内蒙古维拉斯托锡多金属矿床含矿斑岩体钾长石斑晶的有序度及成因探讨     

杨帆  汪岩  樊志勇  付俊彧  那幅超  张广宇  刘航 《地质与资源》2017,26(2):124-128

钾长石有序度及结构温度可以为探讨成矿物化条件等提供依据.为阐明本区钾长石的成因,通过对维拉斯托斑岩体中钾长石斑晶的红外光谱分析,其有序度为0.85~0.95,三斜度为0.7~0.9,测定的结构温度为547.17~578.36℃,表明钾长石斑晶为微斜长石.并探讨了钾长石的成因,认为它是热液蚀变的产物.  相似文献   

环渤海虚拟台网的运行管理   总被引：1，自引：0，他引：1  

许可  刘瑞瑞  孔繁旭  薛娜  高文晶 《华北地震科学》2014,(3):55-60

针对天津市＂十一五＂期间的建设成果环渤海虚拟台网,从系统部署、运行监控、信息发布、系统维护等方面介绍了虚拟台网技术在天津地区的应用情况,并利用JAVA图像裁切技术解决了环渤海虚拟台网对天津地区速报地震的乡镇级震中位置显示问题。该台网的建成,不仅提高了天津台网对渤海海域的地震监测能力和研究水平,同时也为天津市各区县地办完善监测预报体系、提升社会显示度,提供了良好的机遇。  相似文献   

宁夏春季首场透雨的气候预测探索   总被引：4，自引：0，他引：4  

李艳春梁旭  纳丽郑广芬  孙银川 《干旱气象》2005,23(4):46-51

利用目前在统计预报中广泛应用的最优子集回归预报法,作宁夏南部山区及银川地区春季首场透雨出现日期的统计预报,给出了具体的预报方程和拟合效果分析。并对近30 a来宁夏南部山区及银川地区首场透雨出现日期的变化特征进行了较详细的分析。研究结果表明:银川地区3月份出现首场透雨的气候概率为23.3%、4月份为20%、5月份为23.3%、6月份为33.3%,出现机会相对较多。30 a来春季首场透雨出现日期:20世纪70年代相对较晚,80年代偏早,90年代介于70、80年代之间。南部山区春季首场透雨出现时间相对比较集中,其中4月份出现的气候概率为53%,其次是5月份和3月份,分别为20%和17%,最小的是6月份,只占10%,从近30 a来的总趋势看,南部山区春季首场透雨出现日期在波动中略有推迟现象。利用最优子集回归预报法对宁夏春季首场透雨出现日期的预测具有理想的拟合效果。  相似文献   

Detecting the near-surface redox front in crystalline bedrock using fracture mineral distribution,geochemistry and U-series disequilibrium     

Henrik Drake  Eva-Lena Tullborg  Angus B. MacKenzie 《Applied Geochemistry》2009

Oxidizing conditions normally prevail in surface waters and near-surface groundwaters, but there is usually a change to reducing conditions in groundwater at greater depth. Dissolved O₂ originally present is consumed through biogenic and inorganic reactions along the flow paths. Fracture minerals participate in these reactions and the fracture mineralogy and geochemistry can be used to trace the redox front. An important task in the safety assessment of a potential repository for the disposal of nuclear waste in crystalline bedrock, at an approximate depth of 500 m in Sweden, is to demonstrate that reducing conditions can be maintained for a long period of time. Oxygen may damage the Cu canisters that host nuclear waste; additionally, in the event of a canister failure, oxidizing conditions may increase the mobility of some radionuclides. The present study of the near-surface redox front is based on mineralogical (redox-sensitive minerals), geochemical (redox-sensitive elements) and U-series disequilibrium investigations of mineral coatings along open fractures. The fractures have been sampled along drill cores from closely spaced, 100 m deep boreholes, which were drilled during the site investigation work in the Laxemar area, south-eastern Sweden, carried out by the Swedish Nuclear Fuel and Waste Management Co. (SKB). The distribution of the redox-sensitive minerals pyrite and goethite in open fractures shows that the redox front (switch from mainly goethite to mainly pyrite in the fractures) generally occurs at about 15–20 m depth. Calcite leaching by recharging water is indicated in the upper 20–30 m and positive Ce-anomalies suggest oxidation of Ce down to 20 m depth. The U-series radionuclides show disequilibrium in most of the samples, indicating mobility of U during the last 1 Ma. In the upper 20 m, U is mainly removed (due to oxidation) or has experienced complex removal and/or deposition. At depths of 35–55 m, both deposition and removal of U are indicated. Below 55 m, recent deposition of U is generally indicated which suggests removal of U near surface (oxidation) and deposition of U below the redox front. Scattered goethite occurrences below the general redox front (down to ca 80 m) and signs of U removal at 35–55 m mostly correlate with sections of high transmissivity (and/or high fracture frequencies). This shows that highly transmissive fractures are generally required to allow oxygenated groundwaters at depth greater than ca 30 m. Removal of U (oxidation) below 55 m within the last 300 ka is not observed. Although penetration of glacial waters to great depths has been confirmed in the study area, their potential O₂ load seems to have been reduced near the surface.  相似文献   

透空管式防波堤透射系数及反射系数的试验研究     

那婧  拾兵  刘勇  范菲菲 《海洋湖沼通报》2012,(4):41-46

对透空管式防波堤的消浪性能进行了研究,通过进行物理模型试验,深入探讨了管道防波堤的堤顶宽度、斜率、波陡对防波堤消浪效果的影响,得出了该结构的反射系数及透射系数与各影响参数间的关系。研究结果表明,堤顶宽度为1.2Hm,斜率为1∶1.5的模型消浪效果较好。  相似文献   

于DEM光照晕渲模拟的梯田自动提取方法     

代文  那嘉明  杨昕  曹建军 《地球信息科学学报》2017,19(6):754-762

梯田作为黄土高原最为典型的人工地貌之一,有重要的农业生产和水土保持价值。传统的梯田自动提取仅限于梯田所在区域的范围划定,未能对梯田田坎线实现有效的自动化提取。鉴于此,本文提出了一种基于光照晕渲模拟的梯田快速提取方法。首先,对无人机航测生成的1 m分辨率的数字高程模型（DEM）进行4个方向的光照晕渲模拟,并相加取平均值;然后,通过适当的阈值对均值图像进行二值化,并掩膜掉沟谷等非梯田区域;最后,基于二值化图像自动矢量化得到梯田田坎线,并通过适当的长度阈值进行碎线过滤提高提取精度。本文以陕西省长武县王东沟流域为实验样区进行了实验,结果表明,该方法提取结果的准确率为89.09%,具有较好的提取精度。此外,对该方法涉及到的参数进行了讨论,表明光照模拟的方向角采用2个正交的对称方向对、高度角采用田坎坡度的反正切值、二值化阈值采用t=180-σ的经验公式,可以满足黄土高原的梯田自动快速提取。  相似文献   

毛乌素沙地臭柏、油蒿细根分解过程中养分与能量的变化     

秦艳  胡永宁  王林和  那日苏  张国盛 《中国沙漠》2010,30(6):1341-1347

应用埋袋法对毛乌素沙地天然分布的优势种臭柏、油蒿细根分解进行研究。对两年的实验数据进行分析,结果显示,臭柏、油蒿细根分解过程中C、P、K、Mg均表现为释放,释放率油蒿＞臭柏,元素重量损失率K＞P＞C＞Mg;N在臭柏分解中表现为积累,在油蒿分解中表现为释放;Ca在臭柏、油蒿细根分解中都表现为积累的趋势,积累率为油蒿＞臭柏;能量在臭柏、油蒿细根分解过程中表现为释放。该研究为沙区土壤库中的能量转化和流动过程提供了理论依据。  相似文献   

兼容光学雷达影像及地形辅助数据的扎龙湿地遥感分类     

刘蕾  臧淑英  那晓东  裴雪原 《地理与地理信息科学》2013,29(1):36-40,1

结合Landsat TM影像、Envisat ASAR的C波段雷达影像和地形辅助数据,采用决策树方法,包括分类回归树(C1assification and Regression Tree,CART)和随机森林(Random Forest,RF)算法,对扎龙湿地进行遥感分类。用实测GPS样本点对分类结果进行精度验证,并与最大似然监督分类方法(Maximum Likelihood Classification,MLC)对比。结果表明,地形辅助数据和雷达后向散射系数对湿地分类精度的提高起重要作用。基于RF算法分类结果的总精度和Kappa系数分别为92.6%和0.901,沼泽湿地的分类精度达到96.3%,较CART算法和MLC监督分类方法有明显提高。该研究提供了一种快速、高效的内陆淡水沼泽湿地遥感分类技术。  相似文献   

Interactions between river flows and colonizing vegetation on a braided river: exploring spatial and temporal dynamics in riparian vegetation cover using satellite data     

W. Bertoldi  N. A. Drake  A. M. Gurnell 《地球表面变化过程与地形》2011,36(11):1474-1486

Field, laboratory, and numerical modelling research are increasingly demonstrating the potential of riparian tree colonization and growth to influence fluvial dynamics and the evolution of fluvial landforms. This paper jointly analyses multi‐temporal, multispectral ASTER data, continuous river stage and discharge data, and field observations of the growth rates of the dominant riparian tree species (Populus nigra) along a 21 km reach of the Tagliamento River, Italy. Research focuses on the period 2004–2009, during which there was a bankfull flood on 24 October 2004, followed by 2 years with low water levels, nearly 2 years with only modest flow pulses, and then a final period from 15 August 2008 that included several intermediate to bankfull flow events. This study period of increasing flow disturbance allows the exploration of vegetation dynamics within the river's active corridor under changing flow conditions. The analysis demonstrates the utility of ASTER data for investigating vegetation dynamics along large fluvial corridors and reveals both spatial and temporal variations in the expansion, coalescence, and erosion of vegetated patches within the study reach. Changes in the extent of the vegetated area and its dynamics vary along the study reach. In sub‐reaches where riparian tree growth is vigorous, the vegetated area expands rapidly during time periods without channel‐shaping flows, and is subsequently able to resist erosion by bankfull floods. In contrast, in sub‐reaches where tree growth is less vigorous, the vegetated area expands at a slower rate and is more readily re‐set by bankfull flood events. This illustrates that the rate of growth of riparian trees is crucial to their ability to contribute actively to river corridor dynamics. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Early Cambrian Mollusc Watsonella crosbyi: A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2     

LI Guoxiang  ZHAO Xin  Alexander GUBANOV  ZHU Maoyan  NA Lin 《《地质学报》英文版》2011,85(2):309-319

The mollusc Watsonella crosbyi was studied on the basis of material from the lower Cambrian Dahai Member of the Zhujiaqing Formation in eastern Yunnan, China and the Pestrotsvet Formation of the Aldan River region in the Siberian Platform. This fossil had been excessively described under different names in the literature, such as Heraultia varensalensis Cobbold, 1935, H. sibirica Missarzhevsky, 1974, Heraultipegma yunnanensis He and Yang, 1982, H. yannanese He and Yang, 1982, Watsonella yunnanensis, W. crosbyi Grabau, 1900, etc. Taxonomic revision shows that other species are junior synonyms of W. crosbyi. Analysis of functional morphology implies that W. crosbyi may be rather a helcionelloid than a rostroconch since its univalved conch is untorted endogastric and lacks a rostrum and a true internal pegma. Replicas of the original microstructures preserved on the surfaces of phosphatic internal moulds confirm that the shell consists of two layers. The inner layer is lamello-fibrillar, and the outer layer is spherulitic prismatic. The widespread geographical occurrences in both siliciclastic and carbonate rocks of the late Terreneuvian indicate that W. crosbyi is an important index fossil for global correlations and subdivision of the Cambrian Series 1 (Terreneuvian). The first appearance datum (FAD) of W. crosbyi is suggested to be a potential GSSP (Global Boundary Stratotype Section and Point) candidate marker for defining the base of the Cambrian Stage 2.  相似文献