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

Abstract

AbstractA thermo-rheological model of the Monte Capanne pluton, Elba Island, Italy is proposed 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 country rocks is followed for 1 myr after emplacement, which occurred at c. 6.9 Ma. The pluton completely crystallized in c. 210 kyr (±20%). The adjacent rocks reached a thermal peak of 550 °C (±10%), maintaining a temperature higher than 500 °C 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−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−ductile transition and playing a major role in further post-emplacement extension.