Early Permian granitoids of the East Magnitogorsk zone (South- ern Urals): petrology, geochemistry, and geodynamic formation environment

Abstract

The relevance of the problem. The Early Permian magmatism of the Southern Urals is poorly studied with the help of modern methods. The granitoid massifs of this age locally developed in the East Magnitogorsk zone contain important information about the geodynamic conditions of their formation. Clarification of this issue makes an important contribution to the understanding of the geodynamic development of the Urals. The nature of granitoids is still debatable. The connection with the massifs combined in the Balkan complex of gold-tungsten mineralization indicates the need for a comprehensive study. The purpose of the study is to determine the petrological and geochemical features of the rocks of the Balkan complex, to identify the mechanism of their petrogenesis and to establish the geodynamic conditions of their formation. Results. The petrological and geochemical study of the formations of the Balkan complex was carried out and their place in the typical taxonomy of granitoids was determined. Their belonging to the I-type is shown. Mineralogical and petrogeochemical methods were first studied for shonkinite xenoliths in granitoids. The mechanism of petrogenesis of rocks is proposed and the geodynamic setting of their formation is determined. It is shown that the monzonitemonzodiorite-quartz syenite-granosyenite-leucogranite series of rocks was formed as a result of crystallization differentiation of a single parental melting, and it was also concluded that the massifs of the complex are formed under conditions of early collision conditions with the important role of the subduction process. The mechanism of formation of the massifs of the complex is largely similar to mechanism for granitoids in other conflict areas, although it has its own specifics. Conclusions. 1). The Early Permian granitoids of the Balkan complex relates to type I. 2). All rocks of the complex, from monzonites to quartz syenites and leucogranites, including xenolith shonkinites, form a petrogenetic series formed as a result of crystallization differentiation of a single parent alkaline-gabbroic melting with increased water pressure. 3). The Balkan complex was formed in an early collisional setting under the action of deep subduction. 4). Transpression in the upper part of the crust induced formation of the massifs of the complex. 5). The Balkan complex is a kind of indicator of the growth of the newly formed crust as a result of collision and accretion processes.