Lithium Abundances in the Atmospheres of SLR C-Giants WZ Cas and WX Cyg from Resonance and Subordinate Li I Lines

Lithium abundances in the atmospheres of the super Li-rich C-giants WZ Cas and WX Cyg are derived by the spectral synthesis technique using the Li I resonance line at λ670.8 nm and three subordinate lines at λλ 812.6, 610.4 and 497.2 nm. The differences between the Li abundances derived from the λ670.8 nm line and the λλ 497.2, 812.6 nm lines do not exceed ±0.5 dex. The lithium line at λ610.4 nm provides typically lower abundances than the resonance line (by ≈ 1 dex). The mean LTE and NLTE Li abundances from three Li I lines (excluding λ610.4 nm) are 4.7, 4.9 for WZ Cas, and 4.6, 4.8 for WX Cyg, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

梭鱼标准代谢、内源氮排泄与体重和温度的关系

在 13.5 ,18,2 1.5 ,2 4和 2 7℃ 5个温度条件下测定了梭鱼 (体重范围 1.88～ 14.0 2 g)的标准代谢率和内源氮排泄率。梭鱼标准代谢率随体重的增加而增加 ,二者的关系为幂函数关系 ;随温度的升高而增加 ,二者的关系为指数关系 ;标准代谢率与体重和温度的关系可用如下方程表示 :RS=0 .12 4 6 W0 .9954 e0 .0 84 1T(r2 =0 .92 2 0 )。梭鱼的氨氮、尿素、总氮及能量的排泄率随体重和温度的增加而增加 ,与体重为幂函数关系 ,与温度的关系为多项式形式。梭鱼氨氮和尿素日排泄率的变幅分别为 0 .15～ 0 .88mg N/d和 0 .0 3～ 0 .2 9mg N/d。不同温度下 ,尿素排泄量占总氮比例在 9.9%～2 2 .4 9%之间 ,随温度升高该值有逐渐增大的趋势。     

Random wave-current interactions in water of varying depth

Refraction of incoherent random gravity waves with currents and bottom topography results in spatial variations in the spectral characteristics of the free surface. Prediction of such variations based on the radiation transfer equation is in a simple analytic form for the case of one dimensional inhomogeneities in currents and topography. This analytic form is examined in terms of two-dimensional wave number- and polar frequency-direction spectra along the associated dynamic and kinematic constraints relevant to wave breaking and reflection. Results are specialized to the simplest case of horizontal shear currents in deep and shallow water with explicit examples to illustrate the relative and combined effects of currents and topography on free surface spectra.     

Fractional crystallization models and B–Be–Li systematics at Mt Somma-Vesuvius volcano (Southern Italy)

A compilation of B–Be–Li data on rocks that cover the entire eruptive history of Somma-Vesuvius is presented and interpreted in the light of evolution models for the Somma-Vesuvius rocks. Using major and trace element data, fractional crystalllization models are presented for different geochemical units. These data were used to constrain the source mineralogy of the Somma-Vesuvius rocks (ol-opx-cpx-gar-amp of 0.4-0.3-0.1-0.1-0.1), the amount of sediment added (5–10%) and the melt fraction from batch partial melting computations (0.05–0.1). From the B–Li data it is inferred that the main process responsible for the B isotopic signature is sediment recycling. However, the B–Li data show a major variation in Li abundances respect to B which is explained with Li dehydration before the fluid enriched the mantle wedge that produced the arc magmas. The Somma-Vesuvius B isotope composition is intermediate between that of the Campi Flegrei and the broad field of the Eolian Island arc. A low Be isotopes in the recent volcanic rocks can be explained as: (a) the top 1–22 m of the incoming sediment is accreted, (b) large amounts of sediment erosion, (c) a slow rate of subduction which have provoked a long magmatic history for the Vesuvius magma, (d) the sediment component takes several Myr longer than the subducting plate to reach the magma source region beneath Italy.     

不同浓度Li2SO4水溶液结构的X射线衍射研究

用θ～ 2θ型粉末衍射仪反射法精确测量了不同浓度的Li2 SO4水溶液的衍射数据 ,通过数据处理给出了溶液的结构函数和径向分布函数 ,由几何结构模型的最小二乘法精修 ,得到了溶液中阳离子和阴离子第一、二水合层的结构参数。     

Precise/ Small Sample Size Determinations of Lithium Isotopic Compositions of Geological Reference Materials and Modern Seawater by MC-ICP-MS

The Li isotope ratios of four international rock reference materials, USGS BHVO-2, GSJ JB-2, JG-2, JA-1 and modern seawater (Mediterranean, Pacific and North Atlantic) were determined using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). These reference materials of natural samples were chosen to span a considerable range in Li isotope ratios and cover several different matrices in order to provide a useful benchmark for future studies. Our new analytical technique achieves significantly higher precision and reproducibility (< ± O.3%o 2s) than previous methods, with the additional advantage of requiring very low sample masses of ca . 2 ng of Li.     

Magmatic evolution of Li–F, rare-metal granites: a case study of melt inclusions in the Khangilay complex, Eastern Transbaikalia (Russia)

We report compositions of homogenized quartz-hosted melt inclusions from a layered sequence of Li-, F-rich granites in the Khangilay complex that document the range of melt evolution from barren biotite granites to Ta-rich, lepidolite–amazonite–albite granites. The melt inclusions are crystalline at room temperature and were homogenized in a rapid-quench hydrothermal apparatus at 200 MPa before analysis. Homogenization runs determined solidus temperatures near 550 °C and full homogenization between 650 and 750 °C. The compositions of inclusions, determined by electron microprobe and Raman spectroscopy (for H₂O), show regular overall trends of increasing differentiation from the least-evolved Khangilay units to apical units in the Orlovka intrusion. Total volatile contents in the most-evolved melts reach over 11 wt.% (H₂O: 8.6 wt.%, F: 1.6 wt.%, B₂O₃: 1.5 wt.%). Concentrations of Rb range from about 1000 to 3600 ppm but other trace elements could not be measured reliably by electron microprobe. The resulting trends of melt evolution are similar to those described by the whole-rock samples, despite petrographic evidence for albite- and mica-rich segregations previously taken as evidence for post-magmatic metasomatism.

Melt variation trends in most samples are consistent with fractional crystallization as the main process of magma evolution and residual melt compositions plot at the granite minimum in the normative Qz–Ab–Or system. However, melts trapped in the highly evolved pegmatitic samples from Orlovka deviate from the minimum melt composition and show compositional variations in Al, Na and K that requires a different explanation. We suggest that unmixing of the late-stage residual melt into an aluminosilicate melt and a salt-rich dense aqueous fluid (hydrosaline melt) occurred. Experimental data show the effectiveness of this process to separate K (aluminosilicate melt) from Na (hydrosaline melt) and high mobility of the latter due to its low viscosity and relatively low density may explain local zones of albitization in the upper parts of the granite.     

Particularités de la contamination crustale des phonolites : exemple du Velay oriental (Massif central)

Sr and Nd isotopic compositions of one trachyte, eight phonolites and five basalts have been measured. The isotopic characteristics of the trachyte can be explained by a combined assimilation–fractional crystallization process within an upper crustal magmatic chamber. Some phonolites display isotopic signatures identical to basalts, suggesting that they have been protected against any crustal assimilation during their formation. Some others have low Sr contents, whereas they are enriched in radiogenic Sr (0.70451<⁸⁷Sr/⁸⁶Sr_i<0.71192), and display basaltic ¹⁴³Nd/¹⁴⁴Nd ratios. Both observations could be explained by very strong alkali feldspar fractionation and by subsequent very low assimilation of surrounding rocks (between 0.3 and 4%) during intrusion. To cite this article: J.-M. Dautria et al., C. R. Geoscience 336 (2004).     

Apport de l'imagerie satellitaire radar pour l'exploration géologique en zones arides

The potential of radar imagery in geological exploration was investigated at a study site in Mauritania (Akjoujt region). Compared with optical images, the results obtained show how radar imagery can help not only in detecting surface geological structures such as dykes and veins, but also mapping subsurface structures beneath a shallow layer of sand (palaeochannels). The mapping potential was found to be much better at long wavelengths than at short ones (L-band, compared with C- and X-band). As for optical images, their contribution is much more limited in the mapping of surface geological structures, and inappropriate for detecting subsurface structures. We conclude that spatial remote sensing enables the improvement of existing geological maps and the optimization of cartographic surveying. To cite this article: N. Baghdadi et al., C. R. Geoscience 337 (2005).     

The first araripeneurine antlion in Burmese amber (Neuroptera: Myrmeleontidae)

Burmaneura minuta gen. et sp. nov., the first araripeneurine antlion in amber, is characterized, described and compared with the modern and Mesozoic Myrmeleontidae. The precise position of the fossil within this group is debatable. Interestingly, despite a rather rich fossil record, all Mesozoic Myrmeleontidae belong to subfamilies that are not recorded in the Cenozoic, although this might merely reflect the artificiality of the classification as the extinct groups may be paraphyletic with respect to their younger counterparts (e.g., Araripeneurinae may very well be nothing more than a stem group of no classificatory value).