No abstract

Evidence for HP-LT Hercynian metamorphism within the 'Porphyroïdes' of South Brittany (France). The so-called 'Porphyroïdes' Unit of South Brittany is located below units marked by an early HP-LT event (blueschists from the Île de Groix) and above units marked by Upper Carboniferous HT metamorphism. P -T estimates in the Porphyroïdes (at Belle-Île-en-Mer), using the phengite-chlorite thermobarometer, indicate pressures around 8 kbar and temperatures of 350-400 • C. These new estimates suggest that the early tectonic history of the 'Porphyroïdes' should be linked to that of the overlying Blueschists, and imply a much larger areal extension of the HP-LT domain in this part of the Hercynian Belt.