Imaging the Salinelle Mud Volcanoes (Sicily, Italy) using integrated geophysical and geochemical surveys

Abstract

Geochemical and geophysical prospecting methods (including measurements of soil heat flux and soil CO 2 flux, gravimetry, self-potential and geomagnetism) are used to produce an integrated data set aimed at imaging the migration of fluids in the sub-surface at the Salinelle mud volcanoes, located on the lower southwestern flank of Mt Etna (Sicily, Italy). This area was affected by magmatic eruptions from local volcanic centers between about 48 and 27 ka. Today, only pseudo-volcanic phenomena due to over-pressured multiphase pore fluids there occur. Carbon dioxide of magmatic origin, mixed with biogenic hydrocarbons, warm hypersaline waters and mud, are constantly released at the surface through the main conduits of mud volcanoes, whose activity is characterized by alternation of mild gas bubbling periods and strong paroxysmal phases. The latter produce violent gas eruptions that eject warm water (T ≈ 50° C) to a height up to about 1 m. Surface distribution of the geophysical and geochemical parameters have been investigated to detect the main pathways through which fluids move toward the shallow crust. Integration of geochemical, geophysical and geological maps allowed for the tracing of the fluid flow in the shallowest (a few tens of meters below the surface) part of the local hydrothermal system. Our results showed that the rising of fluids from a deep reservoir is controlled by the main structural and geological features of the area and their temporal and spatial evolution depends on pressure conditions inside the hydrothermal system.

Gravity Data Allow to Image the Shallow‐Medium Subsurface Below Mud Volcanoes

“…In 1997 the eruption of the Piparo mud volcano (Island of Trinidad) buried roads and houses, damaged electrical and water infrastructures and killed animals and livestock (Blake et al., 2021). In 2014, the violent and unexpected eruption of the Macalube di Aragona mud volcano, (Italy) caused two fatalities (Gattuso et al., 2021; Napoli et al., 2020). For these reasons, the understanding of the mechanisms driving mud volcanism is important for hazard assessment evaluation.…”

“…The gravimetric data can be valuable in distinguishing the volumes characterized by a high gas/fluid saturation (i.e., low density) from the hosting materials with higher density. Gravity surveys performed in mud volcanoes zones (e.g., Kadirov et al., 2005; Mauri, Husein, Mazzini, Irawan, et al., 2018, Mauri, Husein, Mazzini, Karyono, et al., 2018; Napoli et al., 2020; Odonne et al., 2021; Riffo et al., 2021; Sayyadul, 2005) are useful to constrain the actual location of gas saturated volumes. We show that they can also give important information about the mechanisms that influenced the actual Nirano morphology and provide guidance about hazards of mud‐fluid emissions in the area.…”