Effects of anthropogenic feeding on the growth rate, nutritional status and migratory behaviour of free-ranging cod in an Icelandic fjord     

Bjornsson  Bjorn 《ICES Journal of Marine Science》2002,59(6):1248-1255

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Solubility mechanisms of fluorine in peralkaline and meta-aluminous silicate glasses and in melts to magmatic temperatures     

Bjorn O. Mysen  George D. Cody 《Geochimica et cosmochimica acta》2004,68(12):2745-2769

Structural interaction between dissolved fluorine and silicate glass (25°C) and melt (to 1400°C) has been examined with ¹⁹F and ²⁹Si MAS NMR and with Raman spectroscopy in the system Na₂O-Al₂O₃-SiO₂ as a function of Al₂O₃ content. Approximately 3 mol.% F calculated as NaF dissolved in these glasses and melts. From ¹⁹F NMR spectroscopy, four different fluoride complexes were identified. These are (1) Na-F complexes (NF), (2) Na-Al-F complexes with Al in 4-fold coordination (NAF), (3) Na-Al-F complexes with Al in 6-fold coordination with F (CF), and (4) Al-F complexes with Al in 6-fold, and possibly also 4-fold coordination (TF). The latter three types of complexes may be linked to the aluminosilicate network via Al-O-Si bridges.The abundance of sodium fluoride complexes (NF) decreases with increasing Al/(Al + Si) of the glasses and melts. The NF complexes were not detected in meta-aluminosilicate glasses and melts. The NAF, CF, and TF complexes coexist in peralkaline and meta-aluminosilicate glasses and melts.From ²⁹Si-NMR spectra of glasses and Raman spectra of glasses and melts, the silicate structure of Al-free and Al-poor compositions becomes polymerized by dissolution of F because NF complexes scavenge network-modifying Na from the silicate. Solution of F in Al-rich peralkaline and meta-aluminous glasses and melts results in Al-F bonding and aluminosilicate depolymerization.Temperature (above that of the glass transition) affects the Qⁿ-speciation reaction in the melts, 2Q³ ⇔ Q⁴ + Q², in a manner similar to other alkali silicate and alkali aluminosilicate melts. Dissolved F at the concentration level used in this study does not affect the temperature-dependence of this speciation reaction.  相似文献   

Solubility and solution mechanism of H₂O in alkali silicate melts and glasses at high pressure and temperature   总被引：2，自引：0，他引：2  

Bjorn O. Mysen  George D. Cody 《Geochimica et cosmochimica acta》2004,68(24):5113-5126

The solubility behavior of H₂O in melts in the system Na₂O-SiO₂-H₂O was determined by locating the univariant phase boundary, melt = melt + vapor in the 0.8-2 GPa and 1000°-1300°C pressure and temperature range, respectively. The NBO/Si-range of the melts (0.25-1) was chosen to cover that of most natural magmatic liquids. The H₂O solubility in melts in the system Na₂O-SiO₂-H₂O (X_H2O) ranges between 18 and 45 mol% (O = 1) with (∂X_H2O/∂P)_T∼14-18 mol% H₂O/GPa. The (∂X_H2O/∂P)_T is negatively correlated with NBO/Si (= Na/Si) of the melt. The (∂X_H2O/∂T)_P is in the −0.03 to +0.05 mol% H₂O/°C range, and is negatively correlated with NBO/Si. The [∂X_H2O/∂(NBO/Si)]_P,T is in the −3 to −8 mol% H₂O/(NBO/Si) range. Melts with NBO/Si similar to basaltic liquids (∼0.6-∼1.0) show (∂X_H2O/∂T)_P<0, whereas more polymerized melts exhibit (∂X_H2O/∂T)_P>0. Complete miscibility between hydrous melt and aqueous fluid occurs in the 0.8-2 GPa pressure range for melts with NBO/Si ≤0.5 at T >1100°C. Miscibility occurs at lower pressure the more polymerized the melt.  相似文献   

Fractionation of major elements between coexisting H₂O-saturated silicate melt and silicate-saturated aqueous fluids in aluminosilicate systems at 1-2 GPa     

Bjorn O Mysen  Jessica Shang 《Geochimica et cosmochimica acta》2003,67(20):3925-3936

From experimental data in the systems Na₂O-Al₂O₃-SiO₂-H₂O, K₂O-Al₂O₃-SiO₂-H₂O at 1100°C, and CaO-Al₂O₃-SiO₂-H₂O at 1200°C in the 1-2 GPa pressure range, the solution behavior of the individual oxides in coexisting H₂O-saturated silicate melts and silicate-saturated aqueous fluids appears to be incongruent. Recalculated on an anhydrous basis, in the CaO-Al₂O₃-SiO₂-H₂O system, CaO^fluid/CaO^melt < 1, whereas in the Na₂O-Al₂O₃-SiO₂-H₂O and K₂O-Al₂O₃-SiO₂-H₂O systems, K₂O^fluid/K₂O^melt and Na₂O^fluid/Na₂O^melt both are greater than 1. The aqueous fluids are depleted in alumina relative to silicate melt.In the Na₂O-Al₂O₃-SiO₂-H₂O, K₂O-Al₂O₃-SiO₂-H₂O, and CaO-Al₂O₃-SiO₂-H₂O systems, fluid/melt partition coefficients for the individual oxides range between ∼0.005 and 0.35 depending on oxide, bulk composition and pressure. The alkali partition coefficients are about an order of magnitude higher than that of CaO. Alumina and silica partition coefficient values in the CaO-Al₂O₃-SiO₂-H₂O system are 10-20% of the values for the same oxides in the Na₂O-Al₂O₃-SiO₂-H₂O and K₂O-Al₂O₃-SiO₂-H₂O systems.Positive correlations among individual partition coefficients and oxide concentrations in the aqueous fluids are consistent with complexing in the fluid that involves silicate polymers associated with alkalis and alkaline earths and aluminosilicate complexes where alkalis and alkaline earths may serve to charge-balance Al³⁺, which is, perhaps, in tetrahedral coordination. Alkali aluminosilicate complexes in aqueous fluid appear more stable than Ca-aluminosilicate complexes.  相似文献   

High-temperature X-ray diffraction and Raman spectroscopy of diopside and pseudowollastonite     

Pascal Richet  Bjorn O. Mysen  Jannick Ingrin 《Physics and Chemistry of Minerals》1998,25(6):401-414

Diopside (CaMgSi₂O₆) and pseudowollastonite (CaSiO₃) have been studied by X-ray powder diffraction and Raman spectroscopy up to their respective melting points. In agreement with previous unit-cell parameters determinations below 1100 K, thermal expansion of diopside along the a and c axis is much smaller than along the b axis. For pseudowollastonite, the axis expansivity increases slightly in the order b>a>c. For both minerals, the change in unit-cell angles is very small and there are no anomalous variations of the other unit-cell parameters near the melting point. With increasing temperatures, the main changes observed in the Raman spectra are strong increases of the linewidths for those bands which mainly represent Si−O−Si bending (near 600 cm⁻¹) or involve Ca−O or Mg−O stretching, in the range 270–500 cm⁻¹ for diopside, and 240–450 cm⁻¹ for pseudowollastonite. At temperatures near the onset of calorimetric premelting effects, this extensive band widening results in a broad Raman feature that can no longer be deconvoluted into its individual components. No significant changes affect the Si−O streching modes. For both diopside and pseudowollastonite, premelting appears to be associated with enhanced dynamics of the alkaline-earth elements. This conclusion contrasts markedly with that drawn for sodium metasilicate in which weaker bonding of sodium allows the silicate framework to distort and deform in such a way as to prefigure the silicate entities present in the melt. Received 16 July 1997 / Revised, accepted: 6 March 1998  相似文献   

Melting and premelting of silicates: Raman spectroscopy and X-ray diffraction of Li2SiO3 and Na2SiO3     

Pascal Richet  Bjorn O. Mysen  Denis Andrault 《Physics and Chemistry of Minerals》1996,23(3):157-172

The isostructural lithium (Li₂SiO₃) and sodium (Na₂SiO₃) metasilicates have been investigated from room temperature up to the melting point by single-crystal Raman spectroscopy and energy-dispersive X-ray powder diffraction. The unit-cell parameters and Raman frequencies of Li₂SiO₃ vary regularly with temperature up to the melting point, which is consistent with the lack of premelting effects in calorimetric measurements. In contrast, Na₂SiO₃ undergoes a transition at about 850 K from orthorhombic Cmc 2₁ symmetry, to a lower symmetry (possibly Pmc 2₁), and shows near 1200 K changes in the Raman spectra that correlate well with the premelting effects as determined from calorimetry observations. In both compounds, a high alkali mobility likely sets in several hundreds of degrees below the melting point. Premelting in Na₂SiO₃ is associated with extensive deformation of the silicate chains as evidenced near the melting point by similarities in the Raman spectra of the crystalline and liquid phases.  相似文献   

青藏高原各拉丹冬冰芯记录的季节气温变化     

张拥军  康世昌  秦大河  任贾文  张玉兰  Bjorn GRIGHOLM  Paul MAYEWSKI 《地理学报》2007,62(5):501-509

2005 年10-11 月中美联合考察队在各拉丹冬峰北部果曲冰川平坦的粒雪盆 (33^o34'37.8"N, 91^o10'35.3"E, 5720 m a.s.l.) 钻取了一支冰芯, 通过对该冰芯进行多参数定年, 恢复了青藏高原中部各拉丹冬地区近70 年来降水中δ¹⁸O 的变化历史。根据冰芯中季风期和非季风期δ¹⁸O 值与临近气象台站气温的正相关性, 重建了该地区70 年来的春季和夏季的气温变化。结果表明, 各拉丹冬冰芯中δ¹⁸O 记录的春季和夏季升温趋势非常明显; 根据回归分析, 冰芯中非季风期的δ¹⁸O 每增大(或减小) 1‰相当于春季气温升高(或降低) 1.3 ^oC; 季风 期的δ¹⁸O 每增大(或减小) 1‰相当于夏季气温升高(或降低) 0.4 ^oC; 各拉丹冬冰芯中δ¹⁸O 记录恢复的春季和夏季气温与北半球春季和夏季的气温变化具有一致的趋势, 但各拉丹冬地区的增温幅度比北半球要大, 同时春季的增温幅度也高于夏季。  相似文献   

Spatial variation in hatch date distributions and origin of pelagic juvenile cod in Icelandic waters   总被引：5，自引：3，他引：2  

Marteinsdottir  Gudrun; Gunnarsson  Bjorn; Suthers  Iain M 《ICES Journal of Marine Science》2000,57(4):1182-1195

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Effects of hypoxia on benthic macrofauna and bioturbation in the Estuary and Gulf of St. Lawrence,Canada     

Rénald Belley  Philippe Archambault  Bjorn Sundby  Franck Gilbert  Jean-Marc Gagnon 《Continental Shelf Research》2010

The bottom water in the >300 m deep Lower St. Lawrence Estuary (LSLE) is persistently hypoxic in contrast to the normoxic bottom waters in the Gulf of St. Lawrence (GSL). We photographed the seabed at 11 stations in the Estuary and Gulf of St. Lawrence (EGSL) during the summers 2006 and 2007 and analysed the images to identify bioturbation traces (lebensspuren) and benthic macrofauna. The objective was to identify the environmental variables that influence the density and diversity of benthic macrofauna and bioturbation traces, and the differences that exist among regions with high, medium and low oxygen levels in the bottom water. The bottom water oxygen concentration is the variable that best explains the densities of total-traces as well as surface-traces. However, the density of these traces was higher in hypoxic regions than in well-oxygenated regions. The higher density of traces in the hypoxic region of the LSLE is mainly due to the activities of the surface deposit feeder Ophiura sp., which occurs in large numbers in this region. Possible explanations explored are stress behaviour of the organisms in response to hypoxia and different benthic macrofauna community structures between the hypoxic regions of the LSLE and the normoxic regions of the GSL. In the former, surface deposit feeders and low-oxygen tolerant species dominate over suspension feeders and low-oxygen intolerant species.  相似文献   

Dual speciation of nitrogen in silicate melts at high pressure and temperature: An experimental study     

Mathieu Roskosz  Bjorn O. Mysen  George D. Cody 《Geochimica et cosmochimica acta》2006,70(11):2902-2918

Solubility and speciation of nitrogen in silicate melts have been investigated between 1400 and 1700 °C and at pressures ranging from 10 to 30 kbar for six different binary alkali and alkaline-earth silicate liquids and a Ca-Mg-alumino silicate. Experiments were performed in a piston-cylinder apparatus. The nitrogen source is silver azide, which breaks down to Ag and molecular N₂ below 300 °C. At high pressure and temperature, the nitrogen content may be as high as 0.7 wt% depending on the melt composition, pressure, and temperature. It increases with T, P and the polymerization state of the liquid. Characterization by Raman spectroscopy and ¹⁵N solid state MAS NMR indicates that nitrogen is not only physically dissolved as N₂ within the melt structure like noble gases, but a fraction of nitrogen interacts strongly with the silicate network. The most likely nitrogen-bearing species that can account for Raman and NMR results is nitrosyl group. Solubility data follow an apparent Henry’s law behavior and are in good agreement with previous studies when the nitrosyl content is low. On the other hand, a significant departure from a Henry’s law behavior is observed for highly depolymerized melts, which contain more nitrosyl than polymerized melts. Possible solubility mechanisms are also discussed. Finally, a multi-variant empirical relation is given to predict the relative content of nitrosyl and molecular nitrogen as a function of P, T, and melt composition and structure. This complex speciation of nitrogen in melts under high pressure may have significant implication concerning crystal-melt partitioning of nitrogen as well as for potential elemental and isotopic fractionation of nitrogen in the deep Earth.  相似文献