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 (easter n Peloponnesus) tectonic windows shows two distinct styles of evolutio n. The metamorphism in the Taygetos window shows at least two conventi onal clockwise P-T-t evolutionary paths characteristic of collision of subduction settings. Metamorphism in the Parnon window, however, is c haracterized by a counter-clockwise P-T-t evolution followed by a late r clockwise P-T-t path. The early evolution in the Parnon window impli es that extension (lithospheric thinning) induced deep local shearing and local thickening of the Phyllite Series prior to collision. We pro pose that this extension was related to a major low-angle normal fault that appeared below the Ionian basin and the Tripolitza platform. Thi s hypothesis implies a late Eocene or older age for the beginning of t he metamorphism that affected the precursors of the Phyllite Series. I t also implies that the closure of Tethys at this time was controlled by a complex system of converging as well as diverging boundaries. Dur ing collision, the Phyllite Series of Parnon began retrograde metamorp hic evolution moving westward, while those of Taygetos underwent a pro grade one below the structural pile of the Tripolitz and Pindos units.