423 International Geology Review, Vol. 50, 2008, p. 423–441. DOI: 10.2747/0020-6814.50.5.423 Copyright © 2008 by Bellwether Publishing, Ltd. All rights reserved. 0020-6814/08/998/423-19 $25.00 Alpine Metamorphism in the Aspromonte Massif: Implications for a New Framework for the Southern Sector of the Calabria-Peloritani Orogen, Italy ANTONINO PEZZINO, GEROLAMO ANGÌ, EUGENIO FAZIO, 1 PATRIZIA FIANNACCA, ANTONINO LO GIUDICE, GAETANO ORTOLANO, ROSALDA PUNTURO, Dipartimento di Scienze Geologiche, Università degli Studi di Catania, Corso Italia 57, 95129 (Catania), Italy ROSOLINO CIRRINCIONE, AND ELOISA DE V UONO Dipartimento di Scienze della Terra, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy Abstract Structural, petrologic, and thermobarometric data presented in this paper contribute to our understanding of the tectono-metamorphic evolution of the lowest tectonic slices of the Aspromonte Massif (southern Calabria, Italy), which crop out in three main tectonic windows. Despite previously being considered different units, they exhibit the following similar features: the same tectonic evo- lution, analogous blasto-deformation relationships, and absence of Hercynian mineralogical assem- blage relics. Similar P-T paths indicate early HP-LT Meso-Alpine metamorphism (400–600° C at 0.95–1.35 GPa), evolving in the Oligocene–Miocene toward a subsequent retrograde shearing event ranging from 480° to 610°C and 0.50 to 0.95 GPa. The latest retrograde evolution is characterized by 350–480°C and 0.32–0.62 GPa. In this new tectonic framework, it is proposed to group the metapelite sequences defining the Madonna di Polsi Unit. Data presented herein suggest that the pre-Alpine geodynamic setting of southern Calabria was a thinned continental margin made up of Hercynian basement and Mesozoic terrigenous-carbonate sedimentary cover. This continental margin evolved during the early Meso-Alpine stage into a subduction zone beneath the European plate, followed by Neo-Alpine syn-convergent exhumation along a deep-seated mylonitic shear zone. These processes are responsible for the Alpine metamorphic overprint on the Hercynian terranes, as well as for Alpine metamorphism of their Mesozoic cover. Introduction and Historical Background THE CALABRIA-PELORITANI OROGEN (CPO; Fig. 1A) occupies a key position in the Alpine-Apennine oro- genic belt because it constitutes the widest crystal- line basement complex of the Apennine chain. The present framework of this orogenic segment (Fig. 1B) consists of an internal Alpine arcuate orogenic belt, characterized by a complex nappe-like struc- ture affected by brittle tectonics, within the western Mediterranean geodynamic puzzle. It is bounded at the northern and southern ends by transpressive fault alignments of the Sangineto and Taormina tectonic lines, respectively. The Pliocene rifted backarc of the Tyrrhenian Sea flanks the northwest boundary of the orogen, whereas the subduction zone of the Ionian plate borders the southeast margin. In this scenario, several questions are still debated concerning the geodynamics of the Calabria-Peloritani system that include the origin of the crystalline basement terranes, the processes leading to their thrusting and emplacement onto the Apennines, and their subsequent exhumation. Since the end of the 19th century, the aforementioned problems have interested many Earth scientists, whose pioneer mapping was based on autochthonis- tic theory (e.g., Cortese, 1896; De Lorenzo, 1904). Such studies resulted in a framework of Calabrian crystalline basement rocks showing an inverse order, compared to the “usual” sequence recognized in other crystalline terranes, thereby advancing the hypothesis of deep gravity processes, which gave rise to local overthrusts due to mega-refolding (De Lorenzo, 1904). For many years, except for a few analytical stud- ies at the beginning of the last century (e.g., Lugeon and Argand, 1906; Limanowsky, 1913), a nappe 1 Corresponding author; email: efazio@unict.it