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641.
Many adverse impacts on the environment can be directly related to the materials dispersed to the environment during processing or use, or after use as refuse and waste. Some materials, such as toxic wastes, are a major concern because they create immediate problems with longerterm effects. Gases released by major manufacturing industries can contribute to long-term regional and global problems such as acid rain or increased carbon dioxide in the atmosphere. The use of other materials, however, appears to be more benign or strictly localized in their impacts. If the current per capita level of material consumption in the United States was achieved worldwide, it would create major stresses on both resource adequacy and the environment. In fact, stresses have been created and will continue from this consumption style (developed countries) even if others don't achieve them.Correspondence should be directed to Earle B. Amey, U.S. Geological Survey, National Center 983, Reston, Virginia 20192. 相似文献
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Large clusters of gold deposits and large-scale metallogenesis in the Jiaodong Peninsula, Eastern China 总被引:2,自引:0,他引:2
The Jiaodong Peninsula is the largest repository of gold in China based on the production in history. It covers less than 0.2% of China’s territory, but production of gold accounts for about one fourth of the whole country. Thus, the Jiaodong Peninsula is a typical area or case of large-scale metallogenesis and a large clusters of mineral deposits in China. It is characterized by the large clusters of gold deposits in large scale, high reserve and short mineralizing stage. In this study, we suggest that the eastern boundary of the large clusters of gold deposits is as same as that of North China Block, the gold deposits are hosted by Archean metamorphic rocks or Mesozoic granites, and the age of gold mineralization is 121.6 to 122.7 Ma. Gold and related ore-forming materials are derived from multisources, i.e. Archean metamorphic rocks, granites and intermediate-mafic dikes, especially, intermediate-mafic dikes and calc-alkaline granites. The metallogenic geodynamic process is constrained by the tectonic evolution of eastern North China Block during Late Mesozoic, and it is the result of the interaction between mantle and crust as the boundary plates are playing role on the block. 相似文献
644.
Excess stress parameters, critical shear stress (τc) and erodibility coefficient (kd), for degrading channels in the loess areas of the midwestern USA are presented based on in situ jet‐testing measurements. Critical shear stress and kd are used to define the erosion resistance of the streambed. The jet‐testing apparatus applies hydraulic stresses to the bed and the resulting scour due to the impinging jet is related to the excess stress parameters. Streams tested were primarily silt‐bedded in texture with low densities, which is typical of loess soils. Results indicate that there is a wide variation in the erosion resistance of streambeds, spanning six orders of magnitude for τc and four orders of magnitude for kd. Erosion resistance was observed to vary within a streambed, from streambed to streambed, and from region to region. An example of the diversity of materials within a river system is the Yalobusha River Basin in Mississippi. The median value of τc for the two primary bed materials, Naheola and Porters Creek Clay Formations, was 1·31 and 256 Pa, respectively. Streambeds composed of the Naheola Formation are readily eroded over the entire range of shear stresses, whereas only the deepest flows generate boundary stresses great enough to erode streambeds composed of the Porters Creek Clay Formation. Therefore, assessing material resistance and location is essential in classifying and modelling streambed erosion processes of these streams. 相似文献
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试谈花岗石石材的放射性 总被引:1,自引:0,他引:1
通过常见花岗石石材岩石矿物特征的论述,介绍了不同的岩石化学成分和矿物组成对花岗石石材放射性强度的影响。指出选用饰面石材时,灰色系列和暗色系列放射性值低较为安全,对于浅色系列需要分别对待,使用前进行放射性活度检测是必要的。 相似文献
649.
地质材料率性相关的内变量本构理论的研究 总被引:1,自引:0,他引:1
本文根据地质材料的基本特性,提出了一种率性相关的内变量本构理论。该理论反映了地质材斟的温度、应变速率、尺寸及其原位损伤等因素的影响。文章中就某些特例进行了分析,并得到较好的结果。 相似文献
650.
Zongshou Yu Marc D. Norman Philip Robinson 《Geostandards and Geoanalytical Research》2003,27(1):67-89
Major and trace element compositions of fifteen silicate rock reference materials have been determined by a combined XRF and laser ablation ICP‐MS (LA‐ICP‐MS) technique on glasses prepared by fusing the sample with a lithium borate flux (sample:flux = 1:3). Advantages of this technique include the ability to measure major and trace element abundances on a single sample using a quick and simple preparation that attacks resistant phases such as zircon without the need for acid dissolution. The method is suitable for a wide variety of bulk compositions including mafic, intermediate and silicic rocks. Abundance‐normalized mass response patterns (the ratio of signal intensity to element concentration) of the LA‐ICP‐MS analyses vary systematically with major element composition, demonstrating the presence of a matrix effect that cannot be compensated by normalisation to a single internal standard element. Increasing the sampling distance between the ICP‐MS cone and the torch reduces the magnitude of this effect, suggesting that a mechanism related to residence time of ablated particles in the plasma may be at least partially responsible for the observed variations in mass response patterns. When using a matrix‐matched calibration, agreement of the LA‐ICP‐MS results with published reference values or those obtained by solution ICP‐MS is 10% relative. Analytical precision based on replicate analyses is typically 5% RSD. Procedural detection limits that include contributions from gas background and flux are 0.01‐0.1 μg g‐1 for the heavy mass trace elements (Rb‐U). Major element analyses by XRF show excellent agreement with results obtained using a conventional heavy element absorbing flux. High quality major and trace element data for silicate rocks can be achieved by a combined XRF and LA‐ICP‐MS analysis of Li2B4O7/LiBO2 fused glasses provided an appropriate matrix‐matched calibration is adopted. 相似文献