Physics of the Earth and Planetary Interiors最新文献

{"title":"Southeastward extrusion of the Tibetan Plateau limited by the strong Emeishan large igneous province from earthquake surface wave tomography","authors":"Yuanyuan V. Fu ,&nbsp;Lun Li ,&nbsp;Junwei Ma ,&nbsp;Nannan Sun","doi":"10.1016/j.pepi.2024.107153","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107153","url":null,"abstract":"<div><p>Active deformation is ongoing in the southeastern margin of the Tibetan Plateau due to the collision of the Indian and Eurasian continents. While large-scale motion of the surface occurs, the nature of deformation at depth remains unresolved. We construct new lithospheric seismic anisotropic (radially and azimuthally) and shear-wave velocity models using fundamental-mode Rayleigh- and Love-wave phase velocity at periods of 20–100 s obtained from the ChinArray experiment to constrain the deformation style of the crust and upper mantle in the southeastern margin of the Tibetan Plateau. The results show that the uppermost mantle (Moho-90 km) underneath the Tibetan Plateau and northwestern part of the western Yangtze block are characterized with NE-SW oriented azimuthal anisotropy, prominent slow velocity and negative radial anisotropy (V_SH &lt; V_SV). We interpret that this seismic pattern reflects the southeastward extrusion of the Tibetan uppermost mantle that may thermally erode the northwestern edge and result in the vertically coherent fabric due to the barriers of the left strong Emeishan large igneous province (i.e., south of the western Yangtze block) dominated by the high shear wave velocities. Low velocity anomaly, N-S trending azimuthal anisotropy, and negative radial anisotropy in the uppermost mantle beneath the eastern Yangtze block are most probably associated with vertical migration of hot mantle material from the lithosphere delamination and/or a branch of the Hainan plume.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"348 ","pages":"Article 107153"},"PeriodicalIF":2.3,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139733024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining Earth's mantle rheology with Love and Shida numbers at the M2 tidal frequency","authors":"Dargilan Oliveira Amorim ,&nbsp;Tamara Gudkova","doi":"10.1016/j.pepi.2024.107144","DOIUrl":"10.1016/j.pepi.2024.107144","url":null,"abstract":"<div><p>We use measurements of Earth's tidal response at the <span><math><msub><mi>M</mi><mn>2</mn></msub></math></span><span> frequency to constrain the rheology of its mantle. The viscoelasticity<span> and anelasticity of the planet are modeled with an Andrade rheology that depends on two parameters: </span></span><span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span>. In this paper, we propose an improved algorithm to compute Earth's tidal deformation. Its Love and Shida numbers <span><math><msub><mi>k</mi><mn>2</mn></msub></math></span>, <span><math><msub><mi>h</mi><mn>2</mn></msub></math></span>, <span><math><msub><mi>k</mi><mn>3</mn></msub></math></span> and <span><math><msub><mi>l</mi><mn>2</mn></msub></math></span> as well as the tidal lag <span><math><mi>ϵ</mi></math></span> were calculated for two viscosity profiles and for a wide range of values of <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span>. By comparing our results with geodetic measurements we obtain the range of values of <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> that successfully describes Earth's viscoelastic behavior. Values of <span><math><mi>ζ</mi></math></span> as high as <span><math><msup><mn>10</mn><mn>5</mn></msup></math></span> can not be excluded. For <span><math><mi>ζ</mi><mo>=</mo><mn>1</mn></math></span>, <span><math><mi>α</mi></math></span> should be in the range from 0.19 to 0.33, while for a <span><math><mi>ζ</mi><mo>=</mo><msup><mn>10</mn><mn>5</mn></msup></math></span>, <span><math><mi>α</mi></math></span><span> is most likely between 0.11 and 0.17. We believe that a similar rheology should be used in geophysical models of other rocky planets and satellites. The obtained results are mostly representative of the lower mantle.</span></p><p>We have also shown that for several combinations of the two parameters <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> we could obtain nearly identical values of Earth's <span><math><mi>ℜ</mi><mfenced><msub><mi>k</mi><mn>2</mn></msub></mfenced></math></span>, <span><math><mi>ℜ</mi><mfenced><msub><mi>h</mi><mn>2</mn></msub></mfenced></math></span>, <span><math><mi>ℜ</mi><mfenced><msub><mi>l</mi><mn>2</mn></msub></mfenced></math></span> and <span><math><mi>ℜ</mi><mfenced><msub><mi>k</mi><mn>3</mn></msub></mfenced></math></span> with considerably different values of the associated tidal lag. This shows that the approach of always setting <span><math><mi>ζ</mi><mo>=</mo><mn>1</mn></math></span> might be too simplistic and an Andrade rheology with two free parameters is needed to constrain both the real and imaginary parts of Love and Shida numbers.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"347 ","pages":"Article 107144"},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139554240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reversal of drift direction during the Laschamp geomagnetic excursion","authors":"Nicole Clizzie,&nbsp;Catherine Constable","doi":"10.1016/j.pepi.2024.107143","DOIUrl":"10.1016/j.pepi.2024.107143","url":null,"abstract":"<div><p><span>Earth's magnetic field changes in both space and time: the temporal changes are called geomagnetic and paleomagnetic secular variations. Westward drift has been noted as a feature of secular variation for several centuries, but eastward drift has received less attention. We use three global geomagnetic field models covering the past 100 kyr to extend temporal coverage for tracking the zonal (azimuthal) motion of the radial magnetic field. The models we use are GGF100k (100–0 ka), GGFSS70 (70–15 ka), LSMOD.2 (50–30 ka); the extent of the models enables the inclusion of the extreme secular variations found during excursions, particularly the Laschamp excursion (42–40 ka). GGFSS70 and LSMOD.2 have higher temporal resolution than GGF100k, but their underlying data have poorer spatial coverage. Spatial structure is greatly diminished in all models for spherical harmonic degrees </span><span><math><mi>l</mi><mo>&gt;</mo><mn>4</mn></math></span>.</p><p><span>We use two types of time-longitude plots, one of the full radial field to expose reverse and intense flux patches at the core-mantle boundary. The second time-longitude plot is processed to enhance zonal motion signatures and allows us to use Radon drift analyses to uncover characteristic time scales of both westward and eastward drift at mid to high latitudes in both the northern and southern hemispheres. Our results differ across the three models, which we attribute to varying degrees of resolution, accuracy, and data distribution. Nevertheless, recurrent episodes of both eastward and westward drift ranging from </span><span><math><mo>±</mo><msup><mn>0.05</mn><mi>o</mi></msup><mo>/</mo></math></span>yr to <span><math><mo>±</mo><msup><mn>0.18</mn><mi>o</mi></msup><mo>/</mo></math></span>yr occur in both the northern and southern hemispheres. Westward drift dominates. We also observe 8–20 kyr intervals between occurrences of high-latitude reverse flux patches correlated with strong drift signals. Focusing on the period 50–30 ka, we observe dominant eastward drift preceding the Laschamp excursion and westward drift subsequently. In a period not associated with an excursion, 90–80 ka, we see strong mid to high latitude drift signatures in the northern hemisphere.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"347 ","pages":"Article 107143"},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139375460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Changes in thermomagnetic and X-ray diffraction properties of Asby dolerite with distance from the Lockne impact structure, Sweden","authors":"Pradyut Phukon ,&nbsp;Amar Agarwal ,&nbsp;Bruno Daniel Leite Mendes ,&nbsp;Agnes Kontny ,&nbsp;Gaurav Joshi","doi":"10.1016/j.pepi.2024.107145","DOIUrl":"10.1016/j.pepi.2024.107145","url":null,"abstract":"<div><p><span>The Lockne impact structure in Sweden formed due to a meteorite impact<span><span> into the Proterozoic basement rocks in the Ordovician. The dykes of Asby </span>dolerite are part of the target basement and are located outside the crater rim. We investigated the variation in thermomagnetic properties and X-ray diffraction (XRD) spectra of Asby dolerite with distance from the crater centre to find evidence of a potential low shock overprint. Ti-poor, (Ti)-magnetite with dominantly pseudo-single domain behaviour is the main magnetic carrier in the studied samples. Towards the centre of the crater, the Verwey transition temperature (T</span></span>_v<span>) and Curie temperature (T</span>_c) decrease, whereas alteration indices increase systematically. Higher alteration indices and lower T_v<span> near the crater centre may be owed to more intense fracturing of the silicate minerals<span> which facilitated low-temperature oxidation of (Ti)-magnetite and alteration of mafic dykes by improving fluid circulation in a network of fractures in the silicate minerals. Higher deformation near the crater centre is supported by our XRD results, as the peak position (2θ value) of plagioclase (040), pyroxene </span></span><span><math><mo>(</mo><mover><mn>3</mn><mo>¯</mo></mover><mn>11</mn></math></span>) and magnetite (311) peaks decrease, while the width of the plagioclase (040) and pyroxene <span><math><mo>(</mo><mover><mn>3</mn><mo>¯</mo></mover><mn>11</mn></math></span><span>) peaks increase towards the centre. This study shows that changes in thermomagnetic properties and lattice parameters of magnetite are a powerful tool to characterise low shock pressure deformation in impacted target rocks.</span></p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"348 ","pages":"Article 107145"},"PeriodicalIF":2.3,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139657850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dislocations in naturally deformed olivine: Example of a mylonitic peridotite","authors":"Sylvie Demouchy ,&nbsp;Alexandre Mussi ,&nbsp;Timmo Weidner ,&nbsp;Emmanuel Gardés ,&nbsp;Patrick Cordier","doi":"10.1016/j.pepi.2023.107125","DOIUrl":"10.1016/j.pepi.2023.107125","url":null,"abstract":"<div><p>We have investigated the microstructure of naturally deformed olivine (chemically equilibrated at 1000 °C) by conventional transmission electron microscopy and electron tomography. The peridotite specimen, from Oman ophiolite, has a mylonitic microstructure with remnant, strongly deformed, millimetric porphyroclasts co-existing with small newly formed olivine grains generated by dynamic recrystallization. Imaging by transmission electron microscopy reveals that both newly formed grains and porphyroclasts display [100] and [001] dislocations activity. Subgrain boundaries are composed of either [100] or [001] dislocations. The characterization of this natural sample also permits to identify sporadic [100] dislocation loops, rare [010] dislocation, infrequent melt, and intragranular bubbles or along subgrain boundaries. Electron tomography permits to identify several glide planes, which are similar to previous observations acquired on experimentally deformed polycrystalline olivine, more importantly electron tomography also permits to evidence combination of glide, climb and mixed climb (dislocation moving in an intermediate plane between the plane of glide plane and the plane of pure climb). Our study further infers the diversity of linear defects responsible for plastic deformation of olivine at lithospheric conditions.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"346 ","pages":"Article 107125"},"PeriodicalIF":2.3,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920123001516/pdfft?md5=cc66e8ce0cda1c2e2e67f22720ed7d09&pid=1-s2.0-S0031920123001516-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138580856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robust estimates of the ratio between S- and P-wave velocity anomalies in the Earth's mantle using normal modes","authors":"Federica Restelli ,&nbsp;Christophe Zaroli ,&nbsp;Paula Koelemeijer","doi":"10.1016/j.pepi.2023.107135","DOIUrl":"10.1016/j.pepi.2023.107135","url":null,"abstract":"&lt;div&gt;&lt;p&gt;Seismic tomography allows us to image the interior of the Earth. In general, to determine the nature of seismic anomalies, constraints on more than one seismic parameter are required. For example, the ratio &lt;span&gt;&lt;math&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; between perturbations in &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; (&lt;span&gt;&lt;math&gt;&lt;mi&gt;dln&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mi&gt;dln&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, respectively) is studied extensively in the lowermost mantle and interpreted in terms of thermal and/or chemical anomalies. However, to jointly interpret tomographic models of variations in &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; or their ratio &lt;span&gt;&lt;math&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, it is essential for them to share the same local resolution. Most existing models do not provide resolution information, and thus cannot guarantee to honour this condition. In addition, uncertainties are typically not provided, making it difficult to robustly interpret the ratio &lt;span&gt;&lt;math&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;dln&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;dln&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. To overcome these issues, we utilise the recently developed SOLA tomographic method, a variant of the linear Backus–Gilbert inversion scheme. SOLA retrieves local-average model estimates, together with information on their uncertainties, whilst it also provides direct control on model resolution through target kernels. In this contribution, we apply SOLA to normal-mode data with sensitivity to both &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, as well as density throughout the mantle. Specifically, we aim to develop models of both &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; with the same local resolution. We test our methodology and approach using synthetic tests for various noise cases (random noise, data noise or also additional &lt;em&gt;3D Earth noise&lt;/em&gt; due to variations in other physical parameters than the one of interest). We find that the addition of the 3D noise increases the uncertainties in our model estimates significantly, only allowing us to find model estimates in six or four layers for &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, respectively. While the synthetic tests indicate that no satisfactory density models can be obtained, we easily manage to construct models of &lt;span&gt;&lt;math&gt;&lt;mi&gt;dln&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mi&gt;dln&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; with almost identical resolution, from which the ratio &lt;span&gt;&lt;math","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"347 ","pages":"Article 107135"},"PeriodicalIF":2.3,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920123001619/pdfft?md5=f7fd9a864f0d0a2ad0ff7365f36ad0f3&pid=1-s2.0-S0031920123001619-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139064074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluid-assisted intra-plate seismicity at the edge of the Gawler Craton, South Australia","authors":"Shubham Agrawal ,&nbsp;Caroline M. Eakin ,&nbsp;John P. O'Donnell","doi":"10.1016/j.pepi.2023.107133","DOIUrl":"10.1016/j.pepi.2023.107133","url":null,"abstract":"<div><p>The Australian continent, being void of active plate boundaries, is often perceived as seismically quiescent. However, earthquakes of moderate magnitude (M6+) occur on the continent around once per decade. Such intra-plate activity can pose a significant risk as these earthquakes can occur along fault lines that are either unknown or considered inactive, are often non-periodic, and poorly understood. Within Australia, the spatial distribution of intra-plate seismicity is non-uniform, instead tending to concentrate along certain weak zones of increased activity. One such region is the eastern margin of the Gawler Craton in South Australia, one of the oldest building blocks of the continent. Recently, several new temporary seismic arrays have been deployed in the region, transforming data coverage across southern Australia. In total, 139 new local earthquakes have been recorded, most of which went undetected by the national seismic network. Following relocation, the pattern of earthquakes becomes more localised and appears to coincide with the edge of the Gawler Craton. Further, a spatial association was found between earthquakes and mound springs, which act as the discharge point for groundwater migrating from the Great Artesian Basin. Enhanced fluid pressures (mantle-degassing) within permeable crustal scale fault systems, responding to a regional contractional strain field, appear to be a key driver of seismicity in the area.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"346 ","pages":"Article 107133"},"PeriodicalIF":2.3,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920123001590/pdfft?md5=685e288962ef149288edbcfd34b60c1b&pid=1-s2.0-S0031920123001590-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138580845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-pressure single-crystal elasticity of corundum: Implication for multiple seismic structure of 660-km discontinuity","authors":"Xinyue Zhang ,&nbsp;Wei Wei ,&nbsp;Luo Li ,&nbsp;Yingxin Yu ,&nbsp;Zhu Mao","doi":"10.1016/j.pepi.2023.107134","DOIUrl":"10.1016/j.pepi.2023.107134","url":null,"abstract":"<div><p>The complex multi-discontinuity structure at 660‐800 km depth is likely attributable to lateral mantle composition heterogeneities, which are closely related to the mid-ocean ridge basalts (MORB). To decipher the impact of varying composition on the seismic properties of MORB, detailed knowledge of the elasticity of candidate minerals is thus important. Here we employed Brillouin scattering coupled with diamond anvil cells to determine the single-crystal elasticity of corundum up to 14 GPa and 300 K. Using third-order finite strain equation of state, we calculate the pressure derivatives of adiabatic bulk modulus and shear modulus of corundum, which yields <em>K</em>_S0’ = 3.8(1), <em>G</em>₀’ = 1.8(1) with <em>K</em>_S0 = 256(1) GPa and <em>G</em>₀ = 163(1) GPa and <em>ρ</em>₀ = 3.987(1) g/cm³. Combined with previous high-temperature data, the velocity and anisotropy of corundum have been calculated at 300 K or along normal geotherm. Our results are applied to model the density and velocity profiles of normal and alkali-depleted MORB. Our modeling demonstrates that varying the alkali content and temperature of MORB can significantly impact the discontinuity depth and velocity jump at 660–800 km depth. For normal MORB, reducing the temperature by 300 K from normal mantle geotherm results in a shift of the velocity jump from 670–710 to 650–710 km depth but hardly affects the magnitude of the velocity jump (5.8–6.8(3)% for <em>V</em>_P and 10.0–10.8(5)% for <em>V</em>_S). By contrast, in alkali-depleted MORB, the discontinuity will occur at a greater depth from 705–730 to 720–745 km depending on temperature with a <em>V</em>_P jump of 3.8–4.6(2)% and <em>V</em>_S jump of 6.3–7.4(4)%.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"346 ","pages":"Article 107134"},"PeriodicalIF":2.3,"publicationDate":"2023-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920123001607/pdfft?md5=71a15fcd6b132d68f225d96f5fd705ec&pid=1-s2.0-S0031920123001607-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138580508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal deformation and thickness variation from Zagros to Alborz in Iran: New insights from H-κ-c method","authors":"Mohsen Azqandi ,&nbsp;Mohammad Reza Abbassi ,&nbsp;Meysam Mahmoodabadi ,&nbsp;Esmaeil Shabanian ,&nbsp;Ahmad Sadidkhouy","doi":"10.1016/j.pepi.2023.107124","DOIUrl":"https://doi.org/10.1016/j.pepi.2023.107124","url":null,"abstract":"<div><p>The collision between Arabia and Eurasia has had a significant impact on the Iranian plateau, making it a prime location for investigating crustal deformation. The Neotethys Ocean closure and subsequent collision during the Cenozoic era led to extensive deformation in the northern part of the Iranian plateau, in particular development of the Alborz mountain range. In this study, we aim to determine crustal thickness and azimuthal anisotropic parameters in order to gain insights into the patterns of crustal deformation in the region. Using the H-<em>κ</em>-c method (Li et al., 2019), we conducted an investigation into the impact of seismic anisotropy on the estimation of the crustal thickness (H) and <em>Vp</em>/Vs ratio (<em>κ</em>) at 26 seismic stations. Our analysis unveiled significant variations in Moho depth across the studied region. The collisional zones featured a deeper Moho depth when compared to Central Iran. In particular, the Central Iran region demonstrated a relatively thinner crust, characterized by an average Moho depth of 43 km, while the Sanandaj-Sirjan zone showcased a thicker crust, boasting a Moho depth of 59 km. The Alborz mountain ranges demonstrated an average Moho depth of 50 km. Notably, the Central Iran stations exhibited elevated <em>κ</em> values, potentially attributable to fluid contents and thick sedimentary cover. To characterize the anisotropic properties of the crust, we employed curve fitting techniques on the sinusoidal moveouts of the <em>Ps</em>-converted phases originating from the Moho and major intracrustal interfaces. Our analysis identified intracrustal discontinuities at seven stations, indicating the presence of two distinct anisotropic crustal layers. These anisotropic layers displayed maximum delay times of up to 0.6 s. Furthermore, our examination of crustal and mantle anisotropy patterns revealed that the deformation observed in the region cannot be solely attributed to a vertically coherent regime.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"346 ","pages":"Article 107124"},"PeriodicalIF":2.3,"publicationDate":"2023-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920123001504/pdfft?md5=6130d69f91c569c2ab8fe5a7b6061041&pid=1-s2.0-S0031920123001504-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138472728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Partial melt composition of enstatite chondritic mantle around the rheological transition at 23 GPa: Implications for the chemical differentiation of the Earth's mantle","authors":"Hideharu Kuwahara","doi":"10.1016/j.pepi.2023.107123","DOIUrl":"https://doi.org/10.1016/j.pepi.2023.107123","url":null,"abstract":"<div><p>Terrestrial planets are thought to be made of chondritic materials. However, previous studies have suggested that the Earth's upper mantle is depleted in some incompatible refractory lithophile elements (RLEs), such as U and Th in comparison with chondritic values. To explain the compositional contradiction between the upper mantle and chondrites, a hidden reservoir for incompatible RLEs in the lower mantle has been proposed. These studies have invoked a possible formation of hidden reservoir for incompatible RLEs during magma ocean solidification and by subsequent mantle overturn due to the gravitational instability of Fe-rich dense cumulates. However, the density of partial melt and its fate in a crystallizing deep magma ocean is still debated. Here we report partial melt compositions of enstatite chondritic mantle at 23 GPa as a function of the extent of melting. The results show that bridgmanite crystallized in a chondritic magma ocean becomes enriched in Fe and Ca with decreasing extent of melting and prevents the crystallization of ferropericlase and CaSiO₃ perovskite (Davemaoite). At the rheological transition (the extent of melting of 40% based on mass balance calculation), where the solid-liquid separation efficiently occurs even in the case of equilibrium crystallization, the solid part is mostly composed of bridgmanite with a trace amount of majorite, and the melt becomes enriched in FeO and CaO compared to the initial chondritic composition. The calculated density of the melt at the rheological transition is lighter than bridgmanite, but denser than majorite, suggesting that the melt may have ponded at the bottom of the mantle transition zone. The melt ponded around 660 km depth may have been enriched in incompatible RLEs and formed the hidden reservoir for missing RLEs if this melt-bearing region is stable against subsequent mantle convection.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"346 ","pages":"Article 107123"},"PeriodicalIF":2.3,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920123001498/pdfft?md5=f0a346752bbe73bb3f8971d8b79687bb&pid=1-s2.0-S0031920123001498-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138472729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}