三峡水库对大宁河沉积环境的影响——碳酸盐和常量元素含量的变化     

吴旭东  李红春  李俊云  刘子琦  王勇  李廷勇  高彦芳 《地质论评》2008,54(3):419-426

对2006年10月采自长江巫山段一级支流大宁河河底的三根岩芯作了常量元素（K、Na、Ca、Mg）的分析。研究结果表明,沉积物中稀酸可溶相常量元素的含量能够反映沉积物的特征和来源。大宁河中—上游沉积物中碳酸盐含量平均为23%,反映岩溶地区石灰岩风化的影响;而与长江交接处的沉积物中碳酸盐含量平均为10%,显示长江主流有明显不同的沉积物来源。三峡大坝的建成蓄水,水位提高,使得碳酸盐含量低的红色粘土进入双龙镇段大宁河沉积,造成碳酸盐含量、稀酸可溶相常量元素含量急剧下降、沉积物的颜色发生显著变化。受到蓄水作用的影响,大宁河泥沙沉积速率大幅度提高,自2004年12月蓄水以来,大宁河双龙镇附近沉积物厚达10cm以上。  相似文献   

Mathematical,Constitutive and Numerical Modelling of Catastrophic Landslides and Related Phenomena   总被引：3，自引：0，他引：3  

M. Pastor  J. A. Fernández Merodo  M. I. Herreros  P. Mira  E. González  B. Haddad  M. Quecedo  L. Tonni  V. Drempetic 《Rock Mechanics and Rock Engineering》2008,41(1):85-132

  相似文献   

Chemical weathering of granite under acid rainfall environment, Korea   总被引：1，自引：0，他引：1  

Seung Yeop Lee  Soo Jin Kim  Min Hoon Baik 《Environmental Geology》2008,55(4):853-862

Chemical weathering was investigated by collecting samples from five selected weathering profiles in a high elevation granitic environment located in Seoul, Korea. The overall changes of chemistry and mineralogical textures were examined reflecting weathering degrees of the samples, using polarization microscopy, X-ray diffraction (XRD), electron probe micro analysis (EPMA), X-ray fluorescence spectroscopy (XRF), and inductively coupled plasma–mass spectroscopy (ICP–MS). The chemical distribution in the weathering profiles shows that few trace elements are slightly immobile, whereas most major (particularly Ca and Na) and trace elements are mobile from the beginning of the granite weathering. On the other hand, there were mineralogical changes initiated from a plagioclase breakdown, which shows a characteristic circular dissolved pattern caused by a preferential leaching of Ca cation along grain boundaries and zoning. The biotite in that region is also supposed to be sensitive to exterior environmental condition and may be easily dissolved by acidic percolated water. As a result, it seems that some rock-forming minerals in the granitic rock located in Seoul are significantly unstable due to the environmental condition of acidic rainfall and steep slopes, where they are susceptible to be dissolved incongruently leading some elements to be highly depleted.  相似文献   

Petrogenesis of Volcanic Rocks from Saipan and Rota, Mariana Islands, and Implications for the Evolution of Nascent Island Arcs   总被引：2，自引：0，他引：2  

Reagan  Mark K.; Hanan  Barry B.; Heizler  Matthew T.; Hartman  Brian S.; Hickey-Vargas  Rosemary 《Journal of Petrology》2008,49(3):441-464

An ⁴⁰Ar/³⁹Ar age of 45·1 Ma determined for lavas fromnorthern Saipan confirms that these high-silica rhyolites eruptedduring the ‘proto-arc’ stage of volcanism in theIzu–Bonin–Mariana system, which is characterizedelsewhere by eruption of boninitic lavas. Incompatible traceelement concentrations and Sr, Hf, Nd, and Pb isotope ratiosfor these rhyolites are transitional between those of c. 48Ma boninitic lavas and post-38 Ma ‘first-arc’ andesitesand dacites from Saipan and Rota that have typical subduction-relatedcompositions. These transitional compositions are modeled bycrystal fractionation of parental tholeiitic basalt combinedwith assimilation of young boninitic crust. A second stage ofRayleigh fractionation in the upper crust is required by SiO₂concentrations that exceed 77 wt % and near-zero compatibleelement concentrations. First-arc magma compositions are consistentwith fractionation of basalt and assimilation of crust similarin composition to the first-arc magmas themselves. The mantlesources of the proto-arc and first-arc lavas from Saipan andRota are similar to those of Philippine back-arc basin basaltsbased on Nd and Hf isotopic compositions. The Pb isotope compositionsof these lavas are between those of Pacific sea-floor basaltsand Jurassic and younger cherty and clay-rich sediments. Thiscontrasts with the boninitic proto-arc volcanic rocks from Guamand Deep Sea Drilling Project Sites 458 and 459 that have Pbisotope compositions similar to Pacific basin basalts and volcaniclasticsediments. The preferred explanation for the difference in thenature of proto-arc volcanism between Saipan and other fore-arclocations is that the crust ceased extending 3–4 Myr earlierbeneath Saipan. This was caused by a change from mantle upwelling,fore-arc extension, and shallow melting to an environment dominatedby more normal mantle wedge convection, stable crust, and deepermelting. KEY WORDS: rhyolite; andesite; Mariana arc; isotope ratios; trace elements  相似文献   

地幔Sr-Nd-Pb同位素演化的综合模型与n维同位素空间 “地幔面”的地质意义     

隋建立  樊祺诚  赵勇伟  杜星星 《岩石学报》2008,24(11):2615-2620

在n维的Sr-Nd-Pb同位素空间中,几乎所有的大洋中脊玄武岩（MORB）和洋岛玄武岩（OIB）都落在一个虚拟平面上,被称为“地幔面（mantle plane）”。“地幔面”描述了大部分玄武岩的同位素地球化学特征,是最重要的、也是最早提出的地幔动力学演化特征之一,但是长期以来关于“地幔面”的内涵和意义并不清楚。本文通过一个综合模型,反演受岩浆作用控制的地幔微量元素（包括各种同位素母体元素）分异、Sr—Nd—Pb同位素演化,并推导出地幔Sr-Nd-Pb同位素演化的二元参数方程形式。模型表明,通过部分熔融向地壳输出相对富硅、富碱的物质成分,是地幔长期演化的主要特点,这个过程受到两个参数一部分融融程度（F）和岩浆分离的时间（t）-的控制,即n维参数可化为2维,因此在n维同位素空间出现“地幔面”的特征。壳源物资循环,能够使局部地幔偏离“地幔面”,就地幔总体统计特征而言,地壳混染的比例很低,不同的统计数据显示大约1％～6％的系统偏差,即可能的地壳混染程度;进一步模拟,可能作出更加精确的估算。  相似文献   

Distribution Characteristics of Sulfur and the Main Harmful Trace Elements in China's Coal   总被引：1，自引：1，他引：0  

TANG Shuheng  SUN Shenglin  QIN Yong  JIANG Yaofa  WANG Wenfeng 《《地质学报》英文版》2008,82(3)

To promote the rational development and use of clean coal resources in China,data on the regional and age distribution of sulfur,arsenic and other harmful elements in Chinese coal was broadly collected,tested for content,and analyzed.Coal in northwestern China is characterized by low to extremely low levels of sulfur;the coal of the Taiyuan Formation in northern China mainly has high-sulfur content;that of the Shanxi Formation is mainly characterized by low sulfur coal;and the Late Permian coal in southern China has overall higher sulfur content;other regions have low sulfur coal.The average content of harmful trace elements in the bulk of China's coal is similar to the corresponding content in the coal of the North America and the rest of the world,whereas the content of various elements(Hg,Sb and Se)is different in magnitude to the corresponding percentage in the crust.The average content of the elements Cr,Se,Co,Be,U,Br in Late Permian coal in S China ranks first in the country whereas the average content of Hg and Cl in the coals of Late Carboniferous to Early Permian age in N China are the highest.The average content of Mn in Early and Middle Jurassic coal is higher in NW China.The high content of harmful elements in some coal should cause particular concern both in the development and utilization of coal.  相似文献   

定位定向系统数据的航空高光谱影像几何校正     

马伟波  丁建伟  谭琨 《测绘科学》2017,42(6)

针对航空高光谱数据几何畸变严重的问题,该文探索了利用POS数据辅助航空高光谱影像几何校正的研究现状,分析了基于POS系统的导航数据的线阵推扫高光谱数据解算成像瞬间外方位元素的原理,以及行方位数据支持的线中心投影影像通过改进的共线方程方法几何校正的过程,实现了无地面控制点数据的直接几何校正。采用高光谱影像分块处理方法,实现了高吞吐快速几何校正。HySpex SWIR-384高光谱影像的实验结果表明,该文的校正算法可达到9.15m的绝对定位精度,最终利用少量地面控制点进行几何精校正,其均方根误差达到0.93m。  相似文献   

武汉市城市空间集聚要素的分布特征与模式   总被引：12，自引：3，他引：9  

焦利民  李泽慧  许刚  张博恩  董婷  谷岩岩 《地理学报》2017,72(8):1432-1443

不同城市要素的集聚现象具有不同的空间模式,定量化研究城市要素集聚模式的差异和联系对于理解城市发展机理、合理制定城市规划具有重要意义。本文以武汉市为例,获取不透水表面、商业服务业网点（POI）、人口、容积率、城市道路等城市要素数据;采用核密度估计法识别城市主次中心,从城市要素的分布形态、集聚程度、集聚模式等来研究城市要素的空间分布格局特征。研究发现,武汉市呈现“一主七副”的多中心结构,各城市要素从城市中心向外呈反S型的圈层递减。采用集聚度指数衡量城市要素的集聚水平,结果显示商业POI、人口密度的集聚程度最大,其次是容积率、道路密度、不透水表面占比。高度集聚的商业POI、人口密度呈现出点状模式与带状模式相结合的分布模式,中度集聚的道路密度、容积率呈现点状模式、环状模式与轴状模式相结合的分布模式,低度集聚的不透水表面密度主要表现为环状模式。城市中心的吸引、立体空间开发等促进了城市要素的向心集聚,交通干线、稀缺景观资源的廊道效应等重塑了城市要素的空间分布形态。  相似文献   

广西致洪暴雨过程的要素场演变特征及物理量诊断分析   总被引：4，自引：0，他引：4  

林开平  张诚忠  董良淼  赵江洁 《气象研究与应用》2001,22(1):12-16

通过对广西致洪暴雨过程中暴雨区附近高空和地面要素场的演变特征分析 ,以及对与暴雨降水密切相关的物理量进行诊断分析 ,试图了解各层的要素场和物理量的分布及演变与致洪暴雨的关系 ,从而了解致洪暴雨的一些形成机制  相似文献   

固—液反应体系CaF2—HCl—H2O内化学振荡的动力学模型     

吴平霄  吴金平等 《岩石学报》2001,17(4):669-672

本文根据物理化学基本原理，提出HF的表面吸附催化机制对于CaF2-HCl-H2O固－液反应体系溶解振荡起着关键性作用。同时建立了该 体系的动力学模型，研究其振荡现象的非线性动力学起因，虽然这一数学模型是基于CSTR反应器为对象而建立的，不过其基本的结论对叠层式流动反应器的情况也是适用的。  相似文献