The "Montagne de Pormenaz" consists of the pre-Stephanian A Pormenaz porphyric monzonitic Ba-rich intrusion. The quartz-barite mineralized veins are hosted by the monzonite. These mineralized veins have been emplaced during Alpine sinistral transpression as extension fractures fillings, and have been controlled by Hercynian and Alpine structures. The microthermometric fluid inclusion study based on (1) quartz and barite crystal intergrowths from the mineralized veins, and (2) barren regional quartz veins shows that the mineralized veins correspond to a thermal anomaly with respect to the regional fluid. Homogenization temperatures indicate minimum temperatures of 200-250 °C during the ore formation process.