Geothermal Characteristics of the Pisa Plain, Italy

Abstract

The Pisa plain IS mainly made up of neoautochthonous deposits that fill a wide graben striking NW-SE. The NE boundary of this graben is represented by the Pisan Mounts where thermal springs with temperature the range 20-40 are distributed along the contact between these reliefs and the alluvial deposits of the Pisa plain. Thermal springs with temperatures around 35 "C are also located the SW margin of the graben. Geochemical thermometers applied to Giuliano hydrothermal system, sited 5km north of Pisa at the foot of the Pisan Mounts, suggest a possible reservoir temperature of about 80 the reservoir being made up of the carbonate-evaporitic complex of the Tuscan Nappe, representing the main regional aquifer and the most important reservoir of the exploited Tuscan geothermal fields. Results obtained from analysis of the temperature data and characteristics of the water produced from wells in the Pisa plain indicate geothermal gradients as high as 60 Gravimetric data reveal the existance of a slightly bumpy structure of the denser substratum below the neoautochthonous of the Pisa plain, with local structural highs at depths of about Thermal gradient wells indicate a temperature of at the top of the denser substratum. Assuming the presence of a continuous carbonate regional aquifer, large volumes of thermal lluids the regional circulation could exist at depth.