Effect of selenium on silver transport and precipitation by hydrothermal solutions: Thermodynamic description of the Ag-Se-S-Cl-O-H system

Akinfiev, N. N.; Тагиров, Б. Р.

doi:10.1134/s1075701506050059

Cited by 18 publications

(3 citation statements)

References 33 publications

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“…New data for the system Ag-Au-X (X=S, Se, Te) (Echmaeva and Osadchii, 2008) is thus welcome, as are improved thermodynamic data for the systems Au-Te (Wang et al, 2006), Au-Bi-Sb (Wang et al, 2007) or the systems Au-Bi and Ag-Au-Bi (Servant et al, 2006;Zoro et al, 2007), the last four allowing greater accuracy in modelling the critical system Au-Bi-Te (Wagner, 2007;Tooth et al, 2008;see below). Fundamental thermodynamic information for Se-bearing systems has also become available (e.g., Xiong, 2003;Akinfiev and Tagirov, 2006a;Osadchii and Echmaeva, 2007), allowing detailed modelling of, for example, selenide-bearing vein and VHMS deposits (Layton-Matthews et al, 2008) and unconformity-related and sandstone-hosted uranium deposits.…”

Section: Phase Systems and Constraints On Mineral Stabilitiesmentioning

confidence: 99%

Understanding gold-(silver)-telluride-(selenide) mineral deposits

et al. 2009

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as part of the epithermal deposit spectrum in his textbook "Mineral deposits". Telluride-enrichment is, however, observed in a far wider range of deposit types, e.g., Au-rich VMS deposits, porphyry Au(Cu) and Au skarns. In at least some of these, a proportion of the gold occurs as Au-(Ag)-tellurides, or as native gold/Au-minerals paragenetically tied with tellurides of other elements, notably bismuth. Despite their enrichment in Te, gold deposits formed under reducing conditions are generally not acknowledged as Au-telluride deposits, because the telluride-rich character is largely expressed through an abundance of Bi-telluride species, commonly stable together with native bismuth. Gold-Bi compounds, such as maldonite and/or jonassonite, contribute to the mineralogical balance of gold ore, instead of Au(Ag)-tellurides (Ciobanu et al., 2005). A modified definition of the term 'gold-telluride deposits' was thus proposed (Cook and Ciobanu, 2005) to encompass the genetic connotation given by the presence of tellurides other than those of Au-Ag. In a preface to a special issue of Mineralogy and Petrology, Ciobanu et al. (2006a) posed a series of questions concerning the 'how?' and 'why?' of gold-telluride deposit formation. They questioned some of the established thinking about how these deposits were understood, not because the ideas are wrong (on the contrary!), but to encourage debate, and look beyond the confines of what was known and which fitted well to certain epithermal deposits. Likewise, Cook and Ciobanu (2005) attempted to build a framework for the role of other types of hydrothermal systems in the generation of telluridebearing deposits, raising certain taboos about classification, alternative settings and deposition mechanisms, the role of tellurides in orogenic gold systems and skarns, and what studies of trace mineralogy could contribute to the broader ore genesis perspective? They stressed the need to expand thermodynamic databases and modelling of oreforming systems (Afifi et al., 1988; Zhang and Spry, 1994a; Simon et al., 1997) to cover a broader range of formation conditions, e.g., pH/eH variation vs. activity/fugacity of various aqueous/gas species in a hydrothermal system. Within a given deposit, telluride-rich ores can be precipitated either at the same site or separately from native gold ore, depending upon precipitation mechanisms and local setting. Contemporary perspectives (e.g., Cooke and McPhail, 2001) include a Te-rich source, generally magmatically-derived, transport of Te as aqueous/vapour species within hydrothermal fluid, and precipitation of Au-Ag-tellurides due to multistage boiling. In an epithermal-porphyry environment (<5 km), these vapours are transported at the upper part of the veins forming a lowgrade Au-Te cap on top of the main Au mineralisation underneath. Whereas this model fits some telluride-bearing Au deposits (e.g., Gold-(silver)-telluride (selenide) ores occur as epithermal orogenic and intrusion related deposits. Although Te and Se are chalcophile elements and share ...

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Section: Phase Systems and Constraints On Mineral Stabilitiesmentioning

confidence: 99%

Understanding gold-(silver)-telluride-(selenide) mineral deposits

et al. 2009

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“…These factors resulted in the significant variation of sulphoselenides and selenides of Ag in ores. According to the results of thermodynamic modeling and experiments [63,64], at such physicochemical conditions, the role of selenium as an ideal precipitator of Ag is multiplied. Here, the buried waters of an oxygen-free marine paleobasin saturated with an organic matter could be the source of selenium [65]; the waters warmed to over 250 • C, and the biologically bound selenium could mobilize into a hydrothermal fluid [66].…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2021

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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).

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“…Different Se contents of primary sulfides from different types of VHMS deposits also depend on the composition of host rocks [49]. Even a low Se content in solutions is sufficient for the precipitation of selenides and their stability area is expanded with decreasing temperature [99].…”

Section: Arguments For Diagenetic Origin Of Banded Sulfides and Baritementioning

confidence: 99%

Mineralogical Features of Ore Diagenites in the Urals Massive Sulfide Deposits, Russia

et al. 2019

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In weakly metamorphosed massive sulfide deposits of the Urals (Dergamysh, Yubileynoe, Yaman-Kasy, Molodezhnoe, Valentorskoe, Aleksandrinskoe, Saf’yanovskoe), banded sulfides (ore diagenites) are recognized as the products of seafloor supergene alteration (halmyrolysis) of fine-clastic sulfide sediments and further diagenesis leading to the formation of authigenic mineralization. The ore diagenites are subdivided into pyrrhotite-, chalcopyrite-, bornite-, sphalerite-, barite- and hematite-rich types. The relative contents of sphalerite-, bornite- and barite-rich facies increases in the progression from ultramafic (=Atlantic) to bimodal mafic (=Uralian) and bimodal felsic (=Baymak and Rudny Altay) types of massive sulfide deposits. The ore diagenites have lost primary features within the ore clasts and dominantly exhibit replacement and neo-formed nodular microtextures. The evolution of the mineralogy is dependent on the original primary composition, sizes and proportions of the hydrothermal ore clasts mixed with lithic serpentinite and hyaloclastic volcanic fragments together with carbonaceous and calcareous fragments. Each type of ore diagenite is characterized by specific rare mineral assemblages: Cu–Co–Ni sulfides are common in pyrrhotite-rich diagenites; tellurides and selenides in chalcopyrite-rich diagenites; minerals of the germanite group and Cu–Ag and Cu–Sn sulfides in bornite-rich diagenites; abundant galena and sulfosalts in barite- and sphalerite-rich diagenites and diverse tellurides characterize hematite-rich diagenites. Native gold in variable amounts is typical of all types of diagenites.

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Effect of selenium on silver transport and precipitation by hydrothermal solutions: Thermodynamic description of the Ag-Se-S-Cl-O-H system

Cited by 18 publications

References 33 publications

Understanding gold-(silver)-telluride-(selenide) mineral deposits

Understanding gold-(silver)-telluride-(selenide) mineral deposits

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

Mineralogical Features of Ore Diagenites in the Urals Massive Sulfide Deposits, Russia

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