Provenance analysis of the granitic ashlars used in the construction of the Roman theatre in Emerita Augusta (Merida, Spain)

The aim of this work is to determine the provenance of the granitic rocks used in the Roman theatre in Emerita Augusta. In order to obtain a reliable provenance of these granitic materials, the sampling in the theatre was carried out to encompass the original granitic rocks present in it. Some ancient quarries, previously documented, were selected taking into account factors like proximity, mining marks, or ancient transport routes. Stone materials and rocks from quarries were analysed and compared. The mineralogical, textural, and geochemical properties of the rocks were obtained. Moreover, ultrasonic pulse velocity (UPV) and hardness rebound tester (HRT) in situ measurements were carried out on the surface of the building’s granite ashlars, yielding representative results for the whole structure, as well as in granitic rocks from documented quarry fronts nearby the city. This multi-technique approach could be considered appropriate and advisable for built heritage materials. The obtained results, specially petrographic characteristics and geochemical signature of the different samples from both monument and quarries, allowed identifying the possible provenance of the granites used in the construction of the Roman theatre showing the stone supply system near the ancient city.