  The Campi Flegrei caldera (southern Italy) is one of the most hazardous
volcanic systems on Earth, having produced >60 eruptions in the past 15 ka. The
caldera remains active and its potential for future eruptions is high, posing a
danger to the dense population living nearby. Despite this, our understanding
of pre-eruptive processes and the architecture of the sub-volcanic system are
poorly constrained. Here, we combine established petrological techniques,
geothermobarometric evaluation, and high resolution trace element crystal
mapping, to present a multifaceted, coherent reconstruction of the complex pre
eruptive dynamics and eruption timescales of Astroni volcano located in the
eastern sector of Campi Flegrei caldera. The Astroni volcano is an important
case study for investigating plumbing system processes and dynamics at Campi
Flegrei caldera because it produced the most recent (ca. 4 ka ago) Plinian
eruption within the caldera (Astroni 6); current long-term forecasting studies
postulate that a similar sized event in this location is a probable future
scenario. Geothermobarometric results indicate interaction between an evolved,
shallow magma chamber, and a less evolved, deeper pocket of magma, in agreement
with previous studies focused on the Astroni 6 eruption products. In addition,
a range of textural and trace element zoning patterns point to a complex
evolution of both magmas prior to their subsequent interaction. High resolution
trace element crystal maps reveal discrete zonations in compatible elements.
These zonations, combined with knowledge of Kfeldspar growth rates, highlight a
recharge event in the shallow plumbing system a few hours to days before the
Astroni 6 eruption.
