Au‐Ag‐S‐Se‐Cl‐Br Mineralization at the Corrida Deposit (Russia) and Physicochemical Conditions of Ore Formation

Abstract

The mineral and chemical compositions of ores from the Corrida epithermal Au-Ag deposit (Chukchi Peninsula, Russia) were studied using the optical and scanning electron microscopy with X-ray energy-dispersion microanalysis. The deposit was formed at the time close to the period when the basic volume of acid magmas had been emplaced within the Okhotsk–Chukotka belt (84 to 80 Ma). The Au–Ag mineralization is distinguished with Au-Ag sulphides and selenides (uytenbogaardtite-fischesserite solid solution, Se-acanthite, S-naumannite) and Ag halides of the chlorargyrite-embolite-bromargyrite series. The ores were formed in two stages. Using microthermometric methods, it has been established that the ore-bearing quartz was formed in the medium-temperature environment (340–160 °C) with the participation of low-salt (3.55 to 0.18 wt.% NaCl eq.) hydrotherms, mostly of the NaCl composition with magnesium, iron and low-density СО2. According to our results of thermodynamic modeling at temperatures from 300 to 25 °C and data on mineral metasomatic alterations of the host rocks, the Au-Ag-S-Se-Cl-Br mineralization was formed at decreasing temperature and fugacity of sulphur (logƒS2 from −6 to −27), selenium (logƒSe2 from −14 to −35), and oxygen (logƒО2 from −36 to −62), with near-neutral solutions replaced by acid solutions. Analysis of the obtained data shows that the Corrida refers to the group of the LS-type epithermal deposits. This deposit is a new example of epithermal deposits with significant quantities of Au–Ag chalcogenides (acanthite, uytenbogaardtite, fischesserite, naumannite and others).

Mineral Assemblages and Ore-Forming Physicochemical Conditions of the La’erma and Qiongmo Au–Se Deposits in the Western Qinling Orogen, Central China

“…Figure 13 also shows that the precipitation of antimonselite requires a more extreme ∑Se/S ratio compared to other selenides. According to Kolova et al [62], the precipitation of selenides is caused by decreasing sulfur and increasing selenium contents, resulting in an increase in ∑Se/S ratio. In summary, the precipitation of selenide was ultimately controlled by the high ∑Se/S ratio in the hydrothermal fluid.…”

Au-Ag-Se-Te-S Mineralization in the Maletoyvayam High-Sulfidation Epithermal Deposit, Kamchatka Peninsula

“…Furthermore, most of the Au-Ag LS epithermal deposits in Chukotka belong to the Se-bearing type (Korrida, Valunistoye, Dvoynoye, etc.) whose ores contain important amounts of selenium-bearing minerals [25,26]. In the Koch-Bulak deposit in Uzbekistan, the main selenium concentrators are sulfides and sulfosalts [27].…”

Acta Geologica Polonica

“…Chlorargyrite forms usually in a hypergenic environment, especially in a dry climate, in the presence of chloride ions as in the Chloride area in Arizona (Bastin 1925) or in the deposits of Dzungar Alatau, Kazakhstan (Umarbekova et al 2020). However, these ions may appear from the buried waters of a marine palaeobasin, as in the Corrida deposit in the Chukchi Peninsula, Russia (Kolova et al 2021), thus this mineral may not necessarily crystallize under surface conditions.…”