The deposit size frequency method for estimating undiscovered uranium deposits     

Richard B. McCammon  Warren I. Finch 《Natural Resources Research》1993,2(2):106-112

The deposit size frequency (DSF) method has been developed as a generalization of the method that was used in the National Uranium Resource Evaluation (NURE) program to estimate the uranium endowment of the United States. The DSF method overcomes difficulties encountered during the NURE program when geologists were asked to provide subjective estimates of (1) the endowed fraction of an area judged favorable (factorF) for the occurrence of undiscovered uranium deposits and (2) the tons of endowed rock per unit area (factorT) within the endowed fraction of the favorable area. Because the magnitudes of factorsF andT were unfamiliar to nearly all of the geologists, most geologists responded by estimating the number of undiscovered deposits likely to occur within the favorable area and the average size of these deposits. The DSF method combines factorsF andT into a single factor (F·T) that represents the tons of endowed rock per unit area of the undiscovered deposits within the favorable area. FactorF·T, provided by the geologist, is the estimated number of undiscovered deposits per unit area in each of a number of specified deposit-size classes. The number of deposit-size classes and the size interval of each class are based on the data collected from the deposits in known (control) areas. The DSF method affords greater latitude in making subjective estimates than the NURE method and emphasizes more of the everyday experience of exploration geologists. Using the DSF method, new assessments have been made for the young, organic-rich surficial uranium deposits in Washington and idaho and for the solution-collapse breccia pipe uranium deposits in the Grand Canyon region in Arizona and adjacent Utah.  相似文献   

辽宁地区主要断裂活动性和地震危险性评估     

曹凤娟  贾丽华  李梦莹  王松阳 《吉林大学学报(地球科学版)》2021,51(1):286-295

基于辽宁地区主要活动断裂的几何特征和空间展布，对1980年以来辽宁地区M_L≥2.0地震的累计频次和1900年以来M_s≥5.0地震的年发生率的空间分布及其与活动断裂构造背景关系进行研究，获得了基于地震学的辽宁省内主要断裂和构造区（带）的活动性与地震危险性的初步评估结果。辽宁地区主要断裂活动性较高的有海城河断裂、金州断裂九寨—盖州北段、朝阳—北票断裂等；辽宁地区未来3年发生M_s≥5.0地震危险性较高的断裂依次有海城河断裂、金州断裂、熊岳—庄河断裂、鸭绿江断裂及赤峰—开原断裂与柳河断裂交汇处等。在判定区域地震危险性和城市地震风险时，除了依据前兆异常的空间分布，还应充分考虑区内主要构造（断裂）的活动性与地震危险性。  相似文献   

新疆第三次荒漠化监测中的问题及其建议   总被引：4，自引：1，他引：4  

程小红  潘存军  彭建新 《云南地理环境研究》2006,18(2):12-16

回顾了新疆3次在荒漠化监测中所进行的荒漠化监测与评价指标体系的建立，也是新疆开展荒漠化监测的基础；介绍了以遥感与地理信息为主要技术的荒漠化监测评价的方法；阐述了新疆第三次荒漠化监测中存在的问题。指出目前新疆荒漠化评价存在的主要问题是评价指标的不确定性、评价指标体系的难操作性和遥感数据源选用的随机性，进而对上述问题的解决途径进行了讨论。  相似文献   

近50 a渭河流域洪水成因分析及防治对策   总被引：6，自引：1，他引：6  

张琼华  赵景波 《中国沙漠》2006,26(1):117-121

 通过对近50 a渭河流域洪水的年际变化、月际变化和潼关高程变化的综合分析得出，造成该流域洪水灾害的原因有降水量年内分配不均和年际变化大，滩面淤积加重，支流河口淤塞以及河势、流态的恶化等。针对这些原因，根据渭河流域洪水灾害的特点，提出了相应的防治措施，即降低下游高程，减少河道的淤积，增大河道泄洪能力；利用水库进行调水调沙，引进客水冲刷渭河下游；防洪工程要除险加固，提高防洪标准与抗洪能力；恢复林草植被，遏止水土流失，从源头上控制泥沙入河等。  相似文献   

三工河流域新老绿洲发育度的比较   总被引：1，自引：0，他引：1  

何新梅  李小玉  肖笃宁  李彦 《干旱区地理》2006,29(3):342-347

绿洲是干旱区最重要的景观单元之一。人工绿洲是在干旱条件下经长期人类活动改造而形成的特殊景观。随着人类对绿洲水土资源开发利用程度的不断加强,绿洲呈现出不同的发展阶段。从天然绿洲到人工绿洲,是人类适应和改造干旱区自然环境的历程。在这一人地相互作用的过程中,绿洲显示出明显的发育演化特征。从多学科综合的角度,提出绿洲发育度的概念,并从灌溉体系的建设状况、水资源的利用水平、植被与生态建设、农业发展程度、社会经济水平和绿洲景观结构等7个方面提出了绿洲发育度的评价指标体系,以天山北坡2个人工绿洲为例,从空间上定量比较2个绿洲的发育程度,其中阜康市绿洲发育度高于222团绿洲(阜北农场)。  相似文献   

Spatial analysis of elements in soils from Chengdu City     

Shuyun XIE Zhengyu BAO Bing LI 《中国地球化学学报》2006,25(B08):7-8

Three kinds of spatial analysis methods （geostatistics, concentration-area fractal model and the multifractal analysis called the moment method） were used for almost 50 elements, including heavy metals, disperse elements, rare elements and even others, in 6586 top soil （0-20 cm） samples and 1833 deep soil （150-200 cm） samples from Chengdu metropolitan area of 12400 km^2, southwestern China. The ranges of spatial correlation revealed by variograms are quite different for different kinds of elements in the top and deep soils. The most interest is the fact that the multifractal spectra of environmentally important elements such as Pb, Cr, Cd and Ni in top soils in the metropolitan area show systematic change from those in the deep soils, revealing a strong anthropogenic addition, while Hg, Zn, As, Cu and all common elements show no such kind of addition. In terms of multifractal properties based on the multifractal spectrum curves, those disperse and rare elements show great deviation from other major and trace elements, which is also of great interest.  相似文献   

Mineralogical controls on the bioaccessibility of arsenic in weathered gold mine tailings     

《中国地球化学学报》2006,25(B08):33-33

  相似文献   

Environmental geohydrochemistry and health of the high altitude population in Ladakh     

Norboo Tsering 《中国地球化学学报》2006,25(B08):69-69

Background： Radiographic signs of Pneumoconiosis found in farming Ladakhi despite absences of mines and industries were believed to be due to exposure to frequent dust storms and domestic fire pollutions. Seasonal Koilonychia （spoon nail） occurring predominantly in farming women in absences of iron deficiency anaemia was thought to arise from exposure to water made alkaline by weathering of hornblende minerals. The relation of these health conditions to environmental geohydrochemistry is postulated as the source of irrigation water in the affected population originates from glaciers in trans-Himalaya range of sedimentary geology and steep landscape favouring flushing of silica/silicate containing silts. Methods and results： Survey in two central Ladakh villages revealed radiographic evidence of silicosis in all middle aged women and half in middle aged men. In a large-scale study of 3105 subjects aged over 30 years from three villages; 101 （22.5%） of the 449 radiographed showed signs of pneumoconiosis （ILO 1980 criteria） including eggshell calcification of hilar gland and progressive massive fibrosis. Indoor dust analyzed using Philips 400T electron microscope with energy dispersive analysis system attached showed SiO2 levels upto 53.27% with particle size of 0.5 to 5.0 microns and the concentration during cooking period in the worst affected area was 7.495 mg/m^3. Microscopy and histopathology from the subject was characteristic of pneumoconiosis. Analysis of the inorganic dust in the lung showed 40.2% muscovite, 37.3% quartz with the extracted dust wt 147.9 mg/gm of dry tissue. Prevalence of chronic cough with chronic phlegm and percentage of villagers with FEV1/FVC ratio of less than 65% rose with age. Of 70 subjects studied 19 women and 2 men had Koilonychia with incidence being highest in summer. Absence of seasonal Koilonychia in villages fed by water derived from northern mountain range glaciers with mainly igneous geology supports our hypothesis.  相似文献   

Ecological risk assessment for heavy metal contamination of a new consideration Agricultural soils     

《中国地球化学学报》2006,25(B08):123-123

  相似文献   

The acid neutralizing capacity （ANC） of South Africa＇s freshwater ecosystems     

Stephanie de Villiers 《中国地球化学学报》2006,25(B08):146-146

Acidification is considered the most important one of the primary chemical stress factors that impact on freshwater ecosystems. In unpolluted freshwater systems, the primary controls on the degree of acidification are factors such as the geological substrate of the catchment area, the presence of organic acids secreted by vegetation in the river system, and equilibrium exchange of carbon dioxide with the atmosphere. Anthropogenic factors that can impact on the degree of acidification of freshwater systems include agricultural, mining and industrial activities, either through direct runoff into river systems or through deposition of atmospheric pollutants from these sources. The capacity factors alkalinity and acidity, which represent the acid- and base-neutralizing capacity （ANC and BCN） of an aqueous system, have been used as more reliable measures of the acidic character of freshwater systems than pH. Unlike pH, ANC and BNC are not affected by parameters such as temperature and pressure. Therefore, ANC has been employed as a predictor of biological status in critical load assessments. Freshwater systems with ANC＇s eq/L isμeq/L are considered sensitive to acidification, ANC=0 μbelow 150 commonly used as the predictor for fish species such as trout in lakes, and an eq/L as more realistic for streams. Acid-neutralizing capacity μANC value of 40 （ANC） can be determined by titration with a strong acid to a preselected equivalence point. Alternatively, it can be calculated as the difference between base cations （[BC]） and strong acid anions （[SAA]）： ANC=[BC]- [SAA]=[Ca^2＋]＋[Mg^2＋]＋[Na^＋]＋[K^＋]-[SO4^2-]-[NO3^-]-[Cl^-] To date, there has been no attempt to establish the ANC of South Africa＇s freshwater ecosystems or variability therein, despite the fact that long-term water quality monitoring data exist for all the parameters needed to calculate it according to the above equations. As a result, the relationship between the acid neutralizing capacity of freshwater ecosystems in South Africa and biodiversity factors, such as fish status, is unknown. Results of the first comprehensive （country-wide scale） evaluation of the acid neutralizing capacity of river systems in South Africa will be presented. Long-term monitoring data obtained from the Department of Water Affairs and Forestry （DWAF） from most of South Africa＇s river systems were used to establish geographic and temporal variabilities in ANC. The results show that the Berg and Breede River systems are most susceptible to acidification, and that geological substrate appears to explain most of the geographic variabilities observed.  相似文献