First evidence for leucite-bearing products in the recent stages of activity of the Roccamonfina volcano (central-southern Italy).

The Roccamonfina volcano is one of the first Italian potassic volcanoes to be investigated by detailed petrological studies, which revealed an overall time-related progression of magma compositions from leucite-bearing ultrapotassic to leucite-free shoshonitic. However, sparse accounts reported some deviations to this general scheme, suggesting that the petrological evolution of the volcano is more complex than previously thought. Here we report a detailed investigation of the products of the recent phase of the volcano history (i.e. <305 ka), including both lava and pyroclastic deposits from the eastern side of the Roccamonfina. Along with prevailing leucite-free products, leucite-bearing juvenile clasts and lava samples were also recognised, featuring phenocrysts of clinopyroxene and leucite (olivine) or of leucite only set into a groundmass with clinopyroxene, plagioclase and leucite or clinopyroxene and plagioclase. Bulk-rock compositions are in line with the that of the leucite-bearing products of the oldest stages (>350 ka), although higher SiO2, Cr and Ni, and lower Ba, Sr and V contents are observed at similar degrees of evolution. Also, the compositions of glass from the pyroclastic deposits are in line with that of the oldest stages, being phonotephritic. Interestingly, the Sr-Nd isotopic compositions of the two groups of leucite-bearing rocks are strikingly different, with the youngest products showing lower 87Sr/86Sr (0.70653 vs. 0.70872-0.71079) and higher 143Nd/144Nd (0.51250 vs. 0.51211-0.51222). These preliminary results support the idea that leucite-bearing magmas were not confined to the oldest stages of Roccamonfina history and suggest that they were generated at different times from different mantle sources.