Mineralogy of oxidized ores of the Balkanskoe tungsten deposit (South Urals)

A relatively high WO3 content, reaching 0.5 wt. %, is determined in two representative samples of brown iron ore, which were taken from a borehole drilled in the oxidation zone probably developed after skarns of the Balkanskoe deposit (Gumbeyka group, South Urals). Using X-ray diffraction method, it is established that the W-enriched ochre-clayey rocks of the upper part of the supergene profle consist of the smectite group minerals, kaolinite, Fe3+ and Mn oxyhydroxides, quartz and mica. Goethite aggregates with network structure are dominant in the lower part of the profle, whereas clay minerals and quartz, as well as Mn oxyhydroxides, are less common. According to results of local SEM-EDS microanalysis, the maximum WO3 content of Fe3+ and Mn oxyhydroxides are 4.44 and 6.54 wt. %, respectively. The average WO3 content of Fe and Mn minerals in the upper and lower parts of the supergene profle are 0.13 and 1.19 and 1.57 and 2.13 wt. %, respectively. No W minerals are found. According to results of phase chemical analysis, hübnerite is the main mode of occurrence of W in the studied samples, which is inconsistent with results of mineralogical analysis. This is probably explained by the formation of tungstate clusters as a result of recrystallization of primary gel-like Mn and Fe3+ oxyhydroxides. These features of W chemical behavior in poor oxidized ores should be taken into account under evaluation of similar objects.