Deep Lithospheric Structure Research Articles

A tectono-thermal perspective on the petroleum generation, accumulation and preservation in the southern Ordos Basin, North China

The southern Ordos Basin has excellent petroleum exploration prospects. However, the tectono-thermal history and the controls on petroleum generation, accumulation and preservation conditions in southern basin are unclear. In this study, we analyzed the present geothermal field, paleo-geothermal gradient, maturity of the hydrocarbon source rocks, uplift and cooling process and tectono-thermal evolution history. In the study area, for the Ordovician, Permain and the Triassic strata, the present temperature is low (30−70 °C) in the southeastern area but high (80−140 °C) in the northwestern area. The paleo-geothermal gradient varied from 24 °C/km to 30 °C/km with a heat flow of 58–69 mW/m2 (i.e., a medium-temperature basin). The paleo-temperatures are higher than the present temperatures and the maximum paleo-temperatures controlled the thermal maturity of the source rocks. The vitrinite reflectance (Ro) values of the Triassic strata are >0.7% and the thermal maturity reached the middle-mature oil generation stage. The Ro values of the Permian-Ordovician strata are >1.8% and the thermal maturity reached the over-mature gas generation stage. The southern Ordos Basin has experienced the multiple tectonic events at the Late Ordovician Caledonian (452 Ma), Late Triassic (215 Ma), Late Jurassic (165−160 Ma), End-Early Cretaceous (110−100 Ma) and Cenozoic (since 40 Ma). A large-scale tectono-thermal event occurred at the End-Early Cretaceous (110−100 Ma), which was controlled by lithospheric extension, destruction and thinning. This event led to the highest paleo-temperatures and thermal maturities and coeval with the peak period of petroleum generation and accumulation. The southern Ordos Basin has undergone rapid and large-scale uplift since the Late Cretaceous due to expansion of the northeastern margin of the Tibetan Plateau, uplift of the Qinling orogenic belt and thrust faulting in the Liupanshan tectonic belt. The southern Ordos Basin experienced tectonic overprinting that was strong in the south and weak in the north. The strongest overprinting occurred in the southwestern part of the basin. The large-scale uplift, denudation and faulting led to oil and gas loss from reservoirs. The petroleum generation, accumulation and preservation in the southern Ordos Basin were affected by deep lithospheric structures and the tectono-thermal evolution. This work provides a novel tectono-thermal perspective on the petroleum generation, accumulation and preservation condition of the southern Ordos Basin.

Some Results of Direct FR Technology Applied to Study Methane Seepage Areas in the Arctic Region

The experimental study of the seepage processes' sources formation in structures of the Arctic Region was carried out using modified methods of frequency-resonance (FR) processing and decoding of satellite images and photographs with the vertical scanning of the cross-sections. The newly obtained results show that the intensity and dynamics of the methane seeps and pockmarks fields’ formation depend on active deep degassing processes in the continental margin structures. The use of direct FR-sounding technologies allows for determining the probable origin and depth of geological sources of gas migration at marginal migration centers in Greenland, and Norwegian and Barents Seas. New results confirm the crust-mantle gas fluids’ influence on the nature and degassing processes features in the scan points of polar marginal structures. These data are important arguments in favor of the “volcanic model” of various structural elements formation in this and other regions. The FR technologies data also showed a possibility of seeps use as shallow and deep hydrocarbon field indicators in gas emission areas. These independent data can be used in compiling models of the deep lithosphere structure and possible mechanisms of abiogenetic hydrocarbon formation in Arctic margin structures. The authors suppose that hydrocarbons through deep channels migrate (from 57 km deep) to the upper crustal horizons where their fields can form. During this migration, gas seeps and pockmarks are formed on the sea bottom and part of the gas can migrate into the atmosphere. Data show that basaltic volcanoes in Greenland scan points can be the real channels through which hydrogen migrates to the upper crustal horizons and further into the atmosphere. Active gas migration in Arctic seepage areas can be an important factor in the global climate change processes.

Gas flares and modern degasation processes in the Arctic seas (on the frequency resonance results-based)

The newly obtained results of the frequency-resonance (FR) technologies application for the study of the sources and processes of seeps and pockmarks formation in the Arctic Region (Norwegian, Barents Sea) and the North Sea are considered. The experimental study of the seepage processes' source formation was carried out using modified methods of the FR-processing, and decoding of satellite images and photographs with the vertical scanning of the cross-sections. The study results of the methane seeps and pockmarks fields show that the intensity and dynamics of their formation partly depend on the inflow of gas fluids from deep sources because of active degassing processes. The use of FR-sounding technologies allows us to remotely determine the spatial regularities of zones of intense gas emission formation and the geological sources of migration probable depth. The study of seep and pockmark field results confirms the significant, but insufficiently taken into account, the influence of crust-mantle gas fluids on the nature and degassing processes features in the structures of the continental margins. New results confirm the crust-mantle gas fluids influence on the nature and degassing processes features in the scan points of Polar marginal structures. These data are important arguments in favor of the "volcanic model" of various structural elements formation in this Region. The FR- technologies data also showed a possibility of seeps and pockmarks use as shallow and deep hydrocarbon field indicators in gas emission areas. These independent data can be used in modeling the deep lithosphere structure and possible mechanisms of abiogenic hydrocarbon formation in Arctic margin structures. We suppose that hydrocarbons through deep channels migrate (from 57 km deep) to the upper crustal horizons where can form hydrocarbon fields. During this migration, gas seeps and pockmarks are formed on the sea bottom and part of the gas can migrate into the atmosphere. Modern degassing centers' studies have confirmed the presence of zones of active migration of gases into the atmosphere, which is an important influencing factor in the dynamics of global climate change processes on Earth. The experience of FR- technologies used in the fields of methane seeps and pockmarks study found in the structures of the Arctic Polar seas showed versatility and the possibility of their use in the study of large gas emissions in structures of different regions.

The gravity field and gravity data reduction across the continental area of Nigeria

This research presents the variation of the gravity field and associated gravity field components over the continental area of Nigeria to provide data for geoscience research, geodetic and engineering works, aerodynamic studies and deep crustal inferences. Accurate positions and elevations were observed at 58 of the 59 base stations of the Primary Gravity Network of Nigeria (PGNN), whose absolute gravity values had been accurately determined. The absolute gravity values were plotted against their respective positions to reveal the distribution pattern and strength of the gravity field within the study area. Theoretical gravity values at each base station were generated using the Somigliana's equation. The free-air gravity and free-air anomaly gravity values were generated with respect to the World Geodetic System 1984 (WGS84) ellipsoid using GPS-derived elevation data. Then, the perturbing potential, free-air gravity with respect to the geoid, and the indirect effects were evaluated. The average of the indirect effects was used to adjust the WGS84 gravity formula to produce a gravity formula that better approximates the geoid across the continental area of Nigeria, compatible with the heights measured relative to the geoid, which can serve as a reference for establishing a vertical height control. The Bouguer gravity and Bouguer gravity anomalies across Nigeria revealed a “trans-southern gravity high strip” interpreted to be associated with mantle upwelling. Two new major mega-lineaments related to mantle upwelling were mapped. A batholith province trending NW–SE was delineated, occurring from north central Nigeria to the north western region and containing closures of “Bouguer gravity lows” interpreted as batholiths. A separate closure of “Bouguer gravity low” was detected at Azare, north eastern Nigeria, which may be due to the presence of intrusive granitic body. It is recommended that the mantle structure beneath “the trans-southern gravity high strip”, “delineated batholith province” and “isolated gravity closures” around the northeast of Nigeria should be studied from seismic shear wave splitting analysis for better understanding of the deep lithospheric structures and moho relief.

Deep Electrical Resistivity Structure of the European Lithosphere in Poland Derived from 3-D Inversion of Magnetotelluric Data

Deep Electrical Resistivity Structure of the European Lithosphere in Poland Derived from 3-D Inversion of Magnetotelluric Data

An integrative 3-D model of the deep lithospheric structure beneath Dolsk and Odra fault zones as a result of magnetotelluric data interpretation

SUMMARY Long-period magnetotelluric soundings were carried out in the eastern part of the Fore-Sudetic Monocline in central Europe to determine the deep geoelectrical structure. It is an important area in the contact zone of the Palaeozoic terranes of Western Europe and the Proterozoic East European Craton. The research area includes the Dolsk fault zone and the Odra fault zone, which are essential geological boundaries of a regional nature separating crustal blocks of various origins. There were conducted 51 soundings on the quasi-regular mesh 150 km in SE and 225 km in NE. The research region is highly urbanized, and hence some of the data were strongly disturbed. Careful processing of data was required, and sometimes measurements had to be repeated at other locations. The collected data allow constructing 3-D models of the electrical conductivity distribution. A parallel version of the ModEM 3-D inversion code was used for modelling. The information contained in each used transfer function was also examined by performing a separate inversion of these functions. The obtained resistivity distribution models confirm the Dolsk and Odra faults' location as postulated previously by geologists. They also show that these very deep faults are reaching the lower crust. However, they do not clearly state how far the contemporary lowering of the Baltica reaches under cover of younger Palaeozoic sediments.

Lithospheric structure and transformation of the Songnen and Jiamusi blocks in the eastern segment of the Central Asian Orogenic Belt revealed by 3D magnetotelluric inversion

The Central Asian Orogenic Belt (CAOB) is the largest accretionary orogenic belt in the world. The Songnen and Jiamusi blocks, which are located along the eastern segment of the CAOB, form a complex structure influenced by the Mudanjiang ocean closure and the Paleo-Pacific plate subduction. Constraints on the deep structure of the Songnen and Jiamusi blocks are critical for studying the evolution, transformation and current activity of the CAOB. This study presents an analysis and interpretation of a 450-km-long magnetotelluric profile that imaged the deep lithospheric structure of these two blocks. The best-fit three-dimensional resistivity model, based on the nonlinear conjugate gradient algorithm, highlights the key lithospheric structures. The results show that the lithosphere beneath the Lesser Xing'an Range in the Songnen block is characterized by a high-resistivity structure, which is mainly related to the granite formed in multiple stages. The crust forming the Sanjiang basin in the Jiamusi block possesses a high–low–high resistivity structure in the transverse direction, corresponding well to the tectonic units. The low-resistivity structure of the Fujin uplift extends to the mantle, which represents mantle material that intruded the crust. There is a low-resistivity structure beneath the suture zone of the two blocks that is homologous with the large-scale low-resistivity anomaly beneath the basin and is related to the subducted Paleo-Pacific plate. Strong dehydration at the inflection point of the plate reduces the solidus temperature of the mantle material, resulting in melt and upwelling of mantle material. The Jiamusi block can be divided into southern and northern parts, possessing different structures. The southern part represents an original part of either the Gondwana continent or Tarim craton. The Sanjiang basin, in the northern part, has been heavily influenced by the subducted Paleo-Pacific plate, and is a region of strong activity.

Present-day geodynamics of the Western Alps: new insights from earthquake mechanisms

Abstract. Due to the low to moderate seismicity of the European Western Alps, few focal mechanisms are available in this region to this day, and the corresponding current seismic stress and strain fields remain partly elusive. The development of dense seismic networks in past decades now provides a substantial number of seismic records in the 0–5 magnitude range. The corresponding data, while challenging to handle due to their amount and relative noise, represent a new opportunity to increase the spatial resolution of seismic deformation fields. The aim of this paper is to quantitatively assess the current seismic stress and strain fields within the Western Alps, from a probabilistic standpoint, using new seismotectonic data. The dataset comprises more than 30 000 earthquakes recorded by dense seismic networks between 1989 and 2013 and more than 2200 newly computed focal mechanisms in a consistent manner. The global distribution of P and T axis plunges confirms a majority of transcurrent focal mechanisms in the entire western Alpine realm, combined with pure extension localized in the core of the belt. We inverted this new set of focal mechanisms through several strategies, including a seismotectonic zoning scheme and grid procedure, revealing extensional axes oriented obliquely to the strike of the belt. The Bayesian inversion of this new dataset of focal mechanisms provides a probabilistic continuous map of the style of seismic deformation in the Western Alps. Extension is found to be clustered, instead of continuous, along the backbone of the belt. Robust indications for compression are only observed at the boundary between the Adriatic and Eurasian plates. Short-wavelength spatial variations of the seismic deformation are consistent with surface horizontal Global Navigation Satellite System (GNSS) measurements, as well as with deep lithospheric structures, thereby providing new elements with which to understand the current 3D dynamics of the belt. We interpret the ongoing seismotectonic and kinematic regimes as being controlled by the joint effects of far-field forces – imposed by the anticlockwise rotation of Adria with respect to Europe – and buoyancy forces in the core of the belt, which together explain the short-wavelength patches of extension and marginal compression overprinted on an overall transcurrent tectonic regime.

Linkage of deep lithospheric structures to intraplate earthquakes: A perspective from multi-source and multi-scale geophysical data in the South China Block

The relationship between intraplate earthquakes and intraplate deformation is one of the great conundrums faced by plate tectonics theory. In particular, large earthquakes are more common in Eurasia than in other continents around the world. Formed by the Neoproterozoic collision of the Cathaysia Block and the Yangtze Craton along the Jiangnan Orogenic Belt, the South China Block is well known for its relative stability in the Cenozoic era. However, numerous intraplate earthquakes have occurred in the Yangtze Craton and their mechanism is not well known. Incomplete understanding of the deep geological structure and deep-shallow coupling mechanism has led to two hypotheses about the nature and origin of intraplate earthquakes in the area: the far-field effects of plate subduction and the internal deformation of intraplate lithosphere. In this paper we attempt to provide a new perspective to the intraplate earthquake mechanism in the South China Block. In doing so, we have collected and reviewed multi-source and multi-scale high-precision geophysical data to improve the interpretation of the South China Block at depths from 1000 km to 1 km. The data interpretations help clarify the coupling relationship between the lithospheric structures and intraplate earthquakes in the South China Block. This paper emphasizes the strong structural heterogeneity in the South China Block. In plan view, the block is a mosaic structure formed by the assembly of various continental micro-blocks along several weak zones since the Neoproterozoic. In cross section, the structures of different units are segmented by detachment faults. For our analysis, we have used a three-layer model to describe the coupling of the asthenosphere-lithosphere, lithospheric mantle-crust and within the crust in the South China Block. The three cascade effects are coupled to form an intraplate earthquake triggering mechanism in the Yangtze Craton. The subduction effects of the Pacific Plate and the blocking by the Yangtze Craton are considered to cause a large-scale stress concentration in the Huaying Mountain fold-and-thrust belt; combined with three sets of detachment layers as internal factors, this stress results in numerous small-magnitude intraplate earthquakes occurring in the stable craton. This paper suggests that the deep structures can control the shallow tectonic processes and the plate tectonic responses and that the lithospheric strength can affect the triggering of intraplate earthquakes.

Deep structure of the Hellenic lithosphere from teleseismic Rayleigh-wave tomography

Deep structure of the Hellenic lithosphere from teleseismic Rayleigh-wave tomography

Deep structure of the Hellenic lithosphere from teleseismic Rayleigh-wave tomography

SUMMARYThis research provides new constraints on the intermediate depth upper-mantle structure of the Hellenic lithosphere using a three-step Rayleigh-wave tomography. Broadband waveforms of about 1000 teleseismic events, recorded by ∼200 permanent broad-band stations between 2010 and 2018 were acquired and processed. Through a multichannel cross-correlation technique, the fundamental mode Rayleigh-wave phase-velocity dispersion curves in the period range 30–90 s were derived. The phase-velocities were inverted and a 3-D shear velocity model was obtained down to the depth of 140 km. The applied method has provided 3-D constraints on large-scale characteristics of the lithosphere and the upper mantle of the Hellenic region. Highlighted resolved features include the continental and oceanic subducting slabs in the region, the result of convergence between Adria and Africa plates with the Aegean. The boundary between the oceanic and continental subduction is suggested to exist along a trench-perpendicular line that connects NW Peloponnese with N. Euboea, bridging the Hellenic Trench with the North Aegean Trough. No clear evidence for trench-perpendicular vertical slab tearing was resolved along the western part of Hellenic Subduction Zone; however, subcrustal seismicity observed along the inferred continental–oceanic subduction boundary indicates that such an implication should not be excluded. The 3-D shear velocity model supports an N–S vertical slab tear beneath SW Anatolia that justifies deepening, increase of dip and change of dip direction of the Wadati-Benioff Zone. Low velocities found at depths <50 km beneath the island and the backarc, interrelated with recent/remnant volcanism in the Aegean and W. Anatolia, are explained by convection from a shallow asthenosphere.

The Deep Lithospheric Structure of the Junggar Terrane, NW China: Implications for Its Origin and Tectonic Evolution

AbstractThe Central Asian Orogenic Belt (CAOB) is one of the world's largest and oldest accretionary orogens. The Junggar Terrane, located in the southwestern CAOB, is considered a key tectonic element to understand the evolution of the whole CAOB. However, given the lack of xenoliths and limited geophysical data with sensitivities to mantle depths, the nature of its basement and its deep lithospheric structure are still highly debated. Here we use a probabilistic inverse method to jointly invert newly processed Rayleigh wave dispersion data, surface heat flow, geoid anomalies, and absolute elevation. The output is a 3‐D model of the seismic, temperature, bulk density, and compositional structure of the whole lithosphere beneath the western part of the Junggar Terrane. Our results reveal a subduction‐shaped mantle anomaly beneath the western flank of the Junggar Basin that resembles closely the structure of a fossil subduction zone. We also confirm the presence of a thick lower crust beneath the basin with properties similar to those of basaltic rocks. On account of these results, we further conduct a hypothesis test and demonstrate that an “oceanic model” for the origin of the basement of the Junggar Basin explains the available geophysical and geochemical information better than other alternative models. Based on all these observations, we propose an evolutionary model for the western Junggar Terrane that reconciles a number of previously conflicting interpretations.

Deep lithospheric structure beneath the Polish part of the East European Craton as a result of magnetotelluric surveys

A fundamental tectonic boundary between the Precambrian East European Craton (EEC) and the younger Phanerozoic mountain belts of Europe runs through Poland. Whereas the transition zone between both tectonical units was intensely investigated by means of electromagnetic methods in the past, the image of electric conductivity of the EEC itself has not been detailed so far. In the present study the lithospheric structure beneath the northeast of Poland is investigated by means of three parallel magnetotelluric profiles. As a result the Polish part of the craton does not appear as homogeneously highresistive as repeatedly reported. Beneath a shallow (from 2 to 4 km) sedimentary layer a less resistive structure (several hundred Ωm) under all three profiles in mid-crustal to upper mantle depth becomes apparent in the high-resistive background. It spatially coincides with a magmatic body of the Upper Proterozoic age called Śniardwy lake gabbro intrusion.

Kimberlites distribution in Angola and prospective areas for new discoveries

Based on a comprehensive analysis of kimberlite pipes of Angola, including the near surface structural setting, deep lithospheric structure, pipe morphology and emplacement, mineralogical and petrographic features, diamond characteristics and locations of secondary deposits four geographical regions have been outlined within Angola representing four types of diamond bearing potential. These areas include high diamond bearing potential pipes, possible potential, no potential, and unclear potential areas. It was found that the depth of magmatism and diamond potential of kimberlites increases from the Atlantic coast in southwestern Angola into the continent in the north-easterly direction. Areas prospective for the discovery of new primary diamond deposits have been identified.

Zones of the origin of seismic centers in the Pamir–Tien Shan sector of High Asia

The zones of the origin of seismic centers within highly seismic areas of the Pamirs and Tien Shan are established. The majority of catastrophic earthquakes coincide with them in this part of High Asia. Their establishment is based on the distribution of the most intensive epicenters and the maximal volumes of the seismic energy together with its calculation and forecasting of the possible manifestations of high seismicity. The investigation of the deep structure of these zones allows us to determine the connection of the seismicity with geophysical field anomalies and some factors of the deep and near surface lithosphere and crust structure, which influence the present-day geodynamics. The results of our research enable us to appreciate the level of the seismic danger in different parts of the region investigated.

Symmetry during the syn- and post-rift evolution of extensional back-arc basins: The role of inherited orogenic structures

Rheological heterogeneities in the lithosphere have first order control on the topographical expression of tectonic processes. Pre-existing orogenic suture zones localise extensional deformation resulting in asymmetric basins. Such crustal geometries are often in contrast with the more symmetric regional lithospheric structure observed beneath extensional basins. We study such (a)symmetries and their controlling parameters by conducting a series of 2D thermo-mechanical numerical experiments of the extension of an overthickened, hot lithosphere that contains a weakness zone. The modelling shows that syn-rift subsidence is low to moderate creating asymmetric half grabens where extension migrates in space and time, grouped in an overall symmetrical appearance on a larger scale. The initial lithospheric mantle asymmetry is attenuated by the lateral heat conduction and further dynamic evolution of the thermal anomaly during the “post-rift” phase, resulting in differential vertical movements of the crust including additional 2–3 km subsidence in the basin centre. The modelling shows that the initial crustal and lithospheric thicknesses, rate of extension and surface processes strongly control the thermo-mechanical evolution of the extensional system. The numerical modelling yields new insights into the mechanics of coupling between near-surface kinematics and the evolution of deep lithospheric structure in the Pannonian basin and the Aegean, two of Europe's largest back-arc systems.

Continental extension and break-up—using the Australian margins as a case study

The continental margins of Australia provide an excellent natural laboratory for investigations of continental extension and break-up, with examples of failed rifts, multi-phase extensional systems, and volcanic and non-volcanic margins. The thick sedimentary cover across large parts, however, has hindered understanding of the deep crustal and lithospheric structure due to poor imaging. ION Geophysical has acquired deep, long offset seismic data across Australia’s North West Shelf, as well as the Bight Basin on Australia’s southern margin. These programs provide unique imaging of the deep basement structures and the complete overlying sedimentary section, and across all of the terrains from continental crust to oceanic crust. The authors’ interpretation of these data will be discussed in the context of existing models for continental extension and break-up and the resulting implications for the petroleum system: Models of hyper-extension and possible mantle exhumation will be discussed with regards to the Bonaparte, Browse and Bight basins. Multi-phase extension and the development of intra-sedimentary detachment horizons will be reviewed across many areas. Development of volcanic margins, including the effects of dynamic uplift and magmatic intrusions, will be investigated in the Exmouth Plateau. Creation of enough accommodation space to allow the deposition of the observed (~20 km) sedimentary sections in the Carnarvon and Bonaparte basins.

Insights into mantle-type volatiles contribution from dissolved gases in artesian waters of the Great Artesian Basin, Australia

The geochemical features of the volatiles dissolved in artesian thermal waters discharged over three basins (Millungera, Galilee and Cooper basin) of the Australian Great Artesian Basin (GAB) consistently indicate the presence of fluids from multiple gas sources located in the crust (e.g. sediments, oil reservoirs, granites) as well as minor but detectable contributions of mantle/magma-derived fluids. The gases extracted from 19 water samples and analyzed for their chemical and isotopic composition exhibit amounts of CO2 up to about 340mlSTP/LH2O marked by a δ13CTDC (Total Dissolved Carbon) ranging from −16.9 to +0.18‰ vs PDB, while CH4 concentrations vary from 4.4×10−5 to 4.9mlSTP/LH2O. Helium contents were between 9 and >2800 times higher than equilibrium with Air Saturated Water (ASW), with a maximum value of 0.12mlSTP/LH2O. Helium isotopic composition was in the 0.02–0.21 Ra range (Ra = air-normalized 3He/4He ratio). The three investigated basins differ from each other in terms of both chemical composition and isotopic signatures of the dissolved gases whose origin is attributed to both mantle and crustal volatiles. Mantle He is present in the west-central and hottest part of the GAB despite no evidence of recent volcanism. We found that the partial pressure of helium, significantly higher in crustal fluids than in mantle-type volatiles, enhances the crustal He signature in the dissolved gases, thus masking the original mantle contribution. Neotectonic activity involving deep lithospheric structures and magma intrusions, highlighted by recent geophysical investigations, is considered to be the drivers of mantle/magmatic volatiles towards the surface. The results, although pertaining to artesian waters from a vast area of >542,000km2, provide new constraints on volatile injection, and show that fluids' geochemistry can provide additional and independent information on the geo-tectonic settings of the Great Artesian Basin and its geothermal potential.

Asthenospheric Pacific‐Atlantic flow barriers and the West Scotia Ridge extinction

AbstractThe Drake Passage is considered a gateway for oceanic and asthenospheric flows since its opening, entailing widespread consequences for climate and plate tectonics, respectively. Both the surface and the 50 km upward continued Bouguer anomaly maps of the Scotia Sea and surrounding areas, based on Gravity Recovery and Climate Experiment gravity satellite data, improve our knowledge of deep lithospheric structures and the asthenosphere. We show that the West Scotia Sea is likely to be underlain by an anomalously low‐density upper mantle. Gravity data are compatible with variable lithospheric thicknesses related to asthenospheric currents. The new data suggest that the development of the Shackleton Fracture Zone since the middle Miocene was probably a main factor that determined the evolution of the eastward Pacific mantle flows and the extinction of the West Scotia Sea oceanic spreading around 6 Ma ago. Deep lithospheric roots are likely to divert asthenospheric currents around them, flowing eastward through Drake Passage.

The structure of the lithospheric mantle of the Siberain craton and seismodynamics of deformation waves in the Baikal seismic zone

The structure of the lithospheric mantle of the Siberain craton and seismodynamics of deformation waves in the Baikal seismic zone