PGM minerals from placer of the Murzinka-Adui granite gneissic complex and their possible sources
V.V. Murzin, A.Yu. Kisin, D.A. Varlamov
The paper presents the results of study of PGM minerals found in a small placer of the Murzinka-Adui granite gneissic block, Central Urals. We studied 65 PGM grains 0.1-0.8 mm in size including 42, 21, and 2 grains of the Os-Ir-Ru (±Pt, Rh) and Pt-Fe (±Ir, Rh, Pd) system, and sperrylite (PtAs2), respectively. An assemblage of fusible and refractory PGE minerals in the studied placer is similar to the Nurali-Verkhneyvinsky type of PGE mineralization that may indicate that chromitities from transitional zone between dunite-harzburgite series of ophiolite rocks to the banded dunite-clinopyroxenite ones are the main PGM source. The Os-Ru trend of variation in compositions was distinguished for the first time for the Os-Ir-Ru hexagonal alloys, but the importance of this trend is still unknown. Possible PGM sources including the run-off from the nearest Pt-bearing ultramafic massifs or destruction of small serpentinite bodies known in the studied area are discussed.
Figures 11. Tables 7. References 21.
Key words: Urals, platinum group minerals, granite gneiss, chromite, Murzinka-Adui block.
МINERALOGY № 1 2015