Geodynamic origin of the world’s largest intracontinental West Siberian Basin (WSB) remains enigmatic, although its subsidence history is well established by borehole data. The basement includes a complex mixture of various tectonic terranes and suspected microcontinents, amalgamated during the Pangea supercontinent assembly, which places the WSB within the Tethyan realm. While rifting is unanimously recognized as the mechanism of the WSB formation, lithosphere stretching was too small to explain the basin subsidence, and thermal subsidence associated with the emplacement of the Siberian traps at ca. 250 Ma, when the WSB subsidence has started, has long been proposed as critical subsidence factor.Here we present results of 3D tesseroid gravity modeling for the WSB lithospheric mantle, constrained by available detailed geological and borehole data on the sedimentary structure, geophysical data on seismic velocity structure of the WSB crust, and thermal structure, including lithosphere thickness. Our results show large regional variations in density structure of the lithospheric mantle below tectonically heterogeneous WSB basement. We discuss the results in terms of paleotectonics, trap magmatism and various subsidence mechanisms, and attribute the long-lasting basin subsidence to the presence of a large high-density eclogitic body below the major WSB rift system, associated with the Siberian LIP magmatism.

A strong earthquake sequence in Storfjorden, south of Svalbard, was initiated by an M-w 6.1 event on 2008 February 21. Earthquake distribution and fault plane solutions indicate that seismic activity is controlled by unmapped NE-SW striking oblique-normal faults, contrasting with the major N-S oriented faults mapped onshore Svalbard. We present a geophysical model derived from an ocean bottom seismometer profile crossing the seismogenic zone to identify structures in the crust and uppermost mantle that potentially control the earthquake source mechanism. Traveltime forward modelling using ray tracing, combined with traveltime tomography and gravity-magnetic modelling, reveal distinct crustal domains across the earthquake region. Crystalline crustal P-wave velocities range from 6.1 to 6.7 km s(-1) at the Moho depth in the eastern section. The western profile section exhibits a higher V-p velocity lower crust (6.6-7.0 km s(-1)) with V-p/V-s ratios of 1.75-1.8 and high density (similar to 3100 kg m(-3)). Basement depth reaches 8 km in the west, forming a sedimentary basin, and shallows eastward. The Moho remains relatively flat at 29-32 km depth throughout the profile. The N-S oriented Caledonian suture, identified from deep seismic and potential field data, traverses the Storfjorden earthquake zone. The lithological contacts within the suture zone, inferred from the new OBS data, may facilitate seismic failure oblique to the N-S oriented structure, following the regional stress field.

The Lofoten continental shelf is located at the edge of the Baltic Shield in the northeastern North Atlantic Ocean. It was formed during continental break up in early Eocene associated with intense magmatism, leading to large intrusions and basaltic volcanic rocks now hidden below Cenozoic sediments. The Lofoten shelf is relatively narrow. We present results of ray tracing model of seismic refraction/wide-angle reflection data along the offshore Silver Road profile across the Lofoten Shelf at the northeastern Baltic Shield. The ~300km long WNW/ESE trending offshore section between 63oN and 71oN profile is perpendicular to the coastline and extends a ~300km onshore section. Wide-angle seismic data obtained from air gun shots from the vessel Hakon Mosby along the whole offshore profile were recorded by 16 ocean bottom seismometers on the shelf, slope and oceanic environment as well as by 270 onshore seismic stations. The new offshore crustal velocity - depth model covers the anomalous and heterogeneous transition from shelf to oceanic lithosphere around the North Atlantic Ocean. The results will test existence of crustal root and magmatic intrusions along the offshore profile.

Plate tectonics predicts that mountain ranges form by tectono-magmatic processes at plate boundaries, but high topography is often observed along passive margins far from any plate boundary. The high topography of the Scandes range at the Atlantic coast of Fennoscandia is traditionally assumed isostatically supported by variation in crustal density and thickness. Here we demonstrate, by our Silverroad seismic profile, that the constantly 44 km thick crust instead is homogenous above the Moho, and Pn-velocity abruptly change from 7.6 km s−1 below the Scandes to >8.2 km s−1 below the Proterozoic shield. By modelling gravity anomalies and topography, based on the seismic model, we demonstrate that this change corresponds to an increase in metamorphic eclogitic grade from 35

The Senja onshore-offshore seismic profile is located in the northwestern part of Fennoscandia, extending from onshore Norway into the North Atlantic Ocean. The Fennoscandian lithosphere has been formed by the amalgamation of terranes and microcontinents to an Archean core, primarily during the Palaeoproterozoic. The later Sveconorwegian (Grenvillian) and Caledonian orogenies had strong effect on the western part of Fennoscandia. The Scandia Mountain range extends along the west coast with elevation up to 2500 m, mainly coinciding with the surface outcrops of Caledonian deformed crust. Its location far from any active plate boundary makes this mountain range enigmatic. The offshore continental part of Fennoscandia experienced a long post-Caledonian extensional period for more than 200 My, and it now forms a continental shelf below sea level extending to the continent to ocean transition. We present a crustal-scale seismic profile along the NW-SE striking Senja OBS Profile in northern Scandinavia between 12°E and 20°E. This profile covers both offshore and onshore domains over a total distance of ~300 km across the Norwegian shelf in the North Atlantic Ocean, Senja Island, and mainland Norway. Airgun shots from the vessel Hakon Mosby were used as sourced for the refraction/wide-angle reflection survey. The dataset includes recordings on 5 ocean bottom seismometers (OBS) on the shelf, slope, and oceanic environment, complemented by 68 onshore stations at 1.3-kilometre intervals. We present a seismic p-wave velocity model derived by ray-tracing modelling of P-wave arrivals along the profile. The model includes a deep sedimentary basin extending to ~10 kilometres depth with velocities between ca. 2 km/s and 5.10 km/s, which gradually thickens from the coast to its maximum thickness of 10 km about 25 km from the coast. This deep sedimentary basin is very wide (approximately 8 km). Further offshore the sedimentary cover of the shelf and oceanic environment is relatively thin. The upper crustal velocity below the sedimentary sequence has velocities of ~ 6.0 km/s.

We present a new combined model for the density structure of the lithospheric upper mantle beneath Europe and Siberia, based on a 3D tesseroid gravity modeling. Our results are based on the EuNaRho model (Shulgin & Artemieva, 2019) complimented by similar modeling approach for Siberia. For Siberia modeling is preformed based on a detailed crustal structural database SibCrust (Cherepanova et al., 2013) constrained by regional seismic data. The presented residual lithospheric mantle gravity anomalies are derived by removing the 3D gravitational effect of the crust. Later, these anomalies are converted to lithosphere mantle in situ densities. To evaluate chemical heterogeneities of the lithospheric mantle, thermal effects are removed based on the global continental thermal model TC1 (Artemieva, 2006). The resulting density model at SPT conditions shows a highly heterogeneous structure of the cratonic lithospheric mantle, and distinct change at the transition between different tectonic units. We speculate on the origin of these anomalies.

Summary The automatic machine learning algorithm is developed and tested to predict metal concentration from the onshore geophysical well log data. The algorithm has proven to provide robust results utilizing limited set of geophysical well probes supplemented with core sampled geochemistry. Proper preprocessing of the geophysical data is essential for construction of reliable predictors. The described algorithm after the "training" can be automatically applied to all wells in the area. The method is estimated to predict metal components composition within ±10% margin with a probability of 0.85 – 0.9. The suggested algorithm can be considered as a partial substitute for time-consuming core sampling. The method is easily extendable to predict other properties/compositions by addition of extra geophysical well data.

<p>The Senja onshore-offshore seismic profile is located in the north-western part of Europe across the Norwegian coast into the North Atlantic ocean. A number of terranes and microcontinents collided to form this region from the Archean to the Paleoproterozoic. The Sveconorwegian (Grenvillian) and Caledonian orogenies significantly affected this region and created the major Caledonian mountain belt. Despite being far from any active plate boundaries, the Baltic Shield contains a mountain range called the Scandes that reaches heights of up to 2500 meters. This mountain range is oriented northeast-southwest and mainly correlates with the deformed Caledonian and Sveconorwegian part of the western North Atlantic coastal region.</p><p>We present a crustal scale seismic profile along the northwest-to-southeast-directed Senja OBS Survey Profile in northern Scandinavia between 12°E and 20°E. This profile extends offshore and onshore for a total of ~300 kilometres across the Norwegian shelf in the North Atlantic Ocean, the Senja Island and into mainland Norway. The seismic sources were airgun shots from the vessel Hakon Mosby along the offshore profile. The seismic data set was collected by 68 onshore stations located at 1.3 kilometer distance and 5 ocean bottom seismometers located on the shelf, slope, and within the oceanic environment. The results of this investigation will provide new data for interpretation of the cause of the unusual onshore topography and offshore bathymetry at the North Atlantic Ocean's edge. We present the results from ray tracing modelling of a seismic P-wave velocity section  along the profile.</p><p> </p>

The western edge of the Baltic Shield is covered by the northeast – southwest oriented, 2500 m high mountain range, the Scandes at the northwestern Atlantic Ocean. This mountain range is located far from any active plate boundary and lack of sedimentary sequences precludes direct knowledge of the timing of uplift.We present a crust and upper mantle scale velocity model, obtained along thea 600 km long Silver-Road seismic profile, which extends in a WNW to ESE direction in the northeastern Baltic Shield perpendicular to the coast between 8oE and 20oE. The profile has a 300 km long offshore section on the continental shelf and the deep ocean as well as a 300 km onshore section across Caledonian to Svecofennian units. The seismic data were acquired with 5 onshore explosive sources and offshore air gun shots from the vessel Hakon Mosby along the whole offshore profile. Data was acquired by 270 onshore stations at nominally 1.5 km distance and 16 ocean bottom seismometers on the shelf, slope and oceanic environment. The results of this study will provide new input to interpretation of the anomalous topography the Scandes and continental shelf in the northeast Baltic Shield.We present results of ray tracing and gravity modeling along the profile. The vertical crustal structure in the upper, middle and lower crust are almost constant across the Caledonian and Svecofennian parts of the profile. The crust is 45 km thick along the whole onshore profile and abruptly thins to 25 km thickness in the continental shelf. Pn velocity is low ~7.6-7.8 km/s below the high topography areas with Caledonian nappes, whereas it is 8.4 km/s below the Svecofennian parts. Our gravity models, based on the seismic velocity structure, suggest a low density 3.20 g/cm3 for the low Pn zone below the high Caledonian topography in contrast to the very high density 3.48 g/cm3 below the Svecofennian parts with relatively low topography. We interpret these bodies as eclogitizised basaltic crustal material at different metamorphic grades. Isostatic calculation with a 60 km depth compensation depth predicts 2 km high topography which is ~1 km higher than observed. We therefore propose that the low-grade metamorphic unit below the high topography is underlain by a sequence with relatively high mantle density to 120 km depth.

The Barents Sea shelf has been coverded by a numerous wide-angle seismic profiles, aiming to resolve the crustal structure of the shelf. However, the overall structural arcitecture of the crystaline crust is still not fully understood, due to limited and sparse distribution of deep-sampling seismic profiles. The petroleum related seismic exploration in Norwegian waters has been ongoing for decades. The recent increase of the seismic broadband stations onshore (including temporal deployments) provokes the idea to use these stations and the active seismic sources from the regional seismic reflection surveys, including academic and industry seismic projects, to reveal the crustal scale structure of the western Barents Sea. We have analyzed seismic records from 8 permanent seismic stations from Norway, Sweden and Finland, and 12 temporally deployed broadband seismic stations from the ScanArray seismic network, which recorded more than 100’000 marine airgun shots from academic and oil industry campaigns in the south-western quarter of the Barents Sea. The overall quality of the seismic records is exceptionally good. We clearly identify phases recorded from the offsets reaching 750 km. The identified phases include refracted crustal and mantle arrivals as well as Moho reflections, including both P and S waves. The overall quantity, quality, and the geometry of the seismic data makes it perfect for the application of the 3D joint refraction/reflection travel time seismic tomography to study the crustal structure of the Barents Sea. The preliminary results show very complex and laterally inhomogeneous crustal structure of the Barents Sea, which has been known before. However, with the help of 3D seismic tomography we are able to cover the gaps in between isolated deep-sampling seismic profiles and cross-correlate structures identified on them. In this work we would like to present our up-to-date results from the 3D seismic tomography.

We present a new model for the density structure of the lithosphere mantle（LM） in the region that extends from the Atlantic coast of Eurasia to the Ural mountains and from northern Africa and Arabia to the Arctic shelf（Artemieva and Shulgin, 2019; Shulgin and Artemieva, 2019）.

Knowledge of the crustal structure is the key for understanding physical and chemical conditions of its formation and later modification by geodynamic processes. It has long been recognized that crustal structure is controlled by tectonic settings, and that the crustal thickness is one of the most important parameters that reflects the geodynamic origin of the crust. A long tectonic life of continental crust leads to its significant reworking by plate tectonics processes and crust-mantle interaction, which include mechanical extension,

The Baltic Shield is located in the northern part of Europe, which formed by amalgamation of a series of terranes and microcontinents during the Archean to the Paleoproterozoic, followed by significant modification in Neoproterozoic to Paleozoic time. The Baltic Shield includes an up-to 2500 m high mountain range, the Scandes , along the western North Atlantic coast, despite being a stable craton located far from any active plate boundary. We study a crustal scale seismic profile experiment in northern Scandinavia between 63oN and 71oN. Our Silverroad seismic profile extends perpendicular to the coastline around Lofoten and extends ~300km in a northwest direction across the shelf into the Atlantic Ocean and ~300km in a southeastern direction across the Baltic Shield. The seismic data were acquired with 5 explosive sources and 270 receivers onshore; 16 ocean bottom seismometers and air gun shooting from the vessel Hakon Mosby were used to collect both offshore and onshore. We present the results from raytracing modelling of the seismic velocity structure along the profile. The outputs of this experiment will help to solve high onshore topography and anomalous and heterogeneous bathymetry of the continental lithosphere around the North Atlantic Ocean. The results show crustal thinning from the shield onto the continental shelf and further into the oceanic part. Of particular interest is the velocity below the high topography of the Scandes, which will be discussed in relation to isostatic equilibrium along the profile.

The Barents Sea shelf has been covered by numerous wide-angle seismic profiles aiming to resolve the crustal structure of the shelf. However, the overall structural architecture of the crystalline crust is still not fully understood, due to limited and sparse distribution of deep-sampling seismic profiles. The petroleum related seismic exploration in Norwegian waters has been ongoing for decades. The recent increase of the seismic broadband stations onshore (including temporal deployments) provokes the idea to use these stations and the active seismic sources from the regional seismic reflection surveys, including academic and industry seismic projects, to reveal the crustal-scale structure of the western Barents Sea. We have analyzed seismic records from 8 permanent seismic stations from Norway, Sweden and Finland, and 12 temporally deployed broadband seismic stations from the ScanArray seismic network, which recorded more than 100’000 marine airgun shots from academic and oil industry campaigns in the south-western quarter of the Barents Sea. The overall quality of the seismic records is exceptionally good. We observe clear phases recorded from offsets reaching 750 km. The identified phases include refracted crustal and mantle arrivals as well as Moho reflections, including both P and S waves. The overall quantity, quality, and the geometry of the seismic data makes it perfect for the application of the 3D joint refraction/reflection travel time seismic tomography to study the crustal structure of the Barents Sea. In this work we would like to present our first results from the 3D seismic tomography.

We present a new model, EUNA-rho (Shulgin and Artemieva, 2019, JGR), for the density structure of the European and the North Atlantics upper mantle based on 3D tesseroid gravity modeling and a new regional model for the lithosphere thickness in Europe, Greenland, the adjacent off-shore regions (Artemieva, 2019ab, ESR), and Anatolia (Artemieva and Shulgin, 2019, Tectonics). On continent, there is no clear difference in lithosphere mantle (LM) density between the cratonic and Phanerozoic Europe, yet a ca. 300 km wide zone of a high-density LM along the Trans-European Suture Zone may image a paleosubduction. Kimberlite provinces of the Baltica and Greenland cratons have a low density mantle, while the correlation between LM density and the depth of sedimentary basins indicates an important role of eclogitization in basin subsidence, with the presence of 10-20% of eclogite in LM beneath the super-deep platform basins and the East Barents shelf. The Barents Sea has a sharp transition in lithosphere thickness from 120-150 km in the west to 175-230 km in the eastern Barents. Highly heterogeneous lithosphere structure of Anatolia is explained by the interplay of subduction systems of different ages. The block with 150 km thick lithosphere in the North Atlantics east of the Aegir paleo-spreading may represent a continental terrane. In the North Atlantics, south of the Charlie Gibbs fracture zone (CGFZ) bathymetry, heat flow and mantle density follows half-space cooling model with significant deviations at volcanic provinces. Strong low-density LM anomalies (<-3%) beneath the Azores and north of the CGFZ correlate with geochemical anomalies and indicate the presence of continental fragments and heterogeneous melting sources. Thermal anomalies in the upper mantle averaged down to the transition zone are 100-150o C at the Azores and can be detected seismically, while a <50o C anomaly around Iceland is at the limit of seismic resolution. References: * Artemieva I.M., 2019. The lithosphere structure of the European continent from thermal isostasy. Earth-Science Reviews, 188, 454-468. * Artemieva I.M., 2019. Lithosphere thermal thickness and geothermal heat flux in Greenland from a new thermal isostasy method. Earth-Science Reviews, 188, 469-481. * Shulgin A. and Artemieva I.M., 2019. Thermochemical heterogeneity and density of continental and oceanic upper mantle in the European‐North Atlantic region. Journal of Geophysical Research: Solid Earth, 124, 1-33, doi: 10.1029/2018JB017025 (open access) * Artemieva I.M. and Shulgin A., 2019. Geodynamics of Anatolia: Lithosphere thermal structure and thickness. Tectonics, 38, 1-23, doi: 10.1029/2019TC005594

SUMMARY The crustal architecture of the Barents Sea is still enigmatic due to complex evolution during the Timanian and Caledonian orogeny events, further complicated by several rifting episodes. In this study we present the new results on the crustal structure of the Caledonian–Timanian transition zone in the western Barents. We extend the work of Aarseth et al. (2017), by utilizing the seismic tomography approach to model Vp, Vs and Vp/Vs ratio, combined with the reprocessed seismic reflection line, and further complemented with gravity modelling. Based on our models we document in 3-D the position of the Caledonian nappes in the western Barents Sea. We find that the Caledonian domain is characterized by high crustal reflectivity, caused by strong deformation and/or emplacement of mafic intrusions within the crystalline crust. The Timanian domain shows semi-transparent crust with little internal reflectivity, suggesting less deformation. We find, that the eastern branch of the earlier proposed Caledonian suture, cannot be associated with the Caledonian event, but can rather be a relict from the Timanian terrane assemblance, marking one of the crustal microblocks. This crustal block may have an E–W striking southern boundary, along which the Caledonian nappes were offset. A high-velocity/density crustal body, adjacent to the Caledonian–Timanian contact zone, is interpreted as a zone of metamorphosed rocks based on the comparison with global compilations. The orientation of this body correlates with regional gravity maxima zone. Two scenarios for the origin of the body are proposed: mafic emplacement during the Timanian assembly, or massive mafic intrusions associated with the Devonian extension.

We present a joint continental-oceanic upper mantle density model based on 3D tesseroid gravity modeling. On continent lithospheric mantle (LM) density shows no clear difference between the cratonic and Phanerozoic Europe, yet an ~300‐km‐wide zone of a high‐density LM along the Trans‐European Suture Zone may image a paleosubduction. Kimberlite provinces of the Baltica and Greenland cratons have a low‐density (3.32 g/cm3) mantle where all non‐diamondiferous kimberlites tend to a higher‐density (3.34 g/cm3) anomalies. LM density correlates with the depth of sedimentary basins implying that mantle densification plays an important role in basin subsidence. A very dense (3.40–3.45 g/cm3) mantle beneath the superdeep platform basins and the East Barents shelf requires the presence of 10–20% of eclogite, while the West Barents Basin has LM density of 3.35 g/cm3 similar to the Variscan massifs of western Europe. In the North Atlantics, south of the Charlie Gibbs fracture zone (CGFZ) mantle density follows half‐space cooling model with significant deviations at volcanic provinces. North of the CGFZ, the entire North Atlantics is anomalous. Strong low‐density LM anomalies (< −3%) beneath the Azores and north of the CGFZ correlate with geochemical anomalies and indicate the presence of continental fragments and heterogeneous melting sources. Thermal anomalies in the upper mantle averaged down to the transition zone are 100–150 °C at the Azores and can be detected seismically, while a <50 °C anomaly around Iceland is at the limit of seismic resolution. Presented results is a further development of the EUNA-rho model (doi:10.1029/2018JB017025)

Crustal structure preserves a unique record of physical and chemical conditions of its formation and later modification by geodynamic processes. The existence of broad global correlations between crustal structure and tectonic settings led to models of crustal typization by 1D crustal columns based on absolute thicknesses of crustal layers and the Moho depth. Here we propose a fundamentally different approach to typify the crust and geodynamic models of crustal evolution. We demonstrate that the relative ratio of the thicknesses of three principal crustal layers (sedimentary/felsic-intermediate/mafic in continents and Layerl/Layer2/Layer3 in oceans) is a fundamental characteristic of the crust. The relative ratio uniquely specifies the crustal structure in different tectonic settings and is independent of the absolute values of thickness of the crustal layers and the Moho depth. We analyze this new fundamental characteristic of the crust by ternary diagrams based on seismic models for continental and oceanic crustal structure in the northern Eurasia - northern Atlantics region and for selected oceanic provinces of different geodynamic origin, where seismic models for the crust are available. We present global and regional trends of crustal evolution and, as a practical application of the new approach, calculate average crustal densities in different continental and oceanic tectonic settings. These values range from ca. 2700 kg/m(3) in deep basins, to 2775 kg/m(3) in orogens and shelves, 2800 kg/m(3) in rifts and some ocean hotspots, 2800-2850 kg/m(3) in shields and platforms, 2900 kg/m(3) in back-arc basins and aseismic ridges, and may reach 2950 kg/m(3) in the Pacific hotspots. (C) 2019 Elsevier B.V. All rights reserved.

We present a new model, EUNArho, for the density structure of the lithosphere mantle (LM) in the region that extends from the Atlantic coast of North America to the Ural mountains and from northern Africa and Arabia to the Arctic shelf. Gravity modeling, using tesseroids, is constrained by a regional seismic crustal model EUNAseis, a global continental thermal model TC1 and the half-space cooling model for oceans. On continents, the cratonic LM has a highly heterogeneous density structure and shows no clear distinction from the Phanerozoic LM of western Europe. However, the craton edge along the Trans-European suture zone is marked by a sharp high-density (+1.0+1.5%) LM density anomaly. A low density mantle (3.32 g/cm3) beneath the Archean-early Proterozoic shields of Baltica and Greenland corresponds to the known kimberlite provinces and we find a strong correlation between mantle density and the occurrence of diamondiferous kimberlites. Deep platform basins have a very dense mantle (3.40-3.45 g/cm3), which indicates that eclogitization may have played an important role in their formation. Similar high-density LM is typical of the East Barents shelf, while the West Barents basin has density similar to Proterozoic cratons (ca. 3.35 g/cm3). Platform basins have positive density anomalies of a much smaller amplitude than the cratonic basins, except for the North German basin with +2% density anomaly (>3.41 g/cm3). The Cenozoic collisional orogens of Europe are underlain by a slightly dense (+0.5%) LM associated with subducting slabs. The Gondwana massifs of western Europe have a low-density LM, similar to the cratons. south of the Charlie Gibbs fracture zone (CGFZ), we observe only small lateral variations in mantle density, indicating that it is controlled mostly by temperatures that follow the half-space cooling model. Strong low-density LM anomalies (<-3%) are beneath the Azores and the MOR north of CGFZ, including Iceland, and are well correlated with geochemical data, suggesting the presence of continental fragments in oceanic mantle and different degrees of mantle melting. A comparison of mantle residual gravity anomalies in the North Atlantic ocean with normal oceans (that follow the square-root-of-age pattern) shows that south of the CGFZ major anomalies are associated with hotspots and volcanic provinces of the Azores, the Canaries, and the New England volcanic province, while all ocean north of the CGFZ is anomalous. However, the amplitude of the anomalies in the region around Iceland is small and at the edge of resolution by seismic methods.