Geochemical Evidences that Unrest at Campi Flegrei Resurgent Caldera (Southern Italy) Is Due to Magma Emplacement and Degassing at Shallow Depth Plus Fluxing from a Deep-Seated Regional Body

Abstract

Volcanic calderas are affected by unrest episodes usually dominated by hybrid magmatic-hydrothermal system dynamics. Unrest episodes can evolve to eruptions of variable intensity, up to Plinian. Campi Flegrei caldera (CFc) is a type-location for this kind of activity escalation. CFc offers unique opportunity to join volcanological information to a long record of geochemical parameters. This allows understanding the role that magmatic system plays on variations displayed by the hydrothermal system. We model uneruptive unrest episodes as driven by i) the shallow emplacement (~4 km depth) of one volatile-rich magma batch ascending from a deep (≥ 8 km) magmatic body of regional extent, ii) subsequent gas separation with degassing driven by crystallization and iii) fluxing from the deep magmatic body. Our model matches three decades of geochemical constraints from fumarole discharges, as well as data from melt inclusions of past CFc eruptions. Besides, magma physical properties demanded for modeled degassing conditions are in good agreement with existing geophysical data. Our results open new perspectives to the definition of unrest scenarios at highly-populated CFc, as well as other resurgent calderas (e.g., Orsi et al., This Assembly).