## 4 Local Geology  
The main crystalline rocks in the Vathi area include Paleozoic two-mica gneiss, schists and amphibites of the Vertiskos Unit (Figure 3a-c), which were metamorphosed to the amphibolite facies [42]. The gneiss include quartz, plagioclase (An = 25-30%), K-feldspars, biotite, and muscovite, while garnet, epidote, and titanite occur in minor amounts [42]. The schist consists of quartz, muscovite, biotite, and plagioclase, and it is intercalated with the gneiss. Amphibolite and amphibilic schist occur in lenses and consist of plagioclase, hornblende, titanite, epidote, and minor pyroxene [42]. These metamorphic rocks trend NNE-SSW and dip ESE at \(\sim\)65\({}^{\circ}\)[42]. Un mineralized pegmaties and milky quartz veins crosscut the metamorphic rocks, whereas thin quartz lenses occur occasionally, and they are parallel to the schistosity of these rocks. A serpentinized Paleozoic-Mesozoic peridotite is intercalated with the gneiss at the northwest of the study area (Figure 3). It consists of olivine and pyroxene that were replaced by serpentine and talc, with magnesite veins crosscutting the rock [42]. Magnatic rocks that host the Vathi mineralization comprise subvolcanic stock-like bodies and dikes exhibiting porphyitic texture that intruded the crystalline rocks [16; 42]. Two rock types are distinguished: a latite, extending from Ragain 1 Hill to part of Ragain 2 Hill, and a quartz monzonite outcropping to the north of Ragain 2 Hill (Figure 3a and inset map). The latite at Vathi forms an oval shaped plug covering an area of \(\approx\)0.25 km\({}^{2}\) at Ragain 1 Hill, with a narrow 400 m long apopphysis trending toward the north (Figure 3a). Geophysical investigation reveals that the latite dips to the east to a depth exceeding 240 m [43]. [PERSON] [42] and [PERSON] [44] characterized this intrusion as hyroadice, whereas [PERSON] [16] referred to it as latite. At the surface, small oval-shaped outcrops of quartz monzonite trend E-W and intrude the basement rocks and the latite [45] (Figure 3a and inset map). [PERSON] [16] obtained two U-Pb zircon emplacement ages of 18 \(\pm\) 0.5 Ma and 17 \(\pm\) 1 Ma. An ESE-WNW trending phreatic breccia, approximately 120 m long, 25 m wide, and more than 10 m thick at the surface, intrudes the latite along the eastern part of Ragain 1 Hill (Figure 3a). In addition, more breccia are found southwest of Ragain 1 and 2 Hills (Figure 3; inset map). West and southwest of Ragain 1 and 2 Hills, small barren intrusions of biotite granite and amphibic granite occur (Figure 3a and inset map). These rocks are slightly affected by sericitic alteration. The formation of these rocks was contemporaneous to the subvolcanic intrusions [42]. Tectionically, Vathi lies in a graben bounded by faults with WNW-ESE and E-W trends (Figure 3; inset map). Quartz monzonite and the latite are located near the intersection of two of these faults (Figure 3). Local faults along Ragain 1 and 2 Hills reflect these regional structures (Figure 3). In addition, a group of NE-trending structures is observed. The NE-trending structures strike N52E and dip 51\({}^{\circ}\) to NW, while the NW-trending structures strike N25W and dip 60\({}^{\circ}\) to ENE. The E-trending structures strike N76E and dip 70\({}^{\circ}\) to SSW. The magmatic and hydrothermal activity within the Vathi porphyry system is genetically and spatially associated with these faults and structures (Figure 3). The quartz monzonite occurs in narrow, elongated intrusions which trend E-W. The mineralized phreatic breccia intrudes the latite along an almost E-W direction (Figure 3). Along the northern part of Ragain 1 Hill, a group of structures is present that trends E-W, which is accompanied by several minor conjugate NE-SW structures (Figure 3). Locally, along these E-trending structures, in the latite, a cataclasite is found. Veins, in places as sheeted veins, are associated with the E- and NE-trending group of structures and dip 60\({}^{\circ}\) to 76\({}^{\circ}\) toward SSW.