GEOLOGY, MINERAL COMPOSITION OF ORE AND ALTERED HOST ROCKS OF MASSIVE SULPHIDE MINERALIZATION OF THE AKZHARSKY ORE FIELD (SOUTH URALS)

The article describes the geological structure of the Akzharsky ore field, of five individual massive sulphide mineralization: Yuzhnoye, Yuzhno-Akzharskoye, Novoye, Bezymyannoye and Burozheleznyakovoye. The results of a microscopic study of the mineral composition of ores and altered host rocks are discussed. It is shown that all ore mineralizations are concentrated at a single lithological-stratigraphic level, but differ from each other in details of the structure, scale and mineral composition of mineralization. Massive ores prevail, and embedded and densely embedded ores are subordinate. The composition of the ore is mainly chalcopyrite-pyrite, to a lesser extent sphalerite-chalcopyritepyrite and pyrite. In the direction from south to north of the ore field, there is a change in the direction of increasing «polymetallicity» in ore mineralogy. Texture and structure of the ores of the Akzharsky ore field are rather uniform. Linear structures predominate (from banded to schistosely banded). Massive structures have a sharply subordinate distribution; brecciated ones are noted in isolated cases. Hydrothermal alterations formed mainly in rhyodacite-basalt strata from foot wall of ore bodies and, according to mineral composition, belong to propylites. They are characterized by an unstable set of mineral facies, weak contrast of metasomatic zones, and extremely uneven of rocks alteration. It has been established that the volcanic complexes of the ore field contain deposits not typical for the Ural massive sulphide ore province, differing in the mineral composition of ores, the conditions of their geological setting and the nature of the rocky alterations. This made it possible to concretize the concept of the relationship between the considered mineralization and volcanism and significantly supplement the already known typical models of pyrite-bearing ore-magmatic systems.