The Pisciarelli main fumarole mechanisms reconstructed by electrical resistivity and induced polarization imaging

F D A Tramparulo,M G Di Giuseppe,R Isaia,A Troiano

doi:10.1038/s41598-021-97413-1

F D A Tramparulo, M G Di Giuseppe + Show 2 more

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https://doi.org/10.1038/s41598-021-97413-1

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Abstract

Pisciarelli, together with the adjacent Solfatara maar-diatreme, represents the most active structure of the Campi Flegrei caldera (Italy) in terms of degassing and seismic activity. This paper aims to define the structure of the Pisciarelli hydrothermal system (down to a 20 m depth) through electrical resistivity and time-domain-induced polarization tomography and self-potential mapping. The retrieved 3D image of the area helps reconstruct the Pisciarelli subsurface in its area of maximum degassing, containing the main fumarole (“soffione”) and the mud pool. In particular, a channel has been identified in which fluids stored in a deeper reservoir rise toward the surface. Such a structure seems to be surmounted by a clay-cap formation that could govern the circulation of fluids and the abundance of gases/vapors emitted by the soffione. Based on this new reconstruction of the Pisciarelli fumarolic field structural setting, the first conceptual model has been suggested that is capable of simultaneously explaining the mechanisms governing soffione activity and elucidating the role played by the fluid/gas of deeper origin in the shallow fluid circulation system. The proposed model can potentially help to better monitor the processes occurring throughout the Pisciarelli fumarolic field and provide an evaluation of the associated hazards.

Highlights

Pisciarelli, together with the adjacent Solfatara maar-diatreme, represents the most active structure of the Campi Flegrei caldera (Italy) in terms of degassing and seismic activity
The electrical resistivity tomography (ERT) model consists of a series of 985,230 elements, where the n-th quadruplet has the coordinates of the center of the n-th elementary cell and the electrical resistivity computed by tomography in this cell
To explore the complex resistivity distribution and to extract all of the relevant information, the volume resolved by tomography was divided into three parts, namely, a high-resistivity volume (HRV), a medium-resistivity volume (MRV), and a low-resistivity volume (LRV), by using two cutoff values defined as ρL = 4 Ω·m and ρH = 20 Ω·m

Summary

Introduction

Pisciarelli, together with the adjacent Solfatara maar-diatreme, represents the most active structure of the Campi Flegrei caldera (Italy) in terms of degassing and seismic activity. The hydrothermal area of Pisciarelli (Fig. 1b), together with the adjacent Solfatara maar-diatreme[5,6], currently represents the most active structure on the caldera in terms of degassing and seismic activity[3], manifesting significant morphological variations, changes in the geochemical characteristics of the gases/fluids, the opening of new fumarolic vents, the occurrence of several seismic events, and some episodes of mud emission that have been recorded during the last decade[3,7,8,9]. We show how this combination of geoelectric and induced polarization surveying further improves the diagnostic capability of electrical techniques applied in volcanic environments and enhances the obtained results This combination of tomograms provides in-depth insights into the evolution of the ongoing hydrothermal processes, thereby permitting the mechanisms governing the shallow circulation of volcanic hydrothermal fluids within the PFF to be defined

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