Anatomy of a fumarolic system inferred from a multiphysics approach

Marceau Gresse,Giovanni Chiodini,Tullio Ricci,Alessandra Sciarra,Svetlana Byrdina,Jean Letort,Jean Vandemeulebrouck,Zaccaria Petrillo,Paola Tuccimei,Marc Wathelet,Philippe Roux,Antonio Pio Rinaldi,Carlo Lucchetti

doi:10.1038/s41598-018-25448-y

Abstract

Fumaroles are a common manifestation of volcanic activity that are associated with large emissions of gases into the atmosphere. These gases originate from the magma, and they can provide indirect and unique insights into magmatic processes. Therefore, they are extensively used to monitor and forecast eruptive activity. During their ascent, the magmatic gases interact with the rock and hydrothermal fluids, which modify their geochemical compositions. These interactions can complicate our understanding of the real volcanic dynamics and remain poorly considered. Here, we present the first complete imagery of a fumarolic plumbing system using three-dimensional electrical resistivity tomography and new acoustic noise localization. We delineate a gas reservoir that feeds the fumaroles through distinct channels. Based on this geometry, a thermodynamic model reveals that near-surface mixing between gas and condensed steam explains the distinct geochemical compositions of fumaroles that originate from the same source. Such modeling of fluid interactions will allow for the simulation of dynamic processes of magmatic degassing, which is crucial to the monitoring of volcanic unrest.

Highlights

Studying the geochemical compositions and discharge temperatures of fumaroles is a classical and suitable method to monitor the activity of a volcano[2,3,4,5,6]
The resistivity model obtained from high-resolution 3D electrical resistivity tomography (ERT) by Gresse, et al.[26] reveals the shallow fluid distribution in the fumarolic system (Figs 2 and S4; for a detailed resistivity model, see Gresse, et al.26)
A gas-dominated reservoir of ~25,000 m3 in volume is identified ~60 meters beneath Bocca Grande and Bocca Nuova (Fig. 2a), corresponding to a closed resistive (20–40 Ωm) volume

Summary

Introduction

Studying the geochemical compositions and discharge temperatures of fumaroles is a classical and suitable method to monitor the activity of a volcano[2,3,4,5,6] This can provide understanding of the transition from quiescence to unrest, and what drives the system to a potential eruption. Eruptions are often preceded by increased gas emissions, and by variations in composition that can be monitored at fumarolic vents[7,8] (Fig. 1c,d) These changes that can be perceived at the surface generally result from increased internal pressure and/or temperature, and/or changes in the composition of the magmatic reservoir. This activity is mostly focused underneath the Solfatara volcano (Fig. 1a)

Methods

Results

Discussion

Conclusion