Abstract
The prehistoric (< 7 ka) Zaro eruption at Ischia island (Southern Italy) produced a lava complex overlaying a pyroclastic deposit. Although being of low energy, the Zaro eruption might have caused casualties among the neolithic population that inhabited that area of Ischia, and damages to their settlements. A similar eruption at Ischia with its present-day population would turn into a disaster. Therefore, understanding the magmatic processes that triggered the Zaro eruption would be important for volcanic hazard assessment and risk mitigation, so as to improve a knowledge that can be applied to other active volcanic areas worldwide. The main Zaro lava body is trachyte and hosts abundant mafic and felsic enclaves. Here all juvenile facies have been fully characterized from petrographic, geochemical and isotopic viewpoints. The whole dataset (major and trace element contents; Sr–Nd isotopic composition) leads to rule out a genetic link by fractional crystallization among the variable facies. Thus, we suggest that the Zaro mafic enclaves could represent a deep-origin mafic magma that mingled/mixed with the main trachytic one residing in the Ischia shallow magmatic system. The intrusion of such a mafic magma into a shallow reservoir filled by partly crystallized, evolved magma could have destabilized the magmatic system presumably acting as a rapid eruption trigger. The resulting processes of convection, mixing and rejuvenation have possibly played an important role in pre- and syn-eruptive phases also in several eruptions of different sizes in the Neapolitan area and elsewhere in the world.
Highlights
Ischia is an active volcanic island located in the Neapolitan area and is part of the Phlegraean Volcanic District with the Campi Flegrei caldera and the Procida islet (Fig. 1a)
Proposed here as an interesting archetypal case-study, the Zaro eruption occurred less than 7 ka at Ischia (Vezzoli et al 2009), when the island was already inhabited by Neolithic people, as testified by the findings of archaeological artefacts dated to the 4th millennium B.C. (Buchner 1969)
The whole set of acquired data allows a better understanding of the magmatic processes that occurred before and during the Zaro eruption
Summary
Ischia is an active volcanic island located in the Neapolitan area (south Italy) and is part of the Phlegraean Volcanic District with the Campi Flegrei caldera and the Procida islet (Fig. 1a). Due to the mainly explosive character of its recent volcanism and the large population living or at least spending holidays at Ischia, the risk is extremely high. Expected to resume explosive activity in the future, Ischia is the only active volcano in the Neapolitan area that still lacks a risk mitigation plan. International Journal of Earth Sciences (2020) 109:2829–2849 knowledge of one of the most recent and complex vol- framework for the island, supplying more information for canic events such as Zaro could help refining the hazard risk mitigation. Notwithstanding the relatively low energy, the mixed explosive-effusive character and the seismic activity that presumably accompanied the eruption, might have caused casualties in the population and damages to their settlements
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