward, while those of Taygetos underwent a prograde one below the structural pile of the Tripolitz and Pindos units.