Xitian tin-polymetallic deposit, located in the eastern Hunan Province, SE China, hosts quartz vein and skarn in the contact zone between carbonate and two stages granites. Critical geodynamic questions for South Chin...Xitian tin-polymetallic deposit, located in the eastern Hunan Province, SE China, hosts quartz vein and skarn in the contact zone between carbonate and two stages granites. Critical geodynamic questions for South China are whether different types of mineralization form in the same time and how the magmatism–tectonic system controls the ore-forming process. Based on the distribution of the orebodies, six cassiterite samples from different types of mineralization are collected for dating. In-situ LA-MCICP-MS U–Pb isotopic data yielded concordia low intercept ages between 154 and 157 Ma, indicating that different types of mineralization belong to the same magmatism–mineralization system. Coupled with the study of the kinematic indicators, it suggests that the structural control of the wall rocks constrain the types of mineralization. These results provide further evidence of a close temporal link between the structure and the tin-polymetallic mineralization in Xitian deposit. Considering the structure in the district, granite dome plays an important role in the ore-forming process. The age and structural signatures in Xitian deposit are the response to the subduction of Pacific Plate.展开更多
The tectonic evolution of Southeast China during Late Mesozoic is a prominent topic. Numerous tectonic models on Late Mesozoic evolution ofSoutheast Chinahave been?published in the past 50 years. We synthesized many u...The tectonic evolution of Southeast China during Late Mesozoic is a prominent topic. Numerous tectonic models on Late Mesozoic evolution ofSoutheast Chinahave been?published in the past 50 years. We synthesized many up-to-date and precise zircon U-Pb ages, sedimentary strata, and regional structures and discussed the oxygen fugacity of magmas and related ore deposits. We also analyzed the most current tectonic models published by some scholars. A multistage tectonic stress evolution history during Late Mesozoic was constructed, which included the following stages: 1) Early-Middle Jurassic (196 - 175 Ma) extension, in which many bimodal volcanics formed;2) Middle-Late Jurassic (165 - 140 Ma) compression, which generated largescale gneissic granites, garnet-bearing granites, stratigraphic hiatus, and nappe structures;3) Early Cretaceous (140 ± 5 - 120 Ma) extension, which formed weakly deformed or undeformed granites, alkali granites, metamorphic core complexes, graben basins, and basic dike swarms;4) Early Cretaceous (120 - 110 Ma) compression, which generated nappe structures, volcanic hiatuses, and garnet-bearing granites;and 5) Early-Late Cretaceous (110 - 80 Ma) extension, which generated largescale bimodal volcanics, basic dike swarms, alkali granites, and graben basins. The Late Mesozoic tectonic evolution ofSoutheast Chinamay be attributed to the drifting history of the Paleo-Pacific plate. The drifting direction of the Paleo-Pacific plate has changed several times since 140 Ma, which led to major changes in the tectonicphenomena from Jurassic to Cretaceous and to the formation of Late Mesozoic mineral deposits.展开更多
Thin films of copper indium gallium selenide Cu（In,Ga）Se2 （CIGS） were prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound form...Thin films of copper indium gallium selenide Cu（In,Ga）Se2 （CIGS） were prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound formation, and were studied at temperature as high as 1250℃ for the first time. These films were concurrently studied for their structural properties by X-ray diffraction （XRD） technique. The XRD analyses include phase transition studies, grain size variation and microstrain measurements with the reaction temperature and time.It has been observed that there are three distinct regions of variation in all these parameters. These regions belong to three temperature regimes： 〈450℃, 450-950℃, and 〉950℃. It is also seen that the compound formation starts at 250℃, with ternary phases appearing at 350℃ or above. Whereas, there is another phase shift at 950℃ without any preference to the quaternary compound.展开更多
The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity ex...The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature TN is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic （Fd3m） to low temperature tetragonal （I41amd） structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at Hc2 defined as a steep downward peak in the derivative of the M-H curve is dearly drawn. It is found that TN versus H and Hc2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal （I41amd） to cubic （Fd3m） structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T-H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100K and TN.展开更多
The structural, dielectric, lattice dynamical and thermodynamic properties of zinc-blende CdX （X=S, Se, Te） are studied by using a plane-wave pseudopotential method within the density-functional theory. Our calculat...The structural, dielectric, lattice dynamical and thermodynamic properties of zinc-blende CdX （X=S, Se, Te） are studied by using a plane-wave pseudopotential method within the density-functional theory. Our calculated lattice constants and bulk modulus are compared with the pubfished experimental and theoretical data. In addition, the Born effective charges, electronic dielectric tensors, phonon frequencies, and longitudinal opticaltransverse optical splitting are calculated by the linear-response approach. Some of the characteristics of the phonon-dispersion curves for zinc-blende CdX （X= S, Se, Te） are summarized. What is more, based on the lattice dynamical properties, we investigate the thermodynamic properties of CdX （X= S, Se, Te） and analyze the temperature dependences of the Helmholtz free energy F, the internal energy E, the entropy S and the constant-volume specific heat Cv. The results show that the heat capacities for CdTe, CdSe, and CdS approach approximately to the Petit-Dulong limit 6R.展开更多
Ethyl（（S）-2＇-hydroxy-1,1＇-binaphthalen-2-yl）-（SP）-vinylphosphonate （SBINOL-SP） was synthesized by diastereoselective reaction and characterized by means of NMR spectroscopy, H RMS and X-ray diffraction. The ...Ethyl（（S）-2＇-hydroxy-1,1＇-binaphthalen-2-yl）-（SP）-vinylphosphonate （SBINOL-SP） was synthesized by diastereoselective reaction and characterized by means of NMR spectroscopy, H RMS and X-ray diffraction. The single crystal belongs to the monoclinic system, space group P21/c with a = 7.4983（13）, b = 12.065（2）, c = 21.805（4） ？, β = 90.094（6）°, Mr = 404.38, V = 1972.6（6） ？3, Z = 4, Dc = 1.362 g/cm3, F（000） = 848, μ = 0.168 mm-1, R = 0.0280 and wR = 0.0743. The title compound shows good activities against E. coli, S. albus, B. subtilis and M. tetragenus.展开更多
High-resolution lithospheric structure is essential for understanding the tectonic evolution and deformation patterns of the southeastern Tibetan plateau. This is now possible due to recent advances in ambient noise a...High-resolution lithospheric structure is essential for understanding the tectonic evolution and deformation patterns of the southeastern Tibetan plateau. This is now possible due to recent advances in ambient noise and earthquake surface wave tomography, and great improvements in data coverage from dense portable array stations deployed in SE Tibet. In this review paper, I first give a brief overview of the tomographic methods from ambient noise and earthquake surface waves, and then summarize the major findings about the lithospheric structure and deformation in SE Tibet revealed by ambient noise and earthquake surface wave tomography as well as by other seismic and geophysical observations. These findings mainly include the 3-D distribution of mechanically weak zones in the mid-lower crust, lateral and vertical variations in radial and azimuthal anisotropy, possible interplay of some fault zones with crustal weak zones, and importance of strike-slip faulting on upper crustal deformation. These results suggest that integration of block extrusion in the more rigid upper-middle crust and channel flow in the more ductile mid-lower crust will be more compatible with the current geophysical observations. Finally I discuss some future perspective researches in SE Tibet, including array-based tomography, joint inversion using multiple seismic data, and integration of geodynamic modeling and seismic observations.展开更多
We use observations recorded by 23 permanent and 99 temporary stations in the SE Tibetan plateau to obtain the S-wave velocity structure along two profiles by applying joint inversion with receiver functions and surfa...We use observations recorded by 23 permanent and 99 temporary stations in the SE Tibetan plateau to obtain the S-wave velocity structure along two profiles by applying joint inversion with receiver functions and surface waves. The two profiles cross West Yunnan block （WYB）, the Central Yunnan sub-block （CYB）, South China block （SCB）, and Nanpanjiang basin （NPB）. The profile at -25°N shows that the Moho interface in the CYB is deeper than those in the WYB and the NPB, and the topography and Moho depth have clear correspondence. Beneath the Xiaojiang fault zone （XJF）, there exists a crustal low-velocity zone （LYZ）, crossing the XJF and expanding eastward into the SCB. The NPB is shown to be of relatively high velocity. We speculate that the eastward extrusion of the Tibetan plateau may pass through the XJF and affect its eastern region, and is resisted by the rigid NPB, which has high velocity. This may be the main cause of the crustal thickening and uplift of the topography. In the Tengchong volcanic area, the crust is shown to have alternate high- and low-velocity layers, and the upper mantle is shown to be of low velocity. We consider that the magma which exists in the crust is from the upper mantle and that the complex crustal velocity structure is related to magmatic differentiation. Between the Tengchong volcanic area and the XJF, the crustal velocity is relatively high. Combining these observations with other geophysical evi- dence, it is indicated that rock strength is high and defor- mation is weak in this area, which is why the level of seismicity is quite low. The profile at ~ 23~N shows that the variation of the Moho depth is small from the eastern rigid block to the western active block with a wide range of LVZs. We consider that deformation to the south of the SE Tibetan Plateau is weak.展开更多
We have successfully synthesized two novel compounds[A6Cl][Fe24Se26](A=K,Rb).The key structural units of them are FeSe octamers,consisting of edge-shared FeSe4 tetrahedra.Two kinds of FeSe octamer layers with differen...We have successfully synthesized two novel compounds[A6Cl][Fe24Se26](A=K,Rb).The key structural units of them are FeSe octamers,consisting of edge-shared FeSe4 tetrahedra.Two kinds of FeSe octamer layers with different connection configurations stack along the c axis,forming a three-dimensional(3D)TiAl3-type structure.Interestingly,the 3D structural topology of these ocatmers in one unit cell is similar to the local atomic arrangement of themselves,i.e.,self-similarity in structure.Physical property characterizations indicate that both the compounds exhibit insulating antiferromagnetism with Neel temperatures Tn^110K and 75K for[K6Cl][Fe24Se26]and[Rb6Cl][Fe24Se26].展开更多
The Sinai Peninsula has been recognized as a subplate of the African Plate located at the triple junction of the Gulf of Suez rift,the Dead Sea Transform fault,and the Red Sea rift.The upper and lower crustal structur...The Sinai Peninsula has been recognized as a subplate of the African Plate located at the triple junction of the Gulf of Suez rift,the Dead Sea Transform fault,and the Red Sea rift.The upper and lower crustal structures of this tectonically active,rapidly developing region are yet poorly understood because of many limitations.For this reason,a set of P- and S-wave travel times recorded at 14 seismic stations belonging to the Egyptian National Seismographic Network（ENSN） from 111 local and regional events are analyzed to investigate the crustal structures and the locations of the seismogenic zones beneath central and southern Sinai.Because the velocity model used for routine earthquake location by ENSN is one-dimensional,the travel-time residuals will show lateral heterogeneity of the velocity structures and unmodeled vertical structures.Seismic activity is strong along the eastern and southern borders of the study area but low to moderate along the northern boundary and the Gulf of Suez to the west.The crustal V_P/V_S ratio is 1.74 from shallow（depth≤10 km） earthquakes and 1.76 from deeper（depth 〉 10 km） crustal events.The majority of the regional and local travel-time residuals are positive relative to the Preliminary Reference Earth Model（PREM）,implying that the seismic stations are located above widely distributed,tectonically-induced low-velocity zones.These low-velocity zones are mostly related to the local crustal faults affecting the sedimentary section and the basement complex as well as the rifting processes prevailing in the northern Red Sea region and the ascending of hot mantle materials along crustal fractures.The delineation of these low-velocity zones and the locations of big crustal earthquakes enable the identification of areas prone to intense seismotectonic activities,which should be excluded from major future development projects and large constructions in central and southern Sinai.展开更多
Cux Bi2Se3 is a superconductor that is a potential candidate for topological superconductors. We report our laser- based angle-resolved photoemission measurement on the electronic structure of the CuxBi2Se3 supercondu...Cux Bi2Se3 is a superconductor that is a potential candidate for topological superconductors. We report our laser- based angle-resolved photoemission measurement on the electronic structure of the CuxBi2Se3 superconductor, and a detailed magneto-resistance measurement in both normal and superconducting states. We find that the topological surface state of the pristine Bi2Se3 topological insulator remains robust after the Cu-intercalation, while the Dirae cone location moves downward due to electron doping. Detailed measurements on the magnetic field-dependence of the resistance in the superconducting state establishes an irreversibility line and gives a value of the upper critical field at zero temperature of ～4000 Oe for the Cu0.3Bi2Se3 superconductor with a middle point Tc of 1.g K. The relation between the upper critical field He2 and temperature T is different from the usual scaling relation found in cuprates and in other kinds of superconductors. Small positive magneto-resistance is observed in Cuo.3Bi2Se3 superconductors up to room temperature. These observations provide useful information for further study of this possible candidate for topological superconductors.展开更多
In recent2 0 years,because of the finding ofmany large- superlargegold deposits,we re- new the theories for prospecting and gain many things and conceptions.The current geo- chemical and gold- forming theories underli...In recent2 0 years,because of the finding ofmany large- superlargegold deposits,we re- new the theories for prospecting and gain many things and conceptions.The current geo- chemical and gold- forming theories underline the importance of the early submarine volcano- sedimentation,metamorphic differention,sedimentation of terrigenous clastics,thermal spring and it’s sedimentation,syngenesis process and other hypergene supplying the source for metallogenic materials.According to the study for source bed(rock) and depsitional for- mation of gold,we find that gold will be gradually enriched and mineralized in source bed (rock) ,because of variousgeologicprocesses,such as regional metamorphism ormigmatiza- tion,geothermal bittern,volcanism. The ore- control of deep and giant fault and ductile shear beltand tectono- flash space is emphasized,especially,we should notice the long- term, succession and multistage of the展开更多
基金financially supported by the Public Welfare Project of the Ministry of land and Resources of China (201211024-04)National Key R&D Program of China (2016YFC0600401)+1 种基金National Science Foundation of China (NSFC Grant 41273046)Research Cooperation between Institute and University of Chinese Academy of Sciences Grant (Y552012Y00)
文摘Xitian tin-polymetallic deposit, located in the eastern Hunan Province, SE China, hosts quartz vein and skarn in the contact zone between carbonate and two stages granites. Critical geodynamic questions for South China are whether different types of mineralization form in the same time and how the magmatism–tectonic system controls the ore-forming process. Based on the distribution of the orebodies, six cassiterite samples from different types of mineralization are collected for dating. In-situ LA-MCICP-MS U–Pb isotopic data yielded concordia low intercept ages between 154 and 157 Ma, indicating that different types of mineralization belong to the same magmatism–mineralization system. Coupled with the study of the kinematic indicators, it suggests that the structural control of the wall rocks constrain the types of mineralization. These results provide further evidence of a close temporal link between the structure and the tin-polymetallic mineralization in Xitian deposit. Considering the structure in the district, granite dome plays an important role in the ore-forming process. The age and structural signatures in Xitian deposit are the response to the subduction of Pacific Plate.
文摘The tectonic evolution of Southeast China during Late Mesozoic is a prominent topic. Numerous tectonic models on Late Mesozoic evolution ofSoutheast Chinahave been?published in the past 50 years. We synthesized many up-to-date and precise zircon U-Pb ages, sedimentary strata, and regional structures and discussed the oxygen fugacity of magmas and related ore deposits. We also analyzed the most current tectonic models published by some scholars. A multistage tectonic stress evolution history during Late Mesozoic was constructed, which included the following stages: 1) Early-Middle Jurassic (196 - 175 Ma) extension, in which many bimodal volcanics formed;2) Middle-Late Jurassic (165 - 140 Ma) compression, which generated largescale gneissic granites, garnet-bearing granites, stratigraphic hiatus, and nappe structures;3) Early Cretaceous (140 ± 5 - 120 Ma) extension, which formed weakly deformed or undeformed granites, alkali granites, metamorphic core complexes, graben basins, and basic dike swarms;4) Early Cretaceous (120 - 110 Ma) compression, which generated nappe structures, volcanic hiatuses, and garnet-bearing granites;and 5) Early-Late Cretaceous (110 - 80 Ma) extension, which generated largescale bimodal volcanics, basic dike swarms, alkali granites, and graben basins. The Late Mesozoic tectonic evolution ofSoutheast Chinamay be attributed to the drifting history of the Paleo-Pacific plate. The drifting direction of the Paleo-Pacific plate has changed several times since 140 Ma, which led to major changes in the tectonicphenomena from Jurassic to Cretaceous and to the formation of Late Mesozoic mineral deposits.
文摘Thin films of copper indium gallium selenide Cu（In,Ga）Se2 （CIGS） were prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound formation, and were studied at temperature as high as 1250℃ for the first time. These films were concurrently studied for their structural properties by X-ray diffraction （XRD） technique. The XRD analyses include phase transition studies, grain size variation and microstrain measurements with the reaction temperature and time.It has been observed that there are three distinct regions of variation in all these parameters. These regions belong to three temperature regimes： 〈450℃, 450-950℃, and 〉950℃. It is also seen that the compound formation starts at 250℃, with ternary phases appearing at 350℃ or above. Whereas, there is another phase shift at 950℃ without any preference to the quaternary compound.
基金Supported by the National Basic Research Program of China under Grant No 2011CBA00111the National Natural Science Foundation of China under Grant No U1332143
文摘The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature TN is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic （Fd3m） to low temperature tetragonal （I41amd） structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at Hc2 defined as a steep downward peak in the derivative of the M-H curve is dearly drawn. It is found that TN versus H and Hc2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal （I41amd） to cubic （Fd3m） structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T-H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100K and TN.
基金Supported by the National Natural Science Foundation of China under Grant No 11374217
文摘The structural, dielectric, lattice dynamical and thermodynamic properties of zinc-blende CdX （X=S, Se, Te） are studied by using a plane-wave pseudopotential method within the density-functional theory. Our calculated lattice constants and bulk modulus are compared with the pubfished experimental and theoretical data. In addition, the Born effective charges, electronic dielectric tensors, phonon frequencies, and longitudinal opticaltransverse optical splitting are calculated by the linear-response approach. Some of the characteristics of the phonon-dispersion curves for zinc-blende CdX （X= S, Se, Te） are summarized. What is more, based on the lattice dynamical properties, we investigate the thermodynamic properties of CdX （X= S, Se, Te） and analyze the temperature dependences of the Helmholtz free energy F, the internal energy E, the entropy S and the constant-volume specific heat Cv. The results show that the heat capacities for CdTe, CdSe, and CdS approach approximately to the Petit-Dulong limit 6R.
文摘Ethyl（（S）-2＇-hydroxy-1,1＇-binaphthalen-2-yl）-（SP）-vinylphosphonate （SBINOL-SP） was synthesized by diastereoselective reaction and characterized by means of NMR spectroscopy, H RMS and X-ray diffraction. The single crystal belongs to the monoclinic system, space group P21/c with a = 7.4983（13）, b = 12.065（2）, c = 21.805（4） ？, β = 90.094（6）°, Mr = 404.38, V = 1972.6（6） ？3, Z = 4, Dc = 1.362 g/cm3, F（000） = 848, μ = 0.168 mm-1, R = 0.0280 and wR = 0.0743. The title compound shows good activities against E. coli, S. albus, B. subtilis and M. tetragenus.
基金supported by the National Natural Science Foundation of China (No. 41222028)the Chinese Academy of Sciences/State Administration of Foreign Experts Affairs International Partnership Program for Creative Research Teams
文摘High-resolution lithospheric structure is essential for understanding the tectonic evolution and deformation patterns of the southeastern Tibetan plateau. This is now possible due to recent advances in ambient noise and earthquake surface wave tomography, and great improvements in data coverage from dense portable array stations deployed in SE Tibet. In this review paper, I first give a brief overview of the tomographic methods from ambient noise and earthquake surface waves, and then summarize the major findings about the lithospheric structure and deformation in SE Tibet revealed by ambient noise and earthquake surface wave tomography as well as by other seismic and geophysical observations. These findings mainly include the 3-D distribution of mechanically weak zones in the mid-lower crust, lateral and vertical variations in radial and azimuthal anisotropy, possible interplay of some fault zones with crustal weak zones, and importance of strike-slip faulting on upper crustal deformation. These results suggest that integration of block extrusion in the more rigid upper-middle crust and channel flow in the more ductile mid-lower crust will be more compatible with the current geophysical observations. Finally I discuss some future perspective researches in SE Tibet, including array-based tomography, joint inversion using multiple seismic data, and integration of geodynamic modeling and seismic observations.
基金supported by a National Natural Science Foundation of China (Grant No. 41374097)China National Special Fund for Earthquake Scientific Research in Public Interest (Grant No. 201008001)
文摘We use observations recorded by 23 permanent and 99 temporary stations in the SE Tibetan plateau to obtain the S-wave velocity structure along two profiles by applying joint inversion with receiver functions and surface waves. The two profiles cross West Yunnan block （WYB）, the Central Yunnan sub-block （CYB）, South China block （SCB）, and Nanpanjiang basin （NPB）. The profile at -25°N shows that the Moho interface in the CYB is deeper than those in the WYB and the NPB, and the topography and Moho depth have clear correspondence. Beneath the Xiaojiang fault zone （XJF）, there exists a crustal low-velocity zone （LYZ）, crossing the XJF and expanding eastward into the SCB. The NPB is shown to be of relatively high velocity. We speculate that the eastward extrusion of the Tibetan plateau may pass through the XJF and affect its eastern region, and is resisted by the rigid NPB, which has high velocity. This may be the main cause of the crustal thickening and uplift of the topography. In the Tengchong volcanic area, the crust is shown to have alternate high- and low-velocity layers, and the upper mantle is shown to be of low velocity. We consider that the magma which exists in the crust is from the upper mantle and that the complex crustal velocity structure is related to magmatic differentiation. Between the Tengchong volcanic area and the XJF, the crustal velocity is relatively high. Combining these observations with other geophysical evi- dence, it is indicated that rock strength is high and defor- mation is weak in this area, which is why the level of seismicity is quite low. The profile at ~ 23~N shows that the variation of the Moho depth is small from the eastern rigid block to the western active block with a wide range of LVZs. We consider that deformation to the south of the SE Tibetan Plateau is weak.
基金the National Key R&D Program of China under Grant No.2016YFA0300504the National Natural Science Foundation of China(Nos.11574394,11774423,11822412)the Fundamental Research Funds for the Central Universities,and the Research Funds of Renmin University of China(RUC)(15XNLQ07,18XNLG14,19XNLG17).
文摘We have successfully synthesized two novel compounds[A6Cl][Fe24Se26](A=K,Rb).The key structural units of them are FeSe octamers,consisting of edge-shared FeSe4 tetrahedra.Two kinds of FeSe octamer layers with different connection configurations stack along the c axis,forming a three-dimensional(3D)TiAl3-type structure.Interestingly,the 3D structural topology of these ocatmers in one unit cell is similar to the local atomic arrangement of themselves,i.e.,self-similarity in structure.Physical property characterizations indicate that both the compounds exhibit insulating antiferromagnetism with Neel temperatures Tn^110K and 75K for[K6Cl][Fe24Se26]and[Rb6Cl][Fe24Se26].
文摘SbNb_3(Se_2)_6, Mr=1347.99, tetragonal, P4/mnc,a=b=9.466(2),c=19.075(3) ,V=1709.0(4) ~3, z=4, Dm=5.2(2)g/cm^3, Dc=5.24g/c^3,λ(Moka)=0.71069 ,μ=287.39cm^(-1), F(000)=2328,T=276(1)k,R=5.9％,Rw=6.9％, for 479 unique observed reflections (1>3σ(1)).The structure is composed of [Nb3(Se2)s]∞ chains along the c axis with Sb atoms inserted between them.
文摘The Sinai Peninsula has been recognized as a subplate of the African Plate located at the triple junction of the Gulf of Suez rift,the Dead Sea Transform fault,and the Red Sea rift.The upper and lower crustal structures of this tectonically active,rapidly developing region are yet poorly understood because of many limitations.For this reason,a set of P- and S-wave travel times recorded at 14 seismic stations belonging to the Egyptian National Seismographic Network（ENSN） from 111 local and regional events are analyzed to investigate the crustal structures and the locations of the seismogenic zones beneath central and southern Sinai.Because the velocity model used for routine earthquake location by ENSN is one-dimensional,the travel-time residuals will show lateral heterogeneity of the velocity structures and unmodeled vertical structures.Seismic activity is strong along the eastern and southern borders of the study area but low to moderate along the northern boundary and the Gulf of Suez to the west.The crustal V_P/V_S ratio is 1.74 from shallow（depth≤10 km） earthquakes and 1.76 from deeper（depth 〉 10 km） crustal events.The majority of the regional and local travel-time residuals are positive relative to the Preliminary Reference Earth Model（PREM）,implying that the seismic stations are located above widely distributed,tectonically-induced low-velocity zones.These low-velocity zones are mostly related to the local crustal faults affecting the sedimentary section and the basement complex as well as the rifting processes prevailing in the northern Red Sea region and the ascending of hot mantle materials along crustal fractures.The delineation of these low-velocity zones and the locations of big crustal earthquakes enable the identification of areas prone to intense seismotectonic activities,which should be excluded from major future development projects and large constructions in central and southern Sinai.
基金the National Natural Science Foundation of China under Grant Nos 11190022,91021006 and 11374338the National Basic Research Program of China under Grant Nos 2011CB921703,2011CBA00110 and 2013CB921700the Strategic Priority Research Program(B) of the Chinese Academy of Sciences under Grant No XDB07020300
文摘Cux Bi2Se3 is a superconductor that is a potential candidate for topological superconductors. We report our laser- based angle-resolved photoemission measurement on the electronic structure of the CuxBi2Se3 superconductor, and a detailed magneto-resistance measurement in both normal and superconducting states. We find that the topological surface state of the pristine Bi2Se3 topological insulator remains robust after the Cu-intercalation, while the Dirae cone location moves downward due to electron doping. Detailed measurements on the magnetic field-dependence of the resistance in the superconducting state establishes an irreversibility line and gives a value of the upper critical field at zero temperature of ～4000 Oe for the Cu0.3Bi2Se3 superconductor with a middle point Tc of 1.g K. The relation between the upper critical field He2 and temperature T is different from the usual scaling relation found in cuprates and in other kinds of superconductors. Small positive magneto-resistance is observed in Cuo.3Bi2Se3 superconductors up to room temperature. These observations provide useful information for further study of this possible candidate for topological superconductors.
文摘In recent2 0 years,because of the finding ofmany large- superlargegold deposits,we re- new the theories for prospecting and gain many things and conceptions.The current geo- chemical and gold- forming theories underline the importance of the early submarine volcano- sedimentation,metamorphic differention,sedimentation of terrigenous clastics,thermal spring and it’s sedimentation,syngenesis process and other hypergene supplying the source for metallogenic materials.According to the study for source bed(rock) and depsitional for- mation of gold,we find that gold will be gradually enriched and mineralized in source bed (rock) ,because of variousgeologicprocesses,such as regional metamorphism ormigmatiza- tion,geothermal bittern,volcanism. The ore- control of deep and giant fault and ductile shear beltand tectono- flash space is emphasized,especially,we should notice the long- term, succession and multistage of the
