Eruptive history and petrologic evolution of the Albano multiple maar (Alban hills, central Italy).

A comprehensive volcanological study of the Albano multiple maar (Alban Hills, Italy) using (i) Ar-40/Ar-39 geochronology of the most complete stratigraphic section and other proximal and distal outcrops and (ii) petrographic observations, phase analyses of major and trace elements, and Sr and O isotopic analyses of the pyroclastic deposits shows that volcanic activity at Albano was strongly discontinuous, with a first eruptive cycle at 69 +/- 1 ka producing at least two eruptions, and a second cycle with two peaks at 39 +/- 1 and 36 +/- 1 ka producing at least four eruptions. Contrary to previous studies, we did not find evidence of magmatic or hydromagmatic eruptions younger than 36 +/- 1 ka. The activity of Albano was fed by a new batch of primary magma compositionally different from that of the older activity of the Alban Hills; moreover, the REE and Sr-87/Sr-86 data indicate that the Albano magma originated from an enriched metasomatized mantle. According to the modeled liquid line of descent, this magma differentiated under the influence of magma/limestone wall rock interaction. Our detailed eruptive and petrologic reconstruction of the Albano Maar evolution substantiates the dormant state of the Alban Hills Volcanic District.