PHYSICOCHEMICAL CONDITIONS OF FORMATION OF GOLD AND SILVER PARAGENESES AT THE VALUNISTOE DEPOSIT (Chukchi Peninsula)
T.V. Zhuravkova1,2, G.A. Palyanova1,2, Yu. A Kalinin1,2, N.A. Goryachev3,4, V.Yu. Zinina1,2, L.M. Zhitova1,2
1Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
3A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
4N.A. Shilo Northeastern Complex Research Institute, Far Eastern Branch of the Russian Academy of Sciences, ul. Portovaya 16, Magadan, 685000, Russia
Keywords: Au-Ag chalcogenides, Au-Ag solid solutions, physicochemical parameters of ore formation, Gornyi occurrence, Valunistoe deposit, Okhotsk-Chukchi volcanic belt
Abstract
The mineral composition of ores from the Gornyi occurrence of the Valunistoe epithermal Au-Ag deposit (Chukchi Peninsula) has been studied. It has been found that, in addition to native gold, the Au-Ag mineralization comprises chalcogenides (uytenbogaardtite, petrovskaite, acanthite, naumannite, and cervelleite) and minerals of the pearceite-polybasite series, which occur as microinclusions in fine-grained pyrite. The physicochemical conditions of formation of productive mineral assemblages have been estimated based on the chemical composition of Au and Ag minerals and their relationships with other minerals. It is shown that ores were deposited from weakly acid solutions at the late stages, on the background of a temperature decrease from 350 to 100 ºС, a decrease in the fugacities of sulfur (lg ƒ S2, from -2 to -23), tellurium (lg ƒ Te2, from -5 to -27), and selenium (lg ƒ Se2, from -16.5 to -28), and changes in the redox conditions (lg ƒ O2 , from -23 to -48).
DOI: 10.15372/RGG2019118
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