Geochemistry of Melt Inclusions from the Fondo Riccio and Minopoli 1 Eruptions at Campi Flegrei (Italy)

Campi Flegrei is a large volcanic complex located west of the city of Naples, Italy. The area has been the site of volcanic activity for more than 60 ka and represents a potential volcanic hazard owing to the large local population. In this study, the geochemistry of the magma associated with two different eruptions at Campi Flegrei has been characterized, with the aim to identify geochemical trends that may help to predict the style and nature of future eruptions. Two eruptions of different age and eruptive style have been selected for study, Fondo Riccio (9.5 ka) and Minopoli 1 (11.1 ka). A scoria (CF-FR-C1) and a bomb (CF-FR-C2) were collected from the Fondo Riccio eruption, and two scoria samples were collected from Minopoli 1 (CF-Mi1-C1 and C2) eruption.

The pre-eruptive volatile content of magma plays an important role in the style of eruption and can be assessed from studies of melt inclusions (MI) contained in phenocrysts. Major and trace elements in Fondo Riccio MI show a wider variation compared to those in Minopoli 1 MI suggesting that the Fondo Riccio magma residence time was longer compared to the Minopoli 1 magma. Analyses of volatile contents in MI suggest that Fondo Riccio magma may have been more water-rich than Minopoli 1 magma, consistent with the more explosive character of this eruption compared to Minopoli 1. Trace element data suggest a combination of arc volcanic and upper continental crust magma as the source for the Fondo Riccio and Minopoli 1 eruptions.