## 7 Discussion
### Physicochemical Parameters of the Hydrothermal Fluids  
Exsolution of hydrous fluids and silicate melts during the crystallization of the quartz monzonite at a shallow depth favored the hydraulic fracturing of the quartz monzonite and latite, which enhanced the permeability of the host rocks and the deposition of magnetite, chalcopyrite, bornite, molybden, and pyrite in A-type veins, fractures, and as disseminations in the host rock. This stage of mineralization is associated with the potassic alteration. Fluid inclusions in A-type quartz veins at Vathi show that quartz and related metallic mineralization formed as a result of phase separation from an initial high temperature (at least \(>\)600 \({}^{\circ}\)C), featuring moderate-salinity supercritical magmatic fluid (Figures 19 and 20) under boiling conditions during the ascent and cooling of the fluids. The rapid drop in temperature and pressure favored fluid immiscibility in these veins, resulting in a saline brine (33-47 wt % NaCl equiv; type 2) and a co-existing lower salinity (10-19 wt % NaCl equiv; type 3) low-density vapor-rich fluid at lithostatic pressures that homogenize over the same temperature range, mainly between 390 and 540 \({}^{\circ}\)C. This association, plus the presence of type 4 vapor-rich inclusions, suggests that the potassic alteration was associated with fluid boiling (Figure 19) as has been described elsewhere [62; 66; 69; 70]. The presence of halite and sylvite in fluid inclusions indicates that the ore-bearing fluid in A-type veins was saturated in NaCl and KCl, as well as the likely presence of chalcopyrite and pyrite in type 2 inclusions, shows that the fluids were hypersaline and that Cu at Vathi was likely precipitated by the condensation of metal-rich brines. Fluid inclusions trapped from boiling fluids do not require pressure corrections, and the measured homogenization temperatures represent trapping temperatures [62; 70]. Trapping pressures of co-existing type 2 and 3 fluid inclusions in A-type veins at Vathi range from 248 to 646 bars, which were estimated using the equation of state of Zhang and Frantz [71] and homogenization temperatures. This corresponds to a depth of ore formation between 1.0 and 2.6 km assuming lithostatic conditions (Figure 20). The estimated densities of the hydrothermal fluids are >0.77 g cm\({}^{-3}\) for the highly saline liquid-rich (type 2) fluids, and <0.78 g cm\({}^{-3}\) for the moderate-salinity vapor-rich (type 3) fluids. Fluid boiling can cause extensive hydraulic fracturing of the wall rocks and result in mixing of ascending boiling magmatic fluid with meteoric water at the ductile to brittle transition under hydrostatic pressures [72]. The lower temperature (310-390 \({}^{\circ}\)C) and less saline (8-11 wt % NaCl equiv) type 1 liquid-rich fluid inclusions in the hydrothermal quartz of latite at Vathi (Figure 19) likely represents a late fluid that was associated with decompression under hydrostatic pressures (Figure 20). This decompression was caused by extensive hydrofracturing and generated the fractures associated with the metallic mineralization at Vathi [69], which is associated with the sericitic alteration. Fluid inclusions from the E-type epithermal veins are characterized by low salinity (1.4-2.9 wt % NaCl equiv) and relatively low Th ranging between 205 and 259 \({}^{\circ}\)C, with a maximum at \(\approx\)220 \({}^{\circ}\)C (Figures 19 and 20). These fluid inclusions formed during the final stage of the magmatic-hydrothermal evolution of the system and represent a dilute fluid resulting from the mixing of a moderate saline fluid with circulating meteoric water in the epithermal stage. These non-boiling fluids are associated with the assemblage sphalerite + galena + arsenopyrite \(\pm\) stibnic \(\pm\) tenannite ore.