The Geology, Geochemistry, and Origin of the Porphyry Cu-Au-(Mo) System at Vathi, Serbo-Macedonian Massif, Greece

Abstract

The Vathi porphyry Cu-Au ± Mo mineralization is located in the Serbo-Macedonian metallogenic province of the Western Tethyan Metallogenic Belt. It is mainly hosted by a latite and is genetically associated with a quartz monzonite intrusion, which intruded the basement rocks of the Vertiskos Unit and the latite, 18 to 17 Ma ago. A phreatic breccia crosscuts the latite. The quartz monzonite was affected by potassic alteration, whereas the latite was subjected to local propylitic alteration. Both styles of alteration were subsequently overprinted by intense sericitic alteration. M-type and A-type veins are spatially associated with potassic alteration, whereas D-type veins are related to the sericitic alteration. Three ore assemblages are associated with the porphyry stage: (1) pyrite + chalcopyrite + bornite + molybdenite + magnetite associated with potassic alteration; (2) pyrite + chalcopyrite related to propylitic alteration; and (3) pyrite + chalcopyrite + native gold ± tetradymite associated with sericitic alteration. A fourth assemblage consisting of sphalerite + galena + arsenopyrite + pyrrhotite + pyrite ± stibnite ± tennantite is related to an epithermal overprint. Fluid inclusion data indicate that the A-type veins and related porphyry-style mineralization formed at 390–540 °C and pressures of up to 646 bars (<2.6 km depth) from boiling hydrothermal fluids. A later condensation of vapor-rich inclusions resulted in a moderately saline fluid (8.4–11.2 wt % NaCl equiv) at temperatures between 311 and 392 °C, which were related to sericitic alteration, D-type veins, and associated metallic mineralization. Subsequent dilution of the moderately saline fluid at lower temperatures (205–259 °C) produced a less saline (1.4–2.9 wt % NaCl equiv.) fluid, which is likely associated with the late epithermal overprint.

Rare and Critical Metals in Pyrite, Chalcopyrite, Magnetite, and Titanite from the Vathi Porphyry Cu-Au±Mo Deposit, Northern Greece

“…In the Vertiskos Unit, the extension is documented by ENE-WSW-and eastward-trending shears and related to E-W-, NW-SE-, and NE-SW-trending normal to oblique faults and N-S-trending strike-slip faults [56,58]. The Cenozoic magmatic events and the formation of the Oligocene-Miocene mineralized intrusions were structurally controlled by these faults [53,56].…”

“…The Cenozoic igneous evolution is characterized by four magmatic pulses spanning from the Late Paleocene to the Pliocene and includes I-type plutonic, sub-volcanic, and volcanic rocks, associated with calc-alkaline to high-Kcalcalkaline and shoshonitic affinities [56,62] (Figure 1). The second and the third magmatic pulses (Oligocene-Miocene) are related to mineralized intrusions, located mainly in the Kilkis and the NE Chalkidiki ore districts [37,53,56] (Figure 1).…”

“…The Kilkis ore district, in the northern part of the Vertiskos Unit, includes several porphyry prospects at Vathi, Pontokerasia, Koryfi, Doirani, and Gerakario [37,38,53] (Figure 1). The Vathi porphyry deposit (N41.1458 • , E22.9639 • ) is located near Vathi village, along Ragian Hills 1 and 2 [53] (Figure 2). Exploration projects during the 1970s and the 1980s indicated estimates of more than 258 Mt of ore with 0.40 wt.% Cu and 0.9 g/t Au [37,63].…”

“…The mineralization is hosted by latite and is genetically associated with a quartz monzonite (18 ± 0.5 Ma and 17 ± 1 Ma; U-Pb zircon ages) [52,53], which intruded the crystalline basement rocks and the latite (Figure 2). Both magmatic rocks are silica-saturated and exhibit calc-alkaline to slightly alkaline chemical affinities [52,53].…”

“…The 2020 European Union critical raw materials (CRM) list includes the following metals: Be, Bi, Co, Ga, Ge, Hf, In, Li, Nb, Sb, Sc, Sr, Ta, Ti, V, W, REE, and PGE [5]. [35,38,42,53,55,56]).…”