Platinum mineralization has been studied within two zoned clinopyroxenitedunite massifs of the Urals Platinum Belt. Within the Svetloborsky massif, platinum group minerals (PGM) occur directly in serpentinized dunite. The ore-forming system demonstrates the features of an early evolutionary stage: a significant portion of PtFe alloys belongs to ferroan platinum; native osmium is depleted in Ir; an isoferroplatinumosmium paragenesis is present. Within the Kamenushinsky massif, PGM are genetically related to chromitite and belong to the late-magmatic stage of the ore-forming system evolution: osmium and isoferroplatinum are rich in Ir; both isoferroplatinumosmium and isoferroplatinumiridium magmatic parageneses are present. The elevated Pt in the dunite of the Svetloborsky massif and in the chromitite of the Kamenushinsky massif is the result of two events: the primary-magmatic crystallization of PGM and later hydrothermal overprint.
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 large volume platinum ore deposits. These are rather thick and extended zones of recrystallized dunites with attributes of high temperature 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 two stage comminution of ore with between cycle 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.
Experimental and methodological works were carried out by the thermomagnetic geochemical method (TMGM), one of geoelectrochemical methods, within the Svetlyi Bor platiniferous massif (Central Urals). We have analyzed the results of observation along two (search and test) profiles. The known distribution of platinum contents along the ditch in the test profile confirmed the effectiveness of the used method and made it possible to recognize the best indicators of platinum from the geoelectrochemical research data. The obtained results helped to reveal PGE-promising areas and suggested the presence of deep-seated “blind” orebodies.
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