Studies related to the oceanographic campaigns and sampling (Bibliography) have improved our understanding of this massive volcano revealing that Marsili formed along the spreading center of its basin, acting as a super-inflated ridge. Detailed bathymetric maps reveal that the volcano stretches 70 km NE-SW, is 30 km wide, and rises 3 km from the seafloor, with its summit 500 meters below sea level (Fig. 1). The volcano’s central axis, about 20 km long and 1 km wide, contains a summit cone with two craters. Smaller volcanic cones are present along its flanks, some 1 km wide and 350 m tall. Curved features along its sides may indicate areas prone to instability. The bathymetric data have also been used to create a 3D model of the volcano (Fig. 2). The sampling of different parts of the volcano yielded a significant amount of volcanic and sedimentary samples. Geochemical and petrological studies on a set of the sampled volcanic rocks provided information on: 1. magma types and composition. Marsili has predominantly erupted lavas with an IAB (Island Arc Basalt) affinity, with compositions ranging from basalt to andesite (Fig. 3). Geochemical and petrological data suggest a complex sub-volcanic system involving partial mantle melting, interaction with fluids from the subducting Ionian plate, and mantle flow beneath the basin (Fig. 4). This system explains the vertical growth of the volcano. 2. magma pathways and sub-volcanic architecture. Examination of igneous crystals (olivine, pyroxenes, plagioclase) in the lavas provides insight into magmatic processes. The data point to a feeding system beneath the volcano (Fig. 5), similar to the transcrustal plumbing systems seen in other volcanic regions. This section of the Tyrrhenian Rocks website is curated by the ISMAR-CNR Research Unit in Bologna (Scientific Coordinator: M. Marani), as part of the PRIN2022-AWARE project (Collaboration network). The ISMAR-CNR Research Unit includes C. Cavozzi and T. Trua (University of Parma) as collaborators. This section will be updated with research results from the units involved in the PRIN2022-AWARE project.

Rock sampling activity has targeted various sectors of the volcanic edifice, retrieving a significant quantity of volcanic rocks (predominantly lavas and, less commonly, volcaniclastic deposits) as well as sedimentary rocks (Fig. 4).

Petrological studies conducted thus far indicate that Marsili has primarily erupted basalts and basaltic andesites (Fig. 5). The basalts derive from the cooling of magmas produced by partial melting of a hybrid mantle source, comprising: the mantle wedge beneath the edifice; slab-derived fluids from the underlying, subducting Ionian plate located at about 400 km depth; and an asthenospheric mantle inflow from the lateral edges of the subducting slab (Fig. 1). This complex sub-volcanic configuration has sustained a robust magmatic flux within the Marsili Basin over the past 0.7 Ma, leading to the growth of the Marsili edifice, regarded as the “super-inflated spreading ridge” of the basin (Marani and Trua, 2002). Basaltic andesites record sub-volcanic differentiation processes (cooling, fractional crystallization) affecting parental basaltic magmas. The most evolved erupted lavas, represented by andesites, are restricted to the summit of the volcanic edifice. Reconstruction of a detailed eruptive chronology is presently precluded by the absence of radiometric age constraints for the lava samples.

The study of igneous crystals (olivine, pyroxenes, plagioclase) carried in the lavas provide information on the pre-eruptive history of magmas (Albert et al., 2022; Colle et al., 2024; Marani and Trua, 2021; Trua et al., 2018), suggesting that the sub-volcanic system is highly complex with an architecture similar to that of a transcrustal plumbing system (Fig. 6).”