Distribution of platinum-group elements in Pechenga Cu-Ni sulphide ores and concentrates

摘要

The PGE contents in the Pechenga sulphide ores are rather low, averaging 0.01-0.1 ppm Pt+Pd, and mineralogical studies to date have revealed only rare PGM in the ores. The high sulphur fugacity and the low PGE contents are, apparently, the reasons why the PGE were preferentially distributed as solid solutions in sulphides and sulpharsenides. The results obtained here suggest this PGE distribution and show that the Pt and Pd (93 percent of the total Pt+Pd) are concentrated during flotation in the nickel concentrate, which contains 98.6 percent of the total pentlandite and 88.2 percent of the total pyrrhotite, and extremely rare PGM species. In the ores that have not been significantly altered a direct correlation between PGE values and ore grades is observed. In the metamorphosed ores a redistribution of PGE took place: pentlandite and pyrrhotite lost trace PGE, which were redeposited in the form of discrete PGM or were locked as solid solutions in epigenetic sulpharsenides. Thus, in the primary ores the main PGE carriers are pentlandite and pyrrhotite, whereas in the altered ores the PGE occur mostly as solid solutions in members of the cobaltite-gersdorffite series. Pentlandite may, nevertheless, carry a significant proportion of the Pd and the Pt tends to form discrete minerals, such as sperrylite and atokite.