Pre-eruptive conditions of the Campanian Ignimbrite eruption: Experimental constraints from phase equilibria and volatile solubility studies and its implication for the Campi Flegrei drilling project

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A prerequisite for the understanding and modeling of volcanic and degassing processes at Campi Flegrei is (1) the determination of magma storage conditions, (2) the understanding of magma replenishment processes, especially the composition, temperature, volatile contents of the new magmas injected in magmatic chamber and (3) the simulation of degassing and crystallization processes during magma ascent. So far experimental data and thermodynamic models at elevated pressures and temperatures, allowing us to gain this information, are scarce and can not be directly applied for the phonolitic and trachytic systems of Campi Flegrei. Such information is crucial for the interpretation of drilling products and of observations at the planned drilling site at Campi Flegrei (CFDDP). In this proposal we plan to investigate long term processes in the magma chamber(s), such as crystallization and differentiation, as well as short term processes resulting from new magma inputs occurring in the Campi Flegrei magma chamber prior to eruptions (e.g., degassing, mixing, re-equilibration). Processes during magma ascent from the magma chamber to the surface will be explored in Tübingen (see application of M. Nowak). Different experimental approaches (i.e. phase equilibria, kinetic experiments, solubility of mixed H2O-CO2-Cl-S-bearing volatiles in silicate melts) using trachytic and phonolitic rocks from the Campanian Ignimbrite will be used to investigate magma storage conditions, the properties of end-member magmas before replenishment, as well as the composition of fluids coexisting with melts in the magma chamber. The knowledge of these parameters is crucial to understand and model the evolution of rheological magma properties, fragmentation, eruptive style, which are recorded in the textural patterns of the Campanian Ignimbrite and of the volcanic ashes. The experimental data will provide useful constraints for volcanic hazard assessment at the high risk Campi Flegrei Volcanic Area.