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291.
区域重力调查是一项基础地球物理调查工作。它的成果可用于研究地质构造、资源勘探、环境调查,地震灾害、地球形状、地球物理理论等方面。它象征着一个国家科学技术发展水平,特别是地学方面的水平。地矿部研究了国内外重力勘查情况,于1978年提出并组织、实施了全国范围的区域重力调查。通过十多年的工作,取得了丰硕成果。本文就地矿部区域重力调查成果与展望,予以论述。 相似文献
292.
The characteristic structures of the Precambrian cherts from the Gusui section, Guangdong ,Chi-na, include bedded structure ,laminated structure ,massive structure and pseudobrecciated structure.The chert is characterized by consistently low abundance of TiO2,Al2O3 and most trace elements.Howevver ,it is enriched in Ba,As,Sb,Hg and Se.In Al-Fe-Mn ternary diagrams,it falls into the “hydrothermal field“ .Correspondence analysis and factor analysis show that many elements show up in the factor that represents the leaching of country rocks by hydrothermal solutions,and are the very characteristic element association fo the geochemically anomalous South China basement.Petrologic and geochemical evidence suggests a hydrothermal origin for the chert.The chert may have been formed in a Precambrian fift or an extension zone developed within the Yunkai marginal geosyncline, with a fault system linking it to an unknown heat source at depth. 相似文献
293.
Yongzhang Zhou Edward H. Chown Guangzhi Tu Jayanta Guha Huangzhang Lu 《Mathematical Geology》1994,26(4):419-435
The migration of trace elements from the inner part of solid cells to the weaknesses is the bottleneck in the migration of these elements from their initial positions in the source rock to the final deposition site in ore bodies. Diffusion may play a key role in the reactivation of trace elements. The overall migration pattern of trace elements in source rocks is a fractal structure. There are two general tendencies for trace elements to migrate. One is from within solid cells toward sinks, and the other is from high temperature fields toward low temperature ones. High temperature enhances these two tendencies. Conjugate geochemical anomalies are the inevitable result of a closed geochemical system. 相似文献
294.
在0.2mol/L HCl-1.0mol/LNaCl-0.15mol/L抗坏血酸介质中,用电流氧化微分溶出计时电位法直接测定地质物料中微量Cu。富集电位-0.55V,时间20~40s;电极转速2500r/min;溶出电流0.2~1μA;记录电位范围-0.2~-1.20V;清洗电位-0.10V,时间10s。方法检出限0.2μg/g,线性范围2~400ng/ml,精密度(RSD,n=11,4.1μg/ 相似文献
295.
孕镶钻头的自锐性是保证钻头能继续有效钻进的基本条件。钻杆柱的纵向振动和钻头底唇面上出刃的随机性使得多个扇形块的高度有差异;并且轴向压力集中在高的扇形块上,故使钻头易于自锐。唇面上的金刚石在交变载荷下的碎裂和液流中的岩粉对胎体的磨逝,使新的金刚石裸露,乃是钻进时的重要井底过程,也是孕镶钻头的自锐过程。 相似文献
296.
The data acquired by Gravity Recovery and Climate Experiment (GRACE) satellite provides a new way for monitoring groundwater storage changes in China. It is vital to understand its applications in China. This paper systematically reviewed the research progress of groundwater storage monitoring in China based on GRACE data. First, we used the bibliometric analysis and quantitative analysis to clarify trends and characteristics of related studies. Then, we elaborated on the basic principles, methods and uncertainties of groundwater monitoring based on GRACE data. Furthermore, we reviewed the research progress from the aspects of spatial range, accuracies and findings. It was found that the groundwater storage monitoring in China based on GRACE data has gradually received more attention, and the numbers of relevant publications and total citations in both Chinese and English showed an increasing trend. The methods mainly include the principle of water balance and calibration of hydrological models using GRACE satellite data. Most of the relevant studies focused on the North China Plain. The monitoring results are in good agreement with the measured groundwater data, and their correlation coefficients are higher than 0.6. We suggested that the challenges such as low spatial resolution of GRACE data and the uncertainties in monitoring should be considered. In the future, global positioning system, interferometric synthetic aperture radar and groundwater level observation data can be integrated to improve the reliability of groundwater storage monitoring in China. 相似文献
297.
J Faganeli A Avčin N Fanuko A Malej V Turk P Tušnik B Vrišer A Vukovič 《Marine pollution bulletin》1985,16(2):75-78
Anoxic conditions in the near-bottom layer below the pycnocline were observed in September 1983 causing mass mortality of benthic macrofauna in the central part of the Gulf of Trieste. The vertical transport of particulate organic matter and decomposition of abundant pelagic and benthic organic matter during the summer produced a low oxygen level in the near-bottom layer below the pycnocline when this layer was sufficiently close to the bottom. A high sea water temperature and vertical stability contributed to the development of anoxic conditions in September 1983 in the near-bottom layer. 相似文献
298.
299.
地下水位上升对砂性土地基承载力的影响 总被引:1,自引:0,他引:1
本文主要从土体的物理性质出发,以极限荷载理论为依据,找出砂性土地基承载力随地下水位上 升而下降的变化规律。这在由于温室效应及人为开发而引起地下潜水位不断上升的今天,对于从事 岩土工程和基础工程的研究、设计,具有一定的现实意义。 相似文献
300.
应用主分量分析、气候突变检验、“墨西哥帽”小波分析及谱分析等多种方法对宁波市1953~2003年的年降水量进行了时空特征分析。结果表明:宁波市所辖7个气象站年降水量呈现出从西南往北—东北方向递减的趋势,与全市地形走向基本一致,年降水量最大、最小值相差400 mm左右;全市各地年降水量的年际变化趋势是一致的;宁波市区年降水量在20世纪60年代末到70年代初接近突变临界值,近年也有发生转折的趋势;进入21世纪以来,宁波市年降水量处于偏少的气候背景中,2003年变化最为剧烈;宁波市区年降水量有准4年的振荡周期。 相似文献