Triponzo: a thermal system in a cold area of the Apennines (Italy)

Abstract

Bagni di Triponzo thermal springs, characterised by a Ca-SO4 composition and temperatures up to 30°C, are located in the eastern sector of Umbria region in the Umbria-Marche Apennine (central Italy). The region is characterised by a low geothermal gradient and low conductive heat flux and the composition of Triponzo thermal waters significantly differs with respect to the cold waters circulating in the surrounding areas. The origin of the heat transported by the waters of the Triponzo springs is mainly due to a deep component, characterised by high CO2 and He contents, coming from a deeper reservoir, rising along normal faults and mixing with infiltrating waters of meteoric origin. The total amount of thermal water discharged by the system is about 34 L s-1. According to the ternary SO4-2-F--HCO3- geoindicator for carbonate-evaporite reservoirs, the fluids at reservoir condition are charcterised by a partial pressure of CO2 about 0.5 bar and a temperature between 70-75°C whereas the Silica geothermometers give a temperature about 62°C. The computed thermal energy transported by advection and discharged at the surface by Triponzo springs is about 3.71×1011 ± 0.56×1011 J/day.