Reflection of sequence of geodynamic processes in geological structure of the Bug area

• Main Author: Usenko, O. V.
• Format: Article
• Language: rus
• Published: Subbotin Institute of Geophysics of the NAS of Ukraine 2019
• Subjects: Proterozoic; metamorphism; granulite area; melting; metasomatic substitution; isotopic age
• Online Access: https://journals.uran.ua/geofizicheskiy/article/view/172425

The age of formations composing granulite blocks of the Ukrainian Shield is a pro-blem for disputes. In order to ascertain the primary genesis and conditions of transduction of the Bug area rocks it is proposed to find out how was deep process realized according to composition of magmatic and chemogenic-sedimentary rocks. Description of formations was used and sequence of geological events, given in the paper [Venidictov, 1986] for the Upper Bug area. During the period that began not later than 2.5 Ga and lasted up to 2.0 Ga three tectono-magmatic cycles happened that can be compared with a regime “folded area”. Application of over-all schemes allows to ascertain composition and temperatures of melts and fluids sup-plied to the crust (thermodynamic regime), and to appraise the character of interactions (metasomatic substitution, crystallization, melting-dissolution etc.) between deep material (of the known composition and temperature) and crust material at the ascertained depth (with known lithostatic pressure and temperature). Regime “folded area” is cha-racterized by magmatic rocks generated at depths 220, 150, 100, 50 km. Underlaying of the crust by mantle (ultrabasic) melts and replenishment of melting layers with their upper edge at depths 50 and 20 km, occurs repeatedly, that assumes complication of ba-sic regime. It has been determined that in the Bug area temperatures and pressures of metamorphic transformations exceeded those ones needed for production of the layer of partial melting in the crust. To present-day erosion section the level of asthenosphe-re position, where granites attached to the berdychiv complex was drawn. Sequence of occurrence was replaced by the order of incorporation and substitution. Primary sedimentary rocks were not preserved and there is no relation between occurrence of rocks and their age.