Discriminant petrological features between granitoids from historic quarries of the Guadarrama Range and Toledo Mountains for the study of the provenance of archaeological materials

Abstract

This study focuses on characterizing samples from 23 historic quarries near the Santa María de Abajo archaeological site in Carranque (Toledo). These quarries are located in the Sierra de Guadarrama and the Montes de Toledo batholith. Characterization is performed through petrographic and radiometric analyses to establish discriminant criteria and determine the possible origin of the granitic materials used in Carranque. The results indicate that granites from the Sierra de Guadarrama are mainly equigranular, composed of quartz, K-feldspar, plagioclase, and biotite, with low mineral alteration. In contrast, granites from the Montes de Toledo batholith are predominantly inequigranular and contain two micas (biotite and muscovite), along with quartz, K-feldspar, and plagioclase. Average radiometric values support these differences, allowing the establishment of a threshold value (27 CPS) between both groups and a difference in estimated uranium concentrations. This criterion, combined with the presence or absence of muscovite, serves as a potential discriminant for identifying the historic quarries associated with the site.