Large-volume platinum ore deposits in zonal mafic–ultramafic complexes of the Ural–Alaskan type and the outlook for their development / Крупнотоннажные месторождения платиновых руд в зональных мафит–ультрамафитовых комплексах урало–аляскинского типа

The results of mineralogical–technological studies of PGM mineralization in zonal mafic–ultra mafic complexes of the Ural–Alaskan type are given. All studied massifs in the Urals and Kamchatka are characterized by similar evolution of mineral assemblages. The chromite (platinum–chromitite–dunite) and dunite (platinum–pegmatoid dunite) geological–economic types of small platinum deposits and occur rences are separate enriched sites (ore shoots) of largevolume platinum ore deposits. These are rather thick and extended zones of recrystallized dunites with attributes of hightemperature structural deformations and intense fluid reworking. Low Pt grade in ore (<0.5 gpt) is determined by fine and very fine (grain size class – 80 μm) euhedral PGM crystals distributed rather uniformly in ore mass. The high and occasionally anoma lous Pt contents (up to 1 kgpt and higher) are related to large xenomorphic segregations of PGM, which con centrate largely in the marginal parts of separate chromite segregations. The significant part of productive Pt bearing mineralization is hosted in olivine matrix of igneous rocks, so that recovery of platinum cannot be associated only with separation of chromite ore. The direct gravity concentration of platinum ore without preliminary separation of chromite concentrate is recommended as the main technique of platinum recovery. The technological scheme provides for twostage comminution of ore with betweencycle separation of coarse the PGM fraction into the concentrate as a commodity product. The results obtained allow us to regard the aforementioned mineralization as a new geological and economic type of lode platinum deposits, whose potential is comparable with active platinum reserves in the complex Cu–Ni ores of the Noril’sk dis trict. <...>