FISSION-TRACK THERMOCHRONOLOGICAL STUDY O F THE MONTE-CAPANNE PLUTON DENUDATION (ELBA ISLAND, ITALY)

7 samples of granodiorite were taken between sea level and an altitude of 1 009 m, at the top of Monte Capanne. Fission track ages suggest t hat the samples from the highest altitudes cooled below about 130-degr ees-C, 5.4 Ma ago at least. This result agrees with the K/Ar, Rb/Sr an d U/Pb ages (6-7 Ma) and indicates a fast cooling of the pluton after its emplacement. The measure of the track lengths, according to the mo del of Wagner [1988], indicates that all the samples remained for many Ma in a partial annealing zone (PAZ), at temperatures between 130-deg rees-C and 60-degrees-C. Therefore a still tectonics stage would have followed the emplacement of the pluton. The denudation of the pluton w ould have begun between 3 and 2 Ma and it would be fast; all the sampl es seem to have left the PAZ almost simultaneously 2 Ma ago. We tentat ively attribute this fast cooling to a tectonic denudation of the east ern part of the pluton resulting from the movement of the cover along a fault slightly dipping to the east. Thus, as its intrusive phase, th e post-magmatic history of the Monte Capanne pluton might have been co ntrolled by extensional tectonics associated to the Tyrrhenian Sea evo lution.