Evidence of Tectonic Control on the Geochemical Features of the Volatiles Vented along the Nebrodi-Peloritani Mts (Southern Apennine Chain, Italy)

Figure 4

³He-⁴He-CO₂ diagram. The graph shows the occurrence of CO₂ dissolution phenomena occurring at variable extents for the sampled sites (grey lines). All the samples plot to the left of the grey line showing that their ³He content is always below the atmospheric. The helium isotopic ratio is mainly a binary mixing between the atmosphere and a ⁴He-rich end member, and the grey lines also indicate constant ³He/⁴He ratios. Symbols and labels are as in Figure 3. Open circles refer to bubbling gases from the Calavà and Alì areas.