## 5 Discussion
### Genesis and Geochemistry of the Epithermal Quartz-Stibnite Veins at Gerakario  
The epithermal veins formed from a fluid of low to moderate salinity (7.9 to 10.4 wt.% NaCl equiv.) with homogenization temperatures ranging mainly from 280\({}^{\circ}\) to 320 \({}^{\circ}\)C, with a maximum at 290 \({}^{\circ}\)C (Figure 9). This fluid resulted from the mixing of a high to moderate salinity fluid exsolved from the porphyry system, and meteoric water, at the final stage of the magmatic-hydrothermal system in an epithermal environment. Due to the shallow depth of formation of these veins, the pressure correction should be \(<\)10 \({}^{\circ}\)C (e.g., [PERSON] et al. [60]). For this reason, the homogenization temperatures (280-320 \({}^{\circ}\)C, with a maximum of 290 \({}^{\circ}\)C) correspond to the minimum temperatures of the formation of the epidermal veins. Therefore, for hydrostatic pressures in the range of 65 to 116 bar, a depth of 600 to 1000 m under hydrostatic conditions is proposed for the stibnite mineralization. The local structural setting (NE-SW and E-W trending normal to oblique faults) enhanced hydrothermal fluid circulation and mixing with meteoric water. As a result, base metal mineralization formed in the surrounding metamorphic rocks [39] (Figure 2). The epithermal quartz-stibnite veins are hosted in the sericitically altered genesis. They are mostly continuous, and consist of stibnite + berthierite + native antimony + pyrite + arsenopyrite \(\pm\) (marcasite, pyrrhotite, chalcopyrite, lollingite, native gold) [39; 45] (Figures 3a-d and 5a-d). Bulk geochemical analysis revealed enrichment in Co (<1.8 ppm), Ag (<1.2 ppm), Ga (<0.16 ppm), Ce (<0.12 ppm), La (<0.4 ppm), Au (<0.05 ppm), Cd (<0.05 ppm), and Bi (<0.03 ppm) (Table 1). The depletion in Hg is profound (Table 1) and is in contrast to the Hg enriched character of the Sb ores located in SE China, where the formation of the epithermal deposits is ascribed to mineralizing fluids enriched in Sb-As-Hg-(Au-Ti-U) [16; 21]. Noteworthy are the relatively elevated concentrations of Ce (<0.32 ppm) and La (<86 ppm), as REEs are not commonly incorporated in epithermal systems [10]. Hydrothermal carbonates (e.g., calcite) mainly host REEs in the epithermal systems [21]. In these cases, REE fractionation is dependent upon the composition of the mineralizing fluids and the co-precipitating of other ore, gangue, and alteration minerals [21]. During precipitation of calcite, medium and heavy REEs are preferentially incorporated in its crystal lattice, while light REEs, especially La, are enriched in the residual fluid [21]. Thus, significant contents of La and Ce, and rarely Pr, Nd, and Sm are incorporated in stibnite, which formed after calcite [21]. Leaching of carbonate wall rocks and of rock-forming minerals from the magmatic fluids may introduce REEs to the circulating hydrothermal system [21]. A similar mechanism has been proposed for the REE enrichment detected in the oxidation zone of the adjacent Vathi porphyy Cu-Au \(\pm\) Mo deposit [32] (Figure 1). In addition, REE incorporation in minerals is related to specific physicochemical factors, including the structure of the lattice and complexation (i.e., the combination of individual atom groups, ions or molecules to create one large ion or molecule [61]), as well as sorption and desorption [21]. Magmatic fluids are generally depleted in REEs, while meteoric fluids are slightly enriched in light REEs [62]. The anatomy of the quartz-stibnite veins at Gerakario, the ore assemblage, the bulk geochemistry, and the fluid inclusion study suggest that the ore mineralization was developed from intermediate to low sulfidation hydrothermal fluids, in a fault-induced epithermal stage set at the periphery of the Cu-Au porphyy system. The same could be suggested for all the base metals vein sets found in the vicinity of the Gerakario porphyy system. Epithermal, high to low sulfidation veins are commonly found peripheral to porphyy systems and porphyritic intrusions [19; 63].