Geochemical zonality of ore lode of Novo-Uchaly VMS deposit (South Urals, Russia)

Abstract

Novo-Uchaly essentially zinc (CZn>>CCu) VMS deposit is one of the largest in the Urals. Currently, it is under additional exploration by fans of underground drilling wells and mine workings. The paper describes a novel geochemical zonation of the sulphide deposit (the example of Cu, Zn, Au and In), discusses conditions of formation and factors that caused its complication. We carried geostatistical calculations in addition to the analysis of the zonation of the deposit. The ore deposit is represented by a large subvertical ribbon of a whimsical structure, inclined southward, which is confined to the wing of an inverted large anticlinal fold, cut by mafic dikes and characterized by a complex, combined geochemical zonality. The distribution of Cu and Zn is generally asymmetric. Copper-rich ores tend to the northern wedge of the deposit, and to the south, along its declination, the concentration of Zn increases, while Cu decreases, and the middle part of the deposit is represented by zinc-rich ores. In the section, copper maxima are more often noted in the footwall side of the deposit, and zinc — in the hanging side. The intrusion of a thick gabbro-diorite dyke and subsequent dynamometamorphism, including hydrothermal solutions, caused the redeposition of more mobile Cu in the near-contact zones of the dyke and areas of swell of the ore body thickness. Within the swell of the thickness of the deposit, in the hinge of the fold of the 2nd order, rich copper-zinc ores occur, which are enriched by Zn, Pb, Au, Ag, In, Ba and some other rare elements. The similarity of their behavior in ores is confirmed by their high positive pair correlation. In the ore body, the distribution patterns of gold and indium are rather symmetrical. High concentrations of gold and indium are confined to a sharp bend in the ore body, and small indium maxima occur in the footwall of the ore lode. As a result of dynamometamorphism, the deposit acquired a whimsical structure with the formation of thick swells; ores were significantly recrystallized, and locally enriched by non-ferrous and precious metals.