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961.
Ore-Forming Fluid Characteristics of the Dayingezhuang Gold Deposit, Jiaodong Gold Province, China 总被引:27,自引:0,他引:27
Liqiang Yang Jun Deng Chunying Guo Jing Zhang Shaoqing Jiang Bangfei Gao Qingjie Gong Qingfei Wang 《Resource Geology》2009,59(2):181-193
The Dayingezhuang gold deposit is located in the central part of the Zhaoping Fault Zone, which is one of the most important gold-hosting faults in the Jiaodong gold province of China. Dayingezhuang is a typical large-scale shear zone-hosted disseminated gold deposit with superimposed silver mineralization. Fluid inclusion (FI) petrography and microthermometry, and analysis of oxygen and hydrogen isotopes for fluid inclusions were conducted to determine the characteristics of the ore-forming fluids and the processes of silver mineralization. Microthermometry data of FI indicated that ore-forming fluids are characterized by low salinity and low density. Homogenization pressures of FI are estimated at 20 × 105 –220 × 105 Pa. The change in ore-forming fluids from K2 SO4 type to NaCl type indicates the superposition of two hydrothermal mineralizing events. Ore-forming fluids were dominated by magmatic components in the early mineralization period, and affected by meteoric waters in the late period. Gold may have been transported as Au-S or Au-Cl complexes, whereas silver was transported as Ag-Cl complexes. Early fluid boiling and later fluid mixing are thought to be two of the main factors causing the deposition and superimposing of gold and silver to form the large deposit. 相似文献
962.
In this work, we report diffusion-limited aggregation (DLA)-type Montecarlo computations of a stochastic model of displacement
of a viscous fluid by another that preferentially wets a porous medium, for the case when both fluids are immiscible in the
absence of buoyancy forces. The model has the aim to simulate cooperative invasion processes found in experiments of immiscible
wetting displacement. The model considers the nonlocal effects of the Laplacian pressure field and the capillary forces via hydrodynamic equations in the Darcy regime with a boundary
condition for the pressure at the interface. The boundary condition contains two different types of disorder: the capillary
term, which constitutes an additive random disorder, and a term containing an effective random surface tension, which couples
to a curvature (it constitutes a multiplicative random term that carries nonlocal information of the whole pressure). We generate
different displacement patterns for different setting of the parameters of the model. We analyze these patterns by studying
the scaling properties of the interface that separate the two fluids and calculating the fractal dimension of the interface.
The results show the existence of three distinct regimes of scaling. One regime at the smallest-length scales is due to the
multiplicative random disorder together with the nonlocal coupling; it reveals itself in a roughness exponent α ≈ 0.80. Additionally, we find a DLA-type scaling regime with a roughness exponent α ≈ 0.60 at the largest scales and intermediate scaling regime with α ≈ 0.70 corresponding to invasion percolation with trapping. Each regime has definite scaling ranges that depend on the capillary
number and the relative wetting tendency of the fluids. The behavior of the fractal dimensions of the interfaces of the aggregates
constitutes a further confirmation of the existence of three scaling regimes and the multi-self-affinity of the perimeter
of the interface boundaries. 相似文献
963.
对具有复杂下垫面的小区精细化风环境进行数值模拟是当前城市气象研究的热点,而针对具有复杂地形的山地型城市(如重庆)的研究还比较匮乏。本文采用能显式分辨下垫面陡峭地形和复杂建筑物的计算流体力学(CFD)模式对重庆市渝北区龙湖社区气候态下的精细化风环境进行高分辨率的数值模拟。结果表明,下垫面能显著调节小区内风场的分布,风速大值区主要出现在九龙湖等开阔区域以及与中尺度背景入流方向一致的街道中。在夏季,小区整体风场以东南风为主,而其他3个季节则以偏东风为主。4个季节中,夏季小区内的风速最大,平均风速为0.3 m/s左右,局地能出现大于背景风的风速,可达0.8 m/s;其他3个季节的风速则较弱,区域平均的风速在0.2 m/s左右。不同的建筑物布局对局地风环境的影响也不同:单个孤立高层建筑迎风面的近地面存在明显地绕流,局地风速有所增加,而在背风面则形成尾流区,水平风速较低;在低矮分散的建筑群,建筑物的整体高度不高,区域内流场相对来说比较一致,风速较大,有利于小区的通风;在密集高层建筑群内,由于建筑物群本身的布局比较封闭,加之不同建筑物的环流场存在相互干扰及影响,使得小区近地面风速几乎为零,不利于小区通风和污染物扩散。建筑物的这些影响在城市冠层内尤为明显,高度越高这种影响越弱。 相似文献
964.
965.
目的:分析骨旁脂肪瘤的影像学表现特征,提高对该病的认识及术前影像诊断水平。方法:回顾性分析经病理证实的我院2例骨旁脂肪瘤的临床及影像学表现。结果:2.例骨旁脂肪瘤,男女各1例,分别位于右侧股骨上段、左侧胫骨中下段骨旁软组织内。X线表现为骨旁软组织内的透光肿块;CT、MRI表现为骨旁脂肪密度或脂肪信号、有包膜的椭圆形分叶状肿块,边界清楚;邻近骨皮质形成突向肿瘤内部的珊瑚礁状或树枝状骨性突起。结论:骨旁椭圆形脂肪性肿块,伴有骨皮质突向肿块内的珊瑚礁状、树枝状骨性突起为骨旁脂肪瘤的影像学特征,具有重要的诊断价值。 相似文献
966.
目的:探讨眼眶内血管外皮细胞瘤影像学表现,提高对本病影像学特征的认识。方法:报道1例经手术、病理证实的右侧眼眶内血管外皮细胞瘤,对其CT平扫、MRI平扫及强化表现进行分析。结果:肿瘤CT表现为右侧眶内上方球后团块状软组织密度影。MRI表现为右侧眼眶内上方球后团块状T1WI等及稍低信号,T2WI稍高信号影,动态增强扫描,动脉期及实质期有明显强化。结论:运用多种影像学检查方法,可提高对眼眶内血管外皮细胞瘤的认识,做出准确的诊断。 相似文献
967.
地震尺度下碳酸盐岩储层的岩石物理建模方法(英文) 总被引:3,自引:3,他引:0
碳酸盐岩油藏的强非均质性以及孔隙结构的复杂性,使得作为连接油藏参数与地震参数重要桥梁的岩石物理模型,以及作为油藏预测和定量表征最有效工具的流体替换成为岩石物理建模的难点与重点。在碳酸盐岩储层复杂孔隙结构与地震尺度下碳酸盐岩储层非均质性分析基础上,研究采用岩石网格化方法,将地震尺度下非均质碳酸盐岩储层岩石划分为具有独立岩石参数的均质岩石子体,根据岩石孔隙成因与结构特征采用不同岩石物理模型分步计算岩石子块干岩石弹性模量,并根据不同孔隙连通性进行流体替换,计算饱和不同流体岩石弹性模量。基于计算的岩石子块弹性模量,采用Hashin-Shtrikman-Walpole弹性边界计算理论方法实现地震尺度下碳酸盐岩储层弹性参数计算。通过对含有不同类型孔隙组合碳酸盐岩储层模型的弹性模量进行计算与分析,明确不同孔隙对岩石弹性参数的影响特征,模拟分析结果与实际资料认识一致。 相似文献
968.
The technique of the wavefield polarization is applied to ambient vibrations recorded in the Mefite d’Ansanto area, an important non-volcanic natural emission of low temperature CO2 enriched gases. Twenty-five measurements were performed in the study area, eleven near the emission site and the other fourteen in different sites within an area of 5 km. Polarization is assessed both in the frequency and time domain through the individual-station horizontal-to-vertical spectral ratio and covariance-matrix analysis, respectively. We find a significant tendency of ground motion in the gas emission area to be polarized in the horizontal plane, with a N115° predominant trend. This polarization tends to disappear while moving far from the site. According to previous papers in other study areas, such a directional effect is likely caused by fault-induced fractures and tends to be orthogonal to the fracture strike. The predominant NW–SE regional faulting does not fit the N115° polarization direction. To explain observations, we propose an interpretation in terms of a NE–SW oriented, local transfer fault as inferred from the lineament analysis. The intersection of the damage zone of this fault with the regional NW–SE normal fault system could easily be the responsible for the gas emissions since it favors a locally increased crustal weakness. 相似文献
969.
This study developed a finite element method with the effect of soil–fluid–structure interaction to calculate bridge natural frequencies. The finite element model includes bridge girders, piers, foundations, soil, and water. The effective mass above the soil surface was then used to find the first natural frequency in each direction. A field experiment was performed to validate that the natural frequencies calculated using the proposed finite element method had acceptable accuracy. The calculated natural frequencies with the fluid–structure interaction effect are always smaller than those without this effect. However, the frequency change due to the fluid effect is not obvious, so using the soil–structure interaction model is accurate enough in the bridge natural frequency analysis. The trend of the frequency decreases with the increase of the scour depth, but the curve is not smooth because of non-uniform foundation sections and layered soils. However, when the scour depth is such that pile cap is exposed, the changes in natural frequency with the scour depth are more obvious, and this is useful for measurement of the depth using bridge natural frequencies. 相似文献
970.
Jürgen Reichert 《地球物理与天体物理流体动力学》2013,107(3-4):213-226
Abstract A spherical mean-field dynamo model is considered in which both the mean motion and the mean electro-motive force due to fluctuating motions show some spherical symmetry. It is shown that under some reasonable assumptions the magnetic field is bound to decay to zero. 相似文献