Extension, uplift of rocks and cooling ages in thinned crustal provinces: the Larderello geothermal area (inner Northern Apennines, Italy)

In extensional tectonic settings, vertical movements of the earth's surface are largely controlled by rates of strain. Extensional strain rates within the Larderello geothermal area, located in inner parts of the Northern Apennines, have been evaluated together with uplift rates and 40Ar/39Ar cooling ages. Results indicate that extensional strain rates have been relatively low (5.8×10−17 s−1), since the middle Pliocene. Differential uplift rates are estimated to have been high (c. 0.2 mm/year). Strain and uplift rates within the Larderello region are consistent with the regional tectonic framework. The low strain rate, rapid uplifting and high heat flow within southern Tuscany can be explained by an eastward dipping lithospheric shear maintained since at least middle Pliocene times.