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PLACER GOLD IN NEOGENE AND QUATERNARY DEPOSITS, AMYL–SISTIG-KHEM PLACER REGION (WESTERN SAYAN)​

Ch. M. Khertek 1, А. М. Sazonov 2, N. N. Popova 2, S. G. Prudnikov 1, S. I. Leontiev 2, А. V. Fedorova 2

1 Tuvinian Institute for Exploration of Natural Resources of SB RAS, Kyzyl, Russia; 2 Siberian Federal University, Krasnoyarsk, Russia

The Amyl-Sistig-Khem gold placer region, in itself, represents a morphostructure of Neogene deposits with a dense and widely spread gold-bearing hydrographic network, almost completely inherited by the modern Sistig-Khem and Amyl river systems. The sources of gold are Cretaceous-Paleogene weathering crusts and oxidized ores of gold-quartz and gold-sulfide-quartz occurrences in the region. Gold particles from Quaternary deposits exhibit inherited hypogene ore characteristics at the placer heads; in the middle and tail portions, gold particle morphologies are dominated by lamellar, platy, and scaly forms. Gold grains contain abundant inclusions of sulfides, oxides, carbonates, phosphates, and silicates. Placer gold from Neogene deposits is represented by well-rounded scaly and lamellar shapes. The particles have shagreen surfaces, are covered with films of iron hydroxides and authigenic gold. The polyphase internal structure displays distinctly expressed relict granoblastic core, deformed and mechanically twinned, with intergranular veinlets (970–1000 ‰) and a peripheral microgranoblastic, high-fineness hypergene rim (≈1000 ‰). Kaolinite, hydromica clay minerals, and iron hydroxides are common inclusions within the particles. The kernels of gold particles from Neogene gold ore deposits have a higher fineness and a lower dispersion of Ag, Au concentrations and finenesses, as compared to the Quaternary ones.

Keywords: alluvium, gold, placer, typomorphic features, Western Sayan.

DOI 10.20403/2078-0575-2025-4a-35-49

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