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CONDITIONS FOR THE FORMATION OF WALLROCK MINERALS AND ORES OF THE PINIGIN DEPOSIT (ALDAN-STANOVOY SHIELD, SOUTH OF THE SIBERIAN PLATFORM)

A. A. Kravchenko 1, N. V. Popov 2, A. I. Zhuravlev 1, A. V. Okrugin 1, E. E. Loskutov 1, V. I. Berezkin 1

1 Institute of Diamond and Precious Metals Geology SB RAS, Yakutsk, Russia; 2 Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia

Metamorphogene-hydrothermal sulphide-arsenide mineralization with native gold, bismuth and intermetallides of gold, bismuth and tellurium at the Pinigin deposit (the central part of the Aldan-Stanovoy Shield) is aracterized. Parameters and the metamorphism age of host rocks, material composition of ores and content of accompanying elements in ore minerals are considered. It was found that due to the conditions of the mineral associations formation, metabasites refers to the granulite facies moderate pressure rocks. Regressive metamorphism of amphibolite facies is revealed in ore intervals of metabasites, substitutions are less expressed in the conditions of epidote-amphibolite facies and lower. It is shown that the ore formation process begins with the crystallization of gold-, bismuth-, and telluric loellingite in association with bipyroxene parageneses and amphiboles of granulite and amphibolite facies. Under conditions of the epidote-amphibolite facies, large amounts of pyrrhotine were formed with the decomposition and substitution of loellingite, the removal of gold, bismuth, tellurium and the formation of polymetallic melting. At temperatures below the epidote-amphibolite facies, the polymetallic melting crystallized in fractures in high-temperature minerals together with disseminated deposits of arsenopyrite and pyrite. The temperature values of mineral formation obtained as a result of thermobarometric calculations correlate with effects of gas release and decrepitation of fluid inclusions in plagioclases and pyroxenes (780–480 and 450–180 􀇡C, respectively) associated with processes of metamorphism and superimposed processes of mineral formation.

Keywords: Precambrian, metamorphism, basites and ultrabasites, ore formation conditions.

DOI 10.20403/2078-0575-2025-2-78-93

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