New unspiked K-Ar ages of volcanic rocks of the central and western sector of the Aeolian Islands: reconstruction of the volcanic stages

A geochronological study of the Filicudi, Salina, Lipari and Vulcano Islands (Aeolian Archipelago) using the unspiked potassium-argon technique provides new age data which, combined with stratigraphic correlation, better constrain the temporal evolution of volcanism. The unspiked K-Ar age of the oldest exposed lavas on Filicudi, 219+/-5 ka, is significantly younger than the previous estimation of 1.02 Ma. In the general context of Aeolian volcanism, this new date suggests that the volcanism of the western sector of the Aeolian Archipelago is younger than previously thought. Geochronological data point out on the rapid transition from calc-alkaline to potassic volcanism. The distribution of the K-Ar ages within the Salina-Lipari-Vulcano group shows that the volcanism started on Lipari and propagated over time northward on Salina and southward on Vulcano. Geochronological and geophysical data suggest that the onset of volcanism in the central sector of the Aeolian Arc may be due to a mantle upwelling structure located below Lipari. A change in the style of the eruptions occurred in the Salina-Lipari-Vulcano system at about 100 ka from the present. Low-energy magmatic eruptions occurred between 188 and about 100 ka. From about 100 ka to the present, higher-energy eruptions and low-energy events due to magma-water interaction also occurred. This change in the style of activity, together with the appearance of evolved products (i.e. rhyolites) during the last 50 ka, is consistent with the formation of magmatic reservoirs located at shallower depth with respect to those of the 188-100-ka period. The new geochronological data and available petrological models reveal that a change in the deep source of the primary magmas occurred in a relatively short time interval. (C) 2002 Elsevier Science B.V. All rights reserved.