Baccari, Carolina (2026) STUDY OF MAGMATIC OUTGASSING PROCESSES AT CAMPI FLEGREI THROUGH GEOCHEMICAL AND TEXTURAL ANALYSIS. [Tesi di dottorato]

	Documento PDF Carolina_Baccari_XXXVIII_PNRR_completa.pdf Visibile a [TBR] Amministratori dell'archivio Download (4MB) | Richiedi una copia
	Documento PDF Carolina_Baccari_XXXVIII_PNRR_parziale.pdf Visibile a [TBR] Amministratori dell'archivio Download (1MB) | Richiedi una copia

Abstract

The Campi Flegrei volcanic system is one of the most extensively studied and, at the same time, most high-risk caldera complexes worldwide, due to the combination of high volcanic hazard and significant urbanization in the area (Orsi et al., 2022; Selva et al., 2019; Bevilacqua et al., 2017; Mastrolorenzo et al., 2017). Situated within the Phlegraen Volcanic District (PVD), the Campi Flegrei caldera (CFc) results from a lengthy and complex eruptive history spanning from the Late Pleistocene to the Holocene (Orsi et al., 1996a; Sbrana et al., 2021). The formation of this system has been influenced by the extensional regime linked to the opening of the Tyrrhenian Sea and the ongoing rollback of the subducting Ionian lithosphere (Jolivet et al., 2009). These processes have promoted the development of the Campanian Plain graben and the ascent of magmas through active fault systems (Piochi et al., 2005; Acocella and Funiciello, 2006). The eruptive evolution of Campi Flegrei exhibits pronounced variability in terms of magnitude, eruptive style, and magma composition, shifting substantially from an initial phase characterized by a small number of eruptions—two of which were cataclysmic (Campanian Ignimbrite - CI, ~40 ka, Dense Rock Equivalent DRE >300 km³; Neapolitan Yellow Tuff - NYT, ~15 ka, DRE~40 km³)—to a later phase dominated by numerous explosive events with much smaller magma volumes (Orsi et al., 2022). Post-NYT eruptions occurred into multiple epochs ~15–10.5 ka, 9.6–9.1 ka, and 5.5–3.8 ka, with DRE of 4.2, 0.7, and 2.6 km³ (Di Vito et al., 1999; Smith et al., 2011). During these periods, a dynamic magmatic system, thought to be sustained by deep recharges, fractional crystallization, crustal assimilation and mingling/mixing processes, fed approximately 70 eruptions (Arienzo et al., 2011; Fourmentraux et al., 2012; Cañón-Tapia, 2014; Astbury et al., 2018; Pappalardo and Buono, 2021; Buono et al., 2022). These magmatic processes can occur over short timescales. Estimates suggest that CFc magmas can evolve toward a critical state in relatively short times, on the order of hundreds of years; recharge/mixing episodes prior to eruptions can occur over a few years to several decades, and the final magma ascent from the magma chamber to the surface during an eruption can range from several months to a few hours (Pappalardo and Mastrolorenzo, 2012; Iovine et al., 2017; Pappalardo and Buono, 2021; Pelullo et al., 2022). This indicates a system capable of rapidly responding to external and internal perturbations, with important implications for volcanic hazard assessment. However, there is still extensive debate regarding the architecture and temporal evolution of the Phlegraean magmatic system, and relatively few studies have focused on building comprehensive datasets and an integrated view of the magmatic plumbing system (e.g., Pappalardo et al., 2002; Di Renzo et al., 2011; Pappalardo and Mastrolorenzo, 2012; Esposito et al., 2018; Forni et al., 2018; Pappalardo and Buono, 2021; Balcone-Boissard et al., 2024), despite this being a crucial element for understanding the volcanic dynamics of the CFc. Elucidating this intricate magmatic architecture is particularly important as Campi Flegrei is characterized by a long history of unrest episodes documented both in historical and recent times. After centuries of subsidence following the Monte Nuovo eruption (1538), the system has shown uplift events and intense seismicity at least since the 1950s, with earthquake swarms mostly confined within the first few kilometers of depth. The most recent episode of unrest has been ongoing since 2005 and prompted the Civil Protection to raise the alert level from the base (green) to the warning (yellow) level in 2012 (Orsi et al., 2022). The origin of recent uplift remains debated: shallow magmatic intrusions (~3 km depth), accumulation of magmatic gases, or changes in hydrothermal fluid circulation all represent plausible explanations consistent with the observed data (Kilburn et al., 2017; Bodnar et al., 2007; Troiano et al., 2011; Chiodini et al., 2021; Buono et al., 2022; 2025). As a result, the scientific community remains focused on interpreting geophysical and geochemical signals, and on assessing the likelihood of a potential eruption (Alberico et al., 2002, 2011; Bevilacqua et al. 2015, 2017; Mastrolorenzo et al., 2006; Neri et al., 2015; Orsi et al., 2004, 2009; Selva et al., 2018). Within this highly variable and complex framework, the study of magmatic volatiles represents a key tool for understanding system dynamics. Components such as H₂O, CO₂, S and Cl contain crucial information for reconstructing the storage conditions and dynamics of the magma, as well as directly affecting magma viscosity, density, internal pressure, and, consequently, eruptive behavior. However, restoring the original volatile composition of pre-eruptive magmas can often be complicated by different processes, for example, gases detected through fumarolic emissions, although capable of recording information on the current state of the system, are typically affected by meteoric fluid contamination and fluid–rock interactions occurring during ascent or rest within host rocks (Gresse et al., 2018). Therefore, Melt inclusions (MIs) represent a powerful tool to overcome these limitations. As tiny droplets of melt trapped during crystal growth (Esposito et al., 2018), MIs preserve—when properly interpreted— comprehensive and direct information on magma composition during its storage or ascent (Esposito et al., 2021). MIs allow investigation of: (1) processes, conditions and structure of the magmatic feeding system, and (2) the volatile content of trapped melts, which records the composition of the magmatic volatile phase (MVP), essential for calculating entrapment pressures using volatile–silicate melt solubility models (Papale et al., 2006; Stabile and Carroll, 2019). Nevertheless, interpretation of MIs is not without limitations: the internal variability of volatile contents and the frequent presence of bubbles can significantly affect estimates of pre-eruptive volatile abundances. Given the complexities of the Phlegraean system and the uncertainties associated with volatile quantification, this thesis aims to contribute to understanding the storage depths and dynamics of magmas at Campi Flegrei, which are essential for assessing volcanic hazard. For this purpose, the silicate melt composition and pre-eruptive volatile contents were determined by analyzing MIs in phenocrysts from post–Neapolitan Yellow Tuff (NYT) pyroclastic deposits of eruptions selected to ensure good representativeness in terms of magma composition, and eruption age, vent location, and magnitude (i.e., Santa Teresa, Minopoli, Baia, Montagna Spaccata, Nisida, Agnano-Monte Spina and Astroni samples). The integration of CO₂ data from bubbles, major, trace element compositions and volatile contents in the glass enables the reconstruction of magma evolutionary paths and a better understanding of the transition from deep magma roots to shallower levels of the magmatic system. This approach provides new insights into interpreting magmatic evolution in the Phlegraean Fields, with direct implications for volcanic risk assessment and for understanding ongoing instability signals.

Downloads

Actions (login required)

Modifica documento