Abundances of neutron-capture elements in atmospheres of cool giants

We have determined the atmospheric abundances of Y, Ba, La, Ce, Pr, Nd, and Eu for a sample of 171 giants selected as clump giants with metallicities [Fe/H] between ?0.7 and 0.3 dex, based on photometric criteria. In our analysis, we assumed local thermodynamic equilibrium and fit the parameters of model atmospheres to high-resolution (R = 42 000) echelle spectra with high signal-to-noise ratios. The Ba and Eu abundances were derived using synthetic spectra, including hyperfine structure. We find no significant difference in the abundances of s-or r-process neutron-capture elements between clump giants and ascending-branch giants selected by us earlier. We also analyze the relation between the abundances of neutron-capture elements and [Fe/H].     

Abundances of carbon,nitrogen, oxygen,and other elements in the atmosphere of the giant 30 LMi

We have studied the star 30 LMi using high-dispersion CCD spectra and photographic observations. We estimate the star's effective temperature T_eff=7210 K, gravity log g=3.34, and microturbulence velocity ξ_t=5.8 km/s. The carbon abundance, log ?(C)=8.57, is close to the solar value. Nitrogen (log ?(N)=7.81), oxygen (log ?(O)=8.76), and sulfur (log ?(S)=7.20) are slightly underabundant compared to the Sun, by ?0.16 dex, ?0.11 dex, and ?0.13 dex, respectively. A relatively large underabundance of ?0.27 dex was found for titanium (log ?(Ti)=4.75), whereas zinc shows an over-abundance by +0.21 dex (log ?(Zn)=4.81). Sodium (log ?(Na)=6.26), silicon (log ?(Si)=7.57), calcium (log ?(Ca)=6.38), chromium (log ?(Cr)=5.62), iron (log ?(Fe)=7.51), nickel (log ?(Ni)=6.34), and yttrium (log ?(Y)=2.34) exhibited abundances close to the solar values. We find no chemical anomalies characteristic of Am stars or δ Scuti stars in the spectrum of 30 LMi.     

Abundances of carbon, nitrogen, oxygen, and other elements in the atmosphere of the giant 20 Peg

We have studied the giant 20 Peg using high-resolution spectra. We derive the star’s effective temperature, T _eff=6970 K, gravity, logg=3.35, and microturbulence velocity from FeI lines, ξ_t=2.70 km/s, and from NiI lines, ξ_t=2.45 km/s. The abundances of carbon, log?(C)=8.78, nitrogen, log?(N)=8.28, and silicon, log?(Si)=7.85, are enhanced compared to the solar values by 0.23, 0.31, and 0.30 dex, respectively. The abundances of oxygen, log?(O)=8.83, sodium, log?(Na)=6.37, and sulfur, log?(S)=7.33, are nearly solar. Calcium and nickel show normal abundances, log?(Ca)=6.44 and log?(Ni)=6.32. Iron log?(Fe)=7.63 and yttrium log?(Y)=2.41 are only slightly overabundant compared to the solar values (by 0.13 and 0.17 dex). We find a rather large (0.95 dex) overabundance of barium log?(Ba)=3.08.     

Some problems in determining elemental abundances in the atmospheres of giants and dwarfs of the HR 1614 moving cluster

The atmospheric abundances of various chemical elements and other atmospheric parameters of four stars belonging to the HR 1614 moving cluster are determined and analyzed using a single technique. For three of the stars, the derived atmospheric parameters are typical of stars of their types, and their elemental abundances are close to those determined earlier for these and other stars of the moving cluster. However, the atmospheric parameters derived for the red dwarf HD 32147 would be more typical of a giant, and its metallicity is much lower than is characteristic of stars of this moving group.

     

Analysis of elemental abundances in the atmospheres of three Hyades red giants

Model atmospheres are fitted to spectroscopic data in order to analyze the elemental abundances in the atmospheres of three red giants in the Hyades cluster. The three stars have almost identical chemical compositions, with iron-group elements slightly overabundant compared to the solar values—a pattern that is typical of Hyades dwarfs. The overabundances of the light elements Na, Al, and Si are virtually equal to those observed for field giants. No enrichment in rare-earth elements relative to iron was found, in sharp contrast to field giants. It is concluded that these discrepancies are due to the age difference between the two groups of stars, which have resulted in different degrees of convective overshooting.     

Chemical abundance analysis for the atmospheres of red giants in the Hercules moving group

The results of a comparative analysis of the kinematics, ages, and elemental abundances for 17 red giants in the Hercules moving group are presented. Model atmospheres are used to determine the parameters of the stellar atmospheres and the abundances of about 20 elements. The masses and ages of the stars are estimated, and the components of their Galactic velocities and the elements of their Galactic orbits are calculated. Our analysis demonstrates that the Hercules stream is a heterogeneous group of objects from the thin and thick disks.     

Analysis of the Na,Mg, Al,and Si abundances in the atmospheres of red giants of different spectral subgroups

We analyze the Na, Mg, Al, and Si abundances in the atmospheres of more than 40 stars, includingred giants of different spectral subgroups (normal red giants, mild and classical barium stars) and several supergiants. All these elements exhibit abundance excesses, with the overabundance increasing with the star’s luminosity. The dependence of the overabundances for each of these elements on the luminosity (or log g) is the same for all the spectral subgroups, testifying to a common origin: they are all products of hydrogen burning in the NeNa and MgAl cycles that have been dredged up from the stellar interiors to the outer atmospheric layers by convection that gradually develops during the star’s evolution from the main sequence to the red-giant stage. The sodium abundances derived for several stars are lower than for other stars with similar atmospheric parameters. The ages and kinematic characteristics of these two groups of stars suggest that they probably belong to different stellar generations.     

Abundances of chemical elements in the Earth’s crust

The evaluation of the abundances of chemical elements in the Earth’s crust is a pivotal geochemical problem. Its first solutions in the early 20th century formed the empirical groundwork for geochemistry and justified concepts about the unity of the material of the Universe, the genesis of the chemical elements, and the geochemical differentiation of the Earth. The accumulation of newly obtained data called for the revision of this problem, and a series of papers by A.P. Vinogradov, which were published in Geokhimiya in 1956–1962, presented reevaluated contents of elements in the continental crust. In these papers, A.P. Vinogradov relied on the classic idea of the geochemical balance of the sedimentary process. These generalizations provided the foundation for the quantitative characterization of the geochemical background of the biosphere and allowed Vinogradov to formulate the principles of the melting and degassing of material in the outer Earth’s shells during the geologic history, a concept that became universally acknowledged in modern geochemistry and geology. The composition of the Earth’s crust can also be evaluated based not on the principle of geochemical balance in the sedimentary process but on data on the actual abundances of major magmatic, metamorphic, and sedimentary rock types. The possibility of this solution was provided after the extensive research of A.B. Ronov, who managed to develop a quantitative model for the structure of the Earth’s sedimentary shell. Based on these data, A.B. Ronov, A.A. Yaroshevsky, and A.A. Migdisov published a series of papers in Geokhimiya in 1967–1985 that presented a model for the chemical structure of the Earth’s crust with regard for the material composing not only the upper part of the continental crust but also its deep-seated granulite-basite layer and the oceanic crust. The quantitative estimates thus obtained led the authors to important conclusions: first, it was demonstrated that the estimated abundances of elements in the granite-metamorphic layer of the continental crust presented in the classic works by A.P. Vinogradov are confirmed by independent materials, which are based on data on the actual abundance of rocks. Second, incredible as it was, the principle of geochemical balance in the sedimentary process in application to Ca and carbonates appeared to be invalid. This problem remains unsettled as of yet and awaits its resolution.     

中国花岗岩类化学元素丰度及特征

在全国范围内 750个有代表性的大中花岗岩类岩体上,采集了 6 080件样品,组合成 768件组合样.所有样品完全采用无污染加工方案进行加工和制备.选用了以电感耦合等离子体质谱 (ICP-MS)、仪器中子活化和 X射线荧光光谱为主的多种先进的分析方法对这些花岗岩类样品进行了分析测试,实测元素近 70种.使用国家一级地球化学标准物质和重复测试样品进行质量监控,确保了分析数据的准确性和可靠性.依据这些实测分析数据,计算并提出了中国花岗岩类和不同构造单元、不同时代花岗岩类的近 70种化学元素或成分的丰度,探讨了中国花岗岩类和不同构造单元、不同时代花岗岩类元素丰度的特征.     

A comparative analysis of chemical abundances in the atmospheres of red giants of different age groups

We analyze previously published chemical abundances in the atmospheres of red giants. Excess abundances are observed not only for Na, but also for Al and Si, with the overabundances increasing with the stars’ luminosity. The observed anomalies provide evidence that, in addition to the CNO hydrogen-burning cycle, the Mg-Al and Ne-Na cycles operate in the interiors of main-sequence stars; their products are brought to the stellar atmospheres by convection after the transition to the red-giant phase. The abundance anomalies for s-process elements, also observed in the atmospheres of field stars, testify to the presence of a substantial number of neutrons. The s-process abundance anomalies are absent from giants of the young Hyades cluster.     

Abundances and sources of rare-earth elements in the modern volcanogenic hydrothermal systems of Kamchatka

Sources of modern hydrothermal systems are considered on the basis of high-precision REE data on representative samples of characteristic hydrochemical types of hydrothermal systems of the Eastern Volcanic Belt of Kamchatka and data available on modern magmatogenic fluid systems of the Kamchatka, Kuriles, and oceanic rift zones. It was found that modern high-temperature chloride-sodium hydrothermal vents have elevated REE contents and that all considered hydrochemical types of the Kamchatka hydrothermal systems are characterized by similar REE patterns. High REE contents in the hydrothermal vents with pH up to 5.0 show bimodal distribution. Correlations established between La/Yb ratios in the hydrothermal vents of various types and in the igneous rocks of the Eastern Volcanic Belt of Kamchatka are interpreted in genetic terms. A positive correlation was found between rare-earth elements, chlorine and boron contents. It was noted that all considered hydrochemical types show distinct negative europium anomaly, whereas submarine hydrothermal vents of oceanic rift zones are characterized by positive europium anomaly. It was proposed that REE was transported in the hydrothermal vents from apical zones of deep-seated magma chambers containing acid derivatives.     

Carbon,hydrogen and nitrogen in carbonaceous chondrites: Abundances and isotopic compositions in bulk samples

Whole-rock samples of 25 carbonaceous chondrites were analysed for contents of C, H and N and δ¹³C, δD and δ¹⁵N. Inhomogeneous distribution of these isotopes within individual meteorites is pronounced in several cases. Few systematic intermeteorite trends were observed; N data are suggestive of isotopic inhomogeneity in the early solar system. Several chondrites revealed unusual compositions which would repay further, more detailed study. The data are also useful for classification of carbonaceous chondrites; N abundance and isotopic compositions can differentiate existing taxonomic groups with close to 100% reliability; Al Rais and Renazzo clearly constitute a discrete “grouplet”; and there are hints that both CI and CM groups may each be divisible into two subgroups.     

Abundances of chemical elements of the granitoids in different geotectonic units of China and their characteristics

On the basis of actual analytical data of 767 composited samples collected mainly from about 750 large to middle representative granitoid bodies all over China, the average chemical compositions and element abundances of about 70 chemical elements of SiO₂, Al₂O₃, Fe₂O₃, FeO, MgO, CaO, Na₂O, K₂O, H₂O⁺, CO₂, TFe₂O₃, Ag, As, Au, B, Ba, Be, Bi, Cd, Cl, Co, Cr, Cs, Cu, F, Ga, Ge, Hf, Hg, Li, Mn, Mo, Nb, Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ta, Th, Ti, Tl, U, V, W, Zn, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y in alkalifeldspar granite, syenogranite and adamellite in 7 geotectonic units in China such as Tianshan-Xing’an orogenic series, Sino-Korean metaplatform, Kunlun-Qilian-Qinling orogenic series, Yunnan-Tibet orogenic series, Yangtze metaplatform, South China-Youjiang orogenic zone and Himalayan orogenic belt, are calculated and presented in this paper. In addition, the characteristics of petrochemical parameters, trace element contents and rare earth element distributions of different rock types of the granitoids in different geotectonic units are also sufficiently discussed. Translated from Acta Geologica Sinica, 2007, 81(1): 47–59 [译自: 地质学报]     

中国不同岩石类型花岗岩类元素丰度及特征

依据采自全国范围内约750个有代表性的大、中型花岗岩类岩体上的768件组合样的实测分析数据,这里计算并提出了碱长花岗岩、正长花岗岩、二长花岗岩、花岗闪长岩、石英二长岩、石英二长闪长岩等中国不同岩石类型的花岗岩类岩石近七十种化学元素或成份的丰度,探讨了中国不同花岗岩类岩石的岩石化学特征和微量元素丰度的特征。     

C、O、Sr同位素及微量元素组成在生物礁礁体环境研究中的应用

分析生物礁灰岩中C,O,Sr同位素及微量元素组成有助于研究生物礁体的形成环境.研究表明:δ 13C值的变化与生物埋藏量、埋藏速率、海平面的变化有着很密切的关系;海平面上升,δ 13C值增大,同时表明造礁生物大量繁殖;δ 18O值的变化反映古环境的温度变化,δ 18O升高,温度降低; 87Sr/ 86Sr的比值与海平面的升降变化表现一种负相关性,海平面上升, 87Sr/ 86Sr的比值降低.Sr, Mn等微量元素可以间接指示礁体环境变化,并且验证了所采集的样品数据的准确性.环境变化是决定生物礁发育的重要影响因素.     

Atmospheric lithium abundances of the carbon giants AQ And,HK Lyr,UX Dra,and WZ Cas

The LTE lithium abundances, logN (Li), have been determined for the atmospheres of the four carbon giants AQ And, HK Lyr, UX Dra, and WZ Cas, applying the synthetic-spectrum technique to the LiI λ670.8 nm resonance doublet. We used estimates of the effective temperatures T _eff, metallicities, elemental abundances, and carbon-isotope ratios for these stars from the literature [12C/13C]. The resulting lithium abundances depend significantly on the adopted T _eff, so that we can find each star’s range of possible logN(Li) values for a given range of effective temperatures (ΔT _eff = 200−300 K). The uncertainty in the derived logN(Li) values is 1.3 for AQ And and UX Dra, 0.5 for HK Lyr, and 0.8 for WZ Cas. Our most probable logN(Li) values (or ranges) are −1.25 for AQ And, −1.2 for HK Lyr, −1.0 ≤ logN(Li) ≤ +0.3 for UX Dra, and 4.3 ≤ logN(Li) ≤ 4.8 for WZ Cas. The derived C/O ratios for the stellar atmospheres also depend on T _eff. Possible uncertainties in other atmospheric parameters do not change logN(Li) by more than 0.2.     

Calcification rate and the stable carbon, oxygen, and nitrogen isotopes in the skeleton, host tissue, and zooxanthellae of bleached and recovering Hawaiian corals

We tested the effectiveness of stable isotopes as recorders of physiological changes that occur during coral bleaching and recovery. Montipora capitata and Porites compressa fragments were bleached in outdoor tanks with seawater temperature raised to 30 °C (treatment corals) for one month. Additional fragments were maintained at 27 °C in separate tanks (control corals). After one month, (0 months recovery), buoyant weight was measured and a subset of fragments was frozen. Remaining fragments were returned to the reef for recovery. After 1.5, 4, and 8 months, fragments were collected, measured for buoyant weight, and frozen. Fragments were analyzed for stable carbon and oxygen isotopic compositions of the skeleton (δ¹³C_s; δ¹⁸O_s) and nitrogen and carbon isotopic compositions of the host tissue (δ¹⁵N_h; δ¹³C_h) and zooxanthellae (δ¹⁵N_z; δ¹³C_z). δ¹³C_s decreased immediately after bleaching in M. capitata, but not in P. compressa. δ¹⁸O_s of both species failed to record the warming event. During the remaining months of recovery, δ¹³C_s and δ¹⁸O_s were more enriched in treatment than control corals due to decreases in calcification and metabolic fractionation during that time. Increased δ¹⁵N_h of treatment P. compressa may be due to expelled zooxanthellae during bleaching and recovery. Increased δ¹⁵N_z at 1.5 months in treatment fragments of both species reflects the increased incorporation of dissolved inorganic nitrogen to facilitate mitotic cell division and/or chl a/cell recovery. Changes in δ¹³C_h and δ¹³C_z at 1.5 months in treatment M. capitata indicated a large increase in heterotrophically acquired carbon relative to photosynthetically fixed carbon. We experimentally show that isotopes in coral skeleton, host tissue and zooxanthellae can be used to verify physiological changes during bleaching and recovery, but their use as a proxy for past bleaching events in the skeletal record is limited.     

Abundances and modes of occurrence of trace elements in the Çan coals (Miocene), Çanakkale-Turkey

This study presents the concentrations and modes of occurrence of trace elements in 81 coal samples from the Çan basin of northwestern Turkey. The concentration of trace elements in coal were determined by inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry. Additionally, traditional coal parameters were studied by proximate, ultimate, X-ray diffraction, and petrographic analyses. Twenty trace elements, including As, B, Ba, Be, Cd, Cu, Co, F, Hg, Mo, Ni, Pb, Sb, Se Sn, Th, Tl, U, V, and Zn, receive much attention due to their related environmental and human health concerns. The Çan coals investigated in this study are lignite to sub-bituminous coal, with a broad range of ash yields and sulphur contents. The trace element concentrations show variety within the coal seams in the basin, and the affinities vary among locations. The concentrations of B, Ba, Be, Cd, Cu, Co, F, Hg, Mo, Ni, Pb, Sb, Se, Sn, Tl, and Zn in Çan coals are within the Swaine's worldwide concentration range, with the exception of As, Th, U, and V. On the other hand, compared with world coals, the Çan basin coals have higher contents of As, B, Cu, Co, Mo, Pb, Th, U, V, and Zn. Based on statistical analyses, most of the trace elements, except for U, show an affinity to ash yield. Elements including As, Cd, Hg, Se, Cu, Mo, Ni, and Zn, show a possible association with pyrite; however, the elements Se, B, and Mo can be have both organic and inorganic associations.