## 4 Results and Discussion
### Hydrothermal Vents and Products of the SE Tyrrhenian Sea
Active or fossil hydrothermal vents have been widely documented along the entire Palinuro chain thanks to seafloor sampling (minerals and copper crusts, iron and manganese nodules and crusts, and other cobalt-rich nodules), as well as from the geochemistry of the water column (He\({}^{3}\)/He\({}^{4}\) isotopic ratio), geophysics (demagnetization of rocks altered by hydrothermalism), and OBS with seismic activity due to active hydrothermalism detected by seismic waveforms recorded with ocean bottom seismometers [31; 39; 43; 44; 45; 106; 107; 108; 109; 110; 111; 112; 113]. All these activities reveal that the rejuvenation sector included in the easternmost caldera area could be the most promising for DSM purposes. The Marsili Seamount (Figure 7) is 70 km long and 30 km wide ridge that is elevated ca. 3000 m from surrounding seafloor [50], which represents the inflated spreading ridge [46] of the 2 Ma old Marsili back-arc basin associated to the subduction of the Ionian Sea below the Calabrian Arc and the Tyrrhenian Sea. Its morphology shows signs of differentiated eruptive styles, also including mono- and polygenetic central cones, fissural volcanic features, and hydrothermal mounds [51]. Petrologic analysis [72,112] and visual inspection by ROV [114,115] indicate the presence of active or past hydrothermal activities on its top. Magnetic and gravity data suggest the presence of demagnetized sectors due to hydrothermal alteration in the central sector of the Seamount, while geochemical analyses of the water column and local seismicity are consistent with the presence of active hydrothermal phenomena from the top of the seamount itself [31,49]. Magnetic data indicate (like for Palinuro Seamount) rejuvenation areas as the most interesting for hydrothermal vent products [111,115,116]. The spatial resolution of the available magnetic data, while informative, remains too coarse to resolve fine-scale hydrothermal features. Moreover, the link between magnetic demagnetization and specific mineral deposit types remains partly inferential and must be confirmed through ground-truthing via ROV surveys, coring, and geochemical assays. Additionally, the long-term ecological consequences of mining activity in these unique environments remain poorly understood. To address these gaps, future research should focus  
Figure 6: Morphology of the Palinuro Volcanic Chain, composed of several seamounts and different morpho-volcanic items. GS: Glabro Seamount; ES: Enotrio Seamount; OS: Ovidio Seamount. The rejuvenation area (black circle within the caldera’s frame) seems to be the most promising for DSM. Figure 7: (**A**) Detailed morphology of the Marsili Seamount. The shallower rejuvenation area (ca. 500 m bsl, in the black-dotted circle) seems to show a higher percentage of metals. (**B**) 3D view of the Marsili Seamount and of its rejuvenation sector. on (1) high-resolution geophysical and geochemical surveys at priority sites to better constrain the nature and extent of subsurface mineralization, also including advanced facies recognition with reflection seismic profiles acquired with deep-towed systems and specifically processed to properly understand the real dimensions of DSM facies (e.g., [117]) and (2) in situ biological and ecological studies to assess vulnerability and species endemism in hydrothermal vent communities and integrated impact assessments that model the cumulative effects of potential DSM operations within sensitive volcanic and hydrothermal ecosystems. In the Southeastern Tyrrhenian Sea, where ecologically sensitive seamounts coincide with hydrothermally active areas, evaluating the environmental impacts of potential deep-sea mining is crucial. Long-term studies [4,8] show that seabed disturbances cause persistent ecological degradation, including sediment plumes that affect regions far beyond the immediate impact zone. Modeling efforts [7,10] warn of risks to benthic food webs and metal bioaccumulation, highlighting potential long-term toxicity.