минералы платиновой группы, изотопный состав осмия, os-изотопный возраст, условия образования, золоторудное поле эвандер, витватерсрандский бассейн, южная африка, platinum-group minerals, osmium isotope composition, os-isotope age, conditions of formation, witwatersrand basin, south africa, Engineering geology. Rock mechanics. Soil mechanics. Underground construction, TA703-712

We firstly report compositional and isotope-geochemical characteristics of Ru-Os-Ir(-Pt) alloys, Ru-Os sulfides and polycomponent solid solutions of the system Ru-Os-Ir-Pt (±Fe) derived from the Kimberley Reef within Evander Goldfield of the Witwatersrand Basin (South Africa). The study employed electron microprobe analysis and laser ablation attached to multiple collector inductively coupled plasma mass spectrometry. The obtained results are consistent with: 1) high-temperature formation of the studied platinum-group minerals, 2) sub- hondritic Archean source of platinum-group elements, 3) similarity of the initial Os-isotope composition in coexisting Os-rich alloys and Ru-Os sulfides and 4) significant Os-isotope variations in individual Ru-Os-Ir alloys, Ru-Os sulfides and polycomponent solid solutions of the Ru-Os-Ir-Pt (±Fe) system. 187Os/188Os ages are used to discriminate between different models of noble metal mineralization origin within the Witwatersrand basin.