The taimyrite-tatyanaite series and zoning in intermetallic compounds of Pt, Pd, Cu and Sn from Noril'sk, Siberia, Russia

We report on the existence of a newly recognized extensive solid-solution s eries between taimyrite and tatyanaite, its Pt-dominant analogue. Copper pr obably occupies a separate site. Substitution involving Pd and Cu also is i mportant, such that taimyrite-tatyanaite forms a solid-solution series with cabriite, which is structurally closely related to taimyrite and tatyanait e. These platinum-group minerals (PGM) occur in base-metal sulfide (BMS) or es in the Oktyabr'sky deposit, Noril'sk complex. Siberia, Russia. The taimy rite-tatyanaite is present as single grains and aggregates, associated with a heterogeneous Ag-Au alloy, and also as zoned intergrowths of Pt-Pd-Cu st annides. These intergrowths commonly, but nor necessarily, occur within cha lcopyrite and typically display the following sequence of crystallization, based on textural and compositional data: atokite-rustenburgite --> tatyana ite --> Pt-rich taimyrite --> taimyrite poorer in Pt --> late-stage Ag-Au a lloys. Subsolidus re-equilibration of the atokite-rustenburgite core with t he Cu-rich host is considered unlikely to produce the peripheral zones of t he Cu-rich PGM around this core. These zoned PGM probably formed from a tra pped liquid rich in noble metals, Cu, and Sn. Decrease in temperature and i ncrease in activity of Cu in the remaining liquid seem to have been the mai n factors to control the order of crystallization of the PGM in the zoned i ntergrowths.