甘肃祁连山西段金矿分布特征及控矿因素分析          下载免费PDF全文

佘小龙  矫润田  赵梦  贾志磊 《甘肃地质》2018,(2):43-52

祁连西段是甘肃省重要的金成矿带,分布有鹰嘴山、寒山、阳凹大泉、车路沟、金湾子等金矿床,近年又新发现豹子沟南、滴水山、牛毛泉、积阴功台金矿,显示出较大的区域找矿潜力。本文通过典型金矿床和新发现金矿成矿地质条件分析,总结了甘肃祁连山西段金矿的空间分布特征、控矿因素。初步研究认为祁连山西段主要的金矿床呈带状分布于阿尔金走滑断裂与北祁连褶皱断裂构造带交汇部位,明显受不同规模、不同序次的韧、脆性断裂构造破碎带控制;成矿与区域内不同规模中酸性—中基性岩体及岩脉有关;古生代火山碎屑岩、浅变质碎屑岩为主要容矿岩性及含矿建造;矿体普遍具有延深大于延长、深部明显富集的特征。新发现金矿多以化探异常查证为重点,不断浓缩异常源,实现找矿突破。本文对祁连山西段的金矿勘查具有指导意义,对该地区的金矿研究也提供了重要的基础资料。  相似文献   

Detection and mapping of bracken fern weeds using multispectral remotely sensed data: a review of progress and challenges     

Trylee Nyasha Matongera  Onisimo Mutanga  Timothy Dube  Romano Trent Lottering 《国际地球制图》2018,33(3):209-224

Bracken fern is one of the major invasive plants distributed all over the world currently threatening socio-economic and ecological systems due to its ability to swiftly colonize landscapes. The study aimed at reviewing the progress and challenges in detecting and mapping of bracken fern weeds using different remote sensing techniques. Evidence from literature have revealed that traditional methods such as field surveys and modelling have been insufficient in detecting and mapping the spatial distribution of bracken fern at a regional scale. The applications of medium spatial resolution sensors have been constrained by their limited spatial, spectral and radiometric capabilities in detecting and mapping bracken fern. On the other hand, the availability of most of these data-sets free of charge, large swath width and their high temporal resolution have significantly improved remote sensing of bracken fern. The use of commercial satellite data with high resolution have also proven useful in providing fine spectral and spatial resolution capabilities that are primarily essential to offer precise and reliable data on the spatial distribution of invasive species. However, the application of these data-sets is largely restricted to smaller areas, due to high costs and huge data volumes. Studies on bracken fern classification have extensively adopted traditional classification methods such as supervised maximum likelihood classifier. In studies where traditional methods performed poorly, the combination of soft classifiers such as super resolution analysis and traditional methods of classification have shown an improvement in bracken fern classification. Finally, since high spatial resolution sensors are expensive to acquire and have small swath width, the current study recommends that future research can also consider investigating the utility of the freely available recently launched sensors with a global footprint that has the potential to provide invaluable information for repeated measurement of invasive species over time and space.  相似文献   

南秦岭柞山地区铅银锌矿成矿规律及找矿模型     

王鹏 《江苏地质》2021,45(4):349-365

南秦岭柞水银洞子—山阳桐木沟铅银锌矿带地处陕西柞山地区中部,位于中秦岭晚古生代弧前盆地的柞水—山阳矿集区内。该带东西长约71 km,南北宽1～7 km。对带内银洞子（铜）铅银菱铁矿床、黑沟铅锌菱铁矿床、桐木沟锌矿床、南沟（银）铅矿床和松林沟铅矿点的地质、矿体、蚀变、矿化规律进行总结,发现矿体均严格产于中-上泥盆统青石垭组,具有明显的时控、层控、岩控及后期热液改造成矿特征,属典型的海底热水喷流沉积-热液改造层控矿床,构成与晚古生代海底热水喷流沉积-热液改造作用有关的铅锌银成矿系列。建立以层控+热液改造为主控矿条件,以青石垭组热水沉积岩+断裂+化探异常+硫化物、重晶石、菱铁矿蚀变分带为组合的找矿模型,对柞山地区金属矿的找矿突破具有重要的指导意义。  相似文献   

GRAPES全球集合预报系统模式扰动随机动能补偿方案初步探究   总被引：10，自引：5，他引：5  

彭飞  李晓莉  陈静  李红祺 《气象学报》2019,77(2):180-195

为了体现次网格尺度能量升尺度转换过程中存在的不确定性, 文中将随机动能补偿(Stochastic Kinetic Energy Backscatter, SKEB)方案应用于GRAPES(Global/Regional Assimilation and Prediction System)全球集合预报系统(GRAPES-GEPS), 以更好地表征模式误差并且增大集合离散度。使用的SKEB方案基于具有一定时、空相关特征的随机型以及由数值扩散导致的局地动能耗散率来构造随机流函数强迫。并根据流函数与水平风速旋转分量的关系, 将SKEB方案中的流函数强迫转化为适用于GRAPES全球模式的水平风速扰动。结果表明, SKEB方案的使用一方面能够提高GRAPES对大气动能谱的模拟能力; 另一方面能够改善GRAPES-GEPS的集合离散度与集合平均误差的关系, 增加了集合离散度, 并在一定程度上减小了集合平均误差, 尤其是在热带地区这种改进更为显著。而且该方案使得热带地区连续分级概率评分(CRPS评分)显著减小。就降水预报而言, 从Brier评分与相对作用特征面积(AROC, Area under the Relative Operating Characteristics)的结果来看, SKEB方案有助于改善中国地区小雨[0.1 mm, 10 mm)、中雨[10 mm, 25 mm)与大雨[25 mm, 50 mm)量级降水的概率预报技巧, 而对暴雨[50 mm, ∞)量级降水预报技巧影响很小(24 h降水量)。总体上, 模式扰动随机动能补偿方案提高了GRAPES-GEPS的概率预报技巧。   相似文献   

陆面过程模式BCC_AVIM中地表覆盖数据现状     

周文艳  罗勇  史学丽  李伟平  张艳武 《气象》2019,45(10):1476-1482

地表覆盖是陆面和气候模式中的一个重要基础数据。以陆面过程模式BCC_AVIM为例,介绍模式中的地表覆盖数据变量、数据分辨率、不同类型数据的来源,重点比较分类方法差异巨大且类型众多的植被覆盖。综述比较了国际和国内常用的几套全球地表覆盖数据的来源、分类系统和分类方法以及空间分辨率,根据陆面过程模式的地表覆盖数据需求,确定不同全球土地覆盖数据在模式中的应用方法,讨论分析了全球地表覆盖产品在模式应用中存在的差距,提出不同遥感数据产品之间一致性较差的可能解决方案,探讨遥感数据产品在模式中应用的可能方式,以期更好地发挥全球地表覆盖数据产品的作用。  相似文献   

全球寒武系四统划分框架正式确立   总被引：33，自引：4，他引：29  

彭善池 《地层学杂志》2006,30(2):147-148

国际地层委员会最近陆续发布了2005和2006年版《国际地层表》(http://www.stratigraphy.org/cheu.pdf),这两张新表较以往各版最为突出的变动是将寒武系分为四个统和十个阶,不再采用国际地学界沿用了近一百七十年的上、中、下3统的传统划分方法。这一改写是全球地层学的重大事件  相似文献   

Trends in stream and river temperature     

B. W. Webb 《水文研究》1996,10(2):205-226

Information on past and likely future trends in water temperature from different parts of the world is collated. The potential causes of trends in the thermal regimes of streams and rivers are many, but the existing database of water temperature information is inadequate to provide a global perspective on changes during the recent, let alone the more remote, past. Data from Europe suggest that warming of up to ca. 1°C in mean river temperatures has occurred during the 20th century, but that this trend has not been continuous, is distorted by extreme hydrological events, is not correlated with simple hydrometeorological factors and has been influenced by a variety of human activities. Predictive studies indicate that an accelerated rise in stream and river temperatures will occur during the next century as a consequence of global warming. However, forecasts must be tentative because future climatic conditions are uncertain and interactions between climate, hydrological and vegetation changes are complex.  相似文献   

Using Statistical Downscaling to Quantify the GCM-Related Uncertainty in Regional Climate Change Scenarios： A Case Study of Swedish Precipitation   总被引：2，自引：0，他引：2  

Deliang CHEN  Christine ACHBERGER  Jouni R¨AIS¨ANEN  Cecilia HELLSTR¨OM 《大气科学进展》2006,23(1):54-60

There are a number of sources of uncertainty in regional climate change scenarios. When statistical downscaling is used to obtain regional climate change scenarios, the uncertainty may originate from the uncertainties in the global climate models used, the skill of the statistical model, and the forcing scenarios applied to the global climate model. The uncertainty associated with global climate models can be evaluated by examining the differences in the predictors and in the downscaled climate change scenarios based on a set of different global climate models. When standardized global climate model simulations such as the second phase of the Coupled Model Intercomparison Project （CMIP2） are used, the difference in the downscaled variables mainly reflects differences in the climate models and the natural variability in the simulated climates. It is proposed that the spread of the estimates can be taken as a measure of the uncertainty associated with global climate models. The proposed method is applied to the estimation of global-climate-model-related uncertainty in regional precipitation change scenarios in Sweden. Results from statistical downscaling based on 17 global climate models show that there is an overall increase in annual precipitation all over Sweden although a considerable spread of the changes in the precipitation exists. The general increase can be attributed to the increased large-scale precipitation and the enhanced westerly wind. The estimated uncertainty is nearly independent of region. However, there is a seasonal dependence. The estimates for winter show the highest level of confidence, while the estimates for summer show the least.  相似文献   

气候变暖对黄河源区生态环境的影响   总被引：15，自引：2，他引：13  

曹文炳  万力  曾亦键  胡伏生  陈劲松 《地学前缘》2006,13(1):40-47

黄河源区位于多年冻土区,严酷寒冷的气候条件和冻土共同构建成一种特殊的冻结水环境,使地下水类型和水文地质结构均发生变化,与非冻土区有显著的差别,形成特殊的水文地质区。近几十年来,由于全球性气候温变暖,出现大面积冻土退化,以及过度放牧、鼠害加剧等原因,造成草场退化,沙漠化趋势日渐明显,严重地冲击着黄河河源区的水源养涵功能,导致黄河在源头段多次出现断流。通过水平衡计算,探讨了气候变暖对黄河源区多年冻土退化的影响,并阐述了冻结层上水环境变化和人类活动对生态环境的影响。  相似文献   

Intraseasonal oscillation intensity over the western North Pacific:Projected changes under global warming          下载免费PDF全文

Yi Fan  Ke Fan  Zhiqing Xu 《大气和海洋科学快报》2021,14(4):1-6

本文利用8个CMIP5模式的日资料,预估了RCP4.5和RCP8.5情景下全球增温达1.5℃和2.0℃时西北太平洋夏季30～60天和10～20天季节内振荡(ISO)强度的变化情况.大多数模式都认为,无论增温水平或情景如何,预估结果均显示从中南半岛南部到菲律宾以东的带状区域内ISO强度增加,并且关键气象要素背景的变化会对...  相似文献