## 6 Results
### Hydrothermal Alteration
#### 6.4.1 Hypogene Mineralization  
The mineralization forms disseminations, aggregates, veins, and veinlets. Four assemblages are present: (1) pyrite + chalcopyrite + bornite + molybden + magnetite associated with potassic alteration, (2) pyrite + chalcopyrite related to propylitic alteration, (3) pyrite + chalcopyrite + native gold \(\pm\) tetradymite associated with sericitic alteration, and (4) sphalerite + galena + arsenopyrite + pyrrhotite + pyrite \(\pm\) stibnite \(\pm\) tenannite related to the epithermal overprint (Figure 11). Furthermore, four early to late-stage hydrothermal vein types correspond to M-, A-, D-, and epithermal (E-type) veins, as described by for example, [PERSON] et al. [55] and [PERSON] [56]. The mineralization associated with the potassic alteration occurs in quartz monzonite and is present mainly along drill hole D1 (66-75 m interval) [46]. It forms A- and M-type veins and disseminations, and it consists mostly of pyrite and chalcopyrite with minor molybden, bornite, and magnetite. A-type quartz veins (up to 2 cm wide) are rare but were observed in the drill core samples (Figure 12a). The M-type veins, found on the surface and at the depth, contain magnetite with quartz and titanite (Figure 12b). At a depth of 140 m, pyrite and chalcopyrite are present in approximately equal amounts, whereas at 166 m, only chalcopyrite and molybden occur. Restricted amounts of pyrite and chalcopyrite were observed in the propylitic alteration that extends in both magmatic rock types at the surface and at a depth of 40 to 140 m.  
Pyrite and chalcopyrite, as well as minor amounts of rutile and ilmenite, occur in sericitic alteration mainly in latite but also in the phreatic breccia and surrounding metamorphic rocks [46]. The mineralization forms disseminations, aggregates, and D-type veins and veinlets and associated halos along cracks in the latite rock mass (Figure 12c). In some cases, D-type sheeted veins trending E-W form a dense system crosscutting the latite  
Figure 10: Photomicrographs of textures and minerals of the hydrothermal alterations (plane polarized light: a, b; cross-polarized light: c, d): (**a**) Hydrothermal biotite (Bt), quartz (Qz), and pyrite (Py) from an A-type veinlet of the potassic alteration in a quartz monzonite drill core sample; (**b**) Hydrothermal chlorite (Chl) and pyrite (Py) of the propylitic alteration in the quartz monzonite; (**c**) Sericitic (Ser) in altered K-feldspar of the sericitic alteration in latite; (**d**) Clusters and disseminations of quartz (Qz) and pyrophyllite (Prl) replaced by iron oxides in the groundmass of cataclasite. (Figure 6). They are usually less than 1 cm wide, locally reaching up to 5 cm in width.A subsequent epithermal overprint is documented locally within the potassic and seritic alteration. It mainly occurs as E-type veins at depth and consists of sphalerite, galena, arsenopyrite, pyrrhotite, and traces of tennantite, stibnite, rutile, and ilmenite. Pyrite is the most common sulfide in the Vathi porphyry system, and it is intergrown with chalcopyrite, bornite, pyrrhotite, sphalerite, and galena. Locally, it hosts rounded inclusions of chalcopyrite, as well as euhedral inclusions of magnetite and molybdenite. It occurs as disseminations or intergrowths of anhedral to euhedral grains, with sizes varying from 25 to 200 \(\upmu\)m and from 400 \(\upmu\)m to 2 cm, respectively (Figure 13a). Pyrite also forms veinlets (up to 3 mm in size) and minor dispersions, in which galena locally appears in the interstices (Figure 13b). Chalcopyrite is the second most abundant sulfide and is found mainly in the potassic alteration where it is intergrown with pyrite, magnetite, molybdenite, and bornite (Figure 13c-f). It occurs as disseminated grains (<200 \(\upmu\)m in size), irregular aggregates (<300 \(\upmu\)m in size), and rounded inclusions (<20 \(\upmu\)m in diameter) in pyrite. Chalcopyrite  
Figure 11: Ore and alteration minerals corresponding to each alteration zone in the Vathi porphyry Cu-Au\(\pm\)(Mo) deposit.