U/Pb age and sources of detrital zircon from upper riphaean sandstones of the Nemskaya upland (South Timan)

In the South Timan, outcrops of the Riphean basement are exposed in the cores of the Dzhezhimparma, Ochparma and Vadyavozh anticlinal structures. The results of U-Pb isotope dating of detrital zircon grains from terrigenous sediments of the middle formation of the Dzhezhim Formation, located in the Vadyavozh quarry, are presented. The rocks were formed no earlier than at the boundary between the Lower and Upper Proterozoic. The age of zircon grains ranges from 3170±43 to 1480±49 Ma. In South Timan, the source of clastic material for the metasandstones of the Dzhezhim Formation is assumed to be crystal complexes of the central parts of the Volga-Ural region. The ages of dated zircons from the lower subformation of the Dzhezhim Formation of the Dzhezhimparma Upland partially coincide with the ages of zircons from the middle subformation of the Dzhezhim Formation, with exception of the Middle-Upper Riphean dating. The grains of detrital zircon contained in the studied metasandstones are much older than the stratigraphic analogues from the northern and middle parts of the Timan Ridge, as well as the Polar and Subpolar Urals. When comparing the data on dating of detrital zircons in the northern and southern sections, a number of differences were established. The majority of zircons from the northern part of Timan are of Middle Riphean age, whereas the number of zircons of Archean and Early Proterozoic age is insignificant. In the South Timan, when studying the age of detrital zircons, the opposite pattern was established: ancient zircons counting 2100 and 2500 million years predominate, and zircons of Middle Riphean age are absent. The formation of Riphean rocks in the South Timan originated from more ancient (Archean-Early Proterozoic) sources, in contrast to the basement rocks in the Middle and North Timan, where the sources were younger (Middle Riphean) complexes.