Listvenite-related gold deposits of the South Urals (Russia): A review |
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| Institution: | 1. Institute of Earth Sciences, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland;2. Univ. Grenoble Alpes, ISTerre, F-38041 Grenoble, France;3. CNRS, ISTerre, F-38041 Grenoble, France;4. Institute of Earth Surface Dynamics, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland;1. Institut für Mineralogie, Westfälische-Wilhelms Universität Münster, Corrensstr. 24, 48149 Münster, Germany;2. Institut für Geologie und Paläontologie, Westfälische-Wilhelms Universität Münster, Corrensstr. 24, 48149 Münster, Germany;3. Institut für Geologie, Universität Bern, Baltzerstrasse 1, 3012 Bern, Switzerland;1. Tuvinian Institute for Exploration of Natural Resources, Siberian Branch of the Russian Academy of Sciences, ul. Internatsional’naya 117a, Kyzyl, Tyva Republic, 667007, Russia;2. Institute of Mineralogy, Uralian Branch of the Russian Academy of Sciences, Miass, Chelyabinsk Region, 456317, Russia |
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| Abstract: | The Urals is a complex fold belt, which underwent long geological evolution. The formation of most gold deposits in the Urals is related to the collision stage. In this paper, we review some relatively small listvenite-related gold deposits, which are confined to the large Main Uralian fault zone and some smaller faults within the Magnitogorsk zone. The Mechnikovskoe, Altyn-Tash, and Ganeevskoe deposits are studied in detail in this contribution. They comprise the ore clusters along with other numerous small gold deposits, and constituted the sources for the gold placers exploited in historical time. The gold is hosted by metasomatites (listvenites, beresites) and quartz veins with economic gold grades (up to 20 g/t Au). Listvenites are developed after serpentinites and composed of quartz, fuchsite, and carbonates (magnesite, dolomite) ± albite. Volcanic and volcanoclastic rocks are altered to beresites, consisting of sericite, carbonates (dolomite, ankerite), quartz and albite. Pyrite and chalcopyrite are major ore minerals associated with gold; pyrrhotite, Ni sulfides, galena, sphalerite, arsenopyrite and Au-Ag tellurides are subordinate and rare. Gold in these deposits is mostly high-fineness (>900‰). The lower fineness (～800‰) is typical of gold in assemblage with polymetallic sulfides and tellurides. The ores have been formed from the NaCl–CO2–H2O ± CH4 fluids of low (～2 wt% NaCl-equiv.) to moderate (8–16 wt% NaCl-equiv.) salinity at temperatures of 210–330 °C. The oxygen isotopic composition of quartz (δ18O) varies from 14.7 to 15.4‰ (Mechnikovskoe deposit), 13.2 to 13.6‰ (Altyn-Tash deposit) and 12.0 to 12.7‰ (Ganeevskoe deposit). The oxygen isotopic composition of albite from altered rocks of the Ganeevskoe deposit is 10.1‰. The calculated δ18OH2O values of the fluid in equilibrium with quartz are in a range of 5.7–6.3, 4.2–4.6 and 6.3–6.7‰ respectively, and most likely indicate a magmatic fluid source. |
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| Keywords: | Orogenic gold South Urals Oxygen isotopes Listvenite Fluid inclusions |
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