Compositional Geometry and Mass Conservation   总被引：1，自引：0，他引：1  

Robert F. Shurtz 《Mathematical Geology》2003,35(8):927-937

A geometrical structure is imposed on compositional data by physical and chemical laws, principally mass conservation. Therefore, statistical or mathematical investigation of possible relations between data values and such laws must be consistent with this structure. This demands that geometrical concepts, such as points that specify both mass and composition in linear space, and lines in projective space that specify composition only, be clearly defined and consistent with mass conservation. Mass thus becomes the norm in composition space in place of the Euclidean norm of ordinary space. Coordinate transformations inconsistent with this geometry are accordingly unnatural and misleading. They are also unnecessary because correlation arising from the constant mass presents no unusual difficulty in the analysis of the underlying quadratic form.  相似文献   

Effect of the chemical composition of the crust on the metamorphic evolution of orogenic wedges   总被引：4，自引：0，他引：4  

B. Goffé  R. Bousquet  P. Henry  X. Le Pichon 《Journal of Metamorphic Geology》2003,21(2):123-141

Petrological data provide a good record of the thermal structure of deeply eroded orogens, and, in principle, might be used to relate the metamorphic structure of an orogen to its deformational history. In this paper, we present two‐dimensional thermal modelling of various subduction models taking into account varying wedge geometry as well as variation of density and topography with metamorphic reactions. The models clearly show that rock type accreted in the wedge has important effects on the thermal regime of orogenic wedges. The thermal regime is dominated by radiogenic heat production. Material having high radioactive heat production, like the granodioritic upper crust, produces high temperature metamorphism (amphibolitic conditions). Material with low radioactive heat production results in low temperature metamorphism of greenschist or blueschist types depending on the thickness of the wedge. Application of this model to seemingly unrelated areas of the Central Alps (Lepontine Dome, Grisons) and Eastern Alps (Tauern Window) explains the coexistence and succession of distinct Barrovian and blueschist facies metamorphic conditions as the result of a single, continuous tectonic process in which the main difference is the composition of the incoming material in the orogenic wedge. Accretion of the European upper continental crust in the Lepontine and Tauern Domes produces Barrovian type metamorphism while accretion of oceanic sediments results in blueschist facies metamorphism in the Valaisan domain.  相似文献   

差异性风化岩石作为桩基持力层设计应注意的若干问题          下载免费PDF全文

隆威  李爱民  杨先斌 《探矿工程》2003,30(5):3-5

基岩中存在软弱夹层为岩石的差异性风化的主要特征。在不均匀性地基土上选用该类地层作为钻孔灌注桩持力层时，它的存在将对桩长、单桩承载力、桩体沉降等带来不同程度的影响。以黄石电厂为例，指出在选用差异性风化岩石作为桩基持力层时应注意的若干问题。  相似文献   

Detailed study on the anisotropy of magnetic susceptibility of arctic marine sediments   总被引：3，自引：0，他引：3  

Norbert R. Nowaczyk 《Geophysical Journal International》2003,152(2):302-317

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Rock-magnetic properties of multicomponent natural remanent magnetization in alluvial red beds (NE Spain)   总被引：1，自引：0，他引：1  

Pauline P. Kruiver  Cor G. Langereis  Mark J. Dekkers  Wout Krijgsman 《Geophysical Journal International》2003,153(2):317-332

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A detailed palaeomagnetic study of the oldest (≈15 Myr) lava sequences in Northwest Iceland     

Leo Kristjansson  Björn S. Hardarson  Haraldur Audunsson 《Geophysical Journal International》2003,155(3):991-1005

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Parameters affecting maximum fluid transport in large aperture fractures   总被引：1，自引：0，他引：1  

Maria Ines Dragila  Noam Weisbrod   《Advances in water resources》2003,26(12):1219-1228

We present results of laboratory experiments to study the behavior of liquids moving in unsaturated wide-aperture fractures. A 5-mm-thick glass plate cut with a 1.7-mm aperture was used as a fractured rock analog to study behavior of film and capillary droplet flow modes. Flow rates ranged between 0.6 and 6.0 ml/min. Variability in the ambient barometric pressure, resulting from weather conditions, seemed to play a role in the natural selection of flow mode. For droplet mode, constant input conditions resulted in highly variable transport properties within the fracture. The advancing meniscus exhibited a dynamic contact angle that was a function of the droplet speed and much larger than the static contact angle. Flow rate was reduced due to the larger contact angle. Analytical expressions for droplet velocity and flow capacity are presented as a function of the dynamic rather than the static contact angle.  相似文献   

A comparison of the evolution of diamondiferous quartz-rich rocks from the Saxonian Erzgebirge and the Kokchetav Massif: are so-called diamondiferous gneisses magmatic rocks?     

Hans-Joachim Massonne 《Earth and Planetary Science Letters》2003,216(3):347-364

The petrography and chemical composition of minerals of quartz-rich diamondiferous rocks from the Kokchetav Massif, especially the zonation of garnet, were studied and compared with diamondiferous quartzofeldspathic rocks from the Saxonian Erzgebirge. Many compositional and textural features were found to be similar. For instance, microdiamonds are enclosed systematically in a specific intermediate growth zone of garnet in these rocks. On the basis of experimental data, a magmatic scenario was constructed to check if the quartz-rich diamondiferous rocks are of magmatic origin. By this, the P-T paths, derived here for the Kokchetav rocks, and the textural observations it is concluded that the minerals of the diamondiferous rocks have crystallized from silicate melts. These melts originated by anatexis of deeply submerged metasediments (Erzgebirge: at T as high as 1200°C, Kokchetav Massif: at 50-100°C lower T) and ascended from at least 200 km depth. Relics of the pre-anatectic evolution are still present, for instance, as garnet cores. After ascent and emplacement of the magma in deep portions of thickened continental crust (Kokchetav Massif: 45-50 km close to 800°C, Erzgebirge: 55-60 km at 30-50°C lower T) considerable quantities of (white and/or dark) micas formed by peritectic reactions from melt. For instance, garnets could be resorbed at this stage and biotite grew instead. After the magmatic stage, retrogression took place much stronger in the Kokchetav Massif. This was accompanied by deformation transforming broadly the magmatic texture of quartz-rich diamondiferous rocks from the Kokchetav Massif to a gneissic texture.  相似文献   

Fluid mixing as the mechanism of formation of the Dajing Cu-Sn-Ag-Pb-Zn ore deposit,Inner Mongolia ——Fluid inclusion and stable isotope evidence   总被引：2，自引：0，他引：2  

刘伟  李新俊  谭骏 《中国科学D辑(英文版)》2003,46(7)

Since the 1990s, interest in the magmatic fluids and their relation to mineralization has been re-aroused[1—6]. Studies on stable isotopes of low-sulfidation deposits commonly show the predominance of meteoric water[7]. Paradoxically, the evidence for me…  相似文献   

Optimum multiple tuned mass dampers for structures under the ground acceleration based on the uniform distribution of system parameters     

Chunxiang Li  Yanxia Liu 《地震工程与结构动力学》2003,32(5):671-690

The five MTMD models, with natural frequencies being uniformly distributed around their mean frequency, have been recently presented by the first author. They are shown to have the near‐zero optimum average damping ratio (more precisely, for a given mass ratio there is an upper limit on the total number, beyond which the near‐zero optimum average damping ratio occurs). In this paper, the eight new MTMD models (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1～US‐MTMD3, UD‐MTMD1 and UD‐MTMD2), with the system parameters (mass, stiffness and damping coefficient) being, respectively, uniformly distributed around their average values, have been, for the first time here, proposed to seek for the MTMD models without the near‐zero optimum average damping ratio. The structure is represented by the mode‐generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the eight MTMD models (i.e. through the implementation of Min.Min.Max.DMF), the optimum parameters and values of Min.Min.Max.DMF for these eight MTMD models are investigated to evaluate and compare their control performance. The optimum parameters include the optimum mass spacing, stiffness spacing, damping coefficient spacing, frequency spacing, average damping ratio and tuning frequency ratio. The six MTMD models without the near‐zero optimum average damping ratio (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1, US‐MTMD2 and UD‐MTMD2) are found through extensive numerical analyses. Likewise, the optimum UM‐MTMD3 offers the higher effectiveness and robustness and requires the smaller damping with respect to the rest of the MTMD models in reducing the responses of structures subjected to earthquakes. Additionally, it is interesting to note, by comparing the optimum UM‐MTMD3 with the optimum MTMD‐1 recently investigated by the first author, that the effectiveness and robustness for the optimum UM‐MTMD3 is almost identical to that for the optimum MTMD‐1 (without inclusion of the optimum MTMD‐1 with the near‐zero optimum average damping ratio). Recognizing these performance benefits, it is preferable to employ the optimum UM‐MTMD3 or the optimum MTMD‐1 without the near‐zero optimum average damping ratio, when installing the MTMD for the suppression of undesirable oscillations of structures under earthquakes. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献