First U-Pb dates for detrital zircons from deposits of Serebryanka Group (Upper Proterozoic, Middle Urals)

Abstract

The results of application of the LA-ICP-MS method for analysis of U-Pb ages of detrital zircons from Serebryanka Group (Middle Urals) has been presented for the first time. It has been found that the detrital zircon population in tillite-like conglomerates of the Tany Formation is represented nearly in equal shares by grains with Neoarchean and Paleoproterozoic U-Pb ages. This allows the basement crystalline rocks from the eastern part of the East European Craton to be considered as the principal source of aluminosilicate clastic material in the beginning of the Serebryanka. The population of detrival zircons in sandstones from the Kernos Formation consists of Meso- and Neoarchean (approximately 15%), Paleoproterozoic (∼60%), and Mesoproterozoic (∼26%) zircon grains. Comparison of the obtained data with the materials on detrital zircons from Tonian and Ediacarian sandstones in the southern Urals has shown that the principal role in formation of Tonian and Ediacaran sedimentary sequences was played by the products of Mid- and Late Paleoproterozoic crystalline rock erosion in the craton socle. In addition to this, accumulation of the Serebryanka Group took place with visible participation of more ancient—Early Paleoproterozoic, Neo- and Mesoarchean—rock associations on the paleo-water catchment areas. The end of the Serebryanka period differed from its beginning by the additional appearance of Mesoproterozoic complexes in alimentation zones; for comparison, the role played by these complexes in formation of Ectasian-Ediacarian deposits of the adjacent southern Urals segment is insufficient, judging by the currently available data. All these facts may indicate that there are significant differences in the spatiotemporal distribution of clastic material sources for Upper Precambrian deposits in the West Megazone of the southern and middle Urals.