Structural characteristics of Marunkeu eclogite-gneiss complex in the Polar Urals inferred from gravi-magnetic data

The physical properties of the polymetamorphic formations of the Marunkeu eclogite-gneiss complex in the Polar Urals were analyzed. The patterns of density distribution and magnetic susceptibility of rocks were revealed. We assessed how primary mineralogical composition of metamorphic rocks and subsequent mineral transformations during polymetamorphism influenced the physical properties of rocks. A qualitative interpretation of materials of magnetic and gravitational surveys was performed. We showed that a wide range of magnetic properties of rocks of the Marunkeu complex were not reflected in a magnetic field, which was associated with the leveling role of polymetamorphism. It was established that a more stable petrophysical characteristic, less dependent on metamorphic transformations of rocks, was their density. It was mainly determined by the composition of the protoliths. Therefore, gravimetric data were crucial for establishing the geology and characteristics of the deep structure of the Marunkeu complex. Based on the interpretation of gravimetric materials, we showed that the formations enriched with high-density rocks (metaperidotites, eclogites and apoeclogitic amphibolites) sank to the north and belong to the lower formation of the Marunkeu complex. It supported an idea of the sublatitudinal structural plan of the Marunkeu complex. This was an additional argument in favor of referring the object under consideration as to early Precambrian formations and interpreting it as a tectonically displaced fragment of the Lower Precambrian crystalline base involved in the structure of rocks of Uralian orogeny.