新疆图拉尔根镁铁-超镁铁质杂岩体镍铜钴成矿岩浆作用过程:流体化学与碳同位素组成制约     

张铭杰  班舒悦  李思奥  宋哲  仇哲  李立武  惠卫东  李中平 《岩石学报》2020,36(12):3673-3682

东天山造山带的图拉尔根镁铁-超镁铁杂岩体为一个早古生代长期活动的幔源岩浆通道，大型铜镍钴硫化物矿体赋存于Ⅰ号超镁铁质岩体的顶部，不同类型岩石中辉石矿物的流体挥发份化学组成以H₂O为主（平均91%，5400.4mm³/g），其次为H₂（2.0%）、H₂S（2.3%）和CO₂（2.1%）；赋矿角闪橄榄岩中CO₂和H₂S含量最高，辉长岩中流体挥发份含量低于辉石橄榄岩和橄榄辉石岩等岩浆早期结晶的岩石。CO₂和CH₄的δ¹³C值位于地壳与甲烷氧化的范围内，甲烷同系物的碳同位素组成具有正序分布模式，部分样品（TLG512）释出的CH₄和C₂H₆具有较重的δ¹³C值和反序分布特征。表明I号岩体不同类型岩石可能是不同期次岩浆活动的产物，成矿岩浆具有富H₂O和H₂S的特征，可能起源于被流体交代的亏损地幔源区，混染壳源组分可能为俯冲板片来源蚀变沉积有机质组分。  相似文献   

长白山天池火山天文峰期黄色浮岩成因研究     

潘波  程滔  徐丹  刘松军 《岩石学报》2020,36(7):2067-2080

长白山天池火口北侧天文峰之上,一套醒目的黄色浮岩引起广泛的关注,其颜色成因问题更是讨论的热点。本文通过野外地质调查、显微形貌和地球化学分析等方法,探索了黄色浮岩的颜色成因问题,并对此次喷发活动(天文峰期喷发)有了更进一步的认识。黄色浮岩与其下部灰白色浮岩应为同一期喷发所形成,两者成分一致且特征相似。黄色浮岩初始颜色为灰白色,后期受所处环境(降水丰富)与本身气孔特征的影响,浮岩内发生了元素析出和元素沉淀的过程。首先,浮岩内Si与H2O结合形成弱硅酸(H2Si O3),而大气中CO2与H2O结合形成弱碳酸(H2CO3),在弱酸环境下火山玻璃逐渐析出Si、K、Al、Ca和Fe等阳离子,而析出的元素易溶于水的部分被流水带走,难溶于水的Fe与Al富集并粘附在火山玻璃壁上,同时由于Fe可与H2O络合形成黄色的Fe的水合物(Fe2O3·n H2O),而Al与H2O络合形成凝胶状白色水合物(Al2O3·n H2O),两者混合形成了黄色胶状物粘附在火山玻璃壁上,改变了浮岩原本的灰白色,形成了黄色浮岩。因此,天文峰期浮岩的黄色是由于后期风化淋滤作用所造成,属于次生色。本研究提高了对火山喷发堆积物风化淋滤作用过程的认识,也为其他地区相似颜色变化问题的讨论提供了借鉴。  相似文献   

Hydrodynamic forces on a partially submerged cylinder at high Reynolds number in a steady flow     

《Applied Ocean Research》2019

The hydrodynamic forces on the stationary partially submerged cylinder are investigated through towing test with Reynolds number ranging from 5 × 10⁴ to 9 × 10⁵. Three test groups of partially submerged cylinders with submerged depths of 0.25 D, 0.50 D, and 0.75 D and one validation group of fully submerged cylinders are conducted. During the experiments, the hydrodynamic forces on the cylinders are measured using force sensors. The test results show a considerable difference in the hydrodynamic coefficients for the partially submerged cylinders versus the fully submerged cylinders. A significant mean downward lift force is first observed for the partially submerged cylinders in a steady flow. The maximum of the mean lift coefficients can reach 1.5. Two distinct features are observed due to the effects of overtopping: random distributions in the mean drag coefficients and a clear quadratic relationship between the mean lift coefficients and the Froude number appear in the non-overtopping region. However, the novel phenomenon of a good linear relationship with the Froude number for the mean hydrodynamic coefficients is clearly shown in the overtopping region. In addition, fluctuating hydrodynamic coefficients are further proposed and investigated. These results are helpful to have a better understanding of the problem and to improve related structural designs.  相似文献   

Quantifying suitable dynamic water levels in marsh wetlands based on hydrodynamic modelling     

Peng Hu  Zefan Yang  Qiande Zhu  Weize Wang  Qin Yang 《水文研究》2021,35(2):e14054

The water level of marsh wetlands is a dominant force controlling the wetland ecosystem function, especially for aquatic habitat. For different species, water level requirements vary in time and space, and therefore ensuring suitable water levels in different periods is crucial for the maintenance of biodiversity in marsh wetlands. Based on hydrodynamic modelling and habitat suitability assessment, we determined suitable dynamic water levels considering aquatic habitat service at different periods in marsh wetlands. The two-dimensional hydrodynamic model was used to simulate the temporal and spatial variation of water level. The habitat suitability for target species at various water levels was evaluated to obtain the fitting curves between Weighted Usable Area (WUA) and water levels. And then suitable water levels throughout the year were proposed according to the fitting curves. Using the Zhalong Wetland (located in northeastern China) as a case study, we confirmed that the proposed MIKE 21 model can successfully be used to simulate the water level process in the wetland. Suitable water levels were identified as being from 143.9–144.2 m for April to May, 144.1–144.3 m for June to September, and 144.3–144.4 m for October to November (before the freezing season). Furthermore, proposed water diversion schemes have been identified which can effectively sustain the proposed dynamic water levels. This study is expected to provide appropriate guidance for the determination of environmental flows and water management strategies in marsh wetlands.  相似文献   

Cotton canopy reflectance under variable solar zenith angles: Implications of use in evapotranspiration models     

Christopher M. U. Neale  Maria P. Gonzalez-Dugo  Angelica Serrano-Perez  Isidro Campos  Luciano Mateos 《水文研究》2021,35(6):e14162

Evapotranspiration (ET) is an important parameter in hydrologic processes and modelling. In agricultural watersheds with competing uses of fresh water including irrigated agriculture, estimating crop evapotranspiration (ET_c) accurately is critical for improving irrigation system and basin water management. The use of remote sensing-based basal crop coefficients is becoming a common method for estimating crop evapotranspiration for multiple crops over large areas. The Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI), based on reflectance in the red and near-infrared bands, are commonly used for this purpose. In this paper, we examine the effects of row crop orientation and soil background darkening due to shading and soil surface wetness on these two vegetation indices through modelling, coupled with a field experiment where canopy reflectance of a cotton crop at different solar zenith angles, was measured with a portable radiometer. The results show that the NDVI is significantly more affected than the SAVI by background shading and soil surface wetness, especially in north–south oriented rows at higher latitudes and could lead to a potential overestimation of crop evapotranspiration and irrigation water demand if used for basal crop coefficient estimation. Relationships between the analysed vegetation indices and canopy biophysical parameters such as crop height, fraction of cover and leaf area index also were developed for both indices.  相似文献   

捷联式航空重力扰动矢量解算及误差补偿     

郭栋  孙中苗  吴富梅  张琪 《大地测量与地球动力学》2018,38(12):1295-1301

介绍捷联式航空重力矢量测量的基本原理，利用波数相关滤波（WCF）、比力线性校正的方法对重力扰动的水平和垂向分量进行误差补偿，评定内符合精度。对国产捷联式航空重力矢量仪的某次试验数据进行处理，以验证和评估航空重力矢量仪的性能。结果表明，在半波长分辨率为7.5 km时，6条重复测线的重力扰动水平分量经波数相关滤波处理后，东、北向分量的平均内符合精度分别从9.77 mGal、9.18 mGal提高到5.95 mGal、3.83 mGal；对比力的垂向分量线性校正后，将解算的重力扰动垂向分量再用WCF方法处理，其平均内符合精度从1.27 mGal提高到0.59 mGal。  相似文献   

顾及地类转换差异的城市空间扩展元胞自动机模型及应用研究     

于明明  曾永年 《地球信息科学学报》2018,20(1):48-56

元胞自动机模型已经成为城市空间扩展模拟研究的重要方法之一,并得到广泛应用。然而,现有的城市扩展元胞自动机模型仍存在不足。由于元胞状态设置较为简单,从而使模型转换规则中对不同用地类型向城市用地转换的差异与强度考虑不够。基于此本文在元胞自动机模型的框架下,设计了多元结构的元胞状态及转换规则,提出了顾及地类转换差异与强度的城市扩展元胞自动机模型。在计算非城市用地向城市用地转换的转换概率时,该模型考虑了3个方面的概率：① 地形地貌、经济发展等城市发展的驱动因素对城市用地扩展的影响概率,该概率采用logistics方法进行计算;② 邻域元胞的用地类型对中心元胞转换概率的影响,该概率采用扩展摩尔型方法进行计算;③ 不同类型的非城市用地（本研究中包括耕地、林地和裸地3种类型）向城市用地转换的强度,该概率由模拟基期土地利用数据与目标年份土地利用数据的叠加,得出不同类型的非城市用地在此时间段内向城市用地转换的规模,进而确定不同类型的非城市用地向城市用地转换的强度。最后,将以上3种概率的乘积作为元胞转换的概率。通过转换概率与转换阈值的对比判断中心元胞是否在下一个阶段转换为城市用地。经过迭代计算,不断增加城市用地元胞的数量。当模拟城市用地的结果与目标年份的城市用地规模差值在一定的范围内时停止模拟,得出最终结果。模型构建完成后,本文以长株潭城市群核心区为例进行了模拟实验。以2001年该地区的土地利用数据为基期数据,模拟2010年该地区的城市用地规模和空间分布。研究结果表明,根据本文提出的模型模拟的城市扩展结果与真实数据相比具有较高的一致性。模拟结果正确率达到68.66%,比基于传统logistics回归的元胞自动机模型的模拟精度提高了4.25%,Kappa系数为0.675。该模型较好地模拟了长株潭城市群核心区城市扩展,在城市空间扩展模拟中具有较好的适应性与有效性。  相似文献   

GPS约束下陇西地区断裂带现今滑动速率的非连续接触模拟研究     

孟庆筱  景鹏旭  何申海  党学会 《大地测量与地球动力学》2018,38(12):1227-1231

以中国地壳运动观测网络1999、2001、2004和2007年4期GPS观测数据为边界条件，使用非连续接触有限元技术构建陇西块体二维有限元模型，在摩擦系数不确定性分析基础上，计算区内主要断裂带滑动速率。结果表明，现今地壳形变运动状态下陇西块体的北东向运动在海原断裂附近受到鄂尔多斯块体、阿拉善块体阻碍，陇西块体周缘的海原断裂带、老虎山断裂、西秦岭北缘断裂呈现左旋走滑特征，滑动速率为3.5 mm/a、2.2 mm/a和1.9 mm/a，说明在青藏高原推挤作用下以上关键部位正在进行快速的构造应变积累。  相似文献   

基于ROMS和4DVAR的沿轨与网格化SSH数据同化效果评价   总被引：1，自引：1，他引：0  

周超杰  丁效华  张杰  杨俊刚  马强 《海洋学报(英文版)》2018,37(9):50-58

Remote sensing products are significant in the data assimilation of an ocean model. Considering the resolution and space coverage of different remote sensing data, two types of sea surface height(SSH) product are employed in the assimilation, including the gridded products from AVISO and the original along-track observations used in the generation. To explore their impact on the assimilation results, an experiment focus on the South China Sea(SCS) is conducted based on the Regional Ocean Modeling System(ROMS) and the four-dimensional variational data assimilation(4 DVAR) technology. The comparison with EN4 data set and Argo profile indicates that, the along-track SSH assimilation result presents to be more accurate than the gridded SSH assimilation, because some noises may have been introduced in the merging process. Moreover, the mesoscale eddy detection capability of the assimilation results is analyzed by a vector geometry–based algorithm. It is verified that, the assimilation of the gridded SSH shows superiority in describing the eddy's characteristics, since the complete structure of the ocean surface has been reconstructed by the original data merging.  相似文献   

参数带椭球约束平差算法的应用     

肖兆兵  宋迎春  谢雪梅 《大地测量与地球动力学》2018,38(9):964-967

针对实际工程应用中遇到的参数带有范围约束的情形，提出带椭球约束的平差算法，并给出其具体模型和解算步骤。数值模拟实验和病态测边网数据计算表明，在处理病态问题时，最小二乘平差（least-squares，LS）已不适用，而与岭估计、奇异值分解法（singular value decomposition，SVD）以及不等式约束相比，本文算法精度更高。  相似文献