Deep structure, age and evolution of the Larderello-Travale geothermal field

Abstract

A main seismic reflecting horizon (K), occurring in the depth range 3-6 km of the Larderello-Travale geothermal field, probably consists of fractured levels, sometimes filled with hot fluids and/or authigenic minerals present at the contact between granites and the overlying basement. After a polyphased Alpine metamorphism, a new thermal event then gave origin to the geothermal field and produced corundum and chiastolite in micaschist, leucogranitic dikelets and the resetting of metamorphic biotite ages to values in the range 1. 6-3. 5 Ma. The different thermal regime in different wells easily explains the variations in the apparent ages of biotite.