Storage conditions of Bezymianny Volcano parental magmas: results of phase equilibria experiments at 100 and 700 MPa   总被引：1，自引：1，他引：0  

Renat R. Almeev  Francois Holtz  Alexei A. Ariskin  Jun-Ichi Kimura 《Contributions to Mineralogy and Petrology》2013,166(5):1389-1414

The crystallization sequence of a basaltic andesite from Bezymianny Volcano, Kamchatka, Russia, was simulated experimentally at 100 and 700 MPa at various water activities (aH₂O) to investigate the compositional evolution of residual liquids. The temperature (T) range of the experiments was 950–1,150 °C, aH₂O varied between 0.1 and 1, and the log of oxygen fugacity (fO₂) varied between quartz–fayalite–magnetite (QFM) and QFM + 4.1. The comparison of the experimentally produced liquids and natural samples was used to constrain the pressure (P)–T–aH₂O–fO₂ conditions of the Bezymianny parental magma in the intra-crustal magma plumbing system. The phase equilibria constraints suggest that parental basaltic andesite magmas should contain ~2–2.5 wt% H₂O; they can be stored in upper crustal levels at a depth of ~15 km, and at this depth they start to crystallize at ~1,110 °C. The subsequent chemical evolution of this parental magma most probably proceeded as decompressional crystallization occurred during magma ascent. The final depths at which crystallization products accumulated prior to eruption are not well constrained experimentally but should not be shallower than 3–4 km because amphibole is present in natural magmas (>150 MPa). Thus, the major volume of Bezymianny andesites was produced in a mid-crustal magma chamber as a result of decompressional crystallization of parental basaltic andesites, accompanied by mixing with silicic products from the earlier stages of magma fractionation. In addition, these processes are complicated by the release of volatiles due to magma degassing, which occurs at various stages during magma ascent.  相似文献   

Observations of Hipparcos short-period red giant stars     

Chris Koen  Dave Laney  Francois van Wyk 《Monthly notices of the Royal Astronomical Society》2002,335(1):223-232

Optical UBV(RI) _C and infrared JHK photometry is presented of a small sample of giant stars with short periods in the Hipparcos catalogue. Observations were limited, but were sufficient to rule out most of the Hipparcos periods. Radial velocity measurement were also made for a few stars, over six successive nights. Low-level variability was detected in a few stars. It is argued that in most cases the brightness variations are primarily due to temperature changes. These findings show that high-overtone pulsations in M giant stars occur, if at all, in a far more limited number of stars than proposed in the authors' previous discussion of the Hipparcos data alone.  相似文献   

星系金属丰度的研究进展(Ⅰ):定标方法     

梁艳春  HAMMER Francois  邓李才  赵刚 《天文学进展》2006,24(4):335-361

金属丰度是表征星系特征的重要参量,对于理解星系的形成与演化具有重要意义。随着观测设备的不断完善与发展,已经获得越来越多的星系(包括近邻星系、中等红移及高红移星系)金属丰度的观测资料。在光致电离模型方面也取得了很大进展．这些对于理解星系中金属及恒星成分的累积历史有非常重要的作用。有多种方法可以用来估计星系的金属丰度(主要是星际介质中气相的O丰度),介绍和评述了估计星系的O丰度的多种方法,包括电子温度的方法、R23方法以及其他一些“强线”比值的方法,并给出了相应的解析公式,同时介绍了电离星云的物理本质及由光致电离模型估计星系金属丰度的方法,还给出了估计星系的C和N元素丰度的方法。  相似文献   

Image recovery of moving objects from quantum limited data     

Sébastien Morel  Laurent Koechlin 《Experimental Astronomy》1997,7(2):117-127

We propose a method for faint object imaging in the case of displacementin the field of the detector during data acquisition. This method is adaptedto photon noise and unknown but linear displacements. We show that it canprovide some improvement also in the case of an arbitrarily non-linearmotion. The algorithms proposed involve a space-time three-dimensionalFourier transform and can take advantage of the sparse matrix nature ofphoton counting images.  相似文献   

The 2011 Draconids: The First European Airborne Meteor Observation Campaign     

Jeremie Vaubaillon  Pavel Koten  Anastasios Margonis  Juraj Toth  Regina Rudawska  Maria Gritsevich  Joe Zender  Jonathan McAuliffe  Pierre-Dominique Pautet  Peter Jenniskens  Detlef Koschny  Francois Colas  Sylvain Bouley  Lucie Maquet  Arnaud Leroy  Jean Lecacheux  Jiri Borovicka  Junichi Watanabe  Jürgen Oberst 《Earth, Moon, and Planets》2015,114(3-4):137-157

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2D modelling of a dry joint masonry wall retaining a pulverulent backfill     

A. S. Colas  J. C. Morel  D. Garnier 《国际地质力学数值与分析法杂志》2010,34(12):1237-1249

This work focuses on an analysis of dry joint retaining structures based on yield design theory: the stability of the masonry is assessed using rigid block and shear failure mechanisms in the wall and its backfill. An application of this simulation on 2D scale‐down brick and wood models is then addressed, showing close agreement between theoretical predictions and experimental results. Further development on this work, including application of this theory on dry‐stone retaining walls, is discussed as a conclusion. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Isotope Dilution Determinations of Lu,Hf, Zr,Ta and W,and Hf Isotope Compositions of NIST SRM 610 and 612 Glass Wafers   总被引：1，自引：0，他引：1  

Oliver Nebel  Melanie L.A. Morel  Pieter Z. Vroon 《Geostandards and Geoanalytical Research》2009,33(4):487-499

Isotope dilution determinations of Lu, Hf, Zr, Ta and W are reported for nine test portions (five for W) of NIST SRM 610 and 612 glass wafers. Additionally, all test portions were analysed for their Hf isotope compositions. In general, high field strength elemental (HFSE) distributions in NIST SRM 610 and 612 were reproducible to ～± 1%, except for Zr (± 5%) in NIST SRM 612, and absolute reported concentrations agreed with previously published values, but with higher precision. The slightly worse reproducibility of Zr in NIST SRM 612 compared to other HFSE is interpreted to result from analytical scatter, rather than sample inhomogeneity. The analyses demonstrated elemental homogeneity for both glass wafers for samples of 1–2 mg with respect to the precision of the method, i.e., ± 1% or better. Average Hf isotope compositions for both glass wafers agreed within uncertainty and the weighted average of all determinations yielded a mean ¹⁷⁶Hf/¹⁷⁷Hf ratio of 0.282111 ± 0.000009 (95% confidence level). However, although mean values for NIST SRM 610 and 612 agreed within analytical limits, NIST SRM 610 test portions showed a tendency of systematically elevated isotope composition of ～ 0.5 _?Hf units when compared to NIST SRM 612, which may indicate a slightly more radiogenic Hf isotope composition of NIST SRM 610. The results of this study suggest that NIST SRM 610 and 612 are valuable calibrators for HFSE in situ analyses within the given uncertainties.  相似文献   

确定数值预报模式中扩散系数的一个客观方法     

朴景辰  邹晓蕾 《南京气象学院学报》2009,32(3):339-350

当数值预报模式的分辨率得到提高时,模式中扩散系数的数值大小必然随之改变。通常情况下,一方面,扩散系数的数值应足够大（即有下限值）,以便过滤掉模式中不想要的小尺度噪音;另一方面,扩散系数的数值应尽量小（即有上限值）,以免出现计算不稳定。本文提出一种确定高分辨率模式中扩散系数数值大小的客观方法,即＂双试验＂（twin experiment）同化方法（初始低分辨率模式的预报结果作为＂观测资料＂,新的高分辨率模式作为同化模式）,从而通过伴随变分同化方法来确定控制变量（即扩散系数）的数值大小。本文采用一维浅水模式测试和描述上述试验方案。通过低分辨率模式预报结果和高分辨率模式预报结果的比较（高、低分辨率模式预报结果的比较在低分辨率模式格点上进行）,采用最小二乘法可客观求得适用于高分辨率模式的扩散系数的＂最优＂值。数值试验结果表明,采用这种方法得到的高分辨率模式的扩散系数,不仅能过滤掉模式中不想要的小尺度噪音,而且能够避免出现计算不稳定。研究还指出,当扩散系数的大小略微超过其上限值时（这种情况在极小化迭代中有可能会出现）,计算不稳定的出现将使目标函数的数值迅速增加,并导致极小化程序收敛的失败;时间步长的减小（约20%）可以显著地改进目标函数的条件数,从而可避免极小化程序收敛的失败。  相似文献   

On the driving force of cation exchange in clays: Insights from combined microcalorimetry experiments and molecular simulation     

Benjamin Rotenberg  Jean-Pierre Morel  Pierre Turq  Nicole Morel-Desrosiers 《Geochimica et cosmochimica acta》2009,73(14):4034-20527

We study the origin of the ionic exchange enthalpy in montmorillonite clays using microcalorimetry measurements and molecular simulation. We first determine the standard reaction enthalpy for well-defined interlayer water contents. We then show by a detailed analysis based on thermodynamic cycles that replacing Na⁺ ions by Cs⁺ in the interlayer of montmorillonite clays is an endothermic process, and that the overall exchange is exothermic only because it is dominated by the exothermic replacement of Cs⁺ by Na⁺ in the aqueous phase. This conclusion from ionic exchange enthalpies supports the one of a recent study of the ionic exchange free energy by Teppen and Miller [Teppen B. J. and Miller D. M. (2006) Hydration energy determines isovalent cation exchange selectivity by clay minerals. Soil Sci. Soc. Am. J.70(1), 31-40] and contradicts long-held views on the role of ion-clay interactions in determining the ionic exchange thermodynamics. This calls for a paradigm shift for the origin of this exchange: The driving force is the “hydrophobicity” of Cs⁺ compared to Na⁺ and not its affinity for clay surfaces.  相似文献   

Diagenesis and fluid system evolution in the Northern Oman Mountains,United Arab Emirates     

Liesbeth Breesch  Rudy Swennen  Benoit Vincent  Francois Roure  Richard Ellison 《Journal of Geochemical Exploration》2009

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