Geological structure and mineralogy of the Mechnikovskoe gold deposit, thе Southern Urals

Abstract

Subject. The article presents the results of study of Mechnikovskoe gold deposit associated with listvenites and beresites of the Miass region of the Southern Urals.Materials and methods. Materials were sampled during the field work of 2010– 2012. The chemical composition of rocks is analyzed by methods of classical chemistry (rock-forming oxides) and ICP MS (trace elements). The mineral composition is determined on an electron microscope with EDS.Results. The deposit is composed of tectonic sheets of serpentinites, carbonatized serpentinites and listvenites (sheet I), metadiabases and plagioclase metabasalts of the Irendyk Formation and beresites and volcanosedimentary rocks and metabasalts of the Karamalytash Formation (sheet II). In the central part of the deposit, the volcanic rocks are intruded by a dike of finegrained island-arc granites. Chromites of serpentinites are characterized (on average) by high Cr# (89) and low Mg# (29) values and low contents of Al2O3 (6.94 wt %) and MgO (5.5 wt %). Gold-bearing rocks include listvenites, beresites and carbonaceous shales. The major ore mineral is pyrite; accessory minerals are Au and Ag minerals, chalcopyrite, fahlores, galena, sphalerite, pyrrhotite, cubanite, vaesite, melonite, secondary copper sulfides, barite, rutile, monazite and xenotime. Gold of the deposit contains low Ag contents (3.52 wt %) and minor amount of Cu and Hg (<1 wt % in most analyses).Conclusions. The listvenites and beresites of the deposit were formed after ultramafic and mafic rocks, respectively. The discovery of gold in various rocks indicates that gold mineralization was deposited after the formation of the geological structure of the deposit. The source of gold was most likely related to a magmatic fluid.

The Ulug-Sair Gold-Bismuth Ore Occurrence (Western Tuva, Russia): PT Parameters, The Composition of Fluids, and Isotopy of S and O

“…Gold mineralization at the Ulug-Sair ore occurrence is confined to dykes of the rhyolite-and granodiorite-porphyry of the Bayankol complex (D3) and accompanied by beresitization of intrusive and sedimentary rocks. It should be noted that the formation of beresites with quartz, pyrite, sericite, ankerite, and siderite for both intrusive (acidic, middle) and sedimentary and volcanic-sedimentary rocks is described for the Mechnikovskoye, Ganeevskoye (South Urals), and Kedrovoye (Transbaikalia) deposits [30][31][32][33][34].…”

“…The isotopic composition of δ 34 Sfluid (from -0.7 to +2.5 ‰) indicates the juvenile or magmatic origin of ore elements. The isotopic composition of δ 34 Ofluid indicates that, during the early substages, the formation of ore occurrence involved a fluid of magmatic or metamorphic origin (from +7.3 to +11.1 ‰), and during the latest substages, it mixed with meteoric waters (from -1.8 to +9.1 ‰). According to [36], Se-containing minerals in ores indicate a high oxidation rate of the ore formation environment that could be caused by a mixing ore-bearing fluid with highly aerated meteoric waters.…”

Золото-Сульфидно-Кварцевое Рудопроявление Арыскан (Западная Тува): Условия Образования И Геохимические Особенности Флюидов

“…Золотое оруденение на рудопроявлении Арыскан парагенетически связано с дайками риолит-и гранодиоритов-порфиров баянкольского комплекса (D 3 ) и сопряжено с процессами березитизации интрузивных и осадочных пород. Отметим, что образование березитов с кварцем, пиритом, серицитом, анкеритом и сидеритом по интрузивным (кислым, средним) и осадочным, вулканогенно-осадочным породам описано на Мечниковском, Ганеевском (Южный Урал) и Кедровом (Забайкалье) месторождениях [15][16][17][18][19]. Fig.…”