Rare earth elements in tourmaline and chlorite from tin-bearing assemblages: Factors controlling fractionation of REE in hydrothermal systems     

N. S. Bortnikov  N. V. Gorelikova  P. G. Korostelev  V. G. Gonevchuk 《Geology of Ore Deposits》2008,50(6):445-461

The REE distribution in minerals from tin-bearing ore-magmatic systems of the Russian Far East, including the Komsomolsk, Khingan, and Badzhal districts in the Amur region and the Kavalerovo, Lesozavodsk, Voznesenka, Furmanovo, and other districts in Primorsky krai, has been studied. The main attention was focused on tourmaline and chlorite; in addition, associated biotite, feldspar, apatite, fluorite, and carbonates were examined. The major factors affecting the REE distribution in the studied minerals are the temperature, Eh, and pH of the mineral-forming medium; crystal chemistry; partition coefficients of REE between fluid and minerals; and complexation that disturbs the coherent behavior of REE. Fluid evolution at different stages is characterized.  相似文献   

Normative quartz as an indicator of the mass transfer intensity during the postmagmatic alteration of the Botuobinskaya pipe kimberlites (Yakutia)     

V.B. Vasilenko  A.V. Tolstov  V.A. Minin  L.G. Kuznetsova  N.V. Surkov 《Russian Geology and Geophysics》2008,49(12):894-907

The intensity of postmagmatic processes in the Botuobinskaya pipe kimberlites was estimated from the calculated content of normative secondary quartz (Q). Several simple algorithms are proposed to calculate the Q content from chemical analyses of kimberlites. Ten groups of altered kimberlites have been recognized from the Q contents. The contents of MgO, some trace elements, and LREE in the groups, the contents of Cr and Ca of crimson garnets, the diamond contents of kimberlites, and the average weight of diamonds decrease as the Q content increases. It is shown that the negative SiO₂–MgO correlation is the most effective indicator of the postmagmatic alteration of kimberlites. As the degree of their secondary alteration increases, the kimberlites transform into an assemblage of quartz and clay minerals enriched in some trace elements and almost completely lacking REE and diamonds.  相似文献   

Soil-to-dwelling radon isotope ratio in the Baikal region     

B.P. Chernyago  A.I. Nepomnyashchikh  G.I. Kalinovskii 《Russian Geology and Geophysics》2008,49(12):971-977

Relations between indoor and soil gas radon were experimentally studied in villages of the Baikal region. On the basis of the obtained data, the soil-to-indoor radon ratio was calculated, which can be used for prediction of radon pollution in buildings of the same kind.  相似文献   

Intrayear irregularities of the Earth’s rotation     

L. D. Akulenko  Yu. G. Markov  V. V. Perepelkin  L. V. Rykhlova 《Astronomy Reports》2008,52(7):590-597

The methods of celestial mechanics can be used to construct a mathematical model for the perturbed rotational motions of the deformable Earth that can adequately describe the astrometric measurements of the International Earth Rotation Service (IERS). This model describes the gravitational and tidal influences of the Sun and Moon. Fine resonant interactions of long-period zonal tides (annual, semiannual, monthly, and biweekly) with the diurnal and semidiurnal tides are revealed. These interactions can be reliably confirmed via a spectral analysis of the IERS data. Numerical modeling of tidal irregularities of the Earth’s axial rotation was carried out, focusing on the analysis and forecasting of variations of the day length occurring within short time intervals of a year or shorter (intrayear variations).  相似文献   

Population synthesis for massive close WR20a-type binaries     

A. I. Bogomazov  A. M. Cherepashchuk 《Astronomy Reports》2008,52(12):1009-1014

We have used the “Scenario Machine” to carry out a population synthesis for close binary systems with the masses of both components and their orbital periods similar to those for the WR20a system. The possible qualitative composition of WR20a, the most massive known binary with non-degenerate components (commonly classified as Wolf-Rayet stars according to their observational parameters), has been studied. Meridional circulation may enrich the envelope of a rapidly rotating main-sequence star in CNO elements. In the most likely model, WR20a consists of a Wolf-Rayet star and a main-sequence star.  相似文献   

The gas density and “volume” Schmidt law for spiral galaxies     

O. V. Abramova  A. V. Zasov 《Astronomy Reports》2008,52(4):257-269

The equilibrium thickness of the isothermal layers of interstellar gas and volume gas densities ρ _gas in the plane of the disk as a function of galactocentric distance R are computed for seven spiral galaxies (including the Milky Way) using an axisymmetrical model. In this model, the thickness of the stellar disk varies with R and remains approximately equal to the minimum thickness of a stable equilibrium disk. We found the disk thickness to increase toward the periphery in at least five of the seven galaxies. The density of the stellar disk decreases with R faster than ρ _gas , so that gas dominates at the disk peripheries in terms of density. A comparison of the azimuthally averaged star formation rate SFR and the gas density shows the absence of a universal Schmidt law SFR ～ρ _gas ⁿ for galaxies. However, the SFRs in various galaxies are better correlated with the volume than the gas surface density. The parameter n in the Schmidt law formally calculated using the least-squares method lies in the interval 0.8–2.4, being, on average, close to 1.5. The values of n calculated separately for the molecular gas display substantial scatter, but are, on average, close to unity. The value of n appears to increase with decreasing ρ _gas , so that the fraction of gas that actively participates in star formation decreases with n.  相似文献   

Long-term variability of a complete sample of flat-spectrum radio sources at declinations of 4°–6° (B1950)     

A. G. Gorshkov  V. K. Konnikova  M. G. Mingaliev 《Astronomy Reports》2008,52(4):278-298

We present the results of twenty-year observations of a complete sample of 68 flat-spectrum radio sources with flux densities S _{3.9 GHz} > 200 mJy carried out at centimeter wavelengths with the RATAN-600 radio telescope. Since 1995, we have observed simultaneously at six frequencies between 0.97 and 21.7 GHz. Of the 56 sources identified with optical objects, 41 are quasars with redshifts between 0.293 and 3.263. Based on our analysis of the spectral shapes, we divide the sources into four classes. Changes of spectral class for individual sources are fairly rare. Based on the light curves and spectra, in most cases, a flare’s evolution is in accordance with a model in which the variations result from the evolution of a shock in the radio jet. The main result of our study is that there is no redshift dependence for the true linear sizes of the radiating regions, the variability indices derived for all 20 years of data or for individual flares, or the peak frequencies of the spectra of the compact radio emission. We suggest that this testifies to an absence of cosmological evolution of the sample quasars, at least to z ≈ 3.  相似文献   

The mass of the compact object in the X-ray binary her X-1/HZ her     

M. K. Abubekerov  E. A. Antokhina  A. M. Cherepashchuk  V. V. Shimanskii 《Astronomy Reports》2008,52(5):379-389

We have obtained the first estimates of the masses of the components of the Her X-1/HZ Her X-ray binary system taking into account non-LTE effects in the formation of the H _γ absorption line: m _x = 1.8 M _⊙ and m _v = 2.5 M _⊙. These mass estimates were made in a Roche model based on the observed radial-velocity curve of the optical star, HZ Her. The masses for the X-ray pulsar and optical star obtained for an LTE model lie are m _x = 0.85 ± 0.15 M _⊙ and m _v = 1.87 ± 0.13 M _⊙. These mass estimates for the components of Her X-1/HZ Her derived from the radial-velocity curve should be considered tentative. Further mass estimates from high-precision observations of the orbital variability of the absorption profiles in a non-LTE model for the atmosphere of the optical component should be made.  相似文献   

Spectroscopic monitoring of SS 433: A search for long-term variations of kinematic model parameters     

V. V. Davydov  V. F. Esipov  A. M. Cherepashchuk 《Astronomy Reports》2008,52(6):487-506

Between 1994 and 2006, we obtained uniform spectroscopic observations of SS 433 in the region of Hα. We determined Doppler shifts of the moving emission lines, Hα ₊ and Hα _?, and studied various irregularities in the profiles for the moving emission lines. The total number of Doppler shifts measured in these 13 years is 488 for Hα _? and 389 for Hα ₊. We have also used published data to study possible long-term variations of the SS 433 system, based on 755 Doppler shifts for Hα _? and 630 for Hα ₊ obtained over 28 years. We have derived improved kinematic model parameters for the precessing relativistic jets of S S 433 using five-and eight-parameter models. On average, the precession period was stable during the 28 years of observations (60 precession cycles), at 162.250^d ± 0.003^d. Phase jumps of the precession period and random variations of its length with amplitudes of ≈6% and ≈1%, respectively, were observed, but no secular changes in the precession period were detected. The nutation period, P _nut = 6.2876^d ± 0.00035^d, and its phase were stable during 28 years (more than 1600 nutation cycles). We find no secular variations of the nutation cycle. The ejection speed of the relativistic jets, v, was, on average, constant during the 28 years, β = v/c = 0.2561 ± 0.0157. No secular variation of β is detected. In general, S S 433 demonstrates remarkably stable long-term characteristics of its precession and nutation, as well as of the central “engine” near the relativistic object that collimates the plasma in the jets and accelerates it to v = 0.2561c. Our results support a model with a “slaved” accretion disk in S S 433, which follows the precession of the optical star’s rotation axis.  相似文献   

The Seyfert 1 galaxy Ark 120. Spectral variability in 1992–2005     

V. T. Doroshenko  S. G. Sergeev  V. I. Pronik 《Astronomy Reports》2008,52(6):442-462

We have studied the variability of the Hβ line and the adjacent continuum in the spectrum of the Seyfert galaxy Ark 120, based on spectral observations of the galaxy’s nucleus obtained in the Crimea in 1992–2005, supplemented by published data for 1988–1996. Irregular variability on various timescales (years to days) can be accompanied by periodic brightness variations in both the continuum and the Hβ line, with a period of P ～ 430 days and an amplitude of Δm ～ 0.2 ^m in the continuum, which were traced for more than 13 cycles. In total, in 1988–2005, the flux variations in the line lag those in the continuum by 55 ± 9 days if calculated from the peak of the cross correlation function, or by 72 ± 7 days, if calculated from the centroid of the CCF. The delay is correlated with the continuum brightness, increasing when the continuum flux increases. The Hβ line profiles indicate both a high degree of diversity and the presence of features that recur after various extended time intervals. Analysis of the evolution of the differences between each individual normalized line profile and the mean normalized profile indicates systematic motion of excesses relative to the average profile from negative to positive radial velocities. In contrast, parts of the Hβ line with low radiation relative to the mean normalized profile evolve in the opposite direction (from the red to the blue Hβ wing). This pattern is also typical for the rotating broad-line region, if this region has the form of a disk. The rotation period exceeds 9000–10000 days, or 25–27 years. The size of the broad-line region calculated form this period corresponds to a reverberation time of no fewer than 30 days, consistent with the results of cross-correlation analysis.  相似文献