New data on mineralogy of the oxidation zone of the Sherlovogorsky ore area (Eastern Transbaikalia)

The Sherlovogorsk ore district is located in the South-East of the Trans-Baikal Territory, 24 km north-west of the city of Borzya. The Sherlovogorsk ore-magmatic system, located within this region, is a unique geological object that combines large deposits of gemstone, non-ferrous and rare metals. Arsenopyrite, galena, pyrite, chalcopyrite, sphalerite, pyrrhotite, bismuthinite, native bismuth, arsenic sulfosalols and other minerals are present in hypogenic ores. The diverse composition of hypogenic minerals containing arsenic led to the formation of a large number of arsenates in the hypergenesis zone. Among hypergenic arsenates, the most common is skorodit. Recently, in association with him, we established rooseveltite. It is a bismuth analog of the ferric oxide and is distributed mainly in the oxidation zone of the beryllium-bismuth-tin-tungsten deposit, which is localized in apogranite greisenes. In addition, philipsbornite, carminite, duftite and other complex arsenates were known. This paper presents the results of a study of the mineralogy of the oxidation zone within the Sherlovogorsk oremagmatic system, including the beryllium-bismuth-tin-tungsten in greisens and tinpolymetallic deposits. Thermograms, diffractograms, IR spectroscopy and electron microscopy data of a number of arsenates were first published. Their locations, brief descriptions are given, and the results of instrumental studies are discussed, which made it possible to establish almost universally widespread development of arsenates within the hypergenesis zone of the Sherlovogorsk ore-magmatic system. Along with the well-known almost ubiquitous presence of scorodite, arsenates with varying copper content - Y-agardite (Y,Ca)Cu₆[AsO₄]₃(OH)₆∙3H₂O and rare zincolivenite Cu,Zn[AsO4](OH)) have been established and studied. Lead and iron arsenate was detected as segnitite PbFe3[AsO4]2(OH)5(H2O). Along with the previously known Zn2[AsO4](OH) adamite, an intermediate cuprous (Cu,Zn)[AsO4](OH) member was found adamite - olivenite. This is due to the presence in the primary ores of the parage-netic association of arsenopyrite, chalcopyrite and sphalerite. The presence of pharmacosiderite KFe₄[AsO₄]3(OH)₄∙6-7H2O, which is an arsenate extreme member of the jarosite series - pharmacosiderite, has also been established. New data were obtained for two members of the betapacdalite group - betapacdalite-CaCa and the rarer betapacdalite-CaMg. A feature of the hypergenesis zone of the Sherlovogorsk ore-magmatic system in its greisen part is the presence of the uranylarsenate phase, represented by Cu(UO₂)₂[AsO₄]₂∙8H₂O metazeunerite.

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