The concealed Molai Zn-Pb±(Ag,Ge) stratiform deposit in southeastern Peloponnese is hosted in Triassic intermediate tuffs, ignimbrites and subaerial andesitic flows. The host rocks display trace element signatures of a Supra-Subduction Zone (SSZ) setting. Three ore-forming stages are recognized, with stages I and II related to formation of the epigenetic, stratiform, massive-to-semi-massive ore and a late stage III associated with vein-type mineralization. The O and D isotope geochemistry of gangue chlorite and epidote reveal mixing with fresh meteoric water during the weaning stages of the hydrothermal activity of the late stage II due to uplifting of the hydrothermal system. Sphalerite is the major ore phase, with three different varieties formed during stages I (Sp-I) and II (Sp-II and Sp-III). All sphalerite varieties coexist, depicting gradual change in the chemistry of the ore-forming fluids. Molai ores are characterized by elevated Ag and Ge contents. Tetrahedrite is the major Ag carrier, while among the three sphalerite varieties, early Sp-I comprises the highest Ge contents. The Molai Zn-Pb±(Ag,Ge) deposit is characterized by intermediate features between bimodal felsic massive sulfides and subaerial epithermal systems based on the shallow formation depth, the presence of hydraulic breccias associated with phase separation, the ore formation along high-angle faults, the relatively low ore-forming temperatures below 250 °C obtained from geothermometry, and the absence of the typical structure of bimodal felsic type ores.

This study provides a comprehensive characterization of the low-to-intermediate sulfidation (LS-to-IS) epithermal Molai Zn-Pb±(Ag,Ge) ore (Vigla-Mesovouni orebody) in Laconia, Greece, and provides insights on how such data may be employed in beneficiation flow-sheet design. Detailed mineralogical, chemical, textural, and physicochemical characterization defines a systematic transition from early refractory Ge-rich to late-stage refractory Ag-rich mineralization, including sulfides and fahlores. Germanium, although present in all sphalerite varieties (Sp-I, Sp-II, and Sp-III), is predominantly enriched in early sphalerite (Sp-I, up to 1891.60 ppm). Interestingly, Ge is also enriched in early Py-I pyrite, with content reaching up to 383 ppm. Silver is mainly concentrated in late-stage tetrahedrite Ttr-II (up to 3.60%), galena (Ga-II), and, to a lesser extent, late sphalerite (Sp-III). Liberation studies reveal effective liberation of Py-I and Sp-I, major Ge carriers, in the coarser fractions (+0.150 mm) and near complete liberation of all ore phases below 0.036 mm. Combined beneficiation via Wilfley pre-concentration and differential flotation produced up to ~35% Pb and ~65% Zn at >85% recovery for the smallest fractions (−0.036 mm). Ore characterization revealed that secondary circuits may be developed to further enhance the economic value of Molai ore (Ge from Py-I, and Ag±[Sb,As] from Ttr-II and Ag-bearing sulfosalts), which are dismissed as wastes in Pb and Zn flotation circuits. The results of our study establish a robust foundation for the design of tailored, multi-stage metallurgical flow-sheets aimed at maximizing the economic value of the Molai epithermal resource.