Key issues of geology of the European northeast and north of the Urals

The paper presents an overview of the geological structure of the large Arctic region and the adjacent areas, including the northern Urals, Pai-Khoi, Timan ridge and Pechora lowland. The key geological issues are highlighted, on solution of which depends not only significant progress in the knowledge of the geological structure and history of development of the territory, but also the Urals as a whole, as well as the surrounding areas of the European platform. Among these are the isues of the deep structure of the Pechora plate, age boundaries of Precambrian formations and especially the lower age boundary of the Riphean deposits, time of formation of collisional orogen Pre Uralides-Timanides and laying of Paleouralian ocean, nature of high-pressure metamorphic complexes in the zone of the Main Uralian Fault and time of high-pressure metamorphism display. The modern situation in the study of these issues is revealed. New information on the deep structure of the territory was obtained through the research and analysis of the consolidated volumetrical density models of the Earth's crust and upper mantle tops. Some new previously unknown outputs of the lower Precambrian are fixed. It is shown that in the Upper Precambrian section of the region, in contrast to the southern regions of the Urals, there are no Lower Riphean deposits. This leads to the conclusion that within the territory under consideration the inception of the basin (or basins) of sedimentation in the Late Precambrian was not until the Middle Riphean. It is shown that the upper age limit of the Timan conflict is limited by the late Vendian or the early Cambrian. The substantiation of Ordovician formation of ophiolite massifs is given, which marks the beginning of the development of oceanic spreading and formation of Paleouralian ocean. The problem of the origin and age of high-pressure metamorphic complexes in the zone of the Main Uralian Fault is discussed. Basing on the results of comprehensive studies of high-pressure metamorphic complexes of the north of the Urals (Marunkeu and Hordyu in the Polar Urals and Nerkayu in the Subpolar Urals) the notion that they are fragments of a heterogeneous Low Precambrian crystalline basement involved in the structure of Timanides and Uralides is substantiated.