Structural and petrological investigations on a crustal-scale ductile shear zone in the Sila Piccola Massif: new geodynamic implications for the Castagna Unit (Northern Calabria, Southern Italy)

In the Alpine stacked-nappe edifice of the CalabrianPeloritani Orogen (CPO), the “Castagna Unit” (DUBOIS &GLANGEAUD, 1965) represents a pervasively mylonitizedhorizon consisting of medium-high grade metamorphic rocks(mostly paragneiss, augen gneiss, leucocratic orthogneiss andminor micaschist, marble and amphibolite gneiss), intruded bylate-Hercynian granitoid rocks. This unit, entirely cropping outin the northern CPO (both in the Sila Massif and CoastalChain), is located in the lower-intermediate position within theCalabride continental crust (OGNIBEN, 1973). An integratedstructural and petrological study has been performed in order toreconstruct the tectono-metamorphic history of this discussedportions of the Calabrian crystalline basement.This study, focused on the Sila Piccola area (Fig.1a),delineates an intricate poly-orogenic tectono-metamorphicevolution mainly related to the ductile deformative eventresponsible of the pervasive mylonitic fabric. Yielded resultsallowed to better elucidate the geological significance of theCastagna Unit within the complex geodynamic framework ofthe northern sector of the Calabria Peloritani Orogen.