Seismicity, heat flow, seismic tomography data, prerift and synrift magmatism are considered as intensity indicators of geodynamic processes along the Atlantic-Arctic rift system (AARS). In this rift system, several large (over 100 km ) sub-latitudinal displacements of the rift axis are due to left-lateral strike-slip faulting. The AARS segments are distinguished by the age of splitting of continental plates from each other. A dependence is revealed between the current thermal state of the mantle under the AARS and the age of spreading start. This dependence is established from both seismic tomography and heat flow data. In section δ(Vp/Vs), the locations of the main segmenting faults and 'cold' anomalies in the upper mantle are coincident. Distributions of total seismic moments are practically synchronous in the depth intervals of 0-13, 13-35, and >35 km. The maximum values above the plumes are represented by higher seismic moments in the surface layer. The main demarcation zones differ in maximum energy release values in the AARS with shearing features. Comparison of these values against the age of the start of spreading processes shows trends of heat flow and medium field tomography in the AARS segments. The trends confirm the thermal interpretation of the seismic tomography data and suggest mantle cooling with age and a decrease in the mean temperatures of the mantle. The main factor causing the sublatitudinal asymmetry of heat flow in the AARS is the impact of Coriolis forces on the magma in the asthenospheric source. Most of the synrift igneous formations seem to be related to the influence of long-lived anomalies in the mantle, which had lower rates of magma generation than those typical of the formation of magmatic provinces. In conditions for spreading and the formation of the oceanic crust, the process followed the principle of energy cost minimization, and the prerift magmatic provinces with the pre-processed crust contributed to the choice and positioning of the AARS trajectory. The plume branches are imposed in the tomographic section and thus 'concealing' the relationship between the age and the thermal state. However, that does not change the trend to cooling of the mantle beneath the AARS, proportionally to the time since the start of spreading.
This article presents the first map showing the vertical amplitudes of modern disjunctive dislocations in Northern Atlantic, based on the estimated phase shifts of reflected waves recorded by high-frequency seismic acoustic surveys. The amplitude distribution pattern is mosaic with alternating areas of compression and extension in the flanks of the Knipovich rift system. The modern structure of the Knipovich Ridge, including two strike-slip faults, represents a local rift in the pull-apart setting. The asymmetry of stresses and the presence of compression in the ridge flanks is evidenced by the distribution of the focal mechanisms of strong earthquakes related to reverse faults. In the southeastern Knipovich Ridge, tectonic activity is marked by the asymmetric pattern of the epicenters of small earthquakes.
A cross‐sections of longitudinal (P) and transverse (S) wave anomalies (attribute δ(VP/VS)) is constructed along the sublatitudinal profile from the Atlantic Ocean to the Pacific Ocean across the regions of the latest Eurasian volcanism. It is correlated with surface geophysical parameters interpretable in terms of geodynamics: heat flow, seismicity and integrated conductivity of the lithosphere. All the volcanic groups are related to the negative anomalies of S‐ and P‐wave velocity variations at depths, which are observed in the eastern part of the profile from Central Asia to the Pacific Ocean to depths of 1000 km. Such anomalies correlate with the heat flow anomalies and are thus indica‐ tive of a deep source. The absence of deep roots in the western part of the profile from the Caspian to the Western Mediterranean suggests lateral extension of the anomalously ‘hot’ mantle from the Afar branch of the African super‐ plume. The groups of volcanic formations in the Baikal region and the Far East are spatially associated with heat flow anomalies that are three times higher than the background values. A correlation between intraplate volcanism and the lithosphere conductivity suggests the presence of positive anomalies in all volcanic clusters, despite the fact that their background values are considerably different. In the continental part, velocity anomalies are typical of all volcanic groups with positive conductivity anomalies. It is evidenced by seismic tomography that all the volcanic groups (ex‐ cept the Alpine‐Caucasian) have ‘hot’ roots in the upper mantle to depths of 1200 km. The highest maximum conduc‐ tivity values are typical of the zones wherein high intraplate seismicity is absent. Along the profile, there are several zones of high intraplate seismicity, which are separated by aseismic zones or plate boundaries. This suggest the influ‐ ence of the heated state of the mantle and the occurrence of zones of increased conductivity in the lithosphere.
Cluster analysis is applied for computing stable combinations of geological and geophysical parameters, and areas with such combinations are interpreted as regions that differ in structural and geodynamic features. The shelf areas are distinguished by specific sets and patterns of parameters, including sedimentary cover thickness, tectonic heterogeneity of the basement, heat flow, anomalous magnetic field, and gravity anomalies that reflect the topography of the crust-upper mantle boundary. In the deep oceanic areas, S-wave velocity variations show abnormally 'cold' blocks, while the average heat flow values are high. This combination of parameters is typical of transform zones at the junction of the Atlantic and Arctic segments. Superimposed thermal domes are located symmetrically with respect to the axis of the mid-oceanic ridges (MOR). Such domes may occur on the continents located close to MOR. Similar indicators can be revealed along the transition zone to the north of the East Siberian Sea.
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