K/Ar and fission track age measurements were performed on lava samples of Monte Amiata volcano (Central Italy) which is formed
by a sequence of lava flows and lava domes ranging in composition from trachybasalts to high-SiO
2 quartzlatites.
The ages obtained, except for the oldest volcanic products, range from 290,000 to 180,000 years.
Excess40Ar was found in some mineral separates, especially biotite, causing apparent rather old ages. The correct ages were calculated
by means of K/Ar isochrons, and were found to be very similar to the ages calculated on sanidine separates.
The volcanic activity that built up the outcropping Monte Amiata units seems to have lasted a relatively short time.
Research financially supported by CNR, Italy, Progetto Finalizzato Geodinamica, Grants nos. 78.00825 and 80.01383 (Geodynamics
Project Publ. no. 480).