The paper, based on geological and geophysical data obtained during 55-th expedition of the research vessel “Akademik Nikolaj Strakhov”, examines the structure of the King’s Trough and its immediate surroundings (King’s mesostructural cluster), located on the eastern flank of the Mid-Atlantic Ridge in the North Atlantic. Six provinces were identified within the southeastern part of the King’s Trough, based on the results of bathymetric mapping, each of which has its own morphostructural appearance, which was formed as a result of multistage tectonic and volcanic processes, alternating and conjugate with each other in time. According to seismoacoustic profiling data, three main types of seismic faces have been identified: a) pelagic complexes; b) deposits of turbidite flows; c) chaotic facies of gravitational genesis. It is shown that the anomalous magnetic field of the study area is a superposition of linear and isometric anomalies. The first were formed during the generation of oceanic crust in the axial spreading zone. The second are associated with volcanic massifs formed in intraplate conditions. The obtained data confirm the assumption that the formation of the King’s Trough was preceded by the formation of an extended arched uplift, which became the scene of intense intraplate volcanism, the intensity of which increased from the southeast to the northwest. This stage was followed by subsidence of the axial part of the uplift with the formation of the King’s Trough and the Peak and Freen Troughs.

This paper provides information on the integrated geological and geophysical investigations of the fracture zones of the Tropical Atlantic (cruise 65 of the RV Akademik Ioffe), as well as on the geomagnetic survey, passing observations of wind-generated waves, and quantitative distribution of cetaceans and flying fish in the North Atlantic (cruises 64 and 65 of the RV Akademik Ioffe) in October–December 2023. The preliminary scientific results are discussed.

This paper provides information on the integrated geophysical, sedimentological, and hydrophysical investigations, passing meteorological and biological observations in the Eastern Tropical Atlantic during the cruise 63 of the R/V Akademik Ioffe in October–December 2022. The preliminary scientific results are discussed.

The structure of King’s Trough and its surroundings (King’s mesostructural cluster), located on the eastern flank of the Mid-Atlantic Ridge in the North Atlantic, is described in this paper. This work is based on geological and geophysical data obtained during the 55th expedition of the R/V Akademik Nikolaj Strakhov. Six provinces were identified within the southeastern part of King’s Trough, based on the results of bathymetric survey. Each province has its own morphostructural feature resulting from multistage tectonic and volcanic processes, which alternate and conjugate with each other in time. According to seismoacoustic profiling data, three main types of seismic facies have been identified: (a) pelagic complexes; (b) deposits of turbidite flows; and (c) chaotic facies of gravity origin. It is shown that the anomalous magnetic field of the study area is the superposition of linear and isometric anomalies. The first were formed during the formation of the oceanic crust in the axial zone of spreading. The second are associated with volcanic massifs formed under intraplate conditions. The obtained data confirm the assumption that the formation of King’s Trough was preceded by the formation of an elongated arched rise, which became a scene of intense intraplate volcanism that increased from southeast to northwest. This stage was followed by subsidence of the axial part of the rise with the formation of King’s Trough and the Peake and Freen Troughs.

The geophysical survey on cruise 42 of the R/V Akademik Boris Petrov (2017) in the survey area near site 758 ODP significantly refined knowscarp about the bottom topography of the northern segment of the Ninetyeast Ridge. It is crossed by E–W transversal linear troughs, which are apparently young tectonic fractures. The morphology of the narrow elevated block in the central part of the deep depression between neighboring large volcanic edifices has been characterized in detail. In addition to linear tectonic structures, the main features of this block are two volcanic seamounts. A detailed magnetic survey in this area identified for the first time the nature of sources of magnetic anomalies on the Ninetyeast Ridge. Intense local magnetic anomalies have been observed here, both confined to local structures of the bottom and basement relief, and clearly unrelated to them. These anomalies have a complex interfering nature caused by the superposition of fields from sources separated by magnetization, spatial position, and age. According to the results of paleomagnetic analysis of the anomalies, the age of the structures here is very wide: the youngest features formed about 20 Ma ago, and the oldest, over 80 Ma ago.

The paper deals with the description of new geomagnetic data collected in the North Atlantic during cruises of research vessels of the Russian Academy of Sciences performed in 2020–2022. Modern technologies of geomagnetic measurements in the ocean and methods of their processing are considered. The obtained geomagnetic data indicate the heterogeneous nature of the sources of magnetic anomalies in the Charlie–Gibbs fracture zone and adjacent areas of the Mid-Atlantic Ridge and allow solving a wide range of geological and tectonic problems. Priority directions for further research aimed at adjusting spreading parameters and constructing models of the magnetic layer typical for transform faults and amagmatic segments of the Mid-Atlantic Ridge are formulated.

This article presents new data on the structure and relationship of tectonic and magmatic processes during the formation of the Mid-Atlantic Ridge between the Charlie Gibbs and Maxwell Fracture Zones in the North Atlantic. It is shown that this region is characterized by significant reduction in volcanism, which leads to the uplift of deep-seated rocks (ultramafic rocks and compositionally diverse gabbroids) to the seafloor surface. Both separate oceanic core complexes of the most varied configurations and extended sublatitudinal ridges composed of plutonic rocks are formed. Our analysis showed that this geodynamic regime exists during at least 14–16 Ma. The formation of most oceanic core complexes is associated not only with tectonic factors, but also with the serpentinization of peridotites, which leads to a decrease in density, an increase in volume, and, as a result, to the ascent of large ultramafic massifs, including disintegrated blocks of gabbroids, dolerites, and basalts. Numerous zones of sliding, crushing, abrasion, and deformation of rocks are evidence of tectonic movements. The area of study is characterized by numerous nontransform displacements of different amplitudes, which resulted due to relative displacements of oceanic lithosphere segments in wide areas under shear and extension conditions. The morphology of the forming tectonomagmatic structures is determined by tectonic factors. The exceptions are cases where the volumes of basalt melt that come to the seafloor surface for a short period of time are significantly higher than the average ones for a certain segment of the rift valley. The analysis we performed shows the presence of sources of heterogeneous magnetic anomalies both of volcanic origin and those associated with superimposed tectonic processes.

The article provides information on geological and geophysical studies of the structure of the Mid-Atlantic Ridge between the Charlie Gibbs and Maxwell transform faults in the North Atlantic during cruise 53 of the R/V Akademik Nikolaj Strakhov, July–August 2022. The preliminary results are discussed.

The paper deals with the description of new geomagnetic data collected in the North Atlantic during voyages of research vessels of the Russian Academy of Sciences performed in 2020–2022. Modern technologies of geomagnetic measurements in the ocean and methods of their processing are considered. The obtained geomagnetic data indicate the heterogeneous nature of the sources of magnetic anomalies in the Charlie-Gibbs fault zone and adjacent areas of the Mid-Atlantic Ridge and allow solving a wide range of geological and tectonic problems. Priority directions for further research aimed at adjusting spreading parameters and constructing models of the magnetic layer typical for transform faults and amagmatic segments of the Mid-Atlantic Ridge are formulated.

The volcanic structure of the Seymour Sewell seamount appears to have formed over a relatively long time in at least two stages. Its main massif was formed as a result of volcanic activity in the axial zone of the Central Indian Ridge about 16.3 Ma ago for about 0.5 Ma. Then the volcanic process temporarily stopped and the seamount drifted 260 km southwest along with the supporting African plate. In the last epoch of direct magnetic polarity (Brunes, 680 ka ago), as a result of a new cycle of volcanotectonic activity, the southeastern segment of the seamount collapsed. At this time, a new portion of magmatic material with a high ferrous mineral content was erupted here, reflected in the more intense magnetic anomaly confined to this part of the seamount.

We provide information on geological and geophysical investigations of the structure of the area between the Bight and Charlie Gibbs transform faults in the North Atlantic during cruise 53 of the R/V Akademik Sergey Vavilov in September–October 2021. The structure of the Eastern Tula Rise is also considered. The preliminary results of the expedition are discussed.

The paper presents brief results of integrated studies of the northern part of the Sea of Okhotsk close to of the Kuril arc, obtained on cruise 92 of the R/V Akademik M.A. Lavrentiev in April–May 2021. The relief was refined and the distribution of geophysical and gas-geochemical fields was obtained. Volcanic edifices hidden in the sedimentary layer were discovered. A large array of data was obtained on the distribution of temperature and salinity of surface waters, as well as the concentrations of methane, carbon dioxide, and atomic mercury in the near-water atmosphere along the route of the vessel.

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.

The article presents the results of magnetometric engineering work at the Semakovsky subsoil block within the water area of the Taz Bay of the Kara Sea. The purpose of the work was to determine the coordinates of the exact location of the wellheads of 6 abandoned wells and to examine the wellhead area for the presence of foreign magnetic objects. This paper examines the procedure for finding abandoned wells using marine magnetic surveys and shows their reflection in an abnormal magnetic field. The relevance of the work is related to ensuring the environmental safety of the water area and the requirements of the Safety Rules in the oil and gas industry. To meet the requirements, it is necessary to check the technical condition of the wellheads of abandoned wells for the presence of hydrocarbon omissions. A diving survey of the area in the wellhead zone did not reveal any hydrocarbon passes, however, it confirmed the presence of a number of man-made objects near the wellheads identified by magnetic surveys. When working at shallow depths, the original configuration of the magnetometer was proposed and used.

Geological and geophysical data collected during the 53rd cruise of the R/V Akademik Sergey Vavilov are presented. It is shown that the lateral distribution of the Icelandic plume material to the south is not bounded by the Bight transform fault and continues further to the south. The Bight FZ affects the processes of crustal accretion and the formation of tectonic structures only in a spreading segment directly adjoining the Bight FZ from the south, i.e., the most distant from the Icelandic plume. The anomalous magnetic field studied made it possible to determine the half-spreading rate (11.7 mm/yr) in the westerly direction for the area between the Bight transform fault and the Modred nontransform fault of up to 3.6 Ma in age. It is shown that the flanks of the Mid-Atlantic Ridge represented a shallow-water area with some areas of land in the recent past.

The geological structure of a large volcanic edifice in the eastern flank of the large Charlie Gibbs Fracture Zone in the region of the Eastern Thule submarine rise (North Atlantic) is discussed. It is shown that the volcanic edifice was formed near the axial zone of the Mid-Atlantic Ridge in the interval of 64–67 Ma ago. Subsequently, its summit part was destroyed by wave abrasion, and then it sank along with the oceanic part of the plate to 2500 m deep. It was concluded that volcanism in the Rockall Rift Basin affected the region further to the south, which was already an oceanic basin and was separated from the rift basin with the Charlie Gibbs Fracture Zone.

This paper provides information on the geological and geophysical studies of the structure of the Charlie Gibbs megatransform system in the North Atlantic on cruise 50 of R/V Akademik Nikolaj Strakhov in September–October 2020. The preliminary results of the expedition are discussed.

This paper is based on geological and geophysical data obtained during the 53th expedition of the R/V Akademik Nikolaj Strakhov. We analyze the structure of the Mid-Atlantic Ridge segment, 400 km long, in the North Atlantic (between 48° N and 51.5° N). According to our studies, this segment is characterized by specific structures formed during the formation of the oceanic crust with a reduced supply of basaltic melts. This factor leads to tectonic outcropping of deep and mantle rocks of the lower crust during the continuous extension in the rift valley. These processes, called “dry” spreading, were previously unknown in the North Atlantic.

The geological and geophysical data obtained during the 50th cruise of R/V Akademik Nikolaj Strakhov on the Charlie Gibbs megatransform system structure in the North Atlantic are presented. The structure of the Charlie Gibbs Fracture Zone was examined in detail, considering previously published data. It has been shown that the northern and southern segments of the Mid-Atlantic Ridge, separated by the Charlie Gibbs transform fault, are entirely different in morphology, and hence in terms of formation. The dredged rocks are represented by an entire spectrum from the mantle to upper crustal varieties and allow us to determine the origin of the main structures of the Charlie Gibbs megatransform system considering detailed data on the morphology.