时空概念中的椭球改正     

夏哲仁 《测绘学报》1991,20(3):190-200

  相似文献   

Predicting ground-motion variations at the Turkey-flat test site,California     

J. Zahradník  J. Jech  V. Barták 《Pure and Applied Geophysics》1991,137(1-2):63-84

Results of a single group participating in an international experiment are analyzed. The experiment served to verify computational predictions of the ground-motion variations due to near-surface geological effects at a site established for that purpose by the California Department of Conservation. Based on an acceleration record at a rock location, and geotechnical model of medium, records at the other locations of a nearby sedimentary deposit were predicted. A 2-D finite-difference sensitivity analysis suggested that the lateral wave-propagation effects are negligibly small, and locally 1-D computations are sufficient for the present site. Those computations are compared with observations not available to the authors during the blind prediction. Peak accelerations, peak velocities and RMS accelerations were predicted with errors less than 159%, 114% and 62%, respectively. Maxima of the response spectra were fitted within a factor of 2. The predicted and observed Husid's plots (i.e., the normalized cumulative plots of the acceleration squared) have the correlation coefficients 0.98. The detected misfits do not show any simple relation to the instrument location, component, frequency, or time.  相似文献   

岩体三维节点偶对分析及其应用          下载免费PDF全文

王思敬  张菊明 《地质科学》1991,(3):277-287

本文讨论了节点偶对分析的三维扩展。节点偶对分析是针对摩擦滑动节理单元的约束边界进行的序列矢量判定。在三维节理单元的分析中,几何约束和相应的力学判据极为复杂,采用节点偶对等效结合力方法才能迎刃而解。文中对三维转向节理模型的分析得到合理的结果,它表明本文所提出的方法可成功地应用于节理岩体的有限元分析。  相似文献   

RETRACTION: Numerical simulation of a wind-sand flow under different conditions of atmospheric stability     

LÜ PING  ZHIBAO DONG 《Sedimentology》2008,55(3):721-721

A theoretical model for wind‐sand flow is developed by considering the coupling between wind flow and sand particle motion, the latter subject to the Magnus effect, under different atmospheric stability conditions. Using this model, the characteristics of the wind‐sand flow are discussed in detail. The results show that the atmospheric stability and the Magnus effect both have a strong influence on wind profiles and on the trajectories of sand particles. This approach produces results with characteristics that differ from those previously reported; the latter only applying to atmospheric conditions of neutral stability. The saltating sand reaches a greater height under non‐neutral stability than under neutral stability, while the maximum horizontal distance is greater under unstable conditions and is smaller under stable conditions than under conditions of neutral stability.  相似文献   

The geochemistry of gem opals as evidence of their origin     

Eloïse Gaillou  Aurlien Delaunay  Benjamin Rondeau  Martine Bouhnik-le-Coz  Emmanuel Fritsch  Guy Cornen  Christophe Monnier 《Ore Geology Reviews》2008,34(1-2):113

Seventy-seven gem opals from ten countries were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) through a dilution process, in order to establish the nature of the impurities. The results are correlated to the mode of formation and physical properties and are instrumental in establishing the geographical origin of a gem opal. The geochemistry of an opal is shown to be dependant mostly on the host rock, at least for examples from Mexico and Brazil, even if modified by weathering processes. In order of decreasing concentration, the main impurities present are Al, Ca, Fe, K, Na, and Mg (more than 500 ppm). Other noticeable elements in lesser amounts are Ba, followed by Zr, Sr, Rb, U, and Pb. For the first time, geochemistry helps to discriminate some varieties of opals. The Ba content, as well as the chondrite-normalized REE pattern, are the keys to separating sedimentary opals (Ba > 110 ppm, Eu and Ce anomalies) from volcanic opals (Ba < 110 ppm, no Eu or Ce anomaly). The Ca content, and to a lesser extent that of Mg, Al, K and Nb, helps to distinguish gem opals from different volcanic environments. The limited range of concentrations for all elements in precious (play-of-color) compared to common opals, indicates that this variety must have very specific, or more restricted, conditions of formation. We tentatively interpreted the presence of impurities in terms of crystallochemistry, even if opal is a poorly crystallized or amorphous material. The main replacement is the substitution of Si⁴⁺ by Al³⁺ and Fe³⁺. The induced charge imbalance is compensated chiefly by Ca²⁺, Mg²⁺, Mn²⁺, Ba²⁺, K⁺, and Na⁺. In terms of origin of color, greater concentrations of iron induce darker colors (from yellow to “chocolate brown”). This element inhibits luminescence for concentrations above 1000 ppm, whereas already a low content in U (≤ 1 ppm) induces a green luminescence.  相似文献   

Integrated approach for identification of potential groundwater zones in Seethanagaram Mandal of Vizianagaram District,Andhra Pradesh,India   总被引：1，自引：0，他引：1  

N. C. Mondal  S. N. Das  V. S. Singh 《Journal of Earth System Science》2008,117(2):133-144

Identifying a good site for groundwater exploration in hard rock terrain is a challenging task. In hard rocks, groundwater occurs in secondary porosity developed due to weathering, fracturing, faulting, etc., which is highly variable within short distance and contributing to near-surface inhomogeneity. In such situations topographic, hydrogeological and geomorphological features provide useful clues for the selection of suitable sites. Initially, based on satellite imagery, topographical, geomorphological and hydrogeological features, an area of about 149 km² was demarcated as a promising zone for groundwater exploration in the hard rock tract of Seethanagaram Mandal, Vizianagaram District, Andhra Pradesh, India. A total of 50 Vertical Electrical Soundings (VES) were carried out using Wenner electrode configuration. An interactive interpretation of the VES data sharpened the information inferred from geomorphological and hydrogeological reconnaissance. Ten sites were recommended for drilling. Drilling with Down-The-Hole Hammer (DTH) was carried out at the recommended sites down to 50 to 70 m depths. The interpreted VES results matched well with the drilled bore well lithologs. The yields of bore wells vary from 900 to 9000 liters per hour (lph).  相似文献   

等离子体质谱法测定玄武岩中微量元素三种样品预处理方法的比较   总被引：3，自引：1，他引：2  

韩江伟  熊小林  朱照宇  吴金花 《岩矿测试》2008,27(5):325-328

在测定玄武岩的微量元素时,为了保证得到的微量元素结果反映源区特征,需经预处理去除玄武岩的孔洞中充填的碳酸盐等物质。选取雷州半岛新生代玄武岩三个样品,每一个样品用三种预处理方法进行预处理,等离子体质谱法测定其中的微量元素。分析结果表明,用稀硝酸浸泡样品,会导致玄武岩中大多数微量元素严重丢失,得到的数据失真;而用稀盐酸浸泡去除碳酸盐的方法基本不改变玄武岩中微量元素的含量。  相似文献   

内蒙古敖包吐萤石矿床的Sr、Nd、Pb同位素地球化学特征   总被引：2，自引：1，他引：1  

许东青  聂凤军  刘妍  张万益  云飞  张天俊  林日亮  吕旭光 《矿床地质》2008,27(5):543-558

敖包吐萤石矿床是内蒙古北部苏莫查干地区单一萤石矿集区中的一个代表性矿床,产于早二叠世大石寨组火山-沉积岩与早白垩世敖包吐花岗岩的接触带上。文章通过分析该矿床岩、矿石的微量元素和稀土元素,揭示出萤石的成矿作用可分为2个阶段,即交代作用和充填作用。交代作用过程中大石寨组的结晶灰岩可能为萤石的形成提供了部分Ca来源,萤石矿石的稀土元素配分模式与海水基本类似,具有Ce负异常;成矿作用后期主要表现为充填作用,形成颗粒粗大的萤石,表现为重稀土元素富集的特征,并随着萤石的沉淀析出,稀土元素总量逐渐下降,反映出成矿流体经历了较长期的演化过程。各地层单元、花岗岩体和萤石矿石的Sr、Nd、Pb同位素研究表明,萤石的放射性同位素组成具有壳、幔源混合的特点,成矿物质来源具有多源性。早白垩世敖包吐花岗岩可能是萤石中F的主要来源,而大石寨组的结晶灰岩则可能提供了Ca。另外,Pb、Nd同位素的极大不均一性,有可能是成矿流体在运移过程中对艾力格庙群放射性组分的选择性吸收的结果。萤石成矿作用与钾玄岩的时空关系暗示了萤石的成矿过程可能是中国东部岩石圈减薄和下地壳的置换地质事件的结果。在构造转型的过程中,燕山中期富碱的酸性花岗岩浆的活动分异出富含F的成矿流体,与幔源流体混合,沿区域重新活化的深大断裂和大石寨组的层间破碎带上升,交代其间的灰岩透镜体,从而形成敖包吐中型萤石矿床。  相似文献   

塔里木盆地塔中1井藻纹层白云岩与竹叶状白云岩成因——基于岩石学、元素与同位素地球化学的厘定   总被引：1，自引：0，他引：1  

陈永权  周新源  赵葵东  杨文静  董晨阳  朱长见 《地质学报》2008,82(6):826-834

塔里木盆地寒武系—奥陶系底部发育了大量的白云岩, 白云岩中赋存丰富的油气资源, 但是由于塔里木盆地白云岩研究基础薄弱,限制了塔里木盆地白云岩型油气藏的勘探。本文选择塔中地区塔中1井下奥陶统藻纹层白云岩与夹层竹叶状白云岩作为对象,应用岩石学与地球化学方法对其成因问题进行了研究。藻纹层白云岩与夹层竹叶状白云岩的宏观构造与微观结构指示其可能形成于高能的潮坪环境;低有序度值（0.6）与塔北地区中寒武统阿瓦塔格组潮坪同沉积白云岩(有序度值0.61)特点一致,指示该白云岩结晶速率较快;同时,高Fe、Mn含量与低U、Mo含量也与氧化环境的潮坪相一致。藻纹层白云岩与夹层竹叶状白云岩δ18O值非常集中, 变化在-7.4‰～-5.8‰;87Sr/86Sr组成变化很小,在0.709015～0.709276之间,与前人报道的晚寒武世－早奥陶世海水同位素特征一致,同时白云岩的稀土元素配分模式也与下奥陶统泥晶灰岩一致,指示了白云岩的沉积/成岩物质来源于蒸发海水;白云岩δ13C值变化从-2.5‰～+1.6‰,并有着随深度增加而升高的变化规律,可能指示了古海洋的碳同位素氧化。藻纹层白云岩与夹层竹叶状白云岩的构造特点具有原生沉积特征,同时白云岩CaO与MgO含量的正相关关系也支持该白云岩原生沉积特点。因此,塔里木盆地塔中1井钻遇的下奥陶统藻纹层白云岩与夹层竹叶状白云岩为潮坪环境下,从蒸发海水中快速沉积形成的。  相似文献   

山东省济宁强磁异常区深部铁矿初步验证及其意义   总被引：8，自引：1，他引：7  

宋明春 《地质学报》2008,82(9):1285-1292

山东省济宁磁异常是一个重、磁同源体,面积大于100 km2,磁异常峰值为3800nT。钻探验证在孔深1041.57～1796.54m位置发现铁矿体,矿体总厚度74.04～220m,磁性铁平均品位15.89～25.19%。矿石类型有条带状方解磁铁石英岩和条带状磁铁石英大理岩,矿石的主要组成矿物为石英、方解石、磁铁矿、磁赤铁矿、菱铁矿。矿体产于济宁岩群浅变质岩系中,矿床特征与条带状铁建造（BIF）铁矿或鞍山式铁矿有明显区别,铁矿成因类型属与千枚岩、变质中酸性火山岩、大理岩有关的沉积变质型铁矿床。该区铁矿资源潜力巨大。  相似文献