Open-System Behaviour at the Campi Flegrei Caldera: from Evidence of Magma Mixing to pre-Eruptive Timescales

Abstract We review the evidence of open-system behavior in the volcanic plumbing system of the Campi Flegrei Caldera. Also, we highlight the estimates of magma residence time, magma ascent, and mixing-to-eruption timescales. In detail, we concentrate on the Campanian Ignimbrite ~ 40ka, the Neapolitan Yellow Tuff (~ 15ka), and the recent activity within the Phlegrean area. We start highlighting the evidence of magma mixing on the pyroclastic rocks deriving from different sources (e.g., crystal disequilibria, vertical zonings, and isotopic records). Then we describe geophysical and geochemical data of the magma feeding system with a focus on magma residence times and mixing to eruption timescales. Also, we link the timescales of magma ascent reported in the literature with a physically constrained model based on the magma-driven ascending dyke theory. Results show that considerably fast ascent velocities (i.e., units to tens m/s) can be easily achieved for eruptions fed by both shallow (i.e., 3–4 km) and deep (i.e., ~ 9 Km) reservoirs when characterized by large enough overpressures (i.e., > 25 MPa). Finally, we highlight the volcanological implications of timescale estimates for residence time and ascent in both open- and closed-system behavior of the volcanic plumbing system. The main aim is to provide constraints to the volcanic hazard definition of the area.