Ukrainian
Summary:У монографії викладено результати дослідження двопольовошпатових гранітоїдів Середньопридніпровського мегаблока Українського щита. Висвітлено особливості складу цих гранітоїдів та їхніх мінералів. З’ясовано внутрішню будову кристалів циркону, обґрунтовано можливість їх використання для радіогеохронологічного датування локальним методом. Уточнено вік зазначених гранітоїдів регіону, вперше показано, що вони формувалися протягом майже 200 млн років у мезо-неоархеї. Визначено вікові межі формування порід аульської серії Інгулецької брили і встановлено два етапи їх мігматизації. З’ясовано геохімічну спеціалізацію гранітоїдів. Уперше виявлено прямий зв’язок між первинним ізотопним відношенням стронцію у двопольовошпатових гранітоїдах із вмістом у них барію, лантану і церію, що відображує роль корової речовини у формуванні цих порід.
Reading audience:Для петрографів, геохіміків, мінералогів, аспірантів і студентів геологічних факультетів вищих навчальних закладів.
English
Summary:The book represents results of the study of two-feldspar granitoids (TFG) of the Middle Dnieper region (Ukraine). The peculiarities of the composition of TFG and their minerals are described. The internal structure of zircon crystals has been studied and the possibility of their use for radiogeohronological dating by the local method was justified. The age of TFG was clarified and it was found that they were formed during almost 200 million years in Mesoarchean. The age boundaries of the forming of Aul series within the Ingulets boulder were determined and two stages of its migmatization were revealed. The geochemical specialization of the TFG was determined and it was shown that granitoids of the certain massifs are characterized by certain features. On the basis of the study of strontium isotopic composition and the specific peculiarities of the material composition, it was found that all TFG were formed from an essentially crust substrate.For the first time a direct relation between the primary isotopic ratio of strontium and contents of Ba, La, Ce in two-feldspar granites was established. This result reflects the role of the crust substrate in their formation. The model of formation of TFG of Middle Dnieper region was proposed. According to this model, the paternal sodium-potassium granitoid melts were formed in the zone of instability of biotite (in transitional PT-conditions between amphibolite and granulite facies) as a result of selective melting of crust substance. These paternal melts were enriched with potassium, rubidium and radionuclide isotope 87Sr from destroyed biotite. In the restitе (granulite) there are rocks, where the dominant feldspar is represented by plagioclase, and the isotopic composition of strontium is approaching those of mantle.It is assumed that during the formation of TFG in granulite blocks, such as the Vishnevoe massif of the Slavgorod block, Middle Bug region, biotite served as the source of potassium. In contrast to the above-mentioned granitoids, in this case it was the biotite of the younger, probably Neoarchean or (and) Paleoproperozoic rocks’ associations that were immersed in the depths (PT-conditions) of granulite facies of metamorphism as a result of their subduction in collisional geodynamic conditions. This can explain the wide dissemination of the processes of silicon-potassium metasomatism in Bug region and the formation of biotite- and garnet-biotite gneisses. For petrographs, geochemists, mineralogists, graduate students and students of geological faculties of higher education.