The nature of magnetic anomalies in the southern part of the Barents Sea shelf according to the results of an integrated analysis

Abstract

Research subject. The anomalous magnetic field of the southern part of the Barents Sea Shelf.Materials and methods. The research was based on a digital matrix (grid) of the anomalous magnetic field (AMP) compiled from the materials of magnetic surveys performed in 2002–2007 by a number of research organizations and research and production companies. A model describing the structure and formation of the magneto-active layer of the southern part of the Barentsevomorsk region was developed. An analysis of the radially averaged field spectrum made it possible to establish the confinement of the upper edges of the field sources to several structural horizons. Band filtering in the frequency domain in accordance with the allocated depth ranges allowed anomalies to be distinguished from other sources. To determine the nature of sources of magnetic anomalies at different levels of the earth’s crust, an integrated analysis of gravimagnetic fields, seismic profiling data and ground studies was conducted.Results. At least two levels of magnetic anomaly sources were found: the distribution of effective magnetization for the low-frequency component of AMP, reflecting the depth structure of the region, and the high-frequency component of AMP, reflecting the distribution of local intrusions in the upper part of the foundation and in the sedimentary cover. The lower level is represented by massive blocks of deep laying and corresponds to the SDR (Seaward Dipping Reflectors) complex, which is an alternation of tectonic plates of continental material with ultrabasite basites that were introduced into the crust at the post-rift stage of the continent’s split. The zone of positive linear anomalies of the magnetic field reflects the divergent boundary of the ancient continental plate of the Baltic, which arose during the fragmentation of the supercontinent of Colombia (Paleopangea) in the middle reef and the formation of the Rifean oceanic basin, which was then veiled by subsequent tectonic processes. The upper structural level indicates the introduction of the main composition into the upper layers of the earth’s crust in the zones of rift-forming faults of magma in late Devonian times during the process of continental rifting on the Svalbard Plate. This is confirmed by the presence of manifestations of the main magmatism within the propagation zone of the South Barents riftogenic depression into the body of the Baltic Shield.Conclusions. The conducted integrated analysis of the anomalous magnetic field and other geological and geophysical data allowed the authors to establish the nature of the sources of magnetic anomalies located at different structural levels of the earth’s crust in the southwestern part of the Barents Sea shelf. The magnetoactive layer of this region is characterized by a complex structure, the section of which includes at least two structural levels, each reflecting certain evolutionary stages of the earth’s crust.