Estimating P-T conditions of Alpine-type metamorphism using multistage garnet in the tectonic windows of the Cardeto area (southern Aspromonte Massif, Calabria)

Near the village of Cardeto, in the southern sector of the Aspromonte Massif (southern Calabria, Italy), a greenschist to low amphibolite facies metamorphic complex outcrops in two main tectonic windows beneath the Aspromonte Unit. Petrological and structural similarities from both windows allow them to be grouped into a single metamorphic complex defined here as 'Cardeto Metamorphic Complex' (CMC). The CMC is made up essentially of metapelitic-metapsammitic rocks containing intercalations of marbles and (garnet) amphibolitic-schist lenses, mylonitic strain becoming more intense towards the north. Two stages of metamorphism are recognised: The early stage is sporadically preserved in the form of relics of mineralogical assemblages inside cores of garnet porphyroblasts. P-T conditions are ca. 0.6 GPa and 550 °C. The latter stage of metamorphism is related to the shear deformational episode which produced the widespread mylonitic foliation observed in the CMC rocks. The peak metamorphic conditions of this syn-mylonitic stage are in the range 0.6-0.9 GPa and 550-600 °C. Estimates of PT conditions of metamorphism using compositional isopleths of garnet in phase diagrams in the simplified MnNCKFMASH system allow to constrain the possible PT path. The absence of pre-Alpine mineralogical and structural relics casts doubt on correlation with other Palaeozoic metamorphic units outcropping in the Peloritani Mountains (Sicily) (e.g., Mandanici Unit), due to the same structural position and petrographical features. Rather, a correlation with the Alpine Madonna di Polsi Unit, outcropping in the central sector of the Aspromonte Massif, is plausible.