Fig. 6

Review of the knowledge of the hydrothermal system: a Map of groundwater discharge temperatures (°C) at Ischia (modified from Di Napoli et al. 2009) and location of fumaroles (1-Donna Rachele, 2-Maronti, 3-Panza, 4-Monte Nuovo, 5-Monte Cito, 6-Ischia Porto, 7-Porto S. Antonio, 8-Castello, 9-Carta Romana, 10-Grotta del Mago, Tedesco 1996; Chiodini et al. 2004); b triangular diagrams of cations and anions relative compositions of Ischia groundwaters (modified from Piper, 1953); c Geothermometric Na-K-Mg diagram from Giggenbach (1988). Solid curves represent the attainment of full and partially equilibrium conditions; d diagram of log(H2O/H2) + log (CO/CO2) vs. 3log(CO/CO2) + log (CO/CH4). In the diagram are shown: the theoretical values of both variables in a single saturated vapor phase (vapor line) and in a single saturated liquid phase (liquid line); the vapors generated by boiling of a liquid at fixed original temperature To and different separation temperatures Ts (SSVS lines); the vapors generated by boiling of a liquid at different original temperatures To and at fixed separation temperature Ts (100 °C and 200 °C Ts lines); the analytical gas ratios for Ischia (Donna Rachele) fumaroles are from Tedesco (1996), Chiodini et al. (2004) an unpublished data from INGV