This study aims at precising the thermal history of the Guemassa massif and that of the Hajjar polymetallic deposit, by using a recently-developed method: the Raman Spectroscopy of Carbonaceous Material (e.g. Beyssac et al 2002; Lahfid et al 2010). The Guemassa massif belongs to the Moroccan Meseta domain and is mainly composed of Palaeozoic rocks folded during the Hercynian orogeny. This area underwent tectonic, metamorphic and hydrothermal events that explain the presence of several base metal deposits like Hajjar. The application of Raman Spectroscopy of Carbonaceous Material geothermometry (RSCM) has revealed new temperature peaks superior to 500°C that were unrevealed by other methods (fluid inclusion, chlorite thermometry). This new data set will allow a better understanding of the thermal history and of the mineralization processes in the Guemassa massif.