First Results of U–Pb (LA-ICP-MS) Dating of Acidic Volcanic Rocks from Basal Horizons of the Upper Precambrian of the Subpolar Urals

The paper presents the first results of U–Pb (LA-ICP-MS) dating of zircon grains from acid volcanics coming from the lower part of the Upper Precambrian basal strata section of the Subpolar Urals (Puiva Formation). The obtained age of 647 ± 3 Ma records the time of the earliest manifestations of acid magmatism in the Late Proterozoic history of the Subpolar Ural segment of the Earth’s crust, also setting the upper age limit to the rocks hosting the volcanics. In view of the previously obtained U–Pb (LA-ICP-MS) dates for the detrital zircon grains from metasiltstones of the Puiva Formation (the mean weighted age of the three youngest zircon grains is 883 ± 71 Ma), the possible time interval of its formation has been clarified, and it is 950–650 Ma. The data obtained make it possible to estimate the time of the origin of the Timan passive margin.