Experimental Studies of the Role of Bi, Te, As in Platinum Group Elements (PGE) Fractionation and Remobilization During the Crystallization of a Sulfide Melt

THE ISSUE:

The Platinum Group elements (PGE) in the footwall ores in Sudbury are typically found as Platinum Group Metals (PGM) that contain arsenic, tellurium, and bismuth (e.g. michenerite, moncheite, froodite, sperrylite). To understand the distribution of PGE in Cu-Ni-PGE systems (and the influence of magmatic vs. hydrothermal processes in ore formation), it is necessary to constrain how these three elements (As, Te, Bi) affect the behaviour of PGE.

THE SOLUTION:

Experiments are being conducted in the Laboratory for Experimental Petrology Applied to Ore Deposits at Laurentian University involving the synthesis of sulfide melts, enriched in Bi, Te, As, and PGE to constrain how separation of a Cu-rich sulfide melt from a Fe-rich sulfide residue and separation of a Bi-Te melt from a Cu-rich sulfide residue affect the fractionation of PGE. Synthesis is being done at temperatures ranging from 1200 oC to 550 oC and either at atmospheric pressures (in evacuated silica tubes) or at 5 kbar (in a piston-cylinder press). Synthesized samples were analyzed for distribution and partitioning of PGE among different phases to determine the temperatures at which Bi-Te melts form and to establish how PGE fractionate in the presence of As, Bi, and Te.

INNOVATION IN PROGRESS:

Experiment results indicate that gold, palladium, and platinum can be mobilized away from a main mass of sulfides without the need of hydrothermal fluids, at temperatures down to 600 °C. Below 600°C, any PGE mobilization will likely be hydrothermal. Main results were presented at the GAC-MAC conference in May 2013 and a paper will be submitted for publication by end of 2013. Additional experiments on different aspects of the system are in progress.