Morphological features, internal structure, and compositional signatures of native gold from the Murzinka placer group (Middle Urals): identification of lode sources and conditions of placer formation
- 1 — Junior Researcher South Ural Scientific Centre Mineralogy and Environmental Geology of the Ural branch RAS ▪ Orcid
- 2 — Ph.D. Senior Researcher South Ural Scientific Centre Mineralogy and Environmental Geology of the Ural branch RAS ▪ Scopus
- 3 — Ph.D. Researcher South Ural Scientific Centre Mineralogy and Environmental Geology of the Ural branch RAS ▪ Orcid
- 4 — Junior Researcher South Ural Scientific Centre Mineralogy and Environmental Geology of the Ural branch RAS ▪ Orcid
- 5 — Engineer Saint Petersburg State University ▪ Orcid
Abstract
The paper presents the results of a complex study of native gold from nine placers of the Murzinka group in the Middle Urals. Morphological features, chemical composition, and internal structure of native gold, as well as mineral inclusions within it, are described in detail. Based on the analysis of morphological characteristics and the gold particles rounding degree, the proximity of lode gold sources is inferred ranging from several hundred meters to the first few kilometers. Three types of native gold were identified according to the chemical composition and mineral inclusions. Type I (the predominant type) is characterized by high fineness with Ag and Hg admixture and inclusions of pyrite, chalcopyrite, galena, molybdenite, and petzite. The variation in admixture content within this type allows the definition of subtypes; their distribution in placers reflects the zoning of lode quartz gold mineralization. Type II is distinguished by elevated copper contents and bornite inclusions; Type III is defined by high Ag contents. Lode sources for the different gold types have been identified: for Type I, a quartz gold lode deposits; for Type II, precious metal mineralization in the gabbroids of the Pavdinsky massif. Application of the electron backscatter diffraction (EBSD) technique enabled a detailed characterization of the internal structure of gold particles. The observed high fineness intergranular veins and intergrowths of gold with minerals of the rhabdophane group suggest that native gold was located in the supergene zone during the period of active weathering crust development in the Upper Mesozoic and Palaeogene. It is established that the placer system in the Murzinka River basin formed during the Neogene-Quaternary period, primarily due to lode quartz gold mineralization. The obtained data allow the localization of prospective areas for the exploration of lode gold deposits and expand the understanding of the region’s metallogenic potential.
The study conducted under research topic of the SUSC MEG UbRAS N FUUR-2025-0007.
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