Structural relations of eclogite complexes of the northern part of the Urals with the crystalline basement of the Pechora plate

Abstract

Introduction: Eclogites were found in the north of the Ural in two metamorphic complexes: the Marunkeu eclogite-gneiss complex in the Polar Urals and the Nerkayu eclogite-shale complex in the Nether-Polar Urals. The features of north-western and near east-west orientation of the anomalies of the geophysical fields and their spatial correlations were found above the eclogite complexes of the northern part of the Urals. Structural features and geological relations between the complexes and the surrounding strata allow supporting the hypothesis that the Marunkeu and Nerkayu complexes belong to the fragments of Precambrian basement involved in the structure of the Uralides. A comprehensive interpretation of geophysical fields is presented for the Marunkeu and Nerkayu complexes. We consider the possible deep relations between high-pressure objects and the crystalline basement of the platform region adjacent from the west. Methodology: The data from the comprehensive interpretation of geophysical fields (gravitational and seismic) were consolidated and systemised, which allows solving the issue of the depth of occurrence of the sources of anomalies above eclogite complexes. We focused on the analysis of the transformed maps and construction by the selection of a complex model of the Earth’s crust as well as the geological interpretation of deep structures. Results and discussions: The interpretation of the gravitational field allowed identifying similar features in the structure of the Marunkeu eclogite-gneiss complex and the Nerkayu eclogite-schist complex. The local gravity maxima were confined to the areas of prevalence of the rocks of the basic (and partially ultramafic in the Marunkeu complex) composition. The study of the structure of local fields by intensity, size, and linear north-western direction of anomalous zones and subzones of the Pechora plate and eclogite complexes of the northern part of the Urals allowed establishing a spatial correlation between them at the medium crust level. Conclusions: The identified spatial correlations allow considering the most anomalous areas above the Marunkeu eclogite-gneiss complex and the Nerkayu eclogite-schist complex to be a south-eastern extension of the Varandey-Adzva zone and Verkhnekolvinskaya subzone of intensive positive gravitational anomalies of the Pechora plate. The obtained geological and geophysical data confirm the idea that the Marunkeu and the Nerkayu complexes are fragments of the Precambrian basement involved in the structure of the Uralides.