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滩间山地壳自中元古代蓟县纪以来经历了长期复杂的演化历史。金矿床的形成与本区地壳构造演化密切相关。蓟县纪早期,万洞沟群黑色岩系沉积于NE 向同生断裂控制的凹陷中,矿源层产生;蓟县纪晚期,区域变质作用为成矿奠定了基础;加里东期,韧性剪切带对金矿富集有重要作用;华力西期,脉岩型矿石生成;印支期,伴随推覆作用有微弱矿化的叠加;喜山期,氧化矿石形成。因此,滩间山金矿床是本区地壳构造演化的产物,属黑色岩系同构造多因复成金矿床,即滩间山型金矿床。 相似文献
134.
利用MODIS/EVI时间序列数据分析干旱对植被的影响 总被引:3,自引:0,他引:3
为了分析2006 年四川重庆地区夏季干旱对该地区植被生长的影响, 选取该地区多年中分 辨率成像光谱仪(MODIS)增强植被指数( EVI) 时间序列数据进行研究, 利用时间序列谐波分析 (HANTS) 算法对EVI 数据进行去云处理, 并根据处理后的结果( 重构的EVI 数据以及HANTS 分 析得到相应频率对应的振幅和相位) , 分析干旱对该地区的影响, 同时结合地面气象数据加以补 充说明。将干旱年份和正常年份对比分析, 结果表明, 处理后的EVI 时间序列数据能较好地反映 干旱对地表植被的影响, 振幅和相位的空间分布特征能够很好地反映干旱的影响范围。 相似文献
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The large, extensive tufa deposits of the semi‐arid Naukluft Mountains, Namibia are potentially important palaeoenvironmental indicators in an area with few proxy records. Tufas are reliable indicators of increased moisture availability, and have been shown to be amenable to 234U–230Th dating, although two challenges are detrital contamination and open‐system behaviour. Densely cemented tufa facies are good candidates for dating, minimising these problems. We report attempts to date five densely‐cemented units, which are only found rarely within the Naukluft deposits. We applied a detailed methodology using multiple subsample analysis, measurement of insoluble residues, application of ‘isochron’ mixing lines, and attempted open‐systems modelling, alongside observations of micromorphology and cathodoluminescence in order to assess the validity of any obtained dates. Surprisingly, densely cemented tufas were found not always to be suitable for dating. Two units contained detrital contamination, which could not be corrected for using a single leachate correction or ‘isochron’ methods. Two units contained ‘excess 230Th’. This could result under a closed‐system if initial (234U/238U) was sufficiently high. Alternatively this may be the result of open‐system behaviour, and loss of uranium, or incorporation of initial unsupported 230Th, which render samples unsuitable for 234U–230Th dating. Micromorphological appearance and cathodoluminescence behaviour are used to explore these possibilities. This study exemplifies the need for careful sample selection, and highlights the importance of analysing multiple subsamples from any tufa sample. The detailed methodology applied proves to be a powerful tool for identifying the range of problems that can be encountered when selecting suitable candidate samples for successful dating. It also shows that semi‐arid tufa sequences may contain very little material suitable for dating. A reliable age of c 80 ka was obtained for a banded unit within a large fluvial barrage, with less reliable dates suggesting tufa deposition during times since >350 ka through to the late Holocene. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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The predictive quality of the current drainage class map of Flanders was evaluated using data from two monitoring networks: one with good spatial coverage but poor temporal coverage and another with better temporal but poor spatial coverage. We combine both networks to obtain 1678 point predictions for mean highest water (MHW) and mean lowest water (MLW) tables by applying time series modelling and total least squares regression. The resulting MHW and MLW point data set was used to evaluate the currency of the existing map and to identify regional differences. The quality of the current map is moderate, and large differences occur between regions. Especially the Campine region shows large and systematic differences, whereas the southeastern hills and chalk–loam region is relatively accurate. If more weight is given to errors in the wetter drainage classes, about 50% of the area of Flanders would benefit from remapping. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
138.
D. Labat C. T. Hoang J. Masbou A. Mangin I. Tchiguirinskaia S. Lovejoy D. Schertzer 《水文研究》2013,27(25):3708-3717
Karstic watersheds are highly complex hydrogeological systems that are characterized by a multiscale behaviour corresponding to the different pathways of water in these systems. The main issue of karstic spring discharge fluctuations consists in the presence and the identification of characteristic time scales in the discharge time series. To identify and characterize these dynamics, we acquired, for many years at the outlet of two karstic watersheds in South of France, discharge data at 3‐mn, 30‐mn and daily sampling rate. These hydrological records constitute to our knowledge the longest uninterrupted discharge time series available at these sampling rates. The analysis of the hydrological records at different levels of detail leads to a natural scale analysis of these time series in a multifractal framework. From a universal class of multifractal models based on cascade multiplicative processes, the time series first highlights two cut‐off scales around 1 and 16 h that correspond to distinct responses of the aquifer drainage system. Then we provide estimates of the multifractal parameters α and C1 and the moment of divergence qD corresponding to the behaviour of karstic systems. These results constitute the first estimates of the multifractal characteristics of karstic spingflows based on 10 years of high‐resolution discharge time series and should lead to several improvements in rainfall‐karstic springflow simulation models. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
139.
《水文科学杂志》2013,58(3)
Abstract Abstract Generating pulses and then converting them into flow are two main steps of daily streamflow generation. Three pulse generation models have been proposed on the basis of Markov chains for the purpose of generating daily intermittent streamflow time series in this study. The first one is based on two two-state Markov chains, whereas the second uses a three-state Markov chain. The third model uses harmonic analysis and fits Fourier series to the three-state Markov chain. Results for a daily intermittent streamflow data series show a good performance of the proposed models. 相似文献
140.
Trend identification is a substantial issue in hydrologic series analysis, but it is also a difficult task in practice due to the confusing concept of trend and disadvantages of methods. In this article, an improved definition of trend was given as follows: ‘a trend is the deterministic component in the analysed data and corresponds to the biggest temporal scale on the condition of giving the concerned temporal scale’. It emphasizes the intrinsic and deterministic properties of trend, can clearly distinguish trend from periodicities and points out the prerequisite of the concerned temporal scale only by giving which the trend has its specific meaning. Correspondingly, the discrete wavelet‐based method for trend identification was improved. Differing from those methods used presently, the improved method is to identify trend by comparing the energy difference between hydrologic data and noise, and it can simultaneously separate periodicities and noise. Furthermore, the improved method can quantitatively estimate the statistical significance of the identified trend by using proper confidence interval. Analyses of both synthetic and observed series indicated the identical power of the improved method as the Mann–Kendall test in assessing the statistical significance of the trend in hydrologic data, and by using the former, the identified trend can adaptively reflect the nonlinear and nonstationary variability of hydrologic data. Besides, the results also showed the influences of three key factors (wavelet choice, decomposition level choice and noise content) on discrete wavelet‐based trend identification; hence, they should be carefully considered in practice. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献