Tracking plumbing system dynamics at the Campi Flegrei caldera, Italy: High-resolution trace element mapping of the Astroni crystal cargo

TL;DR

This study uses petrological techniques, geothermobarometry, and high-resolution trace element mapping to reconstruct the pre-eruptive dynamics and timescales of the Astroni volcano in Italy's Campi Flegrei caldera, revealing complex magma interactions and recharge events.

Contribution

It introduces a multifaceted approach combining trace element mapping and geothermobarometry to better understand volcanic plumbing systems and eruption precursors.

Findings

Interaction between shallow and deep magma chambers confirmed

Discrete zonations indicate a recharge event hours to days before eruption

Complex magmatic evolution prior to eruption revealed

Abstract

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.