PALEOVOLCANIC CONDITIONS OF MASSIVE SULPHIDE MINERALIZATION FORMATION OF AKZHARSKOYE ORE FIELD (SOUTHERN URALS)

Abstract

The article considers the geological structure and paleovolcanic conditions for the formation of massive sulphide deposits and ore mineralizations of the Akzharskoye ore field located within the Dzhusinsko- Dombarovsky paleovolcanic belt. It is shown that three strata participate in the structure of the ore-bearing volcanogenic complex: lower basaltic, rhyolite-basalt and upper basaltic. Paleovolcanological analysis of the complex made it possible to reconstruct the following volcanic structures: 1) Akzharskoye shield volcano; 2) Akzharskaya caldera; 3) rhyolite-basalt volcanic apparatus; 4) Alimbayskaya depression; 5) Tyulkubayskaya depression. The history of the development of these structures is detailed in the work. It is shown that the structures are well mapped in physical fields - the volcanic accumulation region differs by an elevated gradient of gravity, its negative values characterize areas with a significant thickness of terrigenous deposits. The assignment of massive sulphide objects of the Akzharskoye ore field to the Urals type is proved. Moreover, they possess a number of specific features similar to those of the dombarovsky type. The ores were formed during the activity of acidic volcanism and are located on a single stratigraphic level marked by rhyodacitic bodies. It is established that the paleostructure of volcanic complexes is due to the combination of three-order synvolcanic structures. The largest of them are the structures of the first (shield volcanoes, relics of volcanic ridges) and the second (caldera depressions, separate apparatus of the central type) of orders, correspond respectively to volcanogenic complexes and ore fields. Placing of pyrite deposits and ore bodies is controlled by third-order structural elements - volcanic-tectonic depressions, local basalt-rhyodacite structures and vertex calderas of volcanicdome apparatus.