Precious metal and telluride mineralogy of large volcanic-hosted massive sulfide deposits in the Urals |
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Authors: | I V Vikentyev |
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Institution: | (1) Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Moscow, Russia |
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Abstract: | Summary The study focuses on the mode of occurrence of Au, Ag and Te in ores of the Gaisk, Safyanovsk, Uzelginsk and other volcanic-hosted
massive sulfide (VHMS) deposits in the Russian Urals. Minerals containing these elements routinely form fine inclusions within
common sulfides (pyrite, chalcopyrite and sphalerite). Gold is mostly concentrated as ‘invisible’ gold within pyrite and chalcopyrite
at concentrations of 1–20 ppm. Silver mainly occurs substituted in tennantite (0.1–6 wt.% Ag). In the early stages of mineralization,
gold is concentrated into solid solution within the sulfides and does not form discrete minerals. Mineral parageneses identified
in the VHMS deposits that contain discrete gold- and gold-bearing minerals, including native gold, other native elements,
various tellurides and tennantite, were formed only in the latest stages of mineralization. Secondary hydrothermal stages
and local metamorphism of sulfide ores resulted in redistribution of base and precious metals, refining of the common sulfides,
the appearance of submicroscopic and microscopic inclusions of Au–Ag alloys (fineness 0.440–0.975) and segregation of trace
elements into new, discrete minerals. The latter include Au and Ag compounds combined with Te, Se, Bi and S. Numerous tellurides
(altaite, hessite, stützite, petzite, krennerite etc.) are found in the massive sulfide ores of the Urals and appear to be
major carriers of gold and PGE in VHMS ores. |
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