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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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Torne, Montserrat, Ivone Jiménez–Munt, Jaume Vergés, Manel Fernàndez, Alberto Carballo, and Margarete Jadamec. "Regional crustal and lithospheric thickness model for Alaska, the Chukchi shelf, and the inner and outer bering shelves." Geophysical Journal International 220, no. 1 (October 7, 2019): 522–40. http://dx.doi.org/10.1093/gji/ggz424.
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SUMMARY This study presents for the first time an integrated image of the crust and lithospheric mantle of Alaska and its adjacent western shelves of the Chukchi and Bering seas based on joint modelling of potential field data constrained by thermal analysis and seismic data. We also perform 3-D forward modelling and inversion of Bouguer anomalies to analyse density heterogeneities at the crustal level. The obtained crustal model shows northwest-directed long wavelength thickening (32–36 km), with additional localized trends of thicker crust in the Brooks Range (40 km) and in the Alaska and St Elias ranges (50 km). Offshore, 28–30-km-thick crust is predicted near the Bearing slope break and 36–38 km in the northern Chukchi Shelf. In interior Alaska, the crustal thickness changes abruptly across the Denali fault, from 34–36 to the north to above 30 km to the south. This sharp crustal thickness gradient agrees with the presence of a crustal tectonic buttress guiding block motion west and south towards the subduction zone. The average crustal density is 2810 kg m−3. The denser crust, up to 2910 kg m−3, is found south of the Denali Fault likely related to the oceanic nature of the Wrangellia Composite Terrane rocks. Offshore, less dense crust (<2800 kg m−3) is found along the sedimentary basins of the Chukchi and Beaufort shelves. At LAB levels, there is a regional SE–NW trend that coincides with the current Pacific Plate motion, with a lithospheric root underneath the Brooks Range, Northern Slope, and Chuckchi Sea, that may correspond to a relic of the Chukotka-Artic Alaska microplate. The obtained lithospheric root (above 180 km) agrees with the presence of a boundary of cold, strong lithosphere that deflects the strain towards the South. South of the Denali Fault the LAB topography is quite complex. East of 150°W, below Wrangellia and the eastern side of Chugach terranes, the LAB is much shallower than it is west of this meridian. The NW trending limit separating thinner lithosphere in the east and thicker in the west agrees with the two-tiered slab shape of the subducting Pacific Plate.
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Xia, B., I. M. Artemieva, and H. Thybo. "Lithosphere structure of the North China Craton: high resolution seismic crustal structure and lithospheric mantle density." Acta Geologica Sinica - English Edition 93, S1 (May 2019): 107. http://dx.doi.org/10.1111/1755-6724.13968.
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Ravat, D., Z. Lu, and L. W. Braile. "Velocity–density relationships and modeling the lithospheric density variations of the Kenya Rift." Tectonophysics 302, no. 3-4 (February 1999): 225–40. http://dx.doi.org/10.1016/s0040-1951(98)00283-2.
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Klitzke, P., J. I. Faleide, M. Scheck-Wenderoth, and J. Sippel. "A lithosphere-scale structural model of the Barents Sea and Kara Sea region." Solid Earth 6, no. 1 (February 12, 2015): 153–72. http://dx.doi.org/10.5194/se-6-153-2015.
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Abstract. We introduce a regional 3-D structural model of the Barents Sea and Kara Sea region which is the first to combine information on the sediments and the crystalline crust as well as the configuration of the lithospheric mantle. Therefore, we have integrated all available geological and geophysical data, including interpreted seismic refraction and reflection data, seismological data, geological maps and previously published 3-D models into one consistent model. This model resolves four major megasequence boundaries (earliest Eocene, mid-Cretaceous, mid-Jurassic and mid-Permian) the top crystalline crust, the Moho and a newly calculated lithosphere–asthenosphere boundary (LAB). The thickness distributions of the corresponding main megasequences delineate five major subdomains (the northern Kara Sea, the southern Kara Sea, the eastern Barents Sea, the western Barents Sea and the oceanic domain comprising the Norwegian–Greenland Sea and the Eurasia Basin). Relating the subsidence histories of these subdomains to the structure of the deeper crust and lithosphere sheds new light on possible causative basin forming mechanisms that we discuss. The depth configuration of the newly calculated LAB and the seismic velocity configuration of the upper mantle correlate with the younger history of this region. The western Barents Sea is underlain by a thinned lithosphere (80 km) resulting from multiple Phanerozoic rifting phases and/or the opening of the NE Atlantic from Paleocene/Eocene times on. Notably, the northwestern Barents Sea and Svalbard are underlain by thinnest continental lithosphere (60 km) and a low-velocity/hot upper mantle that correlates spatially with a region where late Cenozoic uplift was strongest. As opposed to this, the eastern Barents Sea is underlain by a thicker lithosphere (~ 110–150 km) and a high-velocity/density anomaly in the lithospheric mantle. This anomaly, in turn, correlates with an area where only little late Cenozoic uplift/erosion was observed.
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Fu, Guangyu, Yawen She, Guoqing Zhang, Yun Wang, Shanghua Gao, and Tai Liu. "Lithospheric Equilibrium, Environmental Changes, and Potential Induced-Earthquake Risk around the Newly Impounded Baihetan Reservoir, China." Remote Sensing 13, no. 19 (September 29, 2021): 3895. http://dx.doi.org/10.3390/rs13193895.
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The Baihetan hydropower station is the second largest hydropower station worldwide. It began to store water in April 2021. We conducted a dense hybrid gravity and GNSS survey at 223 stations, obtained the free-air and Bouguer gravity anomalies, inversed the lithospheric density structure, and calculated the isostatic additional force (IAF) borne by lithosphere in the reservoir area. Moreover, we studied the gravity change and Coulomb stress change around the Baihetan reservoir due to impoundment. The main findings are the following. (1) Hybrid gravity and GNSS observations significantly improved the spatial resolution of the gravity field, and the maximum improvement reached up to 150 mGal. (2) A new method for risk assessment of reservoir-induced earthquakes is proposed from the perspective of lithospheric equilibrium. It was found that there is an IAF of −30 MPa at approximately 20 km upstream of the Baihetan dam, and the risk of a reservoir-induced earthquake in this area warrants attention. (3) It was found that the Coulomb stress variation on the Xiaojiang fault near Qiaojia at a depth of 10 km exceeded the threshold for inducing an earthquake (0.1 bar).
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D’Angelo, Giulia, Mirko Piersanti, Roberto Battiston, Igor Bertello, Vincenzo Carbone, Antonio Cicone, Piero Diego, et al. "Haiti Earthquake (Mw 7.2): Magnetospheric–Ionospheric–Lithospheric Coupling during and after the Main Shock on 14 August 2021." Remote Sensing 14, no. 21 (October 25, 2022): 5340. http://dx.doi.org/10.3390/rs14215340.
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In the last few decades, the efforts of the scientific community to search earthquake signatures in the atmospheric, ionospheric and magnetospheric media have grown rapidly. The increasing amount of good quality data from both ground stations and satellites has allowed for the detections of anomalies with high statistical significance such as ionospheric plasma density perturbations and/or atmospheric temperature and pressure changes. However, the identification of a causal link between the observed anomalies and their possible seismic trigger has so far been prevented by difficulties in the identification of confounders (such as solar and atmospheric activity) and the lack of a global analytical lithospheric–atmospheric–magnetospheric model able to explain (and possibly forecast) any anomalous signal. In order to overcome these problems, we have performed a multi-instrument analysis of a low-latitude seismic event by using high-quality data from both ground bases and satellites and preserving their statistical significance. An earthquake (Mw = 7.2) occurred in the Caribbean region on 14 August 2021 under both solar quiet and fair weather conditions, thus proving an optimal case study to reconstruct the link between the lithosphere, atmosphere, ionosphere, and magnetosphere. The good match between the observations and novel magnetospheric–ionospheric–lithospheric coupling (M.I.L.C.) modeling of the event confirmed that the fault break generated an atmospheric gravity wave that was able to mechanically perturb the ionospheric plasma density, in turn triggering a variation in the magnetospheric field line resonance frequency.
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Hlavňová, Petra, Miroslav Bielik, Jana Dérerová, Igor Kohút, and Mariana Pašiaková. "A new lithospheric model in the eastern part of the Western Carpatians: 2D integrated modelling." Contributions to Geophysics and Geodesy 45, no. 1 (March 1, 2015): 13–23. http://dx.doi.org/10.1515/congeo-2015-0010.
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Abstract Using 2D integrated geophysical modelling we recalculated lithospheric model along transect KP-X in the eastern part of the Western Carpathians. Our model takes into account the joint interpretation of the heat flow, free air anomalies, topography and geoid data. A more accurate model of lithospheric structure has been created, especially the lithosphere-astenosphere boundary. Lithosphere thickness in the study region increases from the area of the Pannonian Basin where we modelled it at the depth of 80 km towards the oldest and coolest area of the European Platform where it reaches about 150 km. In the Pannonian Basin the modelled Moho depths reach about of 25 km and it decreases towards theWestern Carpathians. The Western Carpathian’s crustal thickness varies from about 30 km to 45 km. The largest crustal thickness (45 km) has been located beneath the Externides (Carpathian Foredeep) of the Western Carpathians. In the direction of the European platform a Moho depth gradually increases until the end of the profile, where the crustal thickness reaches of about 42 km. Our modelling has confirmed the existence of an anomalous body with average density of 2850 kgm−3 seated mostly in the lower crust. Its uppermost boundary reaches a depth of about 12 km. The lower crust beneath the Western Carpathian Externides is much thicker (20 km) in comparison beneath the Pannonian Basin, where it is only 8 km on average.
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Fullea, J., S. Lebedev, Z. Martinec, and N. L. Celli. "WINTERC-G: mapping the upper mantle thermochemical heterogeneity from coupled geophysical–petrological inversion of seismic waveforms, heat flow, surface elevation and gravity satellite data." Geophysical Journal International 226, no. 1 (March 10, 2021): 146–91. http://dx.doi.org/10.1093/gji/ggab094.
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SUMMARY We present a new global thermochemical model of the lithosphere and underlying upper mantle constrained by state of the art seismic waveform inversion, satellite gravity (geoid and gravity anomalies and gradiometric measurements from ESA's GOCE mission), surface elevation and heat flow data: WINTERC-G. The model is based upon an integrated geophysical–petrological approach where seismic velocities and density in the mantle are computed within a thermodynamically self-consistent framework, allowing for a direct parametrization in terms of the temperature and composition variables. The complementary sensitivities of the data sets allow us to constrain the geometry of the lithosphere–asthenosphere boundary, to separate thermal and compositional anomalies in the mantle, and to obtain a proxy for dynamic surface topography. At long spatial wavelengths, our model is generally consistent with previous seismic (or seismically derived) global models and earlier integrated studies incorporating surface wave data at lower lateral resolution. At finer scales, the temperature, composition and density distributions in WINTERC-G offer a new state of the art image at a high resolution globally (225 km average interknot spacing). Our model shows that the deepest lithosphere–asthenosphere boundary is associated with cratons and, also, some tectonically active areas (Andes, Persian Gulf). Among cratons we identify considerable differences in temperature and composition. The North American and Siberian Cratons are thick (>260 km) and compositionally refractory, whereas the Sino-Korean, Aldan and Tanzanian Cratons have a thinner, fertile lithosphere, similar to younger continental lithosphere elsewhere. WINTERC-G shows progressive thickening of oceanic lithosphere with age, but with significant regional differences: the lithospheric mantle beneath the Atlantic and Indian Oceans is, on average, colder, more fertile and denser than that beneath the Pacific Ocean. Our results suggest that the composition, temperature and density of the oceanic mantle lithosphere are related to the spreading rate for the rates up to 50–60 mm yr–1: the lower spreading rate, the higher the mantle fertility and density, and the lower the temperature. At greater spreading rates, the relationship disappears. The 1-D radial average of WINTERC-G displays a mantle geothermal gradient of 0.55–0.6 K km–1 and a potential temperature of 1300–1320 °C for depths >200 km. At the top of the mantle transition zone the amplitude of the maximum lateral temperature variations (cratons versus hotspots) is about 120 K. The isostatic residual topography values, a proxy for dynamic topography, are large (>1 km) mostly in active subduction settings. The residual isostatic bathymetry from WINTERC-G is remarkably similar to the pattern independently determined based on oceanic crustal data compilations. The amplitude of the continental residual topography is relatively large and positive (>600 m) in the East European Craton, Greenland, and the Andes and Himalayas. By contrast, central Asia, most of Antarctica, southern South America and, to a lesser extent, central Africa are characterized by negative residual topography values (>–400 m). Our results show that a substantial part of the topography signal previously identified as residual (or dynamic) is accounted for, isostatically, by lithospheric density variations.
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Li, Chuantao, Guibin Zhang, Xinsheng Wang, Zhengkai Wang, and Jian Fang. "Three-dimensional lithospheric density distribution of China and surrounding regions." Geoscience Frontiers 5, no. 1 (January 2014): 95–102. http://dx.doi.org/10.1016/j.gsf.2013.03.004.
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Sippel, Judith, Christian Meeßen, Mauro Cacace, James Mechie, Stewart Fishwick, Christian Heine, Magdalena Scheck-Wenderoth, and Manfred R. Strecker. "The Kenya rift revisited: insights into lithospheric strength through data-driven 3-D gravity and thermal modelling." Solid Earth 8, no. 1 (January 16, 2017): 45–81. http://dx.doi.org/10.5194/se-8-45-2017.
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Abstract. We present three-dimensional (3-D) models that describe the present-day thermal and rheological state of the lithosphere of the greater Kenya rift region aiming at a better understanding of the rift evolution, with a particular focus on plume–lithosphere interactions. The key methodology applied is the 3-D integration of diverse geological and geophysical observations using gravity modelling. Accordingly, the resulting lithospheric-scale 3-D density model is consistent with (i) reviewed descriptions of lithological variations in the sedimentary and volcanic cover, (ii) known trends in crust and mantle seismic velocities as revealed by seismic and seismological data and (iii) the observed gravity field. This data-based model is the first to image a 3-D density configuration of the crystalline crust for the entire region of Kenya and northern Tanzania. An upper and a basal crustal layer are differentiated, each composed of several domains of different average densities. We interpret these domains to trace back to the Precambrian terrane amalgamation associated with the East African Orogeny and to magmatic processes during Mesozoic and Cenozoic rifting phases. In combination with seismic velocities, the densities of these crustal domains indicate compositional differences. The derived lithological trends have been used to parameterise steady-state thermal and rheological models. These models indicate that crustal and mantle temperatures decrease from the Kenya rift in the west to eastern Kenya, while the integrated strength of the lithosphere increases. Thereby, the detailed strength configuration appears strongly controlled by the complex inherited crustal structure, which may have been decisive for the onset, localisation and propagation of rifting.
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Boutelier, D., and O. Oncken. "3-D thermo-mechanical laboratory modelling of plate-tectonics." Solid Earth Discussions 3, no. 1 (February 18, 2011): 105–47. http://dx.doi.org/10.5194/sed-3-105-2011.
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Abstract. We present an experimental apparatus for 3-D thermo-mechanical analogue modelling of plate-tectonics processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic with softening analogue materials, is submitted to a constant temperature gradient producing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry). Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and changed because of the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.
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Boutelier, D., and O. Oncken. "3-D thermo-mechanical laboratory modeling of plate-tectonics: modeling scheme, technique and first experiments." Solid Earth 2, no. 1 (May 24, 2011): 35–51. http://dx.doi.org/10.5194/se-2-35-2011.
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Abstract. We present an experimental apparatus for 3-D thermo-mechanical analogue modeling of plate tectonic processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic analogue materials with strain softening, is submitted to a constant temperature gradient causing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry). Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and adjusted via the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.
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Lowe, C., and G. Ranalli. "Density, temperature, and rheological models for the southeastern Canadian Cordillera: implications for its geodynamic evolution." Canadian Journal of Earth Sciences 30, no. 1 (January 1, 1993): 77–93. http://dx.doi.org/10.1139/e93-007.
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Two-dimensional density, temperature, and rheological models are constructed for a 350 km northeast-trending transect of the southeastern Canadian Cordillera. All models highlight several major physical differences between foreland and hinterland lithosphere. Significant features of the density model are the presence of an anomalously low-density (3.10 × 103 kg∙m−3) layer, with a maximum thickness of 12 km, beneath the Moho in the hinterland; the similar densities of the Monashee Terrane and the cratonic crust of the foreland; and an increase in crustal thickness beneath the Southern Rocky Mountain Trench. The temperature model shows steeper gradients and higher Moho temperatures beneath the hinterland than beneath the foreland. In the rheological model the hinterland is characterized by a thin, brittle, upper crust beneath which the entire lithosphere is hot, weak, and ductile. In contrast, the foreland is composed of a thick, brittle, upper crust, with an additional brittle zone in the upper mantle. The Moho is a large strength discontinuity beneath the foreland, and the total lithospheric strength there is an order of magnitude larger than in the hinterland. The models are constrained and supported by geological mapping and a number of independent geophysical data sets. Palinspastic cross sections, together with paleotemperature and paleopressure information, are used to generate a time series of one-dimensional paleorheological profiles at a number of times during deformation. This sequence of profiles indicates that the foreland and hinterland have been rheologically distinct since pre-Late Cretaceous times. The profiles are used to clarify the geodynamic evolution of the area and to explain why deformation remained thin skinned in the foreland whereas in the hinterland the entire lithosphere was deformed.
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Tiwari, V. M., D. C. Mishra, and A. K. Pandey. "The lithospheric density structure below the western Himalayan syntaxis: tectonic implications." Geological Society, London, Special Publications 412, no. 1 (October 2, 2014): 55–65. http://dx.doi.org/10.1144/sp412.7.
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Sabadini, Roberto. "Deviatoric stress accumulation and vertical motions forced by lithospheric density anomalies." Physics and Chemistry of the Earth 17 (January 1990): 179–90. http://dx.doi.org/10.1016/0079-1946(89)90023-2.
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Krysiński, Lech, Stanisław Wybraniec, and Marek Grad. "Lithospheric density structure study by isostatic modelling of the European geoid." Studia Geophysica et Geodaetica 59, no. 2 (March 23, 2015): 212–52. http://dx.doi.org/10.1007/s11200-014-1014-z.
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Larionov, Igor, Evgeny Malkin, and Vladimir Uvarov. "Deformation-Electromagnetic Relations in Lithospheric Activity Manifestations." E3S Web of Conferences 62 (2018): 03002. http://dx.doi.org/10.1051/e3sconf/20186203002.
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It has been shown that dipole radiation of accelerated charges, described by Larmor relation, is the basis of the known mechanic-electromagnetic processes of rock deformation. Comparison of crust deformation acceleration with natural electromagnetic field parameters of ELF-VLF range showed good relation. It manifests in the maxima of occurrence frequency density of synchronous deformation-electromagnetic events on two dimensional histograms. The data of a laser strain-meter and a recorder of natural electromagnetic radiation of ELF-VLF range, recorded in a zone of increased seismic activity (Kamchatka, Karymshina site), were used. The authors made an assumption on the existence of stationary regions of deformation process and mechanic-electromagnetic transformations corresponding to regions with different mechanic properties and rock petrographic composition.
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Lee, Sungho, Arushi Saxena, Jung-Hun Song, Junkee Rhie, and Eunseo Choi. "Contributions from lithospheric and upper-mantle heterogeneities to upper crustal seismicity in the Korean Peninsula." Geophysical Journal International 229, no. 2 (December 29, 2021): 1175–92. http://dx.doi.org/10.1093/gji/ggab527.
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SUMMARY The Korean Peninsula (KP), located along the eastern margin of the Eurasian and Amurian plates, has experienced continual earthquakes from small to moderate magnitudes. Various models to explain these earthquakes have been proposed, but the origins of the stress responsible for this region's seismicity remain unclear and debated. This study aims to understand the stress field of this region in terms of the contributions from crustal and upper-mantle heterogeneities imaged via seismic tomography using a series of numerical simulations. A crustal seismic velocity model can determine the crustal thickness and density. Upper-mantle seismic velocity anomalies from a regional tomography model were converted to a temperature field, which can determine the structures (e.g. lithospheric thickness, subducting slabs, their gaps, and stagnant features) and density. The heterogeneities in the crustal and upper mantle governed the buoyancy forces and rheology in our models. The modelled surface topography, mantle flow stress, and orientation of maximum horizontal stress, derived from the variations in the crustal thickness, suggest that model with the lithospheric and upper-mantle heterogeneities is required to improve these modelled quantities. The model with upper-mantle thermal anomalies and east–west compression of approximately 50 MPa developed a stress field consistent with the observed seismicity in the KP. However, the modelled and observed orientations of the maximum horizontal stress agree in the western KP but they are inconsistent in the eastern KP. Our analysis, based on the modelled quantities, suggested that compressional stress and mantle heterogeneities may mainly control the seismicity in the western area. In contrast, we found a clear correlation of the relatively thin lithosphere and strong upper-mantle upwelling with the observed seismicity in the Eastern KP, but it is unclear whether stress, driven by these heterogeneities, directly affects the seismicity of the upper crust.
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Majcin, Dušan, Dušan Bilčík, and Tomáš Klučiar. "Thermal state of the lithosphere in the Danube Basin and its relation to tectonics." Contributions to Geophysics and Geodesy 45, no. 3 (September 1, 2015): 193–218. http://dx.doi.org/10.1515/congeo-2015-0020.
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Abstract The area of the Danube Basin is interesting in the light of the evaluation both of the lithosphere structure and of various theories of Carpathian-Pannonian region tectonic evolution. The aim of this paper is to analyse both the thermal conditions in the Danube Basin and the mutual relations to geological structure and tectonic development of the region under study. First the improved distributions of the terrestrial heat flow density and of the lithosphere thickness were constructed using recently gained geophysical and geological knowledge. Then the critical analysis of existing models of the tectonic development of the region under study was carried out. The tectono-thermal interpretation activities were accomplished by new geothermal modelling approach for transient regime which utilizes also the backstriped sedimentology data as a control parameter of model. Finally the McKenzie’s “pure-shear” model of the Danube basin was constructed as acceptable conception for used geothermal and tectonic data. The determined stretching parameter has an inhomogeneous horizontal distribution and the thinning factors express the depth dependency for separate lithospheric layers.
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Nurmukhamedov, A. G., and M. D. Sidorov. "THE DEEP STRUCTURE MODEL FOR SOUTHERN KAMCHATKA BASED ON 3D DENSITY MODELING AND GEOLOGICAL AND GEOPHYSICAL DATA." Tikhookeanskaya Geologiya 41, no. 2 (2022): 25–43. http://dx.doi.org/10.30911/0207-4028-2022-41-2-25-43.
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In the south of Kamchatka, a number of deep geophysical studies have been conducted along the profile lines. The aim of the research was to study the lithosphere in the zone of present-day volcanism and active seismicity. Geological and geophysical models of the Earth's crust and upper mantle were constructed along the profiles. The results were obtained as part of two-dimensional modeling of geophysical fields. But the analysis of materials shows that the territory is characterized by a complex geological structure, which is reflected in three-dimensional distribution of gravitating masses. For the first time, the article presents the results of volumetric density modeling covering the territory of southern Kamchatka, including areas covered by the Sea of Okhotsk and the Pacific Ocean. The model is based on the technology of three-dimensional imaging of 2D modeling results obtained along the grid of intersecting profiles. The 3D modeling generated isodensity surfaces that enclose regions with layers of high density (≥ 3.33 g/cm3). Thus, the surface identified beneath the ocean is interpreted as a fragment of the top of the subducting plate and the surface under the peninsula is identified as the top of the paleosubduction zone. A subhorizontal high-gradient zone (3.0–3.3 g/cm3) is recognized in the density structures that intersect the 3D model, which is identified with the Moho boundary. A model of subduction interaction between oceanic and continental lithospheric plates is proposed. The two-dimensional model shows the formation of a transitional layer between the Moho boundary of the overhanging lithospheric plate and the top of the paleosubduction zone. In the transition layer, a low-density zone is distinguished, where individual areas of maximum low-density are associated with melting chambers. Conditions are shown for the formation of the crust block with abundant basic-ultrabasic intrusions and the diorite-granodiorite intrusive massif. All ore occurrences and gold deposits of the Karymshinsky ore cluster are located within the contours of projection onto the ground surface of the deep high-gradient zone that encloses the low-density zone. Ore occurrences are genetically related to the zones of crustal weakness where epithermal deposits are formed in closed hydrothermal systems. Based on the analogy, it is possible to prognosticate gold occurrences in other areas of the projection of the high-gradient zone.
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Klitzke, P., J. I. Faleide, M. Scheck-Wenderoth, and J. Sippel. "A lithosphere-scale structural model of the Barents Sea and Kara Sea region." Solid Earth Discussions 6, no. 2 (July 10, 2014): 1579–624. http://dx.doi.org/10.5194/sed-6-1579-2014.
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Abstract. The Barents Sea and Kara Sea region as part of the European Arctic shelf, is geologically situated between the Proterozoic East-European Craton in the south and early Cenozoic passive margins in the north and the west. Proven and inferred hydrocarbon resources encouraged numerous industrial and academic studies in the last decades which brought along a wide spectrum of geological and geophysical data. By evaluating all available interpreted seismic refraction and reflection data, geological maps and previously published 3-D-models, we were able to develop a new lithosphere-scale 3-D-structural model for the greater Barents Sea and Kara Sea region. The sedimentary part of the model resolves four major megasequence boundaries (earliest Eocene, mid-Cretaceous, mid-Jurassic and mid-Permian). Downwards, the 3-D-structural model is complemented by the top crystalline crust, the Moho and a newly calculated lithosphere-asthenosphere boundary (LAB). The thickness distribution of the main megasequences delineates five major subdomains differentiating the region (the northern Kara Sea, the southern Kara Sea, the eastern Barents Sea, the western Barents Sea and the oceanic domain comprising the Norwegian-Greenland Sea and the Eurasia Basin). The vertical resolution of five sedimentary megasequences allows comparing for the first time the subsidence history of these domains directly. Relating the sedimentary structures with the deeper crustal/lithospheric configuration sheds some light on possible causative basin forming mechanisms that we discuss. The newly calculated LAB deepens from the typically shallow oceanic domain in three major steps beneath the Barents and Kara shelves towards the West-Siberian Basin in the east. Thereby, we relate the shallow continental LAB and slow/hot mantle beneath the southwestern Barents Sea with the formation of deep Paleozoic/Mesozoic rift basins. Thinnest continental lithosphere is observed beneath Svalbard and the NW Barents Sea where no Mesozoic/early Cenozoic rifting has occurred but strongest Cenozoic uplift and volcanism since Miocene times. The East Barents Sea Basin is underlain by a LAB at moderate depths and a high-density anomaly in the lithospheric mantle which follows the basin geometry and a domain where the least amount of late Cenozoic uplift/erosion is observed. Strikingly, this high-density anomaly is not present beneath the adjacent southern Kara Sea. Both basins share a strong Mesozoic subsidence phase whereby the main subsidence phase is younger in the South Kara Sea Basin.
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Ramillien, G., and P. Mazzega. "Non-linear altimetric geoid inversion for lithospheric elastic thickness and crustal density." Geophysical Journal International 138, no. 3 (September 1999): 667–78. http://dx.doi.org/10.1046/j.1365-246x.1999.00863.x.
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Naliboff, J. B., C. Lithgow-Bertelloni, L. J. Ruff, and N. de Koker. "The effects of lithospheric thickness and density structure on Earth's stress field." Geophysical Journal International 188, no. 1 (November 2, 2011): 1–17. http://dx.doi.org/10.1111/j.1365-246x.2011.05248.x.
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Gibson, Sally A. "On the nature and origin of garnet in highly-refractory Archean lithospheric mantle: constraints from garnet exsolved in Kaapvaal craton orthopyroxenes." Mineralogical Magazine 81, no. 4 (August 2017): 781–809. http://dx.doi.org/10.1180/minmag.2016.080.158.
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AbstractThe widespread occurrence of pyrope garnet in Archean lithospheric mantle remains one of the 'holy grails' of mantle petrology. Most garnets found in peridotitic mantle equilibrated with incompatible-trace-element enriched melts or fluids and are the products of metasomatism. Less common are macroscopic intergrowths of pyrope garnet formed by exsolution from orthopyroxene. Spectacular examples of these are preserved in both mantle xenoliths and large, isolated crystals (megacrysts) from the Kaapvaal craton of southern Africa, and provide direct evidence that some garnet inthe sub-continental lithospheric mantle formed initially by isochemical rather than metasomatic processes. The orthopyroxene hosts are enstatites and fully equilibrated with their exsolved phases (low-Cr pyrope garnet ± Cr-diopside). Significantly, P-T estimates of the postexsolution orthopyroxenes plot along an unperturbed conductive Kaapvaal craton geotherm and reveal that they were entrained from a large continuous depth interval (85 to 175 km). They therefore represent snapshots of processes operating throughout almost the entire thickness of the sub-cratonic lithosphericmantle.New rare-earth element (REE) analyses show that the exsolved garnets occupy the full spectrum recorded by garnets in mantle peridotites and also diamond inclusions. A key finding is that a few low-temperature exsolved garnets, derived from depths of ∼90 km, are more depleted in light rare-earth elements (LREEs) than previously observed in any other mantle sample. Importantly, the REE patterns of these strongly LREE-depleted garnets resemble the hypothetical composition proposed for pre-metasomatic garnets that are thought to pre-date major enrichment events in the sub-continental lithospheric mantle, including those associated with diamond formation. The recalculated compositions of pre-exsolution orthopyroxenes have higher Al2O3 and CaO contents than their post-exsolution counterparts and most probably formed as shallow residues of large amounts of adiabatic decompression melting in the spinel-stability field. It is inferred that exsolution of garnet from Kaapvaal orthopyroxenes may have been widespread, and perhaps accompanied cratonization at ∼2.9 to 2.75 Ga. Such a process would considerably increase the density and stability of the continental lithosphere.
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Timmerman, Suzette, Anna V. Spivak, and Adrian P. Jones. "Carbonatitic Melts and Their Role in Diamond Formation in the Deep Earth." Elements 17, no. 5 (October 1, 2021): 321–26. http://dx.doi.org/10.2138/gselements.17.5.321.
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Carbonatitic high-density fluids and carbonate mineral inclusions in lithospheric and sub-lithospheric diamonds reveal comparable compositions to crustal carbonatites and, thus, support the presence of carbon-atitic melts to depths of at least the mantle transition zone (~410–660 km depth). Diamonds and high pressure–high temperature (HP–HT) experiments confirm the stability of lower mantle carbonates. Experiments also show that carbonate melts have extremely low viscosity in the upper mantle. Hence, carbonatitic melts may participate in the deep (mantle) carbon cycle and be highly effective metasomatic agents. Deep carbon in the upper mantle can be mobilized by metasomatic carbonatitic melts, which may have become increasingly volumetrically significant since the onset of carbonate subduction (~3 Ga) to the present day.
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Chatterjee, Nilanjan, and Naresh C. Ghose. "Thermobarometry of the Rajmahal Continental Flood Basalts and Their Primary Magmas: Implications for the Magmatic Plumbing System." Minerals 13, no. 3 (March 17, 2023): 426. http://dx.doi.org/10.3390/min13030426.
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The Late Aptian Rajmahal Traps originated through Kerguelen-Plume-related volcanism at the eastern margin of the Indian Shield. Clinopyroxene and whole-rock thermobarometry reveals that the Rajmahal magmas crystallized at P-T conditions of ≤~5 kbar/~1100–1200 °C. These pressures correspond to upper crustal depths (≤~19 km). Modeling shows that the Rajmahal primary magmas were last in equilibrium with mantle at P-T conditions of ~9 kbar/~1280 °C. The corresponding depths (~33 km) are consistent with gravity data that indicate a high-density layer at lower crustal depths below an upwarped Moho. Thus, the high-density layer probably represents anomalous mantle. It is likely that the mantle-derived magmas accumulated below the upwarped Moho and were subsequently transported via trans-crustal faults/fractures to the upper crust where they evolved by fractional crystallization in small staging chambers before eruption. In the lower part of the Rajmahal plumbing system, buoyant melts from the Kerguelen Plume may have moved laterally and upward along the base of the lithosphere to accumulate and erode the eastern Indian lithospheric root. The Rajmahal plumbing system was probably shaped by tectonic forces related to the breakup of Gondwana.
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Pohánka, Vladimír, Peter Vajda, Miroslav Bielik, and Jana Dérerová. "Robustness analysis in forward modelling gravity data in crustal/lithospheric studies." Contributions to Geophysics and Geodesy 41, no. 4 (January 1, 2011): 279–96. http://dx.doi.org/10.2478/v10126-011-0011-2.
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Robustness analysis in forward modelling gravity data in crustal/lithospheric studies The robustness of the gravimetric forward modelling is investigated by applying the harmonic inversion procedure at the input which is the difference of the calculated and measured surface gravity. The gravity data are taken from two profiles in the Carpathian-Pannonian Basin region. The result of the inversion are density models obtained from the original two-layer models with various horizontal boundary depth and density contrast. The deformation of the originally planar boundary is the measure of the mismatch between calculated and measured data. The calculated deformation has reached up to tens of kilometers and thus the uncertainties in determining the geometry of disturbing bodies by the forward modelling are substantial.
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Tenzer, Robert, and Peter Vajda. "Global maps of the step-wise topography corrected and crustal components stripped geoids using the CRUST 2.0 model." Contributions to Geophysics and Geodesy 39, no. 1 (January 1, 2009): 1–17. http://dx.doi.org/10.2478/v10126-009-0001-9.
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Global maps of the step-wise topography corrected and crustal components stripped geoids using the CRUST 2.0 modelWe compile global maps of the step-wise topography corrected and crustal components stripped geoids based on the geopotential model EGM'08 complete to spherical harmonic degree 180 and the CRUST 2.0 global crustal model. The spectral resolution complete to degree 180 is used to compute the primary indirect bathymetric stripping and topographic effects on the geoid, while degree 90 for the primary indirect ice stripping effect. The primary indirect stripping effects of the soft and hard sediments, and the upper, middle and lower consolidated crust components are forward modeled in spatial form using the 2 × 2 arc-deg discrete data of the CRUST 2.0 model. The ocean, ice, sediment and consolidated crust density contrasts are defined relative to the adopted reference crustal density of 2670 kg/m3. Finally we compute and apply the primary indirect stripping effect of the density contrast (relative to the mantle) of the reference crust. The constant value of -520 kg/m3is adopted for this density contrast relative to the mantle. All data are evaluated on a 1 × 1 arc-deg geographical grid. The complete crust-stripped geoidal undulations, globally having a range of approximately 1.5 km, contain the gravitational signal coming from the global mantle lithosphere (upper mantle) morphology and density composition, and from the sub-lithospheric density heterogeneities. Large errors in the complete crust-stripped geoid are expected due to uncertainties of the CRUST 2.0 model, i.e., due to deviations of the CRUST 2.0 model density from the real earth's crustal density and due to the Moho-boundary uncertainties.
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Grimm, Robert E., and Sean C. Solomon. "Limits on modes of lithospheric heat transport on Venus from impact crater density." Geophysical Research Letters 14, no. 5 (May 1987): 538–41. http://dx.doi.org/10.1029/gl014i005p00538.
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Petrishchevsky, M. "The relation of seismicity to lithospheric density inhomogeneities in the Russian Far East." Journal of Volcanology and Seismology 1, no. 6 (December 2007): 410–20. http://dx.doi.org/10.1134/s074204630706005x.
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XIAO, Long, JianNan ZHAO, Le QIAO, Qian HUANG, ZhiYong XIAO, and JinSong PING. "Density and lithospheric thickness of the Marius Hills shield volcano on the Moon." SCIENTIA SINICA Physica, Mechanica & Astronomica 43, no. 11 (October 1, 2013): 1395–402. http://dx.doi.org/10.1360/132013-330.
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Grott, M., and M. A. Wieczorek. "Density and lithospheric structure at Tyrrhena Patera, Mars, from gravity and topography data." Icarus 221, no. 1 (September 2012): 43–52. http://dx.doi.org/10.1016/j.icarus.2012.07.008.
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Svalova, Valentina. "Geodynamics of Alpine Belt and Caribbean Region: Plate - Tectonics and Plume - Tectonics." Journal of Basic & Applied Sciences 18 (December 19, 2022): 126–39. http://dx.doi.org/10.29169/1927-5129.2022.18.13.
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The origin and evolution of geological structures reflect lithosphere-asthenosphere interaction in the process of lithospheric plate movement. Mantle diapirs contribute significantly to the sedimentary basins formation in Alpine belt and Caribbean region. Mantle diapirs are the result of density inversion in the asthenosphere–lithosphere system in the periods of tectonomagmatic activations. Increasing heat flow and mantle diapirs on the phone of convergence of Africa and Eurasia in Alpine belt and North and South Americas in Caribbean region produce intercontinental seas in the Cenozoic. The analytical solution of the problem give possibility to find the critical parameters connecting the mantle flow dynamics with surface relief evolution. In Alpine belt, the mantle diapirs form new basins at the final stage of Africa–Eurasia collision in the Cenozoic. In the Caribbean region, great mantle diapir separates the North and South Americas in the Mesozoic, and then the diapir is the source for different smaller diapirs during the convergence of these continents in the Cenozoic. The Gulf of Mexico and Pre-Caspian Depression are connected with mantle diapirs upwelling and have common geological-geophysical features as very rich oil-gas and salt bearing structures. Geodynamics of Alpine belt and the Caribbean region is determined by plume - tectonics on background of plate - tectonics in these regions.
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Mart, Y. "The structural evolution of oceanic core complexes: A concept based on analog modeling." Geodynamics & Tectonophysics 11, no. 1 (March 19, 2020): 1–15. http://dx.doi.org/10.5800/gt-2020-11-1-0458.
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Oceanic core complexes are lithological assemblages of predominantly peridotites and serpentinites, located along intersections of some slow-spreading oceanic accreting rifts and fracture zones, embedded in the predominantly basaltic oceanic lithosphere, and fresh and old basalts are juxtaposed across the fracture zone. Centrifuge-based experimental models indicated that subduction would initiate at sites where two lithospheric slabs are juxtaposed, provided that the density difference between them is at least 200 kg/m3 and the friction along their contact plane is low. It was discerned that the modeled underthrust denser lithosphere would reach the modeled asthenosphere and represent tectonic subduction. In many such occurrences, extension in the over-riding slab would develop normal faults that could be penetrated by the lighter fraction of the subducted slab, generating volcanism and diapirism. These experiments suggest further that since the density contrasts and the low friction constraints could be satisfied at the intersections of fracture zones and slow-spreading oceanic ridges, subduction could occur there too and not only along ocean-continent boundaries. Furthermore, since the thermal gradient in ridge-fracture zone intersections is very steep and volatiles in the underthrust slab abound in the subducted slab, a portion of the underthrust basalts would undergo serpentinization and another segment could become peridotitic. It is suggested further that the light serpentinite would ascend through the normal faults in the over-riding slab and reach the seafloor diapirically, carrying along large sections of peridotite, to produce the serpentinite-peridotite petrology that typifies oceanic core complex at junctions of fracture zones and slow spreading ridges.
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Lerche, I., and K. Reicherter. "Uplift and Mantle Thickness: A Sensitivity Study." Energy Exploration & Exploitation 25, no. 4 (August 2007): 273–99. http://dx.doi.org/10.1260/014459807783129949.
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This paper derives an inverse set of equations for equilibrium situations to discuss the resolution and sensitivity of models used to describe tectonic uplift and thermal heat flux. The sensitivity of results to variations in single parameters away from a described set of canonical values is given first. This sensitivity study is followed by a detailed treatment describing the probabilities of obtaining mantle thickness, surface heat flux, thermal expansion coefficient, base crustal heat flux, and Moho temperature at or above particular values as the water density, crustal density, asthenospheric density, uplift, crustal thickness, average lithospheric density, base lithospheric temperature, and water depth to the free asthenosphere marker are all allowed to vary simultaneously around their canonical values. In addition, a relative contribution plot for each of the five output variables identifies which of the eight input variables is causing the greatest contribution to the uncertainty. In this way one can identify which variables need to have their ranges of uncertainty narrowed in order to be more precise about the chances of obtaining particular values for the five outputs. A skewness estimate also is given that enables one to determine the most likely directions one should expect improvement to occur with a probability plot of obtaining particular values, or higher, for each of the output variables. Numerical illustrations show how one goes about performing the quantitative assessments and also show how the inverse procedure allows one to be more definitive concerning the five output values, and their ranges of uncertainty, because of uncertainties in the eight input parameter values.
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Pleus, Alexandra, Garrett Ito, Paul Wessel, and L. Neil Frazer. "Rheology and thermal structure of the lithosphere beneath the Hawaiian Ridge inferred from gravity data and models of plate flexure." Geophysical Journal International 222, no. 1 (April 2, 2020): 207–24. http://dx.doi.org/10.1093/gji/ggaa155.
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SUMMARY We examine the rheology and thermal structure of the oceanic lithosphere, expressed in situ by plate flexure beneath the Hawaiian Ridge, where volcanoes of variable sizes have loaded seafloor of approximately the same age, and thus where the lithosphere is expected to have had an approximately uniform age-dependent thermal structure at the time of loading. Shipboard and satellite-derived gravity, as well as multibeam bathymetry data are used in models of plate flexure with curvature-dependent flexural rigidity, the strength of which is limited, in the shallow lithosphere, by brittle failure, and in the deeper lithosphere, by low-temperature plasticity (LTP). We compute relative likelihoods and posterior probabilities for four model parameters: average crustal density ρc, friction coefficient for brittle failure ${\mu _f}$, a pre-exponential weakening factor F controlling the strength of LTP and lithospheric geotherm age t. Results show that if the lithosphere temperatures were as is expected for normal (t = ) 90-Myr-old seafloor at the time of volcano loading, the rheology must be significantly weaker than expected. Specifically, weak brittle strengths (μf ≤ 0.3) show relatively high probabilities for three of the six published LTP flow laws examined. Alternatively, moderate-to-large brittle strengths (μf ≥ 0.5) require all LTP flow laws to be substantially weakened with F = 102 to > 108 or, equivalently, activation energy reduced by 10–35 per cent. In contrast, if the lithosphere has been moderately reheated by the Hawaiian hotspot, represented by geotherms for t = 50–70 Myr, then the flow laws of Evans & Goetze, Raterron et al. and Krancj et al. require little or no weakening. Such modest thermal rejuvenation is allowed by heatflow constraints, supported by regional mantle seismic tomography imaging as well as compositions of mantle xenoliths, and reconciles previously noted discrepancies between the LTP strengths of lithosphere beneath Hawaii versus that entering the Pacific subduction zones.
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Gushurst, Greg, and Rezene Mahatsente. "Lithospheric Structure of the Central Andes Forearc from Gravity Data Modeling: Implication for Plate Coupling." Lithosphere 2020, no. 1 (August 27, 2020): 1–13. http://dx.doi.org/10.2113/2020/8843640.
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Abstract Geodetic and seismological data indicates that the Central Andes subduction zone is highly coupled. To understand the plate locking mechanism within the Central Andes, we developed 2.5-D gravity models of the lithosphere and assessed the region’s isostatic state. The densities within the gravity models are based on satellite and surface gravity data and constrained by previous tomographic studies. The gravity models indicate a high-density (~2940 kg m-3) forearc structure in the overriding South American continental lithosphere, which is higher than the average density of the continental crust. This structure produces an anomalous pressure (20-40 MPa) on the subducting Nazca plate, contributing to intraplate coupling within the Central Andes. The anomalous lithostatic pressure and buoyancy force may be controlling plate coupling and asperity generation in the Central Andes. The high-density forearc structure could be a batholith or ophiolite emplaced onto the continental crust. The isostatic state of the Central Andes and Nazca plate is assessed based on residual topography (difference between observed and isostatic topography). The West-Central Andes and Nazca ridge have ~0.78 km of residual topography, indicating undercompensation. The crustal thickness beneath the West-Central Andes may not be sufficient to isostatically support the observed topography. This residual topography may be partially supported by small-scale convective cells in the mantle wedge. The residual topography in the Nazca ridge may be attributed to density differences between the subducting Nazca slab and the Nazca ridge. The high density of the subducted Nazca slab has a downward buoyancy force, while the less dense Nazca ridge provides an upward buoyancy force. These two forces may effectively raise the Nazca ridge to its current-day elevation.
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Gómez-García, Ángela María, Eline Le Breton, Magdalena Scheck-Wenderoth, Gaspar Monsalve, and Denis Anikiev. "The preserved plume of the Caribbean Large Igneous Plateau revealed by 3D data-integrative models." Solid Earth 12, no. 1 (January 29, 2021): 275–98. http://dx.doi.org/10.5194/se-12-275-2021.
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Abstract. Remnants of the Caribbean Large Igneous Plateau (C-LIP) are found as thicker than normal oceanic crust in the Caribbean Sea that formed during rapid pulses of magmatic activity at ∼91–88 and ∼76 Ma. Strong geochemical evidence supports the hypothesis that the C-LIP formed due to melting of the plume head of the Galápagos hotspot, which interacted with the Farallon (Proto-Caribbean) plate in the eastern Pacific. Considering plate tectonics theory, it is expected that the lithospheric portion of the plume-related material migrated within the Proto-Caribbean plate in a north–north-eastward direction, developing the present-day Caribbean plate. In this research, we used 3D lithospheric-scale, data-integrative models of the current Caribbean plate setting to reveal, for the first time, the presence of positive density anomalies in the uppermost lithospheric mantle. These models are based on the integration of up-to-date geophysical datasets from the Earth's surface down to 200 km depth, which are validated using high-resolution free-air gravity measurements. Based on the gravity residuals (modelled minus observed gravity), we derive density heterogeneities both in the crystalline crust and the uppermost oceanic mantle (<50 km). Our results reveal the presence of two positive mantle density anomalies beneath the Colombian and the Venezuelan basins, interpreted as the preserved fossil plume conduits associated with the C-LIP formation. Such mantle bodies have never been identified before, but a positive density trend is also indicated by S-wave tomography, at least down to 75 km depth. The interpreted plume conduits spatially correlate with the thinner crustal regions present in both basins; therefore, we propose a modification to the commonly accepted tectonic model of the Caribbean, suggesting that the thinner domains correspond to the centres of uplift due to the inflow of the hot, buoyant plume head. Finally, using six different kinematic models, we test the hypothesis that the C-LIP originated above the Galápagos hotspot; however, misfits of up to ∼3000 km are found between the present-day hotspot location and the mantle anomalies, reconstructed back to 90 Ma. Therefore, we shed light on possible sources of error responsible for this offset and discuss two possible interpretations: (1) the Galápagos hotspot migrated (∼1200–3000 km) westward while the Caribbean plate moved to the north, or (2) the C-LIP was formed by a different plume, which – if considered fixed – would be nowadays located below the South American continent.
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Herceg, M., I. M. Artemieva, and H. Thybo. "Sensitivity analysis of crustal correction for calculation of lithospheric mantle density from gravity data." Geophysical Journal International 204, no. 2 (December 3, 2015): 687–96. http://dx.doi.org/10.1093/gji/ggv431.
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Korte, Monika, and Mioara Mandea. "Geopotential field anomalies and regional tectonic features – two case studies: southern Africa and Germany." Solid Earth 7, no. 3 (May 9, 2016): 751–68. http://dx.doi.org/10.5194/se-7-751-2016.
Full textAbstract:
Abstract. Maps of magnetic and gravity field anomalies provide information about physical properties of the Earth's crust and upper mantle, helpful in understanding geological conditions and tectonic structures. Depending on data availability, whether from the ground, airborne, or from satellites, potential field anomaly maps contain information on different ranges of spatial wavelengths, roughly corresponding to sources at different depths. Focussing on magnetic data, we compare amplitudes and characteristics of anomalies from maps based on various available data and as measured at geomagnetic repeat stations. Two cases are investigated: southern Africa, characterized by geologically old cratons and strong magnetic anomalies, and the smaller region of Germany with much younger crust and weaker anomalies. Estimating lithospheric magnetic anomaly values from the ground stations' time series (repeat station crustal biases) reveals magnetospheric field contributions causing time-varying offsets of several nT in the results. Similar influences might be one source of discrepancy when merging anomaly maps from different epochs. Moreover, we take advantage of recently developed satellite potential field models and compare magnetic and gravity gradient anomalies of ∼ 200 km resolution. Density and magnetization represent independent rock properties and thus provide complementary information on compositional and structural changes. Comparing short- and long-wavelength anomalies and the correlation of rather large-scale magnetic and gravity anomalies, and relating them to known lithospheric structures, we generally find a better agreement in the southern African region than the German region. This probably indicates stronger concordance between near-surface (down to at most a few km) and deeper (several kilometres down to Curie depth) structures in the former area, which can be seen to agree with a thicker lithosphere and a lower heat flux reported in the literature for the southern African region.