Aldan-Maadyr gold ore cluster (Western Tuva): features of geological structure and chemical composition of gold

Gold ore deposits of Aldan-Maadyr gold ore cluster are characterized by linear nature of location. Several narrow linear mineralized zones of beresitization and listvenitization saturated by quartz-vein formations with gold mineralization are allocated within this cluster. The most promising deposits are concentrated in nuclear parts of narrow linear anticlines and horst-anticlines of sublatitudinal strike with transgressive blasting faults of the same direction. These structures are favourable for gold ore prospecting, including those on the periphery of the ore cluster. The most productive levels of gold mineralization may be at listvenite contact with basalt conglomerates of the Ordovician in the nuclear parts of anticlines and horst-anticlines (shielding effect). The identified gold-quartz veins in the Ordovician and Silurian deposits must be considered as top-ore formations, which are characteristic for deposits of gold-quartz formation. The composition of Au and Ag minerals of Khaak Sair ore occurrence is characterized by wide variations in gold fineness and a complete range of solid solutions (in Au-Ag-Hg series) from high-fineness gold to Hg-silver. Zonation from high-fineness gold with a clear skip through low-fineness gold and Hg-electrum to Hg-kuestelite is typical for Au and Au minerals of the gold-ore-quartz stage. Margins are folded by Hg-silver in some zoned grains of Hg-kuestelite. Zonation from high-fineness gold to electrum is also typical for the first stage of gold. Mineral compositions of Ulug-Sair deposit, of Aryskan and Duushkunnug occurrences are characterized by Hg presence up to 0.3 wt. %. Evolution of gold deposits to electrum is observed in the ores of Ulug-Sair ore occurrence. The gold of Aryskan and Duushkunnyg ore occurrences is similar in composition to the gold of Ulug-Sair deposit. Weak zoning expressed in a reduced Ag content in the central part of gold grains is observed in gold grains of these objects, compared to margins with Ag content up to 5 wt. %. Typomorphic features of native gold, electrum and Au, Ag ore minerals presence in ores of the Aldan-Maadyr gold cluster indicate the slightly truncated nature of deposits and occurrences and also favourable prospects for mineralization prolongation at deep depth (from 500 up to 1000 m). Geostructural and mineralogical-geochemical characteristics of the explored gold-quartz deposits of the mentioned gold-quartz cluster are indicative for large reserves of gold deposits identification within the cluster.

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