GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.2 GNGTS 2023 Configuration of the active geothermal system of the Campi Flegrei caldera central sector revealed by 3D short-period magnetotelluric imaging and structural data M. G. Di Giuseppe 1 , R. Isaia 1 , J. Natale 2 , A. Troiano 1 , S. Vitale 2 1 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano Naples, Italy. 2 Dipartimento di Scienze della Terra, dell'Ambiente e delle Risorse (DiSTAR), Università degli Studi di Napoli Federico II, Naples, Italy. The Campi Flegrei caldera – Central Sector (CFc- CS) plays a critical role in recent volcanic activity throughout the region. We present a magnetotelluric (MT) imaging, providing insight into the structural setting and configuration of the CFc- CS hydrothermal system. Numerous literature studies have demonstrated the capability of electrical resistivity-based methodologies in reconstructing structural settings of relatively complex geological areas (Di Giuseppe et al., 2017, 2015; Isaia et al., 2022, 2021, 2015; Troiano et al., 2021, 2014; Vitale et al., 2019). These studies show how such techniques can reconstruct the main fault and fracture systems and the principal patterns of hydrothermal fluid circulation. The resulting 3D resistivity model evidences how the CFc-CS comprises two parts located below the Astroni and Solfatara volcanoes (hereafter indicated as A- AHS and the S-PHS, respectively), illustrating the differences between these structures. In correspondence with the A- AHS, a substantial reduction in resistivity was observed, probably related to the presence of hot geothermal water with high concentrations of dissolved salts acting as conductive electrolytes in the rock matrix. On the other side, the S-PHS was found to be an electrical resistive structure, probably due to a drier environment where the liquid phase of circulating fluids is reduced. This diversification, which includes structures at depths greater than 1 km, is likely related to the presence of two different supply systems, each feeding one of these two sectors, combined with the effects of significant volcano-tectonic structures.