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Abstract:
The study deals with a review of pre-eruptive dynamics and evidences of open-system behavior in the volcanic plumbing system beneath Campi Flegrei Caldera (CFC), together with estimates of magma residence time and ascent (mixing-to-eruption timescales). In detail, we compile pre- and syn-eruptive dynamics reported in the literature for Campanian Ignimbrite (~ 40 ka), Neapolitan Yellow Tuff (~ 15 ka), and more recent activity. After summarizing geochemical and textural evidence, we observe a fingerprint of open-system dynamics in the deposits associated to CFC volcanic activity of the last 40 ky. Geophysical and petrological investigations allow us to hypothesize the structure of the magma feeding system: we point at a 9-km deep main storage reservoir that feeds and interacts with shallow reservoirs, mainly 2–4 km deep.Thus, we define a scenario depicting pre-eruptive dynamics of a possible future eruption and provide new constraints on timescales of magma ascent with a physical model based on magma-driven ascending dyke theory. Results show that considerably fast ascent velocities (in the order of m/s) can be easily achieved for eruptions fed by both shallow ( 3–4 km) and deep ( 9 km) reservoirs. Comparing experimental and numerical approaches, it emerges that mixing-to-eruption timescales occurring at shallow reservoirs could be in the order of minutes to hours. Thus, our timescale estimates (magma ascent and mixing to eruption), imply that explosive eruptions could begin with little physical ‘warning’, of the order of days to months. In this case, the onset of volatile saturation might provide pre-eruptive indicators.
