U-Pb age of monazite from hypersthenic quartzite of the Yatran river basin (Yatran block of Ukrainian Shield)

Abstract

Among the crystalline rocks of the Middle Bug region, which are mapped as the Dniester-Bug series in the valley of the Yatran river in the area of the village Rogove, quartzites were discovered, which, unlike the quartzites of the Bug series, are mainly composed of quartz with a small number of feldspars. At the same time, hypersthene plays a prominent role in their composition. To find out the time of crystallization of monazite and the primary nature of quartzite, a sample of hypersthenic quartzite (sample 24/16), which is common on the left bank of the Yatran River (Rogove village), was taken. Under binoculars and a polarizing microscope, the internal structure of zircon crystals was studied in artificial preparations, and the spatial relationship with rock-forming minerals was studied in transparent sections under a polarizing microscope. Age was determined based on the results of U-Pb isotopic dating of multigrain monazite samples. Chemical preparation of multigrain samples of monazite for isotopic dating was performed according to the standard method [5]. A mixed 235U+206Pb tracer was used to determine the content of uranium and lead in monazites. According to the results of U-Pb isotopic dating, the time of crystallization of monazites from hypersten-containing quartzite of the Yatran river basin occupies an intermediate position (2044,7±9,2 million years) between the age of monazites from quartzites common in Kosharo-Olexandrivska structures (2062,4±4,4 million years) and Shamrayivka structures (1857,5±1,1 million years).