基于植被和潮动力作用的潮滩剖面演变数值模拟          下载免费PDF全文

龚政  白雪冰  靳闯  赵堃  周曾  张长宽 《水科学进展》2018,29(6):877-886

为研究多因子共同作用下的潮滩演变机制,开发了基于植被生长和潮动力作用的潮滩剖面演变数学模型。在不考虑植被作用下,模拟得到了潮滩中长期演变后的上凸形剖面特征;泥沙供给是决定潮滩宽度的因素,供给越充分,潮滩宽度越大。模型考虑植被过程时,结果表明不同的植被生物量分布形式对潮滩水动力的影响程度不同,在潮间带上部,生物量抛物线分布时的减流效果强于生物量线性分布形式;而在潮间带下部则相反。模拟结果显示盐沼和光滩之间出现陡坎,且随着滩面的逐步淤高,陡坎逐步向海移动。  相似文献   

Origin of giant post-collisional porphyry Cu metallogenic belt in southern Tibet: constrains from magmatic H2O, fO2, and S     

Rui Wang  Zeng qian Hou  Jeremy P. Richards  Zhi ming Yang  Di cheng Zhu 《《地质学报》英文版》2018,92(Z1):241-242

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A Profile of International Climate Change Science in the Past One Hundred Years*     

Jiansheng Qu  Xiantao Xiao  Jingjing Zeng 《地球科学进展》2018,33(11):1193-1202

Climate change is one of the most active research fields currently, which has attracted extensive attention from the international community. In order to better understand the development situation and research status of international climate change science, in this paper we took the SSCI and SCI databases as data sources, collected the relevant literatures since 1900 based on the key words related to climate change, and made some statistics and analysis of the literatures of the past one hundred years to reveal the development process of climate change research as well as the development and evolution of its research topics and hot spots. The results showed that the climate change research began in the late 18 th century and early 19 th century, and the academic debate about global warming and global cooling started in the early 1970s. The international programs and projects led by a range of international organizations and intergovernmental bodies have contributed significantly to the rapid development of climate change research. The United States and the United Kingdom have long been the core countries of climate change research. The proportion of Chinese papers has risen rapidly in the last decade. The intensity and scope of scientific research cooperation are constantly expanding. Current research focuses on climate model/modeling, climate simulation, climate policy, climate sensitivity, climate change impacts, climate change adaptation, climate change mitigation, and rate of climate change.  相似文献   

云南峨山地区东川群黑山组流纹质碎斑熔岩锆石U－Pb年龄及其地质意义          下载免费PDF全文

刘军平  曾文涛  孙柏东  胡绍斌  关学卿  孙志明  王伟  宋冬虎  吕勃烨 《沉积与特提斯地质》2018,38(3):99-105

滇中地区中元古界"昆阳群"、"东川群"的地层层序是长期争议的重大基础地质问题。本次在峨山地区东川群黑山组中发育的厚近5m厚的流纹质碎斑熔岩采集样品D0023一件,选出120余粒锆石,获得的锆石LA-ICP-MS U-Pb加权平均年龄为(1569. 2±4. 5) Ma。样品锆石的Th/U值均大于0. 5,具有清晰的振荡环带结构,均为岩浆成因的锆石,表明东川群黑山组形成于中元古代早期,属非造山相关的火山岩系,可能是哥伦比亚超大陆裂解作用在扬子陆块的响应,为东川群的地层时代和层序研究增添了新资料。  相似文献   

Garnet amphibolites from the Ganzi–Litang fault zone,eastern Tibetan Plateau: mineralogy,geochemistry, and implications for evolution of the eastern Palaeo-Tethys Realm     

Qiu-Huan Li  Yu-Xiu Zhang  Li-Long Yan  Lu Zeng  Xin Jin 《International Geology Review》2018,60(16):1954-1967

The Ganzi–Litang fault zone, an outstanding tectonic element in the eastern Tibetan Plateau has been intensively debated as an in-situ suture zone marking relict of a subducted Palaeo-Tethyan oceanic crust or a failed intracontinental rift. This paper reports the garnet amphibolites discovered along the Ganzi–Litang fault zone, eastern Tibetan Plateau. These garnet amphibolites are characterized by the garnet–hornblende–rutile–sphene–plagioclase–quartz assemblage. Conventional geothermobarometry figures out the metamorphic temperature and pressure conditions at 582–626°C and 1.61–1.82 GPa, respectively. Geochemical analysis (no Nb–Ta deletions and left-inclined to flat patterns of rare-earth elements) indicates that the garnet amphibolites could represent metamorphic product of the mid-ocean-ridge (MORB)-type mafic rocks that were contaminated by a mantle plume. The protolith of the garnet amphibolites was dated at 236 Ma using in-situ U–Pb zircon method, and the retrograde metamorphism was dated at 218 Ma using in-situ U–Pb sphene method. A comprehensive analysis combined with the development of the Palaeo-Tethys Ocean and the Yidun arc through geologic time indicates a Triassic to Early Jurassic age (236–195 Ma) for the metamorphism of the garnet amphibolites. The low geothermal gradient of 9.8ºC/km and the N-MORB nature of the garnet amphibolites suggest a subduction-zone environment for the high-pressure metamorphism. Therefore, the Ganzi–Litang fault zone is a Palaeo-Tethyan suture separating the Yidun arc and the Songpan–Ganzi terrane, representing the relics of a branch of the Palaeo-Tethys Ocean that was contaminated by a mantle plume.  相似文献   

蚀变洋壳玄武岩俯冲过程中含碳矿物相变质演化及脱碳作用的研究     

朱建江  张立飞  吕增 《岩石矿物学杂志》2018,37(3):404-416

俯冲作用是连接地表系统和地球深部系统的最为关键的地质过程,其对研究地球深部碳循环具有重要的意义。俯冲洋壳岩石圈中的碳主要存储在沉积物、蚀变洋壳玄武岩以及蛇纹岩中。俯冲变质作用过程含碳岩石的变质演化控制着其中含碳矿物相的转变及碳迁移过程。本文选取了蚀变洋壳玄武岩进行相平衡模拟,来研究其含碳矿物相的变质演化过程。计算结果表明,变质玄武岩体系中的碳酸盐矿物之间的转变反应除了受压力控制之外,还受到温度和体系中铁含量的影响。随着压力的升高蚀变玄武岩中碳酸盐矿物会发生方解石/文石-白云石-菱镁矿的转变,但在高压/超高压条件下,温度的升高可以使菱镁矿转变成白云石。碳酸盐矿物中的铁含量受到体系中铁含量的影响,白云石和菱镁矿中的铁含量随着体系中铁含量的增加而增加。在水不饱和条件下,洋壳不管是沿着低温还是高温地热梯度线俯冲到岛弧深度,蚀变玄武岩体系几乎都不发生脱碳作用。然而在水饱和条件下,当洋壳沿着高温以及哥斯达黎加地热梯度线俯冲到岛弧深度时,蚀变玄武岩体系中的碳几乎可以全部脱出去。蚀变玄武岩体系中水含量的增加可以促进体系的脱碳作用。  相似文献   

Bioacoustic application on fisheries management in an artificial reefs’ ecological reserve of Bohai Gulf China     

Lei Zeng  Zhenzhao Tang  Pimao Chen  Chunqiang Hou  Guobao Chen 《Environmental Earth Sciences》2018,77(21):728

Various techniques have been used in marine fishery resources assessment. Among those, acoustic techniques have high efficiency and wide adaptability, and are environment friendly. Therefore, acoustic techniques played a key/indispensable role in the field of ecosystem-based fishery management. Acoustic surveys were conducted during the wet (May) and dry (November) seasons in 2016 in the artificial reefs ecological reserve of Bohai Gulf and a nearby control region to understand the current situation of fishery resources and explore the effectiveness of underwater artificial constructions by a dual-frequency identification sonar (DIDSON) and a scientific split-beam echosounder (120 KHz, Simrad EY60). Fish densities in various seasons and regions showed significant differences and interaction, with a maximum value of 358020.34 ind/n.mile² in the artificial reefs’ region and a minimum value of 71898.35 ind/n.mile² in the control region during the wet season. Fish densities in defined parallel transects revealed a roughly southward migration trend of small-size individuals from wet season to dry season. Single echo detections in the artificial reefs region demonstrated a wider target strength (TS) range (? 60 ~ ? 30 dB vs ? 60 ~ ? 51 dB) and higher mean TS values (? 55.87 dB vs ? 58.31 dB) than the control region both in the wet and dry seasons, which indicated a more complicated and stable fish community structure in the artificial reefs area. The vertical distribution of single echo detections tracked by the echoview post-processing system showed an apparent downward gathering effect. A positive correlation between TS and water depth was discovered from Pearson correlation analysis in the artificial reefs region during the dry season.  相似文献   

A risk evaluation model for karst groundwater pollution based on geographic information system and artificial neural network applications     

Li Bo  Zeng Yi-Fan  Zhang Bei-Bei  Wang Xian-Qing 《Environmental Earth Sciences》2018,77(9):344

The risk analysis on karst groundwater pollution is a research hotspot in current international hydrogeological field as well as the premise of preventing and controlling groundwater pollution. According to the characteristics of groundwater pollution in the typical study area, the study selected main-control factors of risk evaluation on karst groundwater pollution in mountainous areas at first. Based on this, the research determines the method for quantifying the factors and established a risk evaluation index system for karst groundwater pollution. To overcome drawbacks of the method for determining weights of factors in traditional evaluation method, the study determines the structure of the artificial neural network model by combining the selected evaluation factors. And also, the weight coefficients of evaluation factors on each layer are calculated. On this basis, the model for evaluating the risk of karst groundwater pollution is established. Moreover, the risk zoning evaluation map of groundwater pollution in the typical study area is prepared after conducting the weighted stacking of various sub-layers using the geographic information system. The method applied in the study can comprehensively and objectively reflect that the groundwater pollution is controlled by multiple factors and reveal the nonlinear characteristic of the pollution process. Additionally, the evaluation result is institutive and visible, which can provide a certain basis and reference for relevant researches.  相似文献   

Shale experiment and numerical investigation of casing deformation during volume fracturing     

Xueli Guo  Jun Li  Gonghui Liu  Wei Lian  Yijin Zeng  Qian Tao  Xuefeng Song 《Arabian Journal of Geosciences》2018,11(22):723

The casing deformation issues have occurred widely in Changning-Weiyuan National Shale Gas Demonstration Area. During multi-stage volume fracturing process, a large amount of fracturing fluid is injected into the formation, leading to tremendous change of stratum property and formation stress field. To assess the influence of shale formation on casing deformation, the acoustic velocity is measured to obtain the shale rock elastic modulus after saturation with water for different times. Then, the three-dimensional physical and finite element models are established using the stage finite element method considering transient thermal-pressure coupling. Shale anisotropy, shale stiffness degradation, and formation slip are taken into account to investigate the influences on casing deformation. Experiment results indicate that shale stiffness degrades dramatically after saturation with water for 24 h. Numerical simulations indicate that the shale modulus degradation mainly leads to large casing stress. Formation slipping not only causes excessive casing stress, but also causes large casing displacement. When slipping distance is larger than 15 mm, casing stress can reach up to the yield stress for P110 grade casing. Meanwhile, the casing deformation will be 14.95 mm, blocking the fracturing tools into the well bottom. Shale anisotropy has a minor influence on casing deformation.  相似文献   

Quantitative assessment of the impact of an inter-basin surface-water transfer project on the groundwater flow and groundwater-dependent eco-environment in an oasis in arid northwestern China     

Xiaobin Zhu  Jichun Wu  Huijun Nie  Fei Guo  Jianfeng Wu  Kouping Chen  Penghui Liao  Hongxia Xu  Xiankui Zeng 《Hydrogeology Journal》2018,26(5):1475-1485

Inter-basin water transfer projects (IBWTPs) can involve basins as water donors and water receivers. In contrast to most studies on IBWTPs, which mainly impact the surface-water eco-environment, this study focuses on the impacts of an IBWTP on groundwater and its eco-environment in a water donor basin in an arid area, where surface water and groundwater are exchanged. Surface water is assumed to recharge groundwater and a groundwater numerical simulation model was constructed using MODFLOW. The model was used to quantitatively evaluate the impact of an IBWTP located in the upstream portion of Nalenggele River (the biggest river in the Qaidam basin, Northwest China). The impact involved decrease in spring flow, drawdown of groundwater, reduction in oasis area, and an increase in species replacement of oasis vegetation in the midstream and downstream of the river. Results show that the emergence sites of springs at the front of the oasis will move 2–5 km downstream, and the outflow of springs will decrease by 42 million m³/a. The maximum drawdown of groundwater level at the front of the oasis will be 3.6 m and the area across which groundwater drawdown exceeds 2.0 m will be about 59.02 km², accounting for 2.71% of the total area of the oasis. Under such conditions, reeds will gradually be replaced by Tamarix, shrubs, and other alternative plant species. These findings have important implications for the optimization of water resource allocation and protection of the eco-environment in arid regions.  相似文献