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

Abstract

The Vathi porphyry Cu-Au±Mo deposit is located in the Kilkis ore district, northern Greece. Hydrothermally altered and mineralized samples of latite and quartz monzonite are enriched with numerous rare and critical metals. The present study focuses on the bulk geochemistry and the mineral chemistry of pyrite, chalcopyrite, magnetite, and titanite. Pyrite and chalcopyrite are the most abundant ore minerals at Vathi and are related to potassic, propylitic, and sericitic hydrothermal alterations (A- and D-veins), as well as to the late-stage epithermal overprint (E-veins). Magnetite and titanite are found mainly in M-type veins and as disseminations in the potassic-calcic alteration of quartz monzonite. Disseminated magnetite is also present in the potassic alteration in latite, which is overprinted by sericitic alteration. Scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of pyrite and chalcopyrite reveal the presence of pyrrhotite, galena, and Bi-telluride inclusions in pyrite and enrichments of Ag, Co, Sb, Se, and Ti. Chalcopyrite hosts bornite, sphalerite, galena, and Bi-sulfosalt inclusions and is enriched with Ag, In, and Ti. Inclusions of wittichenite, tetradymite, and cuprobismutite reflect enrichments of Te and Bi in the mineralizing fluids. Native gold is related to A- and D-type veins and is found as nano-inclusions in pyrite. Titanite inclusions characterize magnetite, whereas titanite is a major host of Ce, Gd, La, Nd, Sm, Th, and W.

A Fluid Inclusion and Critical/Rare Metal Study of Epithermal Quartz-Stibnite Veins Associated with the Gerakario Porphyry Deposit, Northern Greece

“…Hydrothermal alterations are largely superimposed on each other and have significantly altered both the magmatic rocks and the surrounding metamorphic rocks [39]. Approximately 4 km northeast of Gerakario, the Vathi Cu-Au ± Mo porphyry deposit is enriched in Ag, Au, Bi, Co, Se, and Te, as well as in REE (Ce, Gd, La, Nd, and Sm) [32,33] (Figure 1). In addition, minor mineralized veins are found in the adjacent metamorphic rocks, consisting mainly of pyrite and chalcopyrite (± arsenopyrite, galena, stibnite) [39] (Figure 2).…”

“…The porphyry Cu-Au deposit and the epithermal quartz-stibnite veins at Gerakario are related to the emplacement of a syenite intrusion in two-mica gneiss of the Vertiskos unit during the Miocene (22 ± 0.8 Ma; U-Pb zircon ages [42]), in an extensional structural regime. The mineralization shares many similarities in its geotectonic setting, structural control, magma evolution, hydrothermal alteration, and physicochemical parameters of the hydrothermal fluids with the adjacent Vathi porphyry-epithermal system, which is genetically related to a quartz monzonite [32,33].…”

“…Epithermal, high to low sulfidation veins are commonly found peripheral to porphyry systems and porphyritic intrusions [19,63]. Epithermal veins are associated with several porphyry deposits in Greece (e.g., Pagoni Rachi, Maronia, Vathi) [24,33,64]. However, the veins in these deposits do not host massive stibnite [24].…”

“…Figure 1. Geological setting of the Cenozoic magmatic rocks and the related ore types in the Kilkis ore district, northern Greece (modified after References [23,24,[31][32][33]). The studied area in Gerakario is also shown.…”

“…At Philadelphio, Sb mineralization occurs in shear-zone hosted massive and discordant stibnite veins, crosscutting the metamorphic rocks of the Vertiskos unit [29] Figure 1. Geological setting of the Cenozoic magmatic rocks and the related ore types in the Kilkis ore district, northern Greece (modified after References [23,24,[31][32][33]). The studied area in Gerakario is also shown.…”