南海北部西沙海槽沉积物管状黄铁矿特征及其形成机理^*          下载免费PDF全文

石思思  吴朝东  梁金强  王熠哲  叶云涛  方允鑫  马健  翟俪娜 《古地理学报》2020,22(1):175-192

南海北部西沙海槽S1站位的岩心柱沉积物中广泛发育自生矿物黄铁矿,其形态以管状为主,且具有内部中空的圈层结构。使用扫描电镜、电子探针、LA-ICP-MS、SIMS等测试方法研究了管状黄铁矿的形态及圈层结构,结果显示: (1)管状黄铁矿发育内部中空的圈层结构,其中内圈层(I_py)由莓球状黄铁矿呈五角十二面体紧密堆积组成,外圈层(O_py)由晶形较好晶粒较大的八面体黄铁矿组成,并混有沉积碎屑及钙质生物壳体;(2)内圈层和外圈层分别呈现出贫S富Fe和富S贫Fe的特征,其成因是甲烷渗漏造成的局部还原环境使得As进入黄铁矿中导致晶格空缺或被扭曲,从而促进Ni、Co、Cu、Zn、Pb等微量元素的掺入;(3)内圈层、外圈层发生了明显的硫同位素分馏现象,内圈层中 δ³⁴S 平均为-37.8‰,外圈层中 δ³⁴S 平均为-29.3‰。研究认为,管状黄铁矿作为曾经甲烷渗漏的通道,其生长机制可分为3个阶段: (1)气水通道形成阶段: 向上运移的甲烷流体在沉积物孔隙中逐渐形成气水通道;(2)外圈层形成阶段: 当向上运移的甲烷与硫酸盐发生甲烷厌氧氧化时,逐渐形成晶体较大、晶形较好的八面体黄铁矿外圈层;(3)内圈层形成阶段: 随着甲烷浓度逐渐降低,在气水通道中的微生物作用下,剩余甲烷与向下运移的硫酸盐继续反应形成莓球状黄铁矿内圈层。因此,南海北部的泥岩中大量发育的管状黄铁矿常常与地层中甲烷水合物的存在有关。  相似文献   

基于波形特征的露天钼矿微震事件的识别分析——以卓资山钼矿为例     

赵艳红  包金哲  王树波  翟浩  魏建民  杨智升  张晖  赵铁锁  苏日亚  王磊  王鑫  贾昕晔  刘芳 《震灾防御技术》2019,14(3):662-676

基于前人研究成果以及现场的实测结果，采用卓资山露天钼矿微震监测项目产出资料，提取了5类微震事件的波形特征和时频特征。波形特征显示:微地震的振幅、辐射均匀性和频率变化特征表明微地震是由于岩层受到单力偶和剪切力作用破裂而产生；爆破具有P波初动方向向上、S波不易识别的特点，包含“初震段、主震段、尾波段”三段变化形态；小型边坡滑坡波事件属楔体滑坡，是由多个“加速—缓冲—终止”构成，波形是由包络线呈“V”字形的多组脉冲波列组成；机械开采震动事件具有自振能量不变、脉冲幅度相差很大、持续时间间隔不确定的特点；运输车辆波形振幅具有形态“弱—强—弱”、等频率、包络线呈多段纺锤形的特征。时频空间分布可以分为相对独立、界限分明的两类:一类包含微地震、爆破、机械开采、小型边坡滑坡事件，另一类只包含车辆运输事件。  相似文献   

A brief review of ENSO theories and prediction     

Xianghui FANG  Ruihuang XIE 《中国科学:地球科学(英文版)》2020,63(4):476-491

Although the El Ni?o-Southern Oscillation(ENSO) originates and develops in the equatorial Pacific, it has substantial climatic impacts around the globe. Thus, the ability to effectively simulate and predict ENSO one or more seasons in advance is of great societal importance, but this remains a challenging task. The main obstacles are the diversity, complexity,irregularity, and asymmetry of ENSO. The purpose of this article is to organically integrate the understanding of ENSO based on current progress on the physical mechanisms, prediction, and connections between the interannual ENSO phenomenon and physical processes on other time and space scales, and to provide guidance for future studies by extracting specific important questions.  相似文献   

Variation in the vertical zonality of erodibility and critical shear stress of rill erosion in China's Hengduan Mountains     

Zhengan Su  Donghong Xiong  Jianhui Zhang  Tao Zhou  Hongkun Yang  Yifan Dong  Haidong Fang  Liangtao Shi 《地球表面变化过程与地形》2019,44(1):88-97

Soil erodibility is an essential parameter used in soil erosion prediction. This study selected the Liangshan town watershed to quantify variation in the vertical zonality of rill erodibility (k_r) in China's ecologically fragile Hengduan Mountains. Soil types comprised of yellow–brown (soil A), purple (soil B), and dry-red (soil C) in a descending order of occurrence from the summit to the valley, which roughly corresponds to the vertical climate zone (i.e. cool-high mountain, warm-low mountain, and dry-hot valley sections) of the study area. With elevation, vertical soil zonality varied in both soil organic matter (SOM) content and soil particle-size fractions. A series of rill erosion-based scour experiments were conducted, using water discharge rates of 100, 200, 300, 400, 500, and 600 mL min^-1. Additionally, detachment rates (Dr) were measured under three hydrological conditions (the drainage, saturation, and seepage treatments). Results show that both Dr and flow shear stress (Ʈ) values increased as discharge increased. As elevation increased, the k_r values decreased, while the vertical zonality of critical shear stress (Ʈ_c) values showed no obvious variation. The highest k_r values were observed during the seepage treatment, followed by the saturation treatment then drainage treatment, indicating that variation in vertical hydraulic gradients could significantly alter k_r values. This study also found that land-use types could also alter k_r and Ʈ_c values. Further research, however, is necessary to better quantify the effects of subsurface hydrological conditions and land-use types on k_r under different soil zonalities in China's Hengduan Mountains. © 2018 John Wiley & Sons, Ltd.  相似文献   

Comparisons of Salinity Adaptation in Terms of Growth,Body Composition,and Energy Budget in Juveniles of Rainbow and Steelhead Trouts (Oncorhynchus mykiss)     

XIONG Yinghuai  WANG Xin  DONG Shuanglin  WANG Fang  YANG Jingwen  ZHOU Yangen 《中国海洋大学学报(英文版)》2019,(2)

This study examined the effect of different salinities(0, 5, 10, 15, 20, 25 and 30) on the growth performance and energy budget of juveniles of two different ecotypes of Oncorhynchus mykiss, landlocked rainbow trout and anadromous steelhead trout. In the 42 d experiment, fish were cultured in three replicate tanks per salinity treatment(eight fish per tank). At the end of the experiment, the growth of rainbow and steelhead trouts was significantly higher at salinities of 5 and 10, respectively, than at all other salinities. The protein, lipid and energy content of both ecotypes declined with the increase of salinity. Based on their energy budgets, the percentage of energy consumed for growth by rainbow and steelhead trouts were significantly higher at salinities of 5(34.00% ±1.69%) and 10(43.76% ± 1.29%), respectively, than at all other salinities. The percentage of energy consumed for respiration by rainbow and steelhead trouts was lower at salinities of 5(54.90% ± 1.77%) and 10(46.73% ± 0.62%), respectively, than at all other salinities. Our results indicated that the salinity adaptation ability of juvenile steelhead trout was slightly better than that of juvenile rainbow trout, and salinities of 10 and 5, respectively, were most suitable for growth of these two fishes.  相似文献   

利用偏光显微镜反射光系统观察黑色生油岩电子探针薄片中的生烃母质特征     

郑庆华  刘行军  刘乔  梁秀玲  张小龙  左琴  杨开艳  马婷  许锋 《岩矿测试》2020,39(3):442-450

鄂尔多斯盆地上三叠统延长组长7油层组的黑色泥岩、油页岩等黑色生油岩薄片中的生烃母质,因黑色石油、沥青等黑色有机质的覆盖或不透明,导致其在偏光显微镜透射光系统下观察常局部或整体呈现为黑色。因此,建立一种黑色生油岩薄片中生烃母质有效观察的方法,对致密油、页岩油的生烃研究具有重要的理论和实际意义。本文提出了一种利用电子探针薄片和偏光显微镜的反射光系统观察黑色生油岩中生烃母质特征的方法。该方法能够克服黑色生油岩薄片中生烃母质因被黑色有机质覆盖或不透明,而在偏光显微镜的透射光系统下局部或整体呈黑色的弊端,能够对生烃母质的大小、形态、结构、分布和物质成分等特征进行整体且清晰的观察。实践表明,本文提出的利用偏光显微镜反射光系统观察黑色生油岩电子探针薄片中生烃母质特征的方法,简单有效,易在致密油、页岩油的生烃研究领域推广使用。  相似文献   

太原盆地及周边地区双差层析成像   总被引：2，自引：0，他引：2       下载免费PDF全文

王长在  吴建平  杨婷  王未来  范莉苹  房立华 《地球物理学报》2018,61(3):963-974

山西断陷带位于鄂尔多斯与华北地块交汇处，是我国著名的历史强震活动带之一，尤其是断陷盆地中部区域，6级以上地震频发.本研究旨在揭示忻定盆地中南部、太原盆地及临汾盆地中北部交汇处的深部结构特征，分析盆地的形成和演化，探讨该区域孕震环境.利用山西地震台网观测数据以及固定地震台站融合流动台站得到的地震数据，共7455个地震事件，采用双差层析成像方法，反演得到了太原盆地及周边地区的三维P波速度结构及精定位结果.层析成像结果显示，忻定盆地、太原盆地的中上地壳为明显的低速异常，被高速的石岭关隆起隔开，深部结构特征相对简单.太原盆地、临汾盆地及灵石隆起之间的深部结构特征较为复杂，反映了两个盆地演化过程的复杂性.穿过忻定盆地的速度剖面显示，在中地壳存在明显的低速异常体，且大部分地震都发生在该低速体上方；穿过太原盆地北部的剖面显示，该区域在20~25 km深度范围内有较密集的地震分布，并勾画出交城断裂呈犁形的断层特征；穿过太原盆地中部的剖面显示，太原盆地自西向东沉积层逐渐减薄；穿过临汾盆地的剖面揭示，汾东断裂在浅部倾角较陡，随深度增加倾角逐渐变小，倾向向东.  相似文献   

Influence of land use on the persistence effect of riverine phosphorus          下载免费PDF全文

Dingjiang Chen  Fang Xia  Xu Shang  YuanYuan Liu  Randy A. Dahlgren  Kun Mei 《水文研究》2018,32(1):118-125

The persistence effect contribution of legacy nutrients is often cited as a reason for little or no improvement in water quality following extensive implementation of watershed nutrient mitigation actions, yet there is limited knowledge concerning factors influencing this response, often called the “persistence effect.” Here, we adopted detrended fluctuation analysis and Spearman analysis methods to assess the influence of land use on the watershed phosphorus (P) persistence effect, using monthly water quality records during 2010–2016 in 13 catchments within a drinking water reservoir watershed in eastern China. Detrended fluctuation analysis was used to calculate the Hurst exponent α to assess watershed legacy P characteristics (α  ≈ 0.5, α  > 0.5, and α  < 0.5 indicate white noise, persistence, and anti‐persistence, respectively). Results showed weak to strong P persistence (0.60–0.81) in the time series of riverine P in the 13 catchments. The Hurst exponent α had negative relationships with agricultural land (R = ?.47, p = .11) and developed land (R = ?.67, p = .01) and a positive relationship with forest land cover (R = .48, p = .10). The persistence effect of riverine P was mainly determined by retention ability (biogeochemical legacy) and migration efficiency (hydrological legacy). A catchment with strong retention capacity (e.g., biomass uptake/storage and soil PO₄ sorption) and low migration efficiency results in a stronger persistence effect for riverine P. In practice, source control is more effective in catchments with weak persistence, whereas sink control (e.g., riparian buffers and wetlands) is preferred in catchments with strong persistence effects.  相似文献   

Study on the Moment Magnitude of Small and Moderate Earthquakes Located in the Inner Mongolia Region     

Liu Fang  Zhang Fan  Li Bin  Na Re 《中国地震研究》2018,32(1):53-63

Based on digital seismic waveform data from Inner Mongolia Digital Seismic Network, the source spectrum parameters of 182 small and moderate earthquakes from January, 2009 to September, 2016 are derived, and the seismic moment M₀ and moment magnitude M_W of the earthquakes are calculated. The M_L-M_W relationship and the relationship between stress drop and magnitude are obtained using the linear regression method. It is clear that incorporating the moment magnitude into the seismic quick report catalog and the official earthquake catalog can enrich earthquake observation report content, thus providing better service for earthquake emergency and earthquake scientific research.  相似文献   

Validation of the SCEC Broadband Platform simulations for tall building risk assessments considering spectral shape and duration of the ground motion     

Nenad Bijelić  Ting Lin  Greg G. Deierlein 《地震工程与结构动力学》2018,47(11):2233-2251

Earthquake simulation technologies are advancing to the stage of enabling realistic simulations of past earthquakes as well as characterizations of more extreme events, thus holding promise of yielding novel insights and data for earthquake engineering. With the goal of developing confidence in the engineering applications of simulated ground motions, this paper focuses on validation of simulations for response history analysis through comparative assessments of building performance obtained using sets of recorded and simulated motions. Simulated ground motions of past earthquakes, obtained through a larger validation study of the Southern California Earthquake Center Broadband Platform, are used for the case study. Two tall buildings, a 20‐story concrete frame and a 42‐story concrete core wall building, are analyzed under comparable sets of simulated and recorded motions at increasing levels of ground motion intensity, up to structural collapse, to check for statistically significant differences between the responses to simulated and recorded motions. Spectral shape and significant duration are explicitly considered when selecting ground motions. Considered demands include story drift ratios, floor accelerations, and collapse response. These comparisons not only yield similar results in most cases but also reveal instances where certain simulated ground motions can result in biased responses. The source of bias is traced to differences in correlations of spectral values in some of the stochastic ground motion simulations. When the differences in correlations are removed, simulated and recorded motions yield comparable results. This study highlights the utility of physics‐based simulations, and particularly the Southern California Earthquake Center Broadband Platform as a useful tool for engineering applications.  相似文献