Post-emplacement thermo-rheological history of a granite intrusion and surrounding rocks: the Monte Capanne pluton, Elba Island, Italy

A thermo-rheological model of the Monte Capanne pluton, Elba Island, Italy is pro- posed as having general relevance for the thermal and tectonic evolution of upper crustal granites and their surrounding rocks in extensional regions. The thermal evolution of the pluton and coun- try rocks is followed for 1 myr after emplacement, which occurred at c. 6.9 Ma. The pluton com- pletely crystallized in c. 210 kyr (+20%). The adjacent rocks reached a thermal peak of 550 8C (+10%), maintaining a temperature higher than 500 8C for c. 100 kyr. The temperature distribution is used to construct a model for the time-dependent rheology of the pluton and surrounding rocks. A series of 2D cross-sections shows an upward migration of the regional brittle 2 ductile transition, and the formation of a ductile horizon above the pluton. The former is a combined effect of unroofing and middle crust heating; the latter is the result of temperature increase in rheologically weak country rocks. This ductile horizon has a potential role in the tectonic evolution of the region, since it could favour the formation of upper crustal shear zones and listric faults rooting in the transient brittle 2 ductile transition and playing a major role in further post-emplacement extension.