Готові списки джерел за темами / Lithospheric density

Добірка наукової літератури з теми "Lithospheric density"

Автор: Grafiati

Опубліковано: 1 квітня 2023

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Статті в журналах з теми "Lithospheric density"

Osei Tutu, Anthony, Bernhard Steinberger, Stephan V. Sobolev, Irina Rogozhina, and Anton A. Popov. "Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography." Solid Earth 9, no. 3 (May 16, 2018): 649–68. http://dx.doi.org/10.5194/se-9-649-2018.

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Abstract. The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3-D lithosphere–asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 (WSM2016) and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a seafloor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. The modeled stress field directions, using only the mantle heterogeneities below 300 km, are not perturbed much when the effects of lithosphere and crust above 300 km are added. In contrast, modeled stress magnitudes and dynamic topography are to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a good correlation of 0.51 in continents, but this correction leads to no significant improvement of the fit between the WSM2016 and the resulting lithosphere stresses. In continental regions with abundant heat flow data, TM1 results in relatively small angular misfits. For example, in western Europe the misfit between the modeled and observation-based stress is 18.3°. Our findings emphasize that the relative contributions coming from shallow and deep mantle dynamic forces are quite different for the lithospheric stress field and dynamic topography.

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Moore, William B., and Gerald Schubert. "Lithospheric thickness and mantle/lithosphere density contrast beneath Beta Regio, Venus." Geophysical Research Letters 22, no. 4 (February 15, 1995): 429–32. http://dx.doi.org/10.1029/94gl02055.

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Lynn, C. Elissa, Frederick A. Cook, and Kevin W. Hall. "Tectonic significance of potential-field anomalies in western Canada: results from the Lithoprobe SNORCLE transect." Canadian Journal of Earth Sciences 42, no. 6 (June 1, 2005): 1239–55. http://dx.doi.org/10.1139/e05-037.

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Potential-field anomalies within the Lithoprobe SNORCLE (Slave Northern Cordillera Lithospheric Evolution) transect area provide geometrical constraints for regional crustal and lithospheric structures, as well as for local anomalies when coupled with subsurface geometry visible on nearly 2500 km of deep seismic reflection and refraction profiles. Areal distribution of gravity and magnetic anomalies permit structures to be projected away from seismic cross sections, and forward modelling provides tests of different interpretations of deep (crustal and upper mantle) density structures. In a key result from modelling, a Paleoproterozoic subduction zone beneath the Wopmay orogen probably consists of high-density rocks, such as eclogite, within the upper mantle. This result supports the concept of moderate- to low-angle intra-lithospheric sutures. On an even larger scale, applications of bandpass and directional filters assist in detecting anomalies according to wavelength or azimuthal orientation and thus provide means to track patterns across structural grain. For example, gravity and magnetic trends that are associated with Precambrian rocks of the Canadian Shield can, in some cases, be followed across much of the Cordillera. This result is consistent with North American Precambrian rocks composing much of the crust in the Cordillera and thus that the addition of "new" lithosphere during Mesozoic early Tertiary accretion has been relatively minor.

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Petrishchevsky, A. M. "PROBABILISTIC-DETERMINISTIC GRAVITY MODELS OF THE CENTRAL TYPE STRUCTURES IN THE CRUST AND UPPER MANTLE." Regional problems 24, no. 2-3 (2021): 68–72. http://dx.doi.org/10.31433/2618-9593-2021-24-2-3-68-72.

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The author shows the possibilities of diagnostics and spatial parameterization of central type structures (SCT) by distributions of density contrast and singular points, modeled without aprioristic geologic-geophysical information. The author characterizes the intrusive-dome structures in the crust, formed during the introduction of intrusive bodies, and mantle SCT of plume nature, formed by extrusion of the asthenosphere under the bottom of the lithosphere in the zones of lithospheric plate subduction and in the regional stretching zones.

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Tian, Yu, and Yong Wang. "Sequential inversion of GOCE satellite gravity gradient data and terrestrial gravity data for the lithospheric density structure in the North China Craton." Solid Earth 11, no. 3 (July 1, 2020): 1121–44. http://dx.doi.org/10.5194/se-11-1121-2020.

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Abstract. The North China Craton (NCC) is one of the oldest cratons in the world. Currently, the destruction mechanism and geodynamics of the NCC remain controversial. All of the proposed views regarding the issues involve studying the internal density structure of the NCC lithosphere. Gravity field data are among the most important data in regard to investigating the lithospheric density structure, and gravity gradient data and gravity data each possess their own advantages. Given the different observational plane heights between the on-orbit GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) satellite gravity gradient and terrestrial gravity and the effects of the initial density model on the inversion results, sequential inversion of the gravity gradient and gravity are divided into two integrated processes. By using the preconditioned conjugate gradient (PCG) inversion algorithm, the density data are calculated using the preprocessed corrected gravity anomaly data. Then, the newly obtained high-resolution density data are used as the initial density model, which can serve as constraints for the subsequent gravity gradient inversion. Several essential corrections are applied to the four gravity gradient tensors (Txx, Txz, Tyy, Tzz) of the GOCE satellite, after which the corrected gravity gradient anomalies (T′xx, T′xz, T′yy, T′zz) are used as observations. The lithospheric density distribution result within the depth range of 0–180 km in the NCC is obtained. This study clearly illustrates that GOCE data are helpful in understanding the geological settings and tectonic structures in the NCC with regional scale. The inversion results show that in the crust the eastern NCC is affected by lithospheric thinning with obvious local features. In the mantle, the presented obvious negative-density areas are mainly affected by the high-heat-flux environment. In the eastern NCC, the density anomaly in the Bohai Bay area is mostly attributed to the extension of the Tancheng–Lujiang major fault at the eastern boundary. In the western NCC, the crustal density anomaly distribution of the Qilian block is consistent with the northwest–southeast strike of the surface fault belt, whereas such an anomaly distribution experiences a clockwise rotation to a nearly north–south direction upon entering the mantle.

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Ernst, W. G., Norman H. Sleep, and Tatsuki Tsujimori. "Plate-tectonic evolution of the Earth: bottom-up and top-down mantle circulation." Canadian Journal of Earth Sciences 53, no. 11 (November 2016): 1103–20. http://dx.doi.org/10.1139/cjes-2015-0126.

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Intense devolatilization and chemical-density differentiation attended accretion of planetesimals on the primordial Earth. These processes gradually abated after cooling and solidification of an early magma ocean. By 4.3 or 4.2 Ga, water oceans were present, so surface temperatures had fallen far below low-pressure solidi of dry peridotite, basalt, and granite, ∼1300, ∼1120, and ∼950 °C, respectively. At less than half their T solidi, rocky materials existed as thin lithospheric slabs in the near-surface Hadean Earth. Stagnant-lid convection may have occurred initially but was at least episodically overwhelmed by subduction because effective, massive heat transfer necessitated vigorous mantle overturn in the early, hot planet. Bottom-up mantle convection, including voluminous plume ascent, efficiently rid the Earth of deep-seated heat. It declined over time as cooling and top-down lithospheric sinking increased. Thickening and both lateral extensional + contractional deformation typified the post-Hadean lithosphere. Stages of geologic evolution included (i) 4.5–4.4 Ga, magma ocean overturn involved ephemeral, surficial rocky platelets; (ii) 4.4–2.7 Ga, formation of oceanic and small continental plates were obliterated by return mantle flow prior to ∼4.0 Ga; continental material gradually accumulated as largely sub-sea, sialic crust-capped lithospheric collages; (iii) 2.7–1.0 Ga, progressive suturing of old shields + younger orogenic belts led to cratonal plates typified by emerging continental freeboard, increasing sedimentary differentiation, and episodic glaciation during transpolar drift; onset of temporally limited stagnant-lid mantle convection occurred beneath enlarging supercontinents; (iv) 1.0 Ga–present, laminar-flowing asthenospheric cells are now capped by giant, stately moving plates. Near-restriction of komatiitic lavas to the Archean, and appearance of multicycle sediments, ophiolite complexes ± alkaline igneous rocks, and high-pressure–ultrahigh-pressure (HP–UHP) metamorphic belts in progressively younger Proterozoic and Phanerozoic orogens reflect increasing negative buoyancy of cool oceanic lithosphere, but decreasing subductability of enlarging, more buoyant continental plates. Attending supercontinental assembly, density instabilities of thickening oceanic plates began to control overturn of suboceanic mantle as cold, top-down convection. Over time, the scales and dynamics of hot asthenospheric upwelling versus lithospheric foundering + mantle return flow (bottom-up plume-driven ascent versus top-down plate subduction) evolved gradually, reflecting planetary cooling. These evolving plate-tectonic processes have accompanied the Earth’s thermal history since ∼4.4 Ga.

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Aitken, A. R. A., C. Altinay, and L. Gross. "Australia's lithospheric density field, and its isostatic equilibration." Geophysical Journal International 203, no. 3 (November 3, 2015): 1961–76. http://dx.doi.org/10.1093/gji/ggv396.

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Ebbing, Jörg, Carla Braitenberg, and Hans-Jürgen Götze. "The lithospheric density structure of the Eastern Alps." Tectonophysics 414, no. 1-4 (February 2006): 145–55. http://dx.doi.org/10.1016/j.tecto.2005.10.015.

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Artyushkov, E. V. "Accelerated non-linear destruction of the earth's crust." Discrete Dynamics in Nature and Society 6, no. 4 (2001): 281–90. http://dx.doi.org/10.1155/s1026022601000322.

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The upper part of the Earth—the lithospheric layer,∼100 km thick, is rigid. Segments of this spherical shell–lithospheric plates are drifting over a ductile asthenosphere. On the continents, the lithosphere includes the Earth's crust,∼40 km thick, which is underlain by peridotitic rocks of the mantle. In most areas, at depths∼20–40 km the continental crust is composed of basalts with density∼2900kg m−3. At temperature and pressure typical for this depth, basalts are metastable and should transform into another assemblage of minerals which corresponds to garnet granulites and eclogites with higher densities 3300–3600 kgm−3. The rate of this transformation is extremely low in dry rocks, and the associated contraction of basalts evolves during the time≥108a. To restore the Archimede's equilibrium, the crust subsides with a formation of sedimentary basins, up to 10–15 km deep.Volumes of hot mantle with a water-containing fluid emerge sometimes from a deep mantle to the base of the lithosphere. Fluids infiltrate into the crust through the mantle part of the lithosphere. They catalyze the reaction in the lower crust which results in rock contraction with a formation of deep water basins at the surface during∼106a. The major hydrocarbon basins of the world were formed in this way. Infiltration of fluids strongly reduces the viscosity of the lithosphere, which is evidenced by narrow-wavelength deformations of this layer. At times of softening of the mantle part of the lithosphere, it becomes convectively replaced by a hotter and lighter asthenosphere. This process has resulted in the formation of many mountain ranges and high plateaus during the last several millions of years. Softening of the whole lithospheric layer which is rigid under normal conditions allows its strong compressive and tensile deformations. At the epochs of compression, a large portion of dense eclogites that were formed from basalts in the lower crust sink deeply into the mantle. In some cases they carry down lighter blocks of granites and sedimentary rocks of the upper crust which delaminate from eclogitic blocks and emerge back to the crust. Such blocks of upper crustal rocks include diamonds and other minerals which were formed at a depth of 100–150 km.

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Ognev, I. N., E. V. Utemov, and D. K. Nurgaliev. "The use of «native» wavelet transform for determining lateral density variation of the Volgo-Uralian subcraton." SOCAR Proceedings, SI2 (December 30, 2021): 135–40. http://dx.doi.org/10.5510/ogp2021si200565.

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In the last two decades in conjunction with the development of satellite gravimetry, the techniques of regional-scale inverse and forward gravity modeling started to be more actively incorporated in the construction of crustal and lithospheric scale models. Such regional models are usually built as a set of layers and bodies with constant densities. This approach often leads to a certain difference between the initially used measured gravity field and a gravity field that is produced by the model. One of the examples of this kind of models is a recent lithospheric model of the Volgo-Uralian subcraton. In the current study, we are applying the method of «native» wavelet transform to the residual gravity anomaly for defining the possible lateral density variations within the lithospheric layers of Volgo-Uralia. Keywords: wavelet transform; gravity field inversion; forward gravity modeling; Volgo-Uralian subcraton; satellite gravimetry.

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Більше джерел

Дисертації з теми "Lithospheric density"

Heinicke, Christiane. "Lithospheric-Scale Stresses and Shear Localization Induced by Density-Driven Instabilities." Thesis, Uppsala universitet, Geofysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183725.

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The initiation of subduction requires the formation of lithospheric plates which mostly deform at their edges. Shear heating is a possible candidate for producing such localized deformation. In this thesis we employ a 2D model of the mantle with a visco-elasto-plastic rheology and enabled shear heating. We are able to create a shear heating instability both in a constant strain rate and a constant stress boundary condition setup. For the rst case, localized deformation in our specic setup is found for strain rates of 10-15 1/s and mantle temperatures of 1300°C. For constant stress boundaries, the conditions for a setup to localize are more restrictive. Mantle motion is induced by large cold and hot temperature perturbations. Lithospheric stresses scale with the size of these perturbations; maximum stresses are on the order of the yield stress (1 GPa). Adding topography or large inhomogeneities does not result in lithospheric-scale fracture in our model. However, localized deformation does occur for a restricted parameter choice presented in this thesis. The perturbation size has little effect on the occurrence of localization, but large perturbations shorten its onset time.

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Beller, Stephen. "Imagerie lithosphérique par inversion de formes d’ondes télésismiques – Application aux Alpes Occidentales." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4007/document.

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Dans cette thèse, un algorithme d'inversion de formes d'ondes (FWI) est développé pour l'imagerie 3D des paramètres élastiques de la lithosphère à partir des enregistrements télésismiques dans le but d'accroître la résolution des images lithosphériques. La modélisation sismique est effectuée par un méthode hybride d'injection de champ d'ondes. Une première modélisation est effectuée dans une Terre globale avec le logiciel AxiSEM pour déterminer les champs d’ondes aux bords de la cible lithosphérique. Ces solutions sont ensuite propagées dans cette cible par une méthode aux éléments finis spectraux. Le problème inverse est résolu avec un algorithme d’optimisation locale de type quasi-Newton (l-BFGS). La sensibilité de la méthode à la configuration expérimentale (paramétrisation du milieu, modèle initial, géométrie et échantillonnage du dispositif de capteurs) est tout d’abord analysée avec un modèle synthétique réaliste des Alpes Occidentales. L’algorithme est finalement appliqué à neuf événements de la campagne CIFALPS dans les Alpes occidentales jusqu’à une fréquence de 0.2Hz. Les modèles de vitesses P et S et de densité révèlent les grandes structures lithosphériques de la chaîne alpine, en particulier le corps d’Ivrée et la géométrie des Moho européen et adriatique. Plus profondément, deux anomalies de vitesses lentes sont imagées dans le manteau et sont interprétées comme la signature d’une remontée asthénosphérique et la localisation du détachement du panneau plongeant européen. Ces résultats corroborent l’hypothèse d’une subduction continentale de la croûte européenne et d’une éventuelle déchirure du panneau plongeant européen lors de la phase de collision
In this thesis, a full-waveform inversion (FWI) algorithm is developed with the aim to image the elastic properties (Vp, Vs and density) of 3D lithospheric models from teleseismic recordings with a spatial resolution of the order of the wavelength. Seismic modeling is performed with a wavefield injection hybrid approach. A first simulation is performed in a global radially symmetric Earth with the AxiSEM code to compute the wavefields on the borders of the lithospheric target. Then, these wavefields are propagated in the target with the spectral finite-element method. After linearization, the inverse problem is solved with a quasi-Newton (1-BFGS) optimization algorithm. The sensitivity of the teleseismic FWI to the experimental setup (subsurface parameterization, initial model, sampling and geometry of the station layout) is first assessed with a realistic synthetic model of the Western Alps. The method is finally applied to nine events of the CIFALPS experiment carried out in the Western Alps, up to a frequency of 0.2Hz. Reliable models of P and S wave speeds and density reveal with an unprecedented resolution the crustal and lithospheric structures of the Alpine Belt, in particular the geometry of the Ivrea body, and the European and Adriatic Mohos. Deeper, two slow velocity anomalies beneath the Western Alps are imaged in the mantle. The first, to the west of the chain, is interpreted as the signature of an asthenospheric upwelling, the second near the location of the Ivrea body indicates the European slab break-off. The study supports the hypothesis of the European continental crust subduction and confirms the possible tearing of the European slab

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Girma, Woldetinsae. "The lithosphere of the East African rift and plateau (Afar-Ethiopia-Turkana) insights from integrated 3-D density modelling /." [S.l.] : [s.n.], 2005. http://e-diss.uni-kiel.de/diss_1478/d1478.pdf.

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Chuan-PingLien and 練川平. "Numerical simulation on ionospheric electron density response to currents from lower atmosphere and lithosphere." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/69183000637635238042.

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碩士
國立成功大學
地球科學系
103
In this study, three-dimensional ionosphere electrodynamic model, NRL-SAMI3, is utilized to simulate the ionospheric perturbation due to external direct currents. We formulate a coupling model for a external current‐ionosphere system considering field-aligned or perpendicular disturbance currents that may be propagated upward from lithosphere during seismics. The lithosphere driven current, ranging around 120±20oE, 30±20oN, and 85km altitude, are included in the electrodynamics solver of NRL SAMI3. Our simulation results indicate that the external current produces the total electron content perturbation (∆TEC) as much as -2.6TECu. The negative ∆TEC response is mainly shown in the southwest of external current; while the positive ∆TEC appear in the southeast of external current. The ion/plasma drift velocity modified due to the external currents affect the equatorial plasma fountain effect and electron densities. Further analyses suggest that current along magnetic field line (in q direction) plays a relatively more important role in production of electron density and TEC variations in comparison with those in perpendicular directions (in meridional and zonal directions). The magnitude of elecric field perturbation and its polarity (eastward or westward) are related with the distribution of lithosphere driven current along magnetic field line at 85km alitude and the field-aligned integrated Pedersen conductivity. The electric field perturbation may be overestimated if one uses ionospheric conductivities at lower boundary of 85 km altitude instead of field-aligned integrated conductivities. The simulations of coupling the field-aligned current take into account the integrated conductivities, and results in smaller E×B drift and TEC perturbations.

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[Verfasser], Girma Woldetinsae. "The lithosphere of the East African rift and plateau (Afar-Ethiopia-Turkana) : insights from integrated 3-D density modelling / vorgelegt von Girma Woldetinsae." 2005. http://d-nb.info/977259897/34.

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Книги з теми "Lithospheric density"

Caputo, Michele. Altimetry data and the elastic stress tensor of subduction zones. [Washington, DC: National Aeronautics and Space Administration, 1985.

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Caputo, Michele. Altimetry data and the elastic stress tensor of subduction zones. Greenbelt, Maryland: National Aeronautics and Space Administration, Goddard Space Flight Center, 1987.

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Caputo, Michele. Altimetry data and the elastic stress tensor of subduction zones. [Washington, DC: National Aeronautics and Space Administration, 1985.

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Muršec, Mateja. A Student’s Guide to Practical Work in Soil Science. University of Maribor Press, 2022. http://dx.doi.org/10.18690/um.fkbv.11.2022.

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The student's guide is intended for foreign students choosing Soil science subject at UM. It contains the basics of the geological composition of the lithosphere, classification, mineral composition, and recognition of various rocks. Students are guided through the use of proper equipment and methods of sampling, transportation, preservation, and sample preparation prior to further analysis. Field work and laboratory procedures for determining various physical (soil structure, texture, bulk density, porosity, soil moisture, soil colour) and chemical (soil reaction, organic matter content, nitrogen, phosphorus, and potassium content) characteristics of soil quality are described. Finally, it helps students to describe the soil profile with an accurate description of the general soil horizons and the determination of the soil type.

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Частини книг з теми "Lithospheric density"

Avedik, F., F. Klingelhöfer, M. D. Jegen, and L. M. Matias. "A Global Isostatic Load Model and its Application to Determine the Lithospheric Density Structure of Hotspot Swells." In Oceanic Hotspots, 73–142. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-642-18782-7_4.

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Sabitova, T. M., O. M. Lesik, and A. A. Adamova. "Velocity and Density Heterogeneities of the Tien-Shan Lithosphere." In Geodynamics of Lithosphere & Earth’s Mantle, 539–48. Basel: Birkhäuser Basel, 1998. http://dx.doi.org/10.1007/978-3-0348-8777-9_17.

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Bott, Martin H. P. "Upper Mantle Density Anomalies, Tectonic Stress in the Lithosphere, and Plate Boundary Forces." In Relating Geophysical Structures and Processes: The Jeffreys Volume, 27–38. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm076p0027.

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Romanyuk, Tana V. "The Method of Gravity Inversion: Application to Density Modelling of the Lithosphere Along the Angola-Brazil Geotraverse." In Geodesy and Physics of the Earth, 252–55. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-78149-0_59.

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A. Abu El-Rus, Mohamed, Ali A. Khudier, Sadeq Hamid, and Hassan Abbas. "The Ampferer-Type Subduction: A Case of Missing Arc Magmatism." In Updates in Volcanology - Linking Active Volcanism and the Geological Record [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.109406.

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Ampferer-type subduction is a term that refers to the foundering of hyper-extended continental or embryonic oceanic basins (i.e., ocean-continent transitions) at passive continental margins. The lithospheric mantle underlying these rift basins is mechanically weaker, less dense, and more fertile than the lithospheric mantle underlying bounded continents. Therefore, orogens resulting from the closure of a narrow, immature extensional system are essentially controlled by mechanical processes without significant thermal and lithologic changes. Self-consistent, spontaneous subduction initiation (SI) due to the density contrast between the lithosphere and the crust of ocean-continent transitions is unlikely to occur. Additional far-field external horizontal forces are generally required for the SI. When the lithosphere subducts, the upper crust or serpentinized mantle and sediments separate from the lower crust, which becomes accreted to the orogen, while the lower crust subducts into the asthenosphere. Subduction of the lower crust, which typically consists of dry lithologies, does not allow significant flux-melting within the mantle wedge, so arc magmatism does not occur. As a result of melting inhibition within the mantle wedge during Ampferer-type subduction zones, the mantle beneath the resulting orogenic belts is fertile and thus has a high potential for magma generation during a subsequent breakup (i.e., magma-rich collapse).

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Eshagh, Mehdi. "The Earth’s Gravity Field Role in Geodesy and Large-Scale Geophysics." In Geodetic Sciences - Theory, Applications and Recent Developments. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97459.

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The Earth gravity field is a signature of the Earth’s mass heterogeneities and structures and applied in Geodesy and Geophysics for different purposes. One of the main goals of Geodesy is to determine the physical shape of the Earth, geoid, as a reference for heights, but Geophysics aims to understand the Earth’s interior. In this chapter, the general principles of geoid determination using the well-known methods of Remove-Compute-Restore, Stokes-Helmert and least-squares modification of Stokes’ formula with additive corrections are shortly discussed. Later, some Geophysical applications like modelling the Mohorovičić discontinuity and density contrast between crust and uppermantle, elastic thickness, ocean depth, sediment and ice thicknesses, sub-lithospheric and lithospheric stress, Earthquakes and epicentres, post-glacial rebound, groundwater storage are discussed. The goal of this chapter is to briefly present the roll of gravity in these subjects.

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Zhang, Wenbo, Stephen T. Johnston, and Claire A. Currie. "Numerical models of Cretaceous continental collision and slab breakoff dynamics in western Canada." In Plate Tectonics, Ophiolites, and Societal Significance of Geology: A Celebration of the Career of Eldridge Moores. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2552(06).

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ABSTRACT The North American Cordillera is generally interpreted as a result of the long-lived, east-dipping subduction at the western margin of the North American plate. However, the east-dipping subduction seems problematic for explaining some of the geological features in the Cordillera such as large volume back-arc magmatism. Recent studies suggested that westward subduction of a now-consumed oceanic plate during the Cretaceous could explain these debated geological features. The evidence includes petrological and geochemical variations in magmatism, the presence of ophiolite that indicates tectonic sutures between the Cordillera and Craton, and seismic tomography images showing high-velocity bodies within the underlying convecting mantle that are interpreted as slab remnants from the westward subduction. Here we use 2-D upper mantle-scale numerical models to investigate the dynamics associated with westward subduction and Cordillera-Craton collision. The models demonstrate the controls on slab breakoff (remnant) following collision including: (1) oceanic and continental mantle lithosphere strength, (2) variations in density (eclogitization of continental lower crust and cratonic mantle lithosphere density), and (3) convergence rate. Our preferred model has a relatively weak mantle lithosphere, eclogitization of the lower continental crust, cratonic mantle lithosphere density of 3250 kg/m3, and a convergence rate of 5 cm/yr. It shows that collision and slab breakoff result in an ∼2 km increase in surface elevation of the Cordilleran region west of the suture as the dense oceanic plate detaches. The surface also shows a foreland geometry that extends >1000 km east of the suture with ∼4 km of subsidence relative to the adjacent Cordillera.

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Orme, Antony R. "The Tectonic Framework of South America." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0008.

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Tectonism is the science of Earth movements and the rocks and structures involved therein. These movements build the structural framework that supports the stage on which surface processes, plants, animals and, most recently, people pursue their various roles under an atmospheric canopy. An appreciation of this tectonic framework is thus a desirable starting point for understanding the physical geography of South America, from its roots in the distant past through the many and varied changes that have shaped the landscapes visible today. Tectonic science recognizes that Earth’s lithosphere comprises rocks of varying density that mobilize as relatively rigid plates, some continental in origin, some oceanic, and some, like the South American plate, amalgams of both continental and oceanic rocks. These plates shift in response to deep-seated forces, such as convection in the upper mantle, and crustal forces involving push and pull mechanics between plates. Crustal motions, augmented by magmatism, erosion, and deposition, in turn generate complex three-dimensional patterns. Although plate architecture has changed over geologic time, Earth’s lithosphere is presently organized into seven major plates, including the South American plate, and numerous smaller plates and slivers. The crustal mobility implicit in plate tectonics often focuses more attention on plate margins than on plate interiors. In this respect, it is usual to distinguish between passive margins, where plates are rifting and diverging, and active margins, where plates are either converging or shearing laterally alongside one another. At passive or divergent margins, such as the present eastern margin of the South American plate, severe crustal deformation is rare but crustal flexuring (epeirogeny), faulting, and volcanism occur as plates shift away from spreading centers, such as the Mid-Atlantic Ridge, where new crust is forming. Despite this lack of severe postrift deformation, however, passive margins commonly involve the separation of highly deformed rocks and structures that were involved in the earlier assembly of continental plates, as shown by similar structural legacies in the facing continental margins of eastern South America and western Africa. At active convergent margins, mountain building (orogeny) commonly results from subduction of oceanic plates, collision of continental plates, or accretion of displaced terranes.

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Тези доповідей конференцій з теми "Lithospheric density"

Assumpçăo, Marcelo, David James, and Arthur Snoke. "Crustal Thicknesses in SE Brazilian Shield with Receiver Function: Isostatic Compensation by Density Variations in the Lithospheric Mantle." In 5th International Congress of the Brazilian Geophysical Society. European Association of Geoscientists & Engineers, 1997. http://dx.doi.org/10.3997/2214-4609-pdb.299.289.

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Artemieva, Irina M., and Yulia Cherepanova. "LITHOSPHERE MANTLE DENSITY BENEATH THE SIBERIAN CRATON." In GSA Annual Meeting in Denver, Colorado, USA - 2016. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016am-280146.

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Li, Chuantao, Guibin Zhang, Xinsheng Wang, Zhengkai Wang, and Jian Fang. "Three‐dimensional density distributions of the Asian lithosphere." In GEM Beijing 2011, edited by Xiong Li, Yaoguo Li, and Xiaohong Meng. Society of Exploration Geophysicists, 2011. http://dx.doi.org/10.1190/1.3659109.

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Tsidaev, A. G., I. V. Ladovskiy, and V. V. Kolmogorova. "Velocity and density cuts of Northern Ural’s upper lithosphere." In Geoinformatics. European Association of Geoscientists & Engineers, 2021. http://dx.doi.org/10.3997/2214-4609.20215521035.

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Menshchikova, T., and T. Gudkova. "On load Love numbers for Venus." In ASTRONOMY AT THE EPOCH OF MULTIMESSENGER STUDIES. Proceedings of the VAK-2021 conference, Aug 23–28, 2021. Crossref, 2022. http://dx.doi.org/10.51194/vak2021.2022.1.1.090.

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Load Love coeﬃcients are calculated for diﬀerent rheological models of Venus. A static approach is used, for which two loadlevels are considered: the surface load (the planetary relief) and anomalous density variations located at depth. The planetis modeled as an elastic, self-gravitational body, while the density, elastic modulus and shear modulus being dependent onthe radius. The calculations have been performed up to the spherical harmonic degree and order 70, based on the accuracyof the gravity ﬁeld at the moment. Several types of rheological models of Venus are considered. As a ﬁrst approximation, wetake an elastic model (Model A). In the second case (Model B) we assume the presence of an elastic lithosphere. Beneaththe lithosphere there is a softened layer, which partly lost its elastic properties. Spreading till the core, softened layeris characterized by a reduced (to one-tenth of the initial value) shear modulus. In the third model (Model C) the shearmodulus is changing gradually: one-tenth of the initial value of shear modulus just beneath the crust is increasing up to itselastic value at the core-mantle boundary.

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Artemieva, Irina M., Alexey Shulgin, Bing Xia, Yulia Cherepanova, and Hans Thybo. "DENSITY STRUCTURE OF CRATONIC LITHOSPHERE MANTLE: A TALE OF FOUR CRATONS." In GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-335680.

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Druzhinin, V. S., N. I. Nachapkin, V. Yu Osipov, and L. A. Muravyev. "Seismic-Density Fault-Block Model of Lithosphere Upper Part of The South Kara Depression Along Geotraverse 3-AR." In Engineering and Mining Geophysics 2021. European Association of Geoscientists & Engineers, 2021. http://dx.doi.org/10.3997/2214-4609.202152050.

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