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The application of electron microprobe for mineralogical practice stimulated PGM finding in various geological occurrences in 60s years. For completing our knowledge on PGE mineralogy samples of Cu-Ni-PGE sulfide ores (Noril'sk region deposits) were re-investigated using XRA, scanning electron microscopes equipped by energy dispersive detectors (JSM ? 5300 + INCA, JSM ? 5610 LV + Kevex 5100), and chemical etching. In consequence of this study new information on PGM and PGM-assemblages was obtained.
1. Composition and formula of some PGM are corrected. The problem of "Pt2Fe" is discussed.
2. It is shown that most of minerals considered homogeneous consist of complex intergrowths of two and more phases. Often the inclusions of various PGM are so tiny that could be observed only at high magnifications (x5000). Such heterogeneity causes the presence of so-called isomorphous elements in many PGM [plumbopalladinite, Pd3Pb2, polarite, PdPb-PdBi, Pd-auricupride, (Au,Pd)Cu, stannopalladinite and other PGM].
3. PGE mineralization in different ore types of Talnakh (T) and Oktyabrsk (O) deposits could be compared on the base of textural peculiarities and mineral composition of PGM assemblages.
(T): Monomineral PGM grains are very seldom observed. Complex polymineral assemblages with (Pt,Fe,Ni,Cu) are typical, particularly "zoned" intergrowths of (Pd,Pt)-Sn-Cu minerals with central part rich in Pt, and zone of stannopalladinite, (Pd,Pt)5Sn2Cu. The last often contains tiny inclusions of bornite. Typomorphic minerals for Talnakh deposit are PGM with Pb (Pb-polarite, plumbopalladinite, zvyagintsevite). Large galena grains are rare. But Pb is determined not only in Pd/Pt-Pb minerals. Pd/Pt-Sn-Cu, (Au,Pd,Cu), Pd/Pt-Sn-As minerals etc. could contain up to 6-7 wt.% of Ag.
(O):Monomineral PGM grains prevail over polyminerals assemblages. Practically there is no stannopalladinite, but cabriite, Pd2SnCu, and taimyrite, (Pd,Pt)9Sn4Cu3. (Pt,Fe,Ni,Cu) was found only once as tiny veinlets in taimyrite. There is no Pb in PGM - it forms galena and altaite, seldom clausthalite.
4. Some new natural PGE phases were found - PdCu3, (Au,Pd)Cu3, (Pd,Pt)11Sn2(As,Pb)2, etc.
5. Mineral BORISHANSKIITE, Pd1+x(As,Pb)2 (1975) should be discredited. The revision of holotype of borishanskite from Fersman Museum (Moscow), show that it is POLARITE, Pd(Pb0.73Bi0.27). This "mistake" is caused by non correct choice of analytical line for As (MRSA).
6. The compositions of PGM and their associations vary depending on ore types and assemblages. Based on the data obtained the mechanism of PGM crystallization depending on temperature regime is proposed.
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