Assessment of International GNSS Service Global Ionosphere Map products over China region based on measurements from the Crustal Movement Observation Network of China

The global ionosphere maps(GIM)provided by the International GNSS Service(IGS)are extensively utilized for ionospheric morphology monitoring,scientific research,and practical application.Assessing the credibility of GIM products in data-sparse regions is of paramount importance.In this study,measurements from the Crustal Movement Observation Network of China(CMONOC)are leveraged to evaluate the suitability of IGS-GIM products over China region in 2013-2014.The indices of mean error(ME),root mean square error(RMSE),and normalized RMSE(NRMSE)are then utilized to quantify the accuracy of IGS-GIM products.Results revealed distinct local time and latitudinal dependencies in IGS-GIM errors,with substantially high errors at nighttime(NRMSE:39%)and above 40°latitude(NRMSE:49%).Seasonal differences also emerged,with larger equinoctial deviations(NRMSE:33.5%)compared with summer(20%).A preliminary analysis implied that the irregular assimilation of sparse IGS observations,compounded by China’s distinct geomagnetic topology,may manifest as error variations.These results suggest that modeling based solely on IGS-GIM observations engenders inadequate representations across China and that a thorough examination would proffer the necessary foundation for advancing regional total electron content(TEC)constructions.

Geochemistry of island arc assemblage in the Eastern Desert of Egypt and the role of Pan-African magmatism in crustal growth of the Arabian–Nubian Shield:A review

Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metagabbros-diorites(MGD)and syn-tectonic intrusions of older granitoids(OG).We report here the updates of these four rock units in terms of classification,distribution,chemical characteristics,geodynamic evolution,metamorphism,and ages.In addition,we discuss these integrated data to elucidate a reasonable and reliable model for crustal evolution in the ANS.The main features of these rock units indicate their relation to each other and the geodynamic environment dominated by early immature oceanic island arcs to primitive continental arcs.Integrated information of the island arc metavolcanic and plutonic rocks(gabbros,diorites,tonalites,and granodiorites)furnish evidence of the genetic relationships.These include proximity and a coeval nature in the field;all protolith magmas are subalkaline in nature following calc-alkaline series with minor tholeiitic affinities;common geochemical signature of the arc rocks and subduction-related magmatism;their similar enrichment in LREEs;and similar major element compositions with mafic melts derived from metasomatized mantle wedge.The volcano-sedimentary and the OG rocks underwent multiphase deformation events whereas the MGD complexes deformed slightly.Based on the magmatic,sedimentological,and metamorphic evolutions constrained by geochronological data as well as the progressive evolutionary trend from extensional to compressional regimes,a possible gradual decrease in the subducted slab dip angle is the most infl uential in any geodynamic model for arc assemblage in the ED of Egypt.

Crustal structure in the Anyuan Coal Mine and its adjacent areas of Jiangxi Province by P-wave receiver functions

We collected high-quality teleseismic events recorded by 12 broadband seismographs deployed in the Anyuan Coal Mine and its adjacent areas in Pingxiang City,Jiangxi Province for nearly two years.The H-κ-c stacking method was employed to obtain the crustal thickness and Poisson's ratio distribution,then the characteristics of crustal structure below the stations were obtained by using the time-domain linear inversion method.The crustal thickness in the Anyuan Coal Mine and its adjacent areas ranges from approximately 32~35 km,with an average thickness of 33 km,which is consistent with the crustal thickness results in South China from previous studies using the receiver function method.The average Poisson's ratio of the crustal bulk composition in the study area varies between 0.22 and 0.25,which is lower than the global value with a 0.27 average,indicating a predominantly intermediate-acidic or felsic crustal composition.There is a weak negative correlation between Poisson's ratio and crustal thickness estimates in the Anyuan Coal Mine and its adjacent areas,suggesting that the absence of mafic-ultramafic materials in the lower crust is associated with the process of crustal delamination.The velocity inversion results indicate that the crustal structure including three velocity discontinuity interfaces,with the first at a depth of approximately 1.5 km,the second at about 10~15 km,and the third being the Moho.The study also indicates that the results obtained by the H-κ-c stacking method are significantly better than those obtained by the H-κmethod,effectively reducing the standard deviation and dispersion of crustal thickness and vP/vSratio.

Crustal and uppermost mantle structure of the northeastern Qinghai-Xizang Plateau from joint inversion of surface wave dispersions and receiver functions with P velocity constraints

Lithospheric structure beneath the northeastern Qinghai-Xizang Plateau is of vital significance for studying the geodynamic processes of crustal thickening and expansion of the Qinghai-Xizang Plateau. We conducted a joint inversion of receiver functions and surface wave dispersions with P-wave velocity constraints using data from the Chin Array Ⅱ temporary stations deployed across the Qinghai-Xizang Plateau. Prior to joint inversion, we applied the H-κ-c method(Li JT et al., 2019) to the receiver function data in order to correct for the back-azimuthal variations in the arrival times of Ps phases and crustal multiples caused by crustal anisotropy and dipping interfaces. High-resolution images of vS, crustal thickness, and vP/vSstructures in the Qinghai-Xizang Plateau were simultaneously derived from the joint inversion. The seismic images reveal that crustal thickness decreases outward from the Qinghai-Xizang Plateau. The stable interiors of the Ordos and Alxa blocks exhibited higher velocities and lower crustal vP/vSratios. While, lower velocities and higher vP/vSratios were observed beneath the Qilian Orogen and Songpan-Ganzi terrane(SPGZ), which are geologically active and mechanically weak, especially in the mid-lower crust.Delamination or thermal erosion of the lithosphere triggered by hot asthenospheric flow contributes to the observed uppermost mantle low-velocity zones(LVZs) in the SPGZ. The crustal thickness, vS, and vP/vSratios suggest that whole lithospheric shortening is a plausible mechanism for crustal thickening in the Qinghai-Xizang Plateau, supporting the idea of coupled lithospheric-scale deformation in this region.

Preparation of Ni60-WC Coating by Plasma Spraying, Plasma Re-melting and Plasma Spray Welding on Surface of Hot Forging Die

In order to produce the hear-resistant inner layer of hot-forging die, the plasma spraying and plasma re-melting and plasma spray welding were adopted. Substrate material was W6Mo5Cr4V2, including 10%, 20%, 30% tungsten carbide （WC） ceramic powder used as coating material to obtain different Nickel-based WC alloys coating. Micro-structure and micro-hardness analysis of the coating layer are conducted, as well as thermophysical properties for the coating layer were measured. The experimental results show that the coating prepared with 70%Ni60, 30%WC powder has the best properties with plasma spray welding, in which the micro-hardness can achieve 900HV, meanwhile it can improve the thermal property of hot-forging die dramatically.

Ni60-SiC Coating Prepared by Plasma Spraying, Plasma Re-melting and Plasma Spray Welding on Surface of Hot Forging Die

In order to produce the hear-resistant inner layer of hot-forging die, plasma spraying and plasma re-melting and plasma spray welding were adopted. Substrate material was W6Mo5Cr4V2, including 10%, 20%, 30% SiC ceramic powder used as coating material to obtain different Ni-based SiC alloys coating. Micro-structure and micro-hardness analysis of the coating layer were followed, as well as thermophysical properties for the coating layer were measured. The experimental results show that the coating prepared with 70% Ni60, 30% SiC powder has best properties with plasma spray welding, in which the micro-hardness can achieve 1100 HV, meanwhile can improve the thermal property of hot-forging die dramatically.

Simulation of electro-slag re-melting process of 120t large ingot for nuclear power station and its application

Further research on metallic materials for the super critical rotator and the main pipe line of a nuclear power station is very important for developing the nuclear power industry. In this study, the mathematical model for 120 t large ingot was established, and the computer program ESR3D was developed to simulate the whole electro-slag re-melting (ESR) process. This includes the electrode melting, metallic droplet falling, metal pool forming, metal pool and slag pool rising and moving, installation of top crystallizer, ingot solidifying, etc. The simulated average melting rate of the electrode was in good agreement with that in practical production. The optimized parameters were used to produce 80-120 t large ingots, and the quality of the ingots satisfied the specifications of nuclear power and the super critical generating unit.

Prediction of Melt Pool Dimension and Residual Stress Evolution with Thermodynamically-Consistent Phase Field and Consolidation Models during Re-Melting Process of SLM

Re-melting process has been utilized to mitigate the residual stress level in the selective laser melting(SLM)process in recent years.However,the complex consolidation mechanism of powder and the different material behavior after the first laser melting hinder the direct implementation of the re-melting process.In this work,the effects of re-melting on the temperature and residual stress evolution in the SLM process are investigated using a thermo-mechanically coupled finite element model.The degree of consolidation is incorporated in the energy balance equation based on the thermodynamically-consistent phase-field approach.The drastic change of material properties due to the variation of temperature and material state is also considered.Using the proposed simulation framework,the single-track scanning is simulated first to predict the melt pool dimension and validate the proposed model with the existing experimental data.The obtained thermal histories reveal that the highest cooling rate is observed at the end of the local solidification time which acts as an important indicator for the alleviation of temperature gradient.Then,the scanning of a whole single layer that consists of multiple tracks is simulated to observe the stress evolution with several re-melting processes.After the full melting of powder material in the first scanning process,the increase of residual stress level is observed with one remelting cycle.Moreover,the predicted stress level with the re-melting process shows the variation trend attributable to the accumulated heat in the tracks.The numerical issues and the detailed implementation process are also introduced in this paper.

Constraining the crustal structure under the central and western Tian Shan based on teleseismic receiver functions and gravity anomalies

The Tian Shan is a vast range that spans several countries in Asia.Understanding its evolutionary history may provide valuable insights into intracontinental orogenic dynamics.In this study,we explored the crustal characteristics of the Tian Shan and their relationships to the tectonic evolution of the region.A new H-stacking method that combines the P receiver function and gravity anomalies was used to estimate the thickness and ratio of P-to S-wave velocities(Vp/Vs)for 91 broadband seismic stations in the central and western Tian Shan.Our results revealed significant lateral variations in crustal thickness and Vp/Vs.A—45-km-thick crust and an intermediate-high Vp/Vs(-1.74-1.84)were found in the Kazakh Shield and Tarim Basin,which we interpreted to indicate a mafic crystalline basement and lower crust.The central Tian Shan varied greatly in crustal thickness(40-64 km)and Vp/Vs ratio(1.65-2.00).which may be due to crustal shortening,mafic underplating,and crustal melting.In contrast,we observed a relatively thin crust(42-50 km)with an intermediate Vp/Vs ratio(-1.78)in the western Tian Shan.The differences in the crustal structures between the western and central Tian Shan imply that the Talas-Fergana Fault may be trans-lithospheric.

Zircon U-Pb age evidence of the Mesoarchean(2.9–3.2 Ga)crustal remnant in the Southern Dabie Orogen,South China

1.Objective Unlike the North China Plate where Archean and Paleoproterozoic crustal rocks are widely distributed,Early Precambrian basement rocks in the Yangtze Block of South China are locally exposed(Fig.1a),such as in the Kongling Complex,the Zhongxiang Complex,and the Douling Complex(Zhao GC and Cawood PA,2012).The Dabie Orogen is the eastward extension of the Qinling Orogen.

Geochemical studies of hybrid granite from Madugulapalli area, Eastern Dharwar Craton, Southern India: Implications for crustal mixing

Magma produced by melting of continental crust and mantle at the Archean-Proterozoic boundary are compositionally variable and chemical compositions provide evidence for the mixing of two sources. Understanding the composition of hybrid magma is essential for determining the comparative infl uence of crust and mantle sources during orogenesis. The hybrid granites are less documented in Indian cratons, especially less in Dharwar Craton. Here we present petrographic and whole-rock geochemical data of Madgulapalli granitic rocks situated in the NE part of the Eastern Dharwar Craton(EDC), to elucidate their petrogenesis and role in crust formation. The Madugulapalli granites(MPG) are composed chiefl y of plagioclase, quartz, and alkali feldspar with associated biotite showing alteration and inter-granular textures. Geochemically, they are metaluminous to peraluminous in nature with calc-alkaline hybrid granite. The hybrid granites exhibit both negative and positive europium anomalies;the lower Rb/Sr, Rb, Sr, and higher Sr/Y,(Dy/Yb)N ratios suggest that the interaction of older rocks with residual garnet source melted at high pressures. We hypothesize that hybrid granites are formed by interaction(e.g., metasomatism, mingling, or mixing) between parental magmas and pre-existing rocks with the infl uence of sanukitoid melts(heat source) in a subduction environment. The genesis of the hybrid granites demonstrates the mixing coupled with diff erentiation in the petrogeny’s residue system in a syn-collision setting followed by continental crust stability in EDC during the Neoarchean period.

Upper crustal deformation characteristics in the northeastern Tibetan Plateau and its adjacent areas revealed by GNSS and anisotropy data

The northeastern part of the Tibetan Plateau is a region where different tectonic blocks collide and intersect,and large earthquakes are frequent.Global Navigation Satellite System(GNSS)observations show that tectonic deformation in this region is strong and manifests as non-uniform deformation associated with tectonic features.S-wave splitting studies of near-field seismic data show that seismic anisotropy parameters can also reveal the upper crustal medium deformation beneath the reporting station.In this paper,we summarize the surface deformation from GNSS observations and crustal deformation from seismic anisotropy data in the northeastern Tibetan Plateau.By comparing the principal compressive strain direction with the fast S-wave polarization direction of near-field S-wave splitting,we analyzed deformation and its differences in surface and upper crustal media in the northeastern Tibetan Plateau and adjacent areas.The principal compressive strain direction derived from GNSS is generally consistent with the polarization direction of fast S-waves,but there are also local tectonic regions with large differences between them,which reflect the different deformation mechanisms of regional upper crustal media.The combination of GNSS and seismic anisotropy data can reveal the depth variation characteristics of crustal deformation and deepen understanding of three-dimensional crustal deformation and the deep dynamical mechanisms underlying it.it.

Preparation of Ni60-Cr_3C_2 Coating by Plasma Spraying,Plasma Re-melting and Plasma Spray Welding on W6Mo5Cr4V2

In order to prepare heatresistant inner layer of hot-forging die, plasma spraying, plasma re- melting and plasma spray welding were adopted. Cr3C2 coatings of Ni-Based were prepared respectively with 10%, 20% and 30% Cr3C2 powder and W6Mo5Cr4V2 substrate. The coating microstructure analysis, the micro-hardness test, and the measurement of thermal parameters of coating were conducted. The experimental results show that the coating has the better thermo-physical property by using plasma spray welding method with the powder ratio of 90% Ni60 and 10% Cr3C2, and by this way the micro-hardness of coating can achieve 1100 HV.

Gravity modelling of crustal architecture and heterogeneity in the Nansha Block,South China Sea

The stretched structure and heterogeneity of the crust of the Nansha Block,the southern continental margin of the South China Sea(SCS),are not well understood.We used published ocean bottom seismic(OBS)/multichannel reflection seismic(MCS)profiles across the Nansha Block to establish five two-dimensional crustal structure models.Using gravity modelling with magnetic anomaly inversion,we obtained the distribution of density and local magnetic susceptibility of the crust.The models show that the distribution of density and thickness of the upper crust in the Nansha Block is uneven,and the thick upper crust is prevalent in the regions close to the continent-ocean transition(COT)showing different characteristics.The interpreted Mesozoic granite blocks and Precambrian rigid basement reflects the heterogeneity in the material composition of the SCS continental margin.Based on the thinning styles of different crustal layers,we suggest that the Nansha Block has a three-layer thinning pattern.The uppermost pre-rift layer was deformed via brittle fractures,the upper crust was sheared by discrete shear zones,and the lower crust experienced ductile deformation.The inherited pre-rift thermal regime,mechanical state,and material composition of the SCS continental margin affected the extensional structure of the crust.

Correction:Geochronology and origin of Paleoproterozoic charnockites with old crustal signature in the Haisyn block of the Ukrainian shield

In the original publication of the article,Pbr should be replaced with Pb in Table 2.The correct Table 2 is provided in this article.

Europium anomalies in detrital zircons reveal the crustal thickness evolution of South China in Early Neoproterozoic

The South China Block(SCB)is formed by the amalgamation of the Yangtze and Cathaysia blocks during the Early Neoproterozoic along the Jiangnan Orogen.However,the precise amalgamation time of these two blocks and the location of the united SCB in the Rodinia supercontinent remain highly debatable.Various tectonic models have been proposed and they may have different implications for the crustal thickness evolution of the central SCB in Early Neoproterozoic.To evaluate these models,this paper uses a recently calibrated Eu/Eu*-inzircon proxy to reconstruct crustal thickness evolution of the central SCB during Early Neoproterozoic.I compiled and screened U–Pb ages and trace elements of 900–700 Ma detrital zircons from the central SCB and then calculated the zircon Eu/Eu*values.The age-binned average zircon Eu/Eu*displays a decreasing trend from 870 to 790 Ma,and thus indicates no significant crustal thickening event occurred during this time interval.This finding seems to be inconsistent with tectonic models that the Yangtze and Cathaysia blocks amalgamated during this time interval.Yet,given that available coupled detrital zircon U–Pb and trace element datasets are very limited,additional studies are warranted to further evaluate this hypothesis.

Crustal Structure of the Jurassic Quiet Zone in the West Pacific Ocean:Insights from 2D Multichannel Seismic Reflection Profiles

The Jurassic oceanic crust is the oldest existing oceanic crust on earth,and although distributed sparsely,carries essential information about the earth's evolution.The area around the Pigafetta Basin in the west Pacific Ocean(also known as the Jurassic Quiet Zone,JQZ)is one of a few areas where the Jurassic oceanic crust is present.This study takes full advantage of high-resolution multichannel seismic reflection profiles in combination with bathymetry,magnetic,and gravity data from the JQZ to examine the structure,deformation,and morphology of the Jurassic oceanic crust.Our results show the following insights:1)The Moho lies at 2–3 s in two-way travel time beneath the seafloor with the segmented feature.The gaps between the Moho segments well correspond to the seamounts on the seafloor,suggesting the upward migration of magma from the mantle has interrupted the pre-existing Moho.2)The oceanic crust is predominantly deformed by crustal-scale thrust faults,normal faults cutting through the top of basement,and vertical seismic disturbance zones in association with migration of thermal fluids.The thrust faults are locally found and interpreted as the results of tectonic inversion.3)Seafloor morphology in the JQZ is characterized by fault scarps,fold scarps,seamounts,and small hills,indicating the occurrence of active faults.4)The oceanic crust in the JQZ and East Pacific Rise has many structural and geometrical variations,such as the thickness of sediments,seafloor topography,basement morphology,fault size and type.

Geochronology and origin of Paleoproterozoic charnockites with old crustal signature in the Haisyn block of the Ukrainian shield

Results of a geochemical and geochronological study of the Paleoproterozoic rock assemblage in the Haisyn block of the Ros-Tikych Domain of the Ukrainian Shield are reported.Within the block,the Haisyn Complex comprises granitoids,including pyroxene-bearing diorites,quartz diorites,granodiorites,amphibole-biotite and biotite granites,and aplite and pegmatite granites.Monazite U-Pb isotope age of charnockitic syenite belonging to the Haisyn Complex was defined at 2027±6 Ma.This age coeval with the time of granulite facies metamorphism and emplacement of numerous granitic intrusions in the area.The Sm–Nd apatite isochron yielded an age of 2100±150 Ma.TheεNd isochron value of-5 indicates a long crustal residence time of the crustal protolith.Geochemical data do not indicate any enrichment of the studied rocks in relation to the Eoarchean and Neoarchean charnockites developed in the same area.So,if the model of partial melting of the older crustal protolith is involved then the degree of melting must be quite high.However,deep negative anomalies of Sr,Eu,Zr,and Ti indicate that plagioclase,zircon,and Fe–Ti oxides probably remained unmelted in the source.The Haisyn block was buried in the lower crust at high temperature and pressure conditions in the Paleoproterozoic time.Such a situation resulted in partial melting of the existing crust and formation of melts,containing undigested zircon and bearing ancient Nd isotope signature.

Geodetic constraints on contemporary three-dimensional crustal deformation in the Laji Shan—Jishi Shan tectonic belt

The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in the Holocene remains controversial.We obtain the latest and dense horizontal velocity field based on data collected from our newly constructed and existing GNSS stations.Combined with fault kinematics from geologic observations,we analyze the crustal deformation characteristics along the LJTB.The results show that:(1)The Laji Shan fault(LJF)is inactive,and the northwest-oriented Jishi Shan fault(JSF)exhibits a significant dextral and thrust slip.(2)The transpression along the arc-shaped LJTB accommodates deformation transformation between the dextral Riyue Shan fault and the sinistral west Qinling fault.(3)With the continuous pushing of the Indian plate,internal strains in the Tibetan Plateau are continuously transferred in the northeast via the LJTB as they are gradually dissipated near the LJTB and translated into significant crustal uplift in these regions.

希夏邦马峰地区始新世地壳加厚和隆升过程

中新世中期之前喜马拉雅山脉的隆升历史和深部动力机制,还存在极大的争议、缺乏基本的数据约束。喜马拉雅造山带核部高级变质岩的埋藏和折返过程可以约束地壳加厚和山脉隆升过程,但是现有的变质记录主要为渐新世晚期-中新世中期,始新世变质作用的分布范围、形成过程和地质意义仍然未被充分挖掘。本文首先厘定了希夏邦马峰(8027m)山体的基本岩石组成:下部为高喜马拉雅正/副片麻岩,上部为肉切村群变粒岩及贯入其中的淡色花岗岩席。进一步对1964年希夏邦马峰登山科考采集的眼球状片麻岩进行了变质作用相平衡模拟和独居石微区原位U-Th-Pb定年,确定了始新世变质记录的P-T-t演化轨迹:M1阶段中P/T型变质压力峰期,条件为~1.0GPa、~740℃(~22℃/km),变质年龄为~37Ma;后近等温降压至M2阶段低P/T型变质温度峰期,条件为0.5~0.4GPa、~760℃(45~57℃/km),变质年龄为~25Ma;在~18Ma左右冷却至固相线以下。希夏邦马峰~37Ma的中P/T型变质和地壳加厚事件与北喜马拉雅穹隆、高喜马拉雅主体、前陆飞来峰等地区的记录一致(40~37Ma,20~25℃/km),表明印度-亚洲初始碰撞约20Myr后中上地壳被堆叠埋藏至>33km以下,发生了广泛的整体性加厚和深熔作用。该事件与喜马拉雅内陆残留海最终退却的时间吻合,是喜马拉雅山脉初始隆升的诱因。喜马拉雅山脉不是晚新生代以来隆升的,而是经历了自始新世中期以来的长期地壳堆叠和隆升过程。