Micrometric Inclusions in Platinum-Group Minerals from Gornaya Shoria, Southern Siberia, Russia: Problems and Genetic Significance

Abstract

Micrometric inclusions in platinum-group minerals (PGMs) from alluvial placers carry considerable information about types of primary rocks and ores, as well as conditions of their formation and alteration. In the present contribution, we attempt to show, with concrete examples, the significance of the data on the composition and morphology of micrometric inclusions to genetic interpretations. The PGM grains from alluvial placers of the Gornaya Shoria region (Siberia, Russia) were used as the subject of our investigation. In order to determine the chemical composition of such ultrafine inclusions, high-resolution analytical methods are needed. We compare the results acquired by wavelength-dispersive spectrometry (WDS; electron microprobe) and energy-dispersive spectrometry (EDS) and scanning electron microscopy (SEM) methods. The results obtained have good convergence. The EDS method is multi-elemental and more effective for mineral diagnostics in comparison with WDS, which is its certain advantage. The possible conditions for the formation of inclusions and layers of gold, sulfoarsenides and arsenides in Pt3Fe grains, which have an original sub-graphic and layered texture pattern, are discussed. They are the result of solid solution and eutectic decompositions and are associated with the magmatic stages of grain transformation, including the result of the interaction of Pt3Fe with a sulfide melt enriched with Te and As.

Editorial for the Special Issue “Platinum-Group Minerals: New Results and Advances in PGE Mineralogy in Various Ni-Cu-Cr-PGE Ore Systems”

“…A careful mineralogical study of PGM grains from alluvial placers of the Gornaya Shoria of Russia [7] allowed to postulate the conditions of their formation and alteration. The original sub-graphic and layered texture pattern of PGM and gold indicate that they are the result of solid solution and eutectic decompositions occurred at magmatic stages, including the result of the interaction of Pt 3 Fe with a sulfide melt enriched with Te and As.…”