Height bias and scale effect induced by antenna gravitational deformations in geodetic VLBI data analysis   总被引：2，自引：2，他引：0  

Pierguido Sarti  Claudio Abbondanza  Leonid Petrov  Monia Negusini 《Journal of Geodesy》2011,85(1):1-8

The impact of signal path variations (SPVs) caused by antenna gravitational deformations on geodetic very long baseline interferometry (VLBI) results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying these models in geodetic VLBI data analysis, estimates of the antenna reference point positions are shifted upward by 8.9 and 6.7 mm, respectively. The impact on other parameters is negligible. To simulate the impact of antenna gravitational deformations on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for other antennas according to their size. The effects of the simulations are changes in VLBI heights in the range [−3, 73] mm and a net scale increase of 0.3–0.8 ppb. The height bias is larger than random errors of VLBI position estimates, implying the possibility of significant scale distortions related to antenna gravitational deformations. This demonstrates the need to precisely measure gravitational deformations of other VLBI telescopes, to derive their precise SPV models and to apply them in routine geodetic data analysis.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987110000149     

Xiang Wu  Shan Qin  Leonid Dubrovinsky 《地学前缘(英文版)》2011,2(1):107-114

The structural stability of manganese titanate MnTiO3 at high pressure was investigated by X-ray diffraction and Raman spectroscopy with diamond anvil cells. Ilmenite-type MnTiO3 is stable at least to 26.6 GPa, and lithium niobate type MnTiO3 reversibly transforms at room temperature to perovskite at 2.0 GPa. Bulk moduli (K300) of ilmenite, lithium niobate and perovskite are 174(4) GPa, 179(8) GPa, and 208(5) GPa, respectively (at fixed first pressure derivative K′ = 4). The Grüneisen parameter γ has been estimated to be 1.28 for ilmenite and 1.75 for perovskite. In ilmenite phase, TiO6 octahedra become more regular with increasing pressure. In perovskite phase structural distortion increases with pressure increase.  相似文献   

Crystal chemistry of Fe3+-bearing (Mg,Fe)SiO3 perovskite: a single-crystal X-ray diffraction study     

Ryosuke Sinmyo  Elena Bykova  Catherine McCammon  Ilya Kupenko  Vasily Potapkin  Leonid Dubrovinsky 《Physics and Chemistry of Minerals》2014,41(6):409-417

Magnesium silicate perovskite is the predominant phase in the Earth’s lower mantle, and it is well known that incorporation of iron has a strong effect on its crystal structure and physical properties. To constrain the crystal chemistry of (Mg, Fe)SiO₃ perovskite more accurately, we synthesized single crystals of Mg_0.946(17)Fe_0.056(12)Si_0.997(16)O₃ perovskite at 26 GPa and 2,073 K using a multianvil press and investigated its crystal structure, oxidation state and iron-site occupancy using single-crystal X-ray diffraction and energy-domain Synchrotron Mössbauer Source spectroscopy. Single-crystal refinements indicate that all iron (Fe²⁺ and Fe³⁺) substitutes on the A-site only, where \( {\text{Fe}}^{ 3+ } /\Upsigma {\text{Fe}}\sim 20\,\% \) based on Mössbauer spectroscopy. Charge balance likely occurs through a small number of cation vacancies on either the A- or the B-site. The octahedral tilt angle (Φ) calculated for our sample from the refined atomic coordinates is 20.3°, which is 2° higher than the value calculated from the unit-cell parameters (a = 4.7877 Å, b = 4.9480 Å, c = 6.915 Å) which assumes undistorted octahedra. A compilation of all available single-crystal data (atomic coordinates) for (Mg, Fe)(Si, Al)O₃ perovskite from the literature shows a smooth increase of Φ with composition that is independent of the nature of cation substitution (e.g., \( {\text{Mg}}^{ 2+ } - {\text{Fe}}^{ 2+ } \) or \( {\text{Mg}}^{ 2+ } {\text{Si}}^{ 4+ } - {\text{Fe}}^{ 3+ } {\text{Al}}^{ 3+ } \) substitution mechanism), contrary to previous observations based on unit-cell parameter calculations.  相似文献   

On the electron temperature determination in high-metallicity H ii regions     

Leonid S. Pilyugin 《Monthly notices of the Royal Astronomical Society》2007,375(2):685-690

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Surface abundances of light elements for a large sample of early B-type stars – II. Basic parameters of 107 stars     

Leonid S. Lyubimkov  Tamara M. Rachkovskaya  Sergey I. Rostopchin  David L. Lambert 《Monthly notices of the Royal Astronomical Society》2002,333(1):9-26

Effective temperatures T _eff, surface gravities log  g and interstellar extinctions A _V are found for 107 B stars. Distances d of the stars, which are based on the derived T _eff, log  g and A _V values, show good agreement with those obtained from the Hipparcos parallaxes. Comparing the T _eff and log  g values with evolutionary computations, we infer masses, radii, luminosities, ages and relative ages of the stars. Empirical relations between the T _eff and log  g parameters, on the one hand, and the photometric indices Q , [ c ₁] and β , on the other hand, are constructed; these relations give a fast method for the T _eff and log  g estimation of early and medium B stars. Inclusion of the infrared J , H and K colours into the T _eff, log  g and A _V determination shows that (i) the T _eff and log  g parameters are altered only slightly; (ii) the A _V value is rather sensitive to these colours, so an accuracy better than 0.05 mag in the JHK data is necessary for precise A _V evaluation.  相似文献   

On the relation between electron temperatures in the O⁺ and O⁺⁺ zones in high-metallicity H ii regions     

Leonid S. Pilyugin  José M. Vílchez  Trinh X. Thuan 《Monthly notices of the Royal Astronomical Society》2006,370(4):1928-1934

We suggest a new way to establish the relation between the electron temperature t ₃ within the [O  iii ] zone and the electron temperature t ₂ within the [O  ii ] zone in high-metallicity  (12 + log(O/H) > 8.25)  H  ii regions. The   t ₂– t ₃  diagram is constructed by applying our method to a sample of 372 H  ii regions. We find that the correlation between t ₂ and t ₃ is tight and can be approximated by a linear expression. The new   t ₂– t ₃  relation can be used to determine t ₂ and accurate abundances in high-metallicity H  ii regions with a measured t ₃. It can also be used in conjunction with the ff relation for the determination of t ₃ and t ₂ and oxygen abundances in high-metallicity H  ii regions, where the [O  iii ]λ4363 auroral line is not detected. The derived   t ₂– t ₃  relation is independent of photoionization models of H  ii regions.  相似文献   

Extensive volcaniclastic deposits at the Mid-Atlantic Ridge axis: results of deep-water basaltic explosive volcanic activity?     

Fouquet  Eissen  Ondréas  Barriga  Batiza  & Danyushevsky 《地学学报》1998,10(5):280-286

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Invisible gold in arsenian pyrite and arsenopyrite from a multistage Archaean gold deposit: Sunrise Dam,Eastern Goldfields Province,Western Australia   总被引：5，自引：0，他引：5  

Y.-H. Sung  J. Brugger  C. L. Ciobanu  A. Pring  W. Skinner  L. V. Danyushevsky  M. Nugus 《Mineralium Deposita》2009,44(7):765-791

The Sunrise Dam gold mine (11.1 Moz Au) is the largest deposit in the Archaean Laverton Greenstone Belt (Eastern Goldfields Province, Yilgarn Craton, Western Australia). The deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal-scale structure. The Au content of arsenian pyrite and arsenopyrite from four mineralizing stages (D₁, D₃, D_4a, and D_4b) and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry. Pyrite contains up to 3,067 ppm Au (n = 224), whereas arsenopyrite contains up to 5,767 ppm (n = 19). Gold in arsenopyrite (D_4a stage) was coprecipitated and remained as “invisible gold” (nanoparticles and/or lattice-bound) during subsequent deformation events. In contrast, gold in pyrite is present not only as “invisible gold” but also as micrometer-size inclusions of native gold, electrum, and Au(Ag)–tellurides. Pristine D₁ and D₃ arsenian pyrite contains relatively low Au concentrations (≤26 ppm). The highest Au concentrations occur in D_4a arsenian-rich pyrite that has recrystallized from D₃ pyrite. Textures show that this recrystallization proceeded via a coupled dissolution–reprecipitation process, and this process may have contributed to upgrading Au grades during D_4a. In contrast, Au in D_4b pyrite shows grain-scale redistribution of “invisible” gold resulting in the formation of micrometer-scale inclusions of Au minerals. The speciation of Au at Sunrise Dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple Au-precipitating mechanisms within a single plumbing system.  相似文献   

The Dovyren intrusive complex: Problems of petrology and Ni sulfide mineralization     

A. A. Ariskin  E. G. Konnikov  L. V. Danyushevsky  E. V. Kislov  G. S. Nikolaev  D. A. Orsoev  G. S. Barmina  K. A. Bychkov 《Geochemistry International》2009,47(5):425-453

This paper presents a review of petrological-geochemical studies at the Yoko-Dovyren Massif with an emphasis on relations between parameters of the parental magma, a model for the genesis of the lower contact zone, and the nature of Ni sulfide ore mineralization, including the evaluation of the possible ore potential. Arguments are presented in support of the conclusion that the Dovyren magma brought much intratelluric olivine of the composition Fo _85–87 into the chamber, and the composition of the initial melt corresponded to gabbronorite or moderately magnesian basite with no more than 10 wt % MgO. The probable temperature of the parental magma was approximately 1200–1250°C, and the sulfur solubility did not exceed 0.10–0.12 wt % (P = 1 kbar, WM buffer). The comparison of this estimate with the average S contents in the bottom plagioperidotites (0.12±0.06 wt %) indicates that the initial magma was saturated with a sulfide phase. For the first time the problem of the composition of contaminated dunites was formulated (these rocks occur in the Layered Series and contain more magnesian olivine Fo _87–92). The reason for the increase in the mg# of olivine is thought to be the partial melting and compaction of the original cumulates due to the infiltration of intercumulus melt enriched in volatile components. The volatiles were presumably provided by the thermal decomposition of carbonate xenoliths, a process that resulted in an increase in the CO₂ pressure and the transfer of calcite-magnesite components of carbonates into the melt. This follows from (1) the occurrence of magnesian skarn developing after carbonates, (2) high CaO contents in olivine form the contaminated dunite, (3) the appearance of olivine-bearing pyroxenites and wehrlites in the upper part of the dunite zone, (4) correlation between the olivine and chromite composition in the contaminated and uncontaminated dunites, (5) broad variations in the oxygen isotopic composition of olivine and plagioclase from rocks of the Layered Series, (6) experimental data on the dissolution of carbonates in alkali basalt melts, and (7) analogies with isotopic-geochemical characteristics of rocks from the Jinchuan ultramafic complex. Petrological implications of the interpretation of the Dovyren chamber are discussed with reference to closed and flow-through (during an initial stage) magmatic systems. A petrological-geological model is proposed for the genesis of the Synnyr-Dovyren volcanic-plutonic complex and related Ni sulfide ore mineralization. The potential resources of Cu-Ni sulfide ores in the plagioperidotites are evaluated with regard to the still-unexposed part of the massif.  相似文献   

金川Ⅰ号岩体橄榄石Ni-MgO相互关系及其地质意义   总被引：7，自引：1，他引：6  

陈列锰  宋谢炎  Danyushevsky LV  肖加飞  李士彬  官建祥 《岩石学报》2009,25(12):3369-3378

金川超镁铁质岩体赋存着仅次于加拿大Sudbury和俄罗斯Noril'sk-Talnakh的世界第三大在采铜镍硫化物矿床,岩体以一系列的NE向断层为界分成四个小岩体,由西至东依次为:Ⅲ、Ⅰ、Ⅱ、Ⅳ岩体.Ⅰ号岩体主要由二辉橄榄岩、含辉橄榄岩和橄榄二辉岩构成,橄榄石在各岩相中均为保存较好的主要造岩矿物.本文研究得到金川Ⅰ号岩体上部二辉橄榄岩和含辉橄榄岩中橄榄石的镁橄榄石F_o值介于83.9～85.7,而其Ni含量为1396×10~(-6)～2043×10~(-6),大多低于从S不饱和玄武岩浆中结晶出来的橄榄石的Ni含量.模拟计算结果表明橄榄石较低的Ni含量是因为橄榄石结晶的同时,发生了强烈的硫化物熔离;橄榄石的Fo-Ni关系还因与晶间硅酸盐熔浆的物质交换而发生改变.模拟计算还证明大约有30%的晶间硅酸盐岩浆与橄榄石发生Fe-Mg物质交换反应,导致早结晶橄榄石的Fo值减少了1～1.5.同时,橄榄石较小的Fo值变化表明,在橄榄石结晶和硫化物熔离过程中,不断有新的岩浆贯入和补充.  相似文献