New Inferences on Magma Dynamics in Melilitite‐Carbonatite Volcanoes: The Case Study of Mt. Vulture (Southern Italy).

This study provides the first micro‐thermometric data of fluid inclusions (FIs) in mafic loose (disaggregated) xenocrysts and ultramafic xenoliths in explosive products of the melilitite‐carbonatite Mt. Vulture volcano (southern Italy). Pure CO2 late stage FIs hosted in rock‐forming minerals of wehrlite xenoliths and clinopyroxene xenocrysts were trapped at the local crust‐mantle boundary (32 km). In contrast, trapping pressures within the loose olivine xenocrysts are from 3.2 to 4.5 kbar (8–13 km). Considering the ongoing degassing of mantle‐derived CO2 rich gases, together with seismic evidences of the presence of low amount of melts at depth, and the tectonic control of the past volcanic activity, our study opens new perspective about the hazardous nature of the "quiescent" melilitite‐carbonatite volcanoes. Plain Language Summary: The study of fluid inclusions (FIs) (small amount of fluid trapped within minerals) provides important information on variable environments and magmatological processes in which the host minerals were formed. Investigation of the FIs with respect to their composition, trapping pressure and temperature, allow us to constrain magma ascent history. To understand the last explosive volcanic activity of Mt. Vulture volcano (southern Italy), we investigated FIs in mafic minerals and mantle fragments brought to the surface by a melilitite‐carbonatite magma. Our results show the presence of CO2‐rich FIs with trapping pressure corresponding to a depth of 32 km in mantle fragments, and a shallower depth (8–13 km) in mafic mineral. Estimates on magma ascent rate show rapid ascent dynamics to the surface. Our study emphasizes the importance of a multidisciplinary approach that combine geochemistry and petrology to investigate a volcanic system even if the volcano is considered "quiescent," as is the case of Mt. Vulture volcano, where mantle degassing is still ongoing. Key Points: Micro‐thermometric analyses show the occurrence of high‐density CO2‐rich fluid inclusions hosted by minerals within wehrlite xenolithsAscent rate between melilitite‐carbonatite (≈20 m/s) and kimberlite (≈45 m/s) magma is comparableMelilitite‐carbonatite volcanoes can be hazardous even after long time of quiescence (>105 years) [ABSTRACT FROM AUTHOR]