Mineralogy of iron and manganese ores of the Ushkatyn-III deposit, Central Kazakhstan
Brusnitsyn A. I., Perova E. N., Vereshchagin O. S., Britvin S. N., Platonova N. V., Shilovskikh V. V.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2021. V. 150. N 1. P. 1-29
The Ushkatyn-III in Central Kazakhstan belongs to the weakly metamorphosed hydrothermal-sedimentary ore deposit of the Atasu type. For such objects, an association of stratabound bodies of iron-manganese and so-called polymetallic (lead-zinc and barite-lead) ores is typical. There are iron, manganese and barite-lead ores occurring in Ushkatyn-III. Ores are located in Upper Devonian limestones. Iron ores are composed of hematite, calcite and quartz. Two mineralogical types of manganese ores are distinguished: braunite and hausmannite ones. Hausmannite ores are composed of hausmannite, rhodochrosite, calcite, tephroite, sonolite, alleghanyite, and friedelite. Braunite ores are composed of braunite, calcite, quartz, albite, rhodonite, friedelite, and rhodochrosite. The mineral composition of these ores was formed during transformation of metalliferous sediments under Р ≈ 2 kbar at Т ≈ 250 °С. Initially, deposits accumulated iron and manganese in form of oxides and hydroxides of Fe3+ and Mn3+/Mn4+. Organic matter controlled the nature of post-sedimentary processes. Braunite ores were formed under oxidizing conditions, while hausmannite ores were formed under reducing ones. Hydrated silicates – сaryopilite, friedelite, pennantite, clinochlore, chamosite, and parsettensite are indicators of the low temperatures of metamorphism. There is large number of accessory minerals found in iron and manganese ores. Among them, there are represented minerals containing B, F, S, V, Cu, Zn, As, Sr, Ag, Sb, Te, Ba, Hg, Pb and rare earth elements. Numerous Mn–Zn and Mn–Pb phases have been found here – zinc-bearing hausmannite and jacobsite, hetaerolite, kentrolite and pyrobelonite.The spatial-age relationships between minerals indicate the synchronous accumulation of Fe, Mn, Zn, As, Ba, Pb, and other elements in the primary metalliferous sediments, with their subsequent local redistribution during metamorphism, which led to crystallization of their phases. Presence of minerals of non-ferrous metals and barium makes manganese ores related to the baryte-lead ores occurring in the immediate vicinity to them. Most likely, both of these types of ores were formed simultaneously as products of the evolution of a single hydrothermal system.
Keywords: minerals of iron and manganese ores, metal-bearing sediments, metamorphism, hydrothermal-sedimentary deposits