THE YOUNG LATE PALAEOPROTEROZOIC (1800–1700 MA) AGES OF MONAZITE AND ZIRCON IN ROCKS OF THE DNIESTER-BOUH REGION OF THE UKRAINIAN SHIELD

• Дата: 2025
• Автори: Степанюк, Л.М., Шумлянський, Л.В., Будзинь, Бартош, Слама, Їржі, Довбуш, Т.І., Висоцький, О.Б.
• Формат: Стаття
• Мова: Українська
• Опубліковано: Institute of Geological Sciences, NAS of Ukraine 2025
• Теми: U-Pb age; monazite; enderbite; Dniester-Buoh region
• Онлайн доступ: http://geojournal.igs-nas.org.ua/article/view/321001
• Назва журналу: Geological journal

The results of U-Pb isotope dating (TIMS and LA-ICP MS-method) of monazite from pyroxene-bearing granitoids of the Dniester-Bouh region of the Ukrainian Shield are discussed in the paper. The results of the TIMS dating of the multigrain fractions do not correspond to the Wetherill model. The dating of the individual grains by applying the LA-ICP-MS method yielded both ancient (over 2.0 Ga) and young (1.7–1.8 Ga) ages. The young dates may be caused by either the gradual cooling of rocks after high-grade metamorphism, or, more likely, by the reheating caused by the formation of a large igneous province at 1.80–1.75 Ga, represented by numerous mafic dyke swarms, two gabbro-anorthosite-rapakivi granite massifs in the Volyn and Inhul regions of the Ukrainian Shield (Korosten and Korsun-Novomyrhorod, respectively) and ultramafic, alkaline and felsic rocks in the Azov region. Tectono-magmatic activation, in addition to reheating, was accompanied by the penetration of fluids in zones of tectonic deformations. This could have caused the rejuvenation of the age of monazite and zircon crystals. The irregularity of the fluid penetration can explain the presence of both old and young monazite and zircon crystals in a single sample, and the absence of young crystals of these minerals in rocks collected in other parts of the Ukrainian Shield. It is possible that both factors had a combined effect.