Ba同位素揭示上地幔中广泛存在再循环的沉积物

正Ba同位素由于具有在低温环境中分馏的特性,相比放射性同位素与微量元素,可以更好地示踪地球深部动力学过程中的再循环物质。研究表明沉积物与蚀变洋壳具有明显不同的Ba同位素组成(沉积物富集来自重晶石的Ba),使得Ba同位素成为研究表层与地幔储库间物质交换的有力工具。最近美国伍兹霍尔海洋研究所报道了来自全球洋中脊的21个MORB样品的Ba、Sr、Nd同位素和微量元素组成以及两个钻井中沉积物和蚀变洋壳     

Pyroxene-melt equilibria: an updated model

An updated model for pyroxene-melt equilibria at 1 atm has been developed and calibrated using new and existing experimental data in order to refine calculations of liquid lines of descent, which simulate the effect of igneous differentiation processes. We combine the Davidson and Lindsley (1985) model for activities of components in clinopyroxene and orthopyroxene solid solutions, a _i ^p , where i represents a quadrilateral endmember, with the Nielsen and Drake (1979) expressions for component activities in the melt, a _i ^L (two-lattice melt model). The chemical potential differences for pyroxene-melt equilibria are expressed in the form: $$\Delta \mu _{\iota } = 0 = In \left( {{{a_i^p } \mathord{\left/{\vphantom {{a_i^p } {a_i^L }}} \right.\kern-\nulldelimiterspace} {a_i^L }}} \right) + A_i + {{B_i } \mathord{\left/{\vphantom {{B_i } T}} \right.\kern-\nulldelimiterspace} T}$$ Pyroxene compositions were projected to quadrilateral compositions with the method of Lindsley and Anderson (1983). The regression constants A _i and B _i were calculated from experimental data that consists of 282 pyroxene-melt pairs, including 83 orthopyroxene-melt pairs. These experiments were all performed at 1 atm and represent compositions ranging from basalts (alkali to lunar) to dacites (42–66 wt% SiO₂). The model is calibrated for 1000相似文献   

FTIR studies of reactions between the nitrate radical and haloethenes

Products and mechanisms for the gas-phase reactions of NO₃ radicals with CH₂=CHCl, CH₂=CCl₂, CHCl=CCl₂,cis-CHCl=CHCl andtrans-CHCl=CHCl in air have been studied. The experiments were carried out at 295±2 K and 740±5 Torr in a 480-L Teflon-coated reaction chamber and at 295±2 K and 760±5 Torr in a 250-L stainless steel reactor. NO₃ was generated by the thermal dissociation of N₂O₅. Experiments with¹⁵NO₃ and CD₂CDCl have also been performed. The initially formed nitrate peroxynitrates decay into carbonyl compounds, nitrates, HCl and ClNO₂. In adidtion, there are indications of nitrooxy acid chlorides being produced. The reactions with CH₂=CCl₂ and CHCl=CCl₂ are more complex due to release of chlorine atoms which eventually lead to formation of chloroacid chlorides.A general reaction mechanism is proposed and the observed concentration-time profiles of reactants and products are simulated for each compound. The rate constants for the initial step of NO₃ addition to the chloroethenes are determined as: (2.6±0.5, 9.4±0.9, 2.0±0.4 and 1.4±0.4) × 10^–16 cm³ molecule^–1 s^–1 for CH₂=CHCl, CH₂=CCl₂, CHCl=CCl₂ andcis-CHCl=CHCl, respectively.     

Resistance of a soil layer to horizontal vibration of a pile

The resistance of a soil to horizontal harmonic vibration of a vertical, end bearing pile with circular cross-section is theoretically investigated. The soil is considered to be a continuum with material damping of the hysteretic type. The motions of the soil and pile are expressed as series, and a resistance coefficient on each term in the series of the pile motion is found. The resistance is found to depend on the excitation frequency, the pile slenderness and on the material properties of the soil. Finally a study of the influence of the parameters is carried out.     

Low pressure mineral-melt equilibria in natural anhydrous mafic systems

Contributions to Mineralogy and Petrology - Low pressure phase equilibria for natural mafic systems may be calculated utilizing empirically derived single component distribution coefficients and...     

Experimentally determined mineral-melt partition coefficients for Sc,Y and REE for olivine,orthopyroxene, pigeonite,magnetite and ilmenite

Our current lack of understanding of the partitioning behavior of Sc, Y and the REE (rare-earth elements) can be attributed directly to the lack of a sufficiently large or chemically diverse experimental data set. To address this problem, we conducted a series of experiments using several different natural composition lavas, doped with the elements of interest, as starting compositions. Microprobe analyses of orthopyroxene, pigeonite, olivine, magnetite, ilmenite and co-existing glasses in the experimental charges were used to calculate expressions that describe REE partitioning as a function of a variety of system parameters. Using expressions that represent mineral-melt reactions (versus element ratio distribution coefficients) it is possible to calculate terms that express low-Ca pyroxene-melt partitioning behavior and are independent of both pyroxene and melt composition. Compositional variations suggest that Sc substitution in olivine involves either a paired substitution with Al or, more commonly, with vacancies. The partitioning of Sc is dependent both on melt composition and temperature. Our experimentally determined olivine-melt REE Ds (partition coefficients) are similar to, but slightly higher than those reported by McKay (1986) and support their conclusions that olivines are strongly LREE depleted. Y and REE mineral/melt partition coefficients for magnetite range from 0.003 for La to 0.02 for Lu. Ilmenite partition coefficients range from 0.007 for La to 0.029 for Lu. These experimental values are two orders of magnitude lower than many of the published values determined by phenocryst/matrix separation techniques.     

The radiation balance at Copenhagen

Summary At the Climate and Water Balance Station of the Danish Hydrotechnical Laboratory near Copenhagen incoming radiation has been recorded continuously since 1954 by means of Moll thermopiles in Kipp & Zonen solarimeters and further, since 1955, reflected radiation, too. Since 1956 also net radiation and net long-wave radiation has been recorded by means of thermopiles in heat flow transducers from Beckman & Whitley used as radiometers.Mean daily values are given for incoming radiation as well as monthly mean values for reflected radiation, net long-wave radiation and net radiation. Recorded and calculated values of net long-wave radiation are given and discussed.

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Zusammenfassung An der Klima- und Wasserhaushaltsstation des Dänischen Hydrotechnischen Laboratoriums bei Kopenhagen wurde seit 1954 dauernd die Einstrahlung mittels Moll-Thermosäulen in Kipp & Zonen-Solarimetern registriert und außerdem seit 1955 die Albedo. Seit 1956 wurden auch die Strahlungsbilanz und die effektive Ausstrahlung mittels Thermosäulen in Beckman & Whitley-Wärmestrommessern, die als Strahlungsmesser verwendet wurden, registriert.In einigen Tabellen werden tägliche Mittelwerte der Einstrahlung mitgeteilt wie auch Monatsmittelwerte der Reflexstrahlung, der effektiven Ausstrahlung und der Strahlungsbilanz. Ferner werden beobachtete und berechnete Werte der langwelligen Strahlungsbilanz angeführt und diskutiert.

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Résumé On a effectué des enregistrements du rayonnement incident depuis 1954 et de l'albédo depuis 1955 à la Station d'économie climatologique et hydrologique du laboratoire danois d'hydrotechnique près de Copenhague. Le bilan radiatif fut également mesuré depuis 1956 ainsi que le rayonnement émis effectif.Les auteurs donnent ici des tableaux de valeurs journalières moyennes du rayonnement incident, des moyennes mensuelles de l'albédo, du rayonnement effectif et du bilan radiatif. Enfin des valeurs enregistrés et calculés du rayonnement effectif, sont présentés et discutés.

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Angular distributions of solar protons and electrons

High angular-resolution measurements of directional fluxes of solar particles in space have been obtained with detectors aboard OGO-5 during the cosmic ray event of 18 November 1968. This is the only case on record for which sharply-defined directional observations of protons and electrons covering a wide rigidity range (0.3 MV to 1.5 GV) are available.The satellite experiment provided data for determining pitch-angle distributions with respect to the direction of the local interplanetary magnetic field lines during the lengthy highly anisotropic phase of the event. It was found that the unidirectional differential intensities j(θ) of 3- to 25-MeV protons varied in accordance with the relationship j(θ) = b₀ + b₁cosθ + b₂cos²θ, where b₀ and b₁ ? 0, and b₂, is positive, zero or negative. Soon after onset, 79–266-keV electrons arriving from the direction of the Sun displayed an anisotropic component with the intensity varying as cos θ. Later, a double-peaked distribution appeared at the lower energies, whereas the flux at the upper end of the range covered by the experiment became isotropic. These results have been interpreted in the light of the temporal flux profiles and the state of the interplanetary medium.The observation of the unusually large and long-lasting anisotropies lead to several conclusions including: (1) If injection of the solar particles was instantaneous, the diffusion coefficient was either constant or increasing with distance from the Sun. (2) If the solar source emitted particles over an extended period, and there is evidence to that effect, there was weak scattering in the region between the Sun and the Earth and a strong scattering region beyond the Earth's orbit. (3) Solar electrons were stored near the Sun. (4) The observed angular distribution of 200-MV protons in the magnetosheath was in good agreement with that deduced in an earlier analysis of polar orbiting satellite observations and trajectory calculations.