PLATINUM-PALLADIUM OCCURRENCE VASILINOVSKOE: A NEW TYPE OF NOBLE-METAL MINERALIZATION IN THE URALS

For the first time, a new noble-metal (Pt–Au–Pd) Vasilinovskoe ore occurrence discovered near the village of Kharp in the Yamalo-Nenets Autonomous Okrug is described. It is associated with amphibolized gabbroids and subordinate pyroxenites of the Kershor complex, dated mainly to the Late Ordovician. In these rocks, mineralization zones with an apparent thickness from 0.5 to 50 m (sulfides 3–5 vol.%, occasionally more) are developed. In areas with scattered or finely nested sulfide inclusions, feldspar-quartz, epidote and other veins are often present. According to assay data, in substantially sulfide 0.5–1 kg samples of these, in general, low–sulfide zones, the Pd content reaches 1.4 g/t, Au – 0.8 g/t, and Pt – 0.2 g/t. PGE minerals are represented by abundant secretions of micron–sized palladium tellurides – merenskite PdTe₂, temagamite Pd₃HgTe₃, kotulskite PdTe, as well as other noble metal compounds – sadberite PdSb, arsenopalladinite Pd₈(As,Sb)₃ and others. In addition to these palladium minerals, the magnetite–chalcopyrite–pyrite association contains microinclusions of native silver, native bismuth and native tin. In the later polysulfide–feldspar–carbonate–quartz association, Au and Ag tellurides, native gold (including Hg-bearing), Se-containing argentite, greenockite are found. The formation of parageneses of precious metals is associated with late magmatic processes, as well as with redistribution by subsequent magmatogenic hydrothermal fluids, up to a temperature of ~250°C; pressure decreased from ~0.9–1.3 to ~0.4–0.5 kbar.