TIMING OF VARISCAN MIDCRUSTAL SHEARING AND BATHOLITH INTRUSION IN THECENTRAL PYRENEES (ARIEGE, FRANCE)

A gneiss body in the Variscan Aston massif is overlain by Cambro-Ordov ician metasediments that have been intruded by a granite batholith. At the gneiss-cover contact a 1.2 km-thick zone of highly strained mediu m-grade metasediments occurs. The batholith is surrounded by a zone wh ere metasediments are strained and metamorphosed due to intrusion of t he pluton. This contact aureole overprints the shear zone at the gneis s-cover contact, showing deformation and retrogression of the medium-g rade metasediments. This relationship reveals a younger age for bathol ith intrusion with respect to the formation of the shear zone at the g neiss-cover contact. This observation together with regional correlati on indicates that formation of the shear zone occurred between 292 and 280 Ma ago.