Mineralogy and genesis of the oxidation zone of baryte-lead ores of the Ushkatyn-III deposit, Central Kazakhstan

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Marco E. Ciriotti
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Mineralogy and genesis of the oxidation zone of baryte-lead ores of the Ushkatyn-III deposit, Central Kazakhstan

Messaggio da Marco E. Ciriotti » lun 14 nov, 2022 17:19

Referenza:
▪ Brusnitsyn, A.I., Perova, E., Loginov, E.S., Platonova, N.V., Panova, L.A., Vereshchagin, O.S., Britvin, S.N. (2022): Mineralogy and genesis of the oxidation zone of baryte-lead ores of the Ushkatyn-III deposit, Central Kazakhstan. Zapiski RMO, 151(5), 1-26.

Abstract:
The Ushkatyn-III deposit in Central Kazakhstan is a complex object that combines industrially significant deposits of: a) hydrothermal lead and baryte ores, b) hydrothermal-sedimentary iron and manganese ores, c) supergene (oxidized) lead and baryte ores. The mineralogy of the oxidation zone of baryte-lead ores was studied. Unoxidized hydrothermal barite-lead ores are almost entirely composed of calcite, barite and galena, typical minor minerals are quartz, pyrite, muscovite-phengite, potassic feldspar, albite and fluorite, among the accessory phases hematite, sphalerite, chalcopyrite, chamosite and apatite are the most characteristic. Fe–Mn carbonates (rhodochrosite and manganes-rich siderite) occur sporadically in ores. The following processes occur in the oxidation zone: (1) dissolution of calcite, (2) replacement of galena by cerussite and lead phosphates (pyromorphite and phosphohedyphane), (3) formation of montmorillonite and kaolinite due to decomposition of feldspars, chamosite and mica, (4) formation of goethite due to the alteration of pyrite and, in part, hematite. Baryte remains stable in the oxidation zone, but undergoes local recrystallization and redistribution. The main mineralogical changes in ores occur in the following sequence: 1) assemblages of initial ores: calcite + baryte + galena ± quartz ± pyrite ± ± hematite ± feldspars ± muscovite ± chamosite → 2) assemblages of weakly oxidized ores: calcite + baryte + cerussite + pyromorphite (phosphohedyphane) + quartz ± galena ± pyrite ± hematite ± goethite ± muscovite ± chamosite ± montmorillonite → 3) assemblages of highly oxidized ores: baryte + cerussite + pyromorphite (phosphohedyphane) + quartz + + montmorillonite + kaolinite ± galena ± hematite ± goethite ± muscovite. The bulk of the oxidation zone is composed of highly oxidized ores. Mn–Fe carbonates are less soluble than calcite. Therefore, at the early stages of the development of the oxidation zone, they are preserved in association with galena, baryte, cerussite, phosphohedyphane, quartz, chamosite, and some other minerals. Rhodochrosite and manganese-roch siderite are completely replaced by oxides of tri- and tetravalent manganese at late stages.
Marco E. Ciriotti

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