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911.
A. F. Kholtygin N. P. Sudnik T. E. Burlakova G. G. Valyavin 《Astronomy Reports》2011,55(12):1105-1114
We observed the bright O6If(n) supergiant λ Cep in 1997 with the 6-m optical telescope of the Special Astrophysical Observatory and in 2007 with the 1.8-m telescope
of the Bohyunsan Optical Astronomy Observatory (South Korea). A total of 90 spectra of the star were acquired, with good time
resolution (10 minutes), signal-to-noise ratios 150–300, and spectral resolutions of 45 000–60 000. We detected line-profile
variations of H, HeI, and HeII lines. It is suggested that the detected variations are due to non-radial photospheric pulsations
and the star’s rotation (rotational profile modulation). 相似文献
912.
N. V. Chukanov A. A. Mukhanova R. K. Rastsvetaeva D. I. Belakovsky S. M?ckel O. V. Karimova S. N. Britvin S. V. Krivovichev 《Geology of Ore Deposits》2011,53(7):583-590
Oxyphlogopite is a new mica-group mineral with the idealized formula K(Mg,Ti,Fe)3[(Si,Al)4O10](O,F)2. The holotype material came from a basalt quarry at Mount Rothenberg near Mendig at the Eifel volcanic complex in Rhineland-Palatinate,
Germany. The mineral occurs as crystals up to 4 × 4 × 0.2 mm in size encrusting cavity walls in alkali basalt. The associated
minerals are nepheline, plagioclase, sanidine, augite, diopside, and magnetite. Its color is dark brown, its streak is brown,
and its luster is vitreous. D
meas = 3.06(1) g/cm3 (flotation in heavy liquids), and D
calc = 3.086 g/cm3. The IR spectrun does not contain bands of OH groups. Oxyphlogopite is biaxial (negative); α = 1.625(3), β = 1.668(1), and
γ = 1.669(1); and 2V
meas = 16(2)° and 2V
calc = 17°. The dispersion is strong; r < ν. The pleochroism is medium; X > Y > Z (brown to dark brown). The chemical composition is as follows (electron microprobe, mean of 5 point analyses, wt %; the ranges
are given in parentheses; the H2O was determined using the Alimarin method; the Fe2+/Fe3+ was determined with X-ray emission spectroscopy): Na2O 0.99 (0.89–1.12), K2O 7.52 (7.44–7.58), MgO 14.65 (14.48–14.80), CaO 0.27 ((0.17–0.51), FeO 4.73, Fe2O3 7.25 (the range of the total iron in the form of FeO is 11.09–11.38), Al2O3 14.32 (14.06–14.64), Cr2O3 0.60 (0.45–0.69), SiO2 34.41 (34.03–34.66), TiO2 12.93 (12.69–13.13), F 3.06 (2.59–3.44), H2O 0.14; O=F2 −1.29; 99/58 in total. The empirical formula is (K0.72Na0.14Ca0.02)(Mg1.64Ti0.73Fe0.302+ Fe0.273+Cr0.04)Σ2.98(Si2.59Al1.27Fe0.143+ O10) O1.20F0.73(OH)0.07. The crystal structure was refined on a single crystal. Oxyphlogopite is monoclinic with space group C2/m; the unit-cell parameters are as follows: a = 5.3165(1), b = 9.2000(2), c = 10.0602(2) ?, β = 100.354(2)°. The presence of Ti results in the strong distortion of octahedron M(2). The strongest lines of the X-ray powder diffraction pattern [d, ? (I, %) [hkl]] are as follows: 9.91(32) [001], 4.53(11) 110], 3.300(100) [003], 3.090(12) [112], 1.895(21) [005], 1.659(12) [−135], 1.527(16)
[−206, 060]. The type specimens of oxyphlogopite are deposited at the Fersman Mineralogical Museum in Moscow, Russia; the
registration numbers are 3884/2 (holotype) and 3884/1 (cotype). 相似文献
913.
Charles C. Wall Bradley J. Peterson Christopher J. Gobler 《Estuaries and Coasts》2011,34(6):1262-1277
While many coastal ecosystems previously supported high densities of seagrass and abundant bivalves, the impacts of overfishing,
eutrophication, harmful algal blooms, and habitat loss have collectively contributed to the decline of these important resources.
Despite improvements in wastewater treatment in some watersheds and subsequent reduced nutrient loading to neighboring estuaries,
seagrass and bivalve populations in these locations have generally not recovered. We performed three mesocosm experiments
to simultaneously examine the contrasting effects of nutrient loading and historic suspension-feeding bivalve densities on
the growth of eelgrass (Zostera marina), juvenile bivalves (northern quahogs, Mercenaria mercenaria; eastern oysters, Crassostrea virginica; and bay scallops, Argopecten irradians), and juvenile planktivorous fish (sheepshead minnow, Cyprinodon variegatus). High nutrient loading rates led to significantly higher phytoplankton (chlorophyll a) levels in all experiments, significantly increased growth of juvenile bivalves relative to controls with lower nutrient
loading rates in two experiments, and significantly reduced the growth of eelgrass in one experiment. The filtration provided
by adult suspension feeders (M. mercenaria and C. virginica) significantly decreased phytoplankton levels in all experiments, significantly increased light penetration and the growth
of eelgrass in one experiment, and significantly decreased the growth of juvenile bivalves and fish in two experiments, all
relative to controls with no filtration from adult suspension feeders. These results demonstrate that an appropriate level
of nutrient loading can have a positive effect on some estuarine resources and that bivalve filtration can mediate the effects
of nutrient loading to the benefit or detriment of different estuarine resources. Future ecosystem-based approaches will need
to simultaneously account for anthropogenic nutrient loading and bivalve restoration to successfully manage estuarine resources. 相似文献
914.
In order to ascertain the forms in which uranium is present in ores of the Melovoe rare metal sedimentary deposit of uranium
and rare earth minerals (South Mangyshlak), we investigated a series of typical ore samples that were collected earlier; both
the uranium content and the total content of rare earth metals in them lay within 0.1–0.3%. The study was carried out by analytical
electron microscopy using transmission electron microscopy and scanning electron microscopy, electron microdiffraction, and
microprobing. It was ascertained that both uranium and rare earth elements are present in ore mostly associated with biogenic
phosphate in the form of natural minerals, such as uraninite, ningyoite, coffinite, autenite, and churchite. Iron hydroxides
and graphitized organic matter are present in some samples. It is assumed that the co-occurrence of uranium and rare earth
elements, which is nontypical for the sedimentary process, resulted from secondary epigenetic processes and alternation of
reducing and oxidizing environmental conditions. 相似文献
915.
916.
鄂尔多斯盆地苏里格地区奥陶系马家沟组马五段白云岩的地球化学特征 总被引:1,自引:0,他引:1
苏里格地区奥陶系马家沟组马五段白云岩是重要的油气储集层.多年来,马家沟组白云岩的成因一直是地质研究者讨论的热点话题.对苏里格地区马家沟组马五段白云岩的微量元素及C、O、Sr同位素地球化学资料的分析表明,微量元素表现为高铁、低锰、低锶、低钠;白云石、白云质角砾和孔洞充填白云岩的δ13C和δ18O值较为近似,且白云岩的δ1... 相似文献
917.
新疆东天山地区星星峡群的解体及地质意义 总被引:2,自引:0,他引:2
新疆东天山地区星星峡一带的原星星峡群为一套岩性复杂、变质程度差异很大的变质岩系, 在该区进行的1:50000区调工作中, 通过详细的地表调查和地层剖面测量, 并参考了相关变质侵入体的同位素年龄后认为, 根据岩石组合、变质程度、同位素年龄等地质标志, 可将其初步解体为大致形成于晚太古代—古元古代的天湖岩群(Ar3—Pt1T.)和长城纪星星峡岩群(ChX.)两套时代不同的岩群。该岩群的解体和区域对比表明, 中天山星星峡一带和塔里木北缘库鲁克塔格一带的前南华系基底应该是一致的, 属于统一的塔里木北缘隆起带。 相似文献
918.
919.
920.
Ding Tiping Liu Yushan Wan Defang Liu Zhijian Li Jincheng Zhang Guilan Institute of Mineral Deposits Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》1992,66(3):271-282
Experiments for oxygen isotope exchange between ferberite and water were carried out and the followingequation on oxygen isotope fractionation between ferberite and water against temperature was obtained:Combining this equation with the equation of Clayton et al. (1972) on oxygen isotope fractionation be-tween quartz and water, an equation on oxygen isotope fractionation between quartz and ferberite was ob-tained:The Bigeleison-Mayer function method was used to calculate the oxygen isotope fractionation betweenquartz and ferberite. The theoretical curve obtained agrees with the experimental calibration results quite wellin the temperature range of study.The above calibrated equation has been used in 5 world famous tungsten deposits to determine their tem-peratures of formation. The results show that the temperature range for an idividual deposit determined by thisgeothermometer agrees with those obtained from fluid inclusion determination and other isotopegeothermometers. 相似文献