| Annotation |
The relevance lies in the need to have complete data on the mineralogy of the
ores of large gold deposits. One of such deposits in Transbaikalia is Darasunskoye,
the relatively new veins of which, discovered in 1985, were quickly worked out and
poorly studied. One of these veins, the mineral composition of which is practically not
studied, is the Geneva vein, which is rich in gold content, the complexity of the mineral
composition, and the depth of formation. The purpose of the study is to determine the
mineral forms of gold in a deep-seated gold-quartz-sulfide vein. The object of study
is pilsenite-hessite-uytenbogaardtite-hessite-tsumoite-gold-sphalerite-chalcopyritepyrite
mineral association. The subject of the study is the chemical composition and
forms of yutenbogaardtite isolation. Method and methodology are as follows: optical and electron microscopy to determine the forms of segregations and variations in the
chemical composition of minerals. Results: for the first time in a deep-lying (horizon
617 m from the surface) vein of the Geneva Darasun deposit of the gold-quartzsulfide
formation, Au and Ag sulfide yutenbogaardtite was found in close association
with chalcopyrite and low-grade native gold, mainly electrum, tellurides (tsumoite,
hessite, volynskite, empressite , pilsenite), as well as pyrite, sphalerite, and galena.
The vein minerals are represented by quartz, siderite, and muscovite. The chemical
composition of uytenbogaardtite (wt. %): Ag 42.97 ‒ 53.57; Au 33.78 ‒ 44.62; S 11.28 ‒
13.61; Cu 0.65 ‒ 1.14. Average content of elements: Ag 49.35; Au 37.74; S 12.43;
Cu 0.664. The theoretical content should be Ag 58.46; Au 32.02; S 9.52. A feature of
the chemical composition of uytenbogaardtite is its non-stoichiometric nature, which is
expressed in a lack of silver, a part of gold, and an excess of sulfur. It is probably due
to the peculiarities of the solution-melt composition, expressed in the inhomogeneity
of the Au-Ag-S solid solution containing Cu, Te, Bi as impurities, displayed in close
paragenesis with chalcopyrite and tellurides. Low grade Au, which is associated with
yutenbogardtite, contains from 43.32 to 56.42 % Ag and is electrum by their ratio. |
| References |
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