Hercynian high temperature granulites and migmatites from the Catena Costiera, northern Calabria, southern Italy

ABSTRACT. — The deepest portion of a Hercynian lithospheric section is exposed in the northern sector of the Catena Costiera, Calabrian- Peloritan Arc. The section consists of migmatites and granulites derived from pelitic-arenaceous sequences, of small volumes of granitoid rocks, of Spl-harzburgites and pyroxenites intruded by metagabbros. The Hercynian P-T evolution of the migmatites and granulites follows a clockwise trajectory. The prograde path, in the stability field of sillimanite, reaches the metamorphic peak condition at 750-800°C and 0.9-1.0 GPa. The retrograde path is characterized by a decompression up to 0.5 GPa and 600°C through two intermediate steps at 0.8 Gpa and about 800°C, and 0.6-0.7 Gpa at 650-700°C, respectively accompanied by a general retrogression under lower amphibolite facies and successively under lower greenschist facies conditions. The exhumation of deepest portion of the Hercynian lithospheric section to middle crustal levels took place along HT extensional shear zones. The following stages of exhumation under amphibolitic and greenschist facies conditions were accommodated by LT shear zones, at the ductilebrittle transition. The crustal sequence of the Catena Costiera is crosscut by unmetamorphosed basaltic dyke dated at 120 ± 1.3 Ma. Therefore, the Alpine orogenesis did not overprint the Hercynian lithospheric section of the Catena Costiera, except for the brittle deformation event.