Granitoid stones from Calabria (Southern Italy): petrographic, geochemical and petrophysical characterization of ancient quarries of Roman Age

摘要

This paper reports the results of a petrographic, geochemical and petrophysical study of granitoid rocks from a Roman quarry close to the town of Parghelia (Calabria, southern Italy). Here, remnants of abandoned pillars and well preserved cuts testify that these materials were employed as building stones. The lithotypes cropping out in the Parghelia area consist of Late Variscan (~ 300 Ma) two-mica granitoids, occurring into two varieties: a dominant medium-coarse grained porphyritic granodiorite and a subordinate heterogranular granite. The granitoids from the quarry, for which we propose the term "Granito di Parghelia", exhibit a restricted compositional range and distinctive petrographic characteristics, such as the occurrence of K-feldspar megacrysts and white mica, that result useful for archaeometric purposes. Moreover, ultrasonic investigation showed that Granito di Parghelia is characterised by average velocity values of compressional waves ~ 4.0 km/s, widely ranging even at mesoscopic scale; this heterogenous mechanical behaviour is due to microfractures and megacrysts distribution in the rocks. The above textural and physical features may provide helpful constraints in studies concerning the provenance and diffusion of granitoid rocks employed in monuments of archaeological importance in southern Italy and may shed new light about the granite trade in the Mediterranean during the Roman age.