Palladium and gold minerals from the Baronskoe-Kluevsky ore deposit (Volkovsky complex, Central Urals, Russia)

Petrogenesis of the Platinum-Group Minerals

“…[Pd 11 As 2 Te 2 ]) PGM. Zaccarini et al (2004a) also reported large patches of kotulskite (~20 µm) intergrown with electrum and an unidentified mineral with a composition close to Pd 3 (As,Te).…”

“…Sperrylite and sudburyite also form veins and rims on the edges of base-metal sulfides. Zaccarini et al (2004a) observed abundant grains of vysotskite associated with patches (50-300 µm) of chalcopyrite (± bornite, ± carrollite; CuCo 2 S 4 ) rimmed by magnetite and disseminated in serpentinized olivine-and apatite-rich rocks, from the zoned complex of Volkovsky in the Central Urals. Vysotskite has been replaced along its grain boundaries by stillwaterite (Pd 8 As 3 ) and unidentified Pd-As-Te (törnroosite?…”

“…Jackson- Brown et al (2014) suggested that formation of the PGM was associated with the intrusion of a Cu-Pt-Pd-bearing melt phase that crystallized separately from the earlier (Ni-Co enriched) main dunite-wehrlite units. Zaccarini et al (2004a) recognized three stages of PGM formation in the Volkovsky Complex (Central Urals, Russia) that they related to chemical changes during fractional crystallization and cooling of the ore system. According to these authors, high initial f S 2 in the melt caused the crystallization of vysotskite and chalcopyrite.…”

“…This was followed by continued cooling that promoted the exsolution of kotulskite from vysotskite and electrum from both vysotskite and chalcopyrite. According to Zaccarini et al (2004a), the occurrence of arsenotellurides and kotulskite in the outer rims of the sulfide blebs indicates that the melt became enriched in Te and As after the first stage. In the final stage, Te activity in the melt decreased significantly and enrichment in As led to the formation of stillwaterite that overgrows arsenotellurides.…”

“…In the final stage, Te activity in the melt decreased significantly and enrichment in As led to the formation of stillwaterite that overgrows arsenotellurides. The observation that stillwaterite often forms intergrowths with magnetite (itself associated with secondary silicates) led Zaccarini et al (2004a) to suggest that the final stage was characterized by high a As , coinciding with the serpentinization of the silicates under relatively oxidizing conditions. Helmy (2004) also proposed a three-stage model to account for the petrogenesis of PGM in the Genina Gharbia intrusion (Eastern Desert, Egypt).…”