The petrogenesis of the Edough amphibolites, Annaba, NE Algeria: two unrelated basic magmas and the lherzolite-harzburgite residue of a possible magma source

Summary The conditions of metamorphism and petrogenesis of Kef Lakhal amphibolites and associated amphibolite and olivine-rich lenses are discussed. The Kef Lakhal amphibolites contain plagioclase ranging from An₈₅ and An₁₂ and Ca-poor normally zoned garnet (< 9 wt% CaO) and were last metamorphosed to upper amphibolite facies. The amphibolite lenses invariably contain calcic plagioclase (An_97-78) and Ca-rich (up to 14 wt% CaO) doubly zoned garnets. Based on garnet zoning, it is found that the lenses experienced the three metamorphisms recorded elsewhere in the massif whereas the main amphibolites suffered only the last two metamorphisms, the last of which reached conditions of about T= 700 ± 80 °C and P= 8–10 Kb. This agrees with two unrelated igneous suites and is supported by the chemistry of the rocks and quantitative modelling. The Kef Lakhal amphibolites were formed by olivine-dominated fractional crystallisation processes from melts derived by partial melting of a homogeneous source and preserve MORB affinities. The amphibolite lenses were also evolved by fractional processes dominated by olivine but from a less homogeneous source and have island arc characteristics. The associated olivine-rich lenses are lherzolite-harzburgite mantle residua which suffered up to 35% melting. Bearing in mind the lack of isotopic and structural information, the data presented in this study indicate that fractional crystallisation of liquids produced through non model melting of these residua does not reproduce the composition of either of the amphibolites. Fractionation of melts similar to those derived from the Ronda peridotites yield compositions similar to the Edough amphibolites.

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Die Entstehung der Edough Amphibolite, Annaba, NE Algerien; zwei basische Magmen und das Lherzolit-Harzburgit-Residuum einer möglichen Magmenquelle

Zusammenfassung Die Metamorphosebedingungen und die Petrogenese der Amphibolite von Kef Lakhal und der mit ihnen assoziierten Amphibolit- und Olivin-reichen Linsen werden diskutiert. Die Kef Lakhal-Amphibolite enthalten Plagioklas, dessen Zusammensetzung von An₈₅ bis An₁₂ schwankt, und Ca-armen, normal zonierten Granat (< 9 Gew % CaO). Sie wurden unter Bedingungen der obenen Amphibolitfacies metamorphosiert. Die Amphibolit-Linsen führen stets Ca-reichen (An_97-78) Plagioklas und doppelt zonierten Granat (bis zu 14 Gew % Ca0). Die Granatzonierung läßt erkennen, daß die Linsen drei Metamorphose-Phasen, die auch sonst in dem Massiv nachgewiesen wurden, ausgesetzt waren. Die letzte Phase erreichte Bedingungen von ungefähr T = 700 ± 80 °C und P = 8–10 kb. Dies weist auf zwei, miteinander nicht verwandte magmatische Gesteinsabfolgen hin; dieses Konzept wird durch die chemische Zusammensetzung und durch quantitative Modellierung unterstützt. Die Kef Lakhal-Amphibolite wurden durch Olivin-dominierte fraktionierte Kristallisation aus Schmelzen gebildet, die durch partielle Aufschmelzung einer homogenen Quelle entstanden sind und MORB-Charakteristik haben. Die Amphibolit-Linsen gehen auch auf Olivin-dominierte Fraktionierungs-Prozesse zurück, hatten aber eine weniger homogene Quelle und zeigen Inselbogen-Charakteristika. Die assoziierten Olivin-reichen Linsen sind Lherzolit-Harzburgit Mantel-Residua, die von bis zu 35% Aufschmelzung betroffen waren. Obwohl zu berücksichtigen ist, daß isotopengeologische und strukturelle Daten fehlen, zeigen die Ergebnisse, daß fraktionierte Kristallisation von Schmelzen, die durch Non-Modell Aufschmelzung der Residua entstanden sind, nicht die Zusammensetzung der Amphibolite reproduzieren können. Hingegen liefert Fraktionierung von Schmelzen, die denen des RondaPeridotits ähnlich sind, Zusammensetzungen, die denen der Edough Amphibolite ähnlich sind.

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With 11 Figures     

Photoelectric photometry of solar granulation in several regions of the continuum

Photospheric brightness fluctuations were recorded photoelectrically across a part of the sun near the center of the disk, and simultaneously for two regions of the continuous spectrum chosen at various wavelengths between λ3500 Å and λ5500 Å. The auto-correlation functions and spatial power spectra were derived for each recording, and the cross-correlation functions, spatial relative phase and coherence spectra were computed for each pair of recordings. The main results are:

1. (1)
   The cross-correlation between any two recordings obtained for various regions of the continuous spectrum, is a function of the wavelength distance Δλ between these regions. The decrease of the cross-correlation with increasing Δλ is due to the fact that separate photometric inhomogeneities radiate in limited spectral ranges.     

Dynamic interaction of bridge–train system under non‐uniform seismic ground motion

The probability that an earthquake occurs when a train is running over a bridge in earthquake‐prone regions is much higher than before, for high‐speed railway lines are rapidly developed to connect major cities worldwide. This paper presents a finite element method‐based framework for dynamic analysis of coupled bridge–train systems under non‐uniform seismic ground motion, in which rail–wheel interactions and possible separations between wheels and rails are taken into consideration. The governing equations of motion of the coupled bridge–train system are established in an absolute coordinate system. Without considering the decomposition of seismic responses into pseudo‐static and inertia‐dynamic components, the equations of motion of the coupled system are formed in terms of displacement seismic ground motions. The mode superposition method is applied to the bridge structure to make the problem manageable while the Newmark‐β method with an iterative computation scheme is used to find the best solution for the problem concerned. Eight high‐speed trains running over a multi‐span steel truss‐arch bridge subject to earthquakes are taken as a case study. The results from the case study demonstrate that the spatial variation of seismic ground motion affects dynamic responses of the bridge–train system. The ignorance of pseudo‐static component when using acceleration seismic ground motions as input may underestimate seismic responses of the bridge–train system. The probability of separation between wheels and rails becomes higher with increasing train speed. Copyright © 2011 John Wiley & Sons, Ltd.     

An examination of the validation of a model of the hydro/thermo/mechanical behaviour of engineered clay barriers

This paper focuses attention on the development of a numerical model of the hydro/thermo/mechanical behaviour of unsaturated clay and its consequent verification and validation. The work presented describes on-going collaboration between the Cardiff School of Engineering and Atomic Energy of Canada. The model development, which was carried out at Cardiff, can be described as being based on a mechanistic approach to coupled heat, moisture and air flow. This is then linked to a deformation analysis of the material within a ‘consolidation’ type of model. The whole is solved via the finite element method to yield a computer software code named COMPASS (COde for Modelling PArtly Saturated Soil). Some aspects of verification and validation of the model have been addressed in-house. However, the purpose of current AECL work is to provide an independent, rigorous, structured programme of validation and the paper will also explore the further validation of COMPASS within this context. © 1998 by John Wiley & Sons, Ltd.     

Persistence of mantle lithospheric Re–Os signature during asthenospherization of the subcontinental lithospheric mantle: insights from in situ isotopic analysis of sulfides from the Ronda peridotite (Southern Spain)

The western part of the Ronda peridotite massif (Southern Spain) consists mainly of highly foliated spinel-peridotite tectonites and undeformed granular peridotites that are separated by a recrystallization front. The spinel tectonites are interpreted as volumes of ancient subcontinental lithospheric mantle and the granular peridotites as a portion of subcontinental lithospheric mantle that underwent partial melting and pervasive percolation of basaltic melts induced by Cenozoic asthenospheric upwelling. The Re–Os isotopic signature of sulfides from the granular domain and the recrystallization front mostly coincides with that of grains in the spinel tectonites. This indicates that the Re–Os radiometric system in sulfides was highly resistant to partial melting and percolation of melts induced by Cenozoic lithospheric thermal erosion. The Re–Os isotopic systematics of sulfides in the Ronda peridotites thus mostly conserve the geochemical memory of ancient magmatic events in the subcontinental lithospheric mantle. Os model ages record two Proterozoic melting episodes at ~1.6 to 1.8 and 1.2–1.4 Ga, respectively. The emplacement of the massif into the subcontinental lithospheric mantle probably coincided with one of these depletion events. A later metasomatic episode caused the precipitation of a new generation of sulfides at ~0.7 to 0.9 Ga. These Proterozoic Os model ages are consistent with results obtained for several mantle suites in Central/Western Europe and Northern Africa as well as with the Nd model ages of the continental crust of these regions. This suggests that the events recorded in mantle sulfides of the Ronda peridotites reflect different stages of generation of the continental crust in the ancient Gondwana supercontinent.     

面向复杂山地的机载LiDAR与无人机影像融合应用

本文针对LiDAR点云与无人机影像数据特征的优缺点,利用LiDAR点云与无人机DOM影像融合,将影像数据光谱信息赋给LiDAR点云数据,使其不仅具备精准的空问结构信息,还能得到清晰的纹理信息.为验证融合数据应用的可行性与数据提取的准确性,对融合前后的点云数据进行地面点提取与DEM构建.试验表明:将无人机影像的光谱信息赋...     

西藏冈底斯驱龙斑岩型铜钼-矽卡岩型铜矿成矿体系:辉钼矿Re-Os同位素年代学证据

在西藏冈底斯驱龙斑岩型铜钼矿床南部2 km和东南4 km处分别发育知不拉和浪母家果矽卡岩型铜矿床,它们与驱龙斑岩矿床空间上相邻。其中,浪母家果矽卡岩型矿床中辉钼矿Re-Os等时线年龄为(17.11±0.55)Ma,表明其形成时间与驱龙和知不拉相近。综合冈底斯成矿带区域成矿作用和典型矿床的最新研究成果认为,驱龙斑岩型铜钼矿床-知不拉矽卡岩型铜矿-浪母家果矽卡岩型铜矿系同一期岩浆热液成矿作用的产物,构成一个完整的斑岩-矽卡岩型成矿体系。因此,区域找矿时,应注意在斑岩型铜矿外围寻找高品位矽卡岩型矿床;同时,在具有矽卡岩型矿化的勘查区内应注意寻找深部可能存在的斑岩型铜钼矿床。     

扬子东南大陆边缘晚前寒武纪古海洋演化的稀土元素记录

本文采用中子活化方法分析了晚震旦～早寒武纪１９件样品的稀土元素组成,发现硅质岩石ＲＥＥ配分形式有着复杂的变化,初步可以划分为五种类型,包括“台地型”、“红海型”、“海水型”及两种特殊的配分形式。剖面上Ｃｅ异常由小到大的演变反映了古海洋底层水由缺氧环境向氧化条件的逐渐转化。正Ｅｕ异常的出现代表了热水沉积事件的存在。     

天然水体中酚的降解动力学

本文报道了天然水体中低浓度酚的降解动力学;计算了它的降解速率常数、降解活化能等。降解半表期是t_(1/2)=1.5d~(-1)(10℃),t_(1/2)=O.74d~(-1)(30℃)。低浓度酚的降解动力学跟天然水体中酚的降解情况比较接近。本文的结果对环境评价、蓄水库工程设计等很有参考价值。     

Experimental determination of argon solubility in silicate melts: An assessment of the effects of liquid composition and temperature

The argon solubility of 38 liquids in the system Na₂O-CaO-MgO-Al₂O₃-SiO₂ (NCMAS) has been determined at 1873 K and 1 bar, the argon concentration of presaturated glasses being measured using a static mass spectrometer. For compositions in the subsystem diopside (CaMgSi₂O₆), nepheline (NaAlSiO₄), albite (NaAlSi₃O₈), anorthite (CaAl₂Si₂O₈), argon solubility is generally a linear function of the relative proportion of each end member, solubility being lowest in diopside melt (1.53 10⁻⁵ cm³ STP · g⁻¹ · bar⁻¹) and highest in albite melt (2.88 10⁻⁴ cm³ STP · g⁻¹ · bar⁻¹). For the tectosilicate joins studied (SiO₂-Na₂Al₂O₄, SiO₂-CaAl₂O₄, SiO₂-MgAl₂O₄) solubility decreases with decreasing silica content in all cases, being highest for Na-bearing liquids and lowest for Mg-bearing liquids at constant molar silica content. Where comparison is possible our results are in good agreement with data from the literature. When our data are considered in isolation we find that argon solubility shows an excellent correlation with calculated ionic porosity. The covariation of argon solubility and liquid density is also reasonable, that with molar volume less convincing and that with polymerization state (as defined by the ratio of the number of nonbridging oxygens and tetrahedral network forming cations; NBO/T) nonexistent. However, when our data are combined with those from the literature no well constrained correlation between argon solubility and ionic porosity is apparent. Based upon this observation and consideration of the temperature dependence of noble gas solubility it is concluded that ionic porosity is not a universally applicable parameter which may be used to predict noble gas solubility as a function of composition, temperature and pressure. Two new models for calculating argon solubility are proposed, both employing the notion of partial molar argon solubilities. The first uses oxide components, for which partial molar argon solubility is directly proportional to partial molar ionic porosity calculated at 1873 K, irrespective of the temperature of experimental equilibration. The second model, which offers the best fit to the available data, employs tetrahedral units rather than oxides as the proposed melt components. This latter model successfully accounts for reported argon solubilities in simple Al-free systems, in simple Al-bearing systems and in natural liquids. This is interpreted to infer that argon is incorporated in large sites in the liquid structure (such as the space within rings of n-tetrahedra) although further work is required to understand the quantitative links between melt structure and noble gas solubility.