鄂尔多斯地块—扬子地块深部电性结构特征及其动力学意义     

吕宏斌  叶高峰  金胜  魏文博  董浩  张乐天  谢成良  尹曜田 《地质论评》2020,66(4):813-828

位于青藏高原东北缘的秦岭造山带在大地构造上南接扬子地块、北接华北地块,是特提斯构造域和古亚洲洋构造域的转换带。本文基于对一条起始于扬子地块,穿过秦岭造山带和鄂尔多斯地块,到达河套地堑的南北向大地电磁测深剖面的研究,探讨秦岭造山带和其北侧的鄂尔多斯地块、南侧的扬子地块之间的接触关系,以及青藏高原物质东北向逃逸等地学问题。对实测数据进行了张量阻抗分解和维性分析等工作,并对剖面进行了二维反演,获得岩石圈电性结构模型。根据电阻率模型认为:在秦岭造山带北部发现大规模"瓶颈状"分布的低阻异常体(C2),可能为华北、华南地块双向俯冲前缘地幔物质的上涌通道,或者是青藏高原中、下地壳物质沿秦岭造山带中构造薄弱位置向东逃逸的通道;在秦岭造山带和大巴山弧形带边界处发现南倾的低阻异常(C1),解释为大巴山弧形带北缘的逆冲断裂在电性上的反映;电性结构模型中,扬子地块高阻异常体(R2、R3和R4)向北倾斜至秦岭造山带下方,而北部鄂尔多斯地块的高阻异常体(R5和R6)向南倾斜至秦岭造山带下方;高阻异常通常被认为是稳定岩石圈的反映,据此推断这两组相向俯冲至秦岭造山带下方的高阻异常是华北地块和扬子地块向秦岭造山带下方汇聚的电性结构探测依据;鄂尔多斯地块南、北电性差异较大,北部中、下地壳大规模分布电阻率值在3～100Ω·m之间的低阻异常体,可能为地幔上涌导致的局部熔融或含盐流体共同作用的结果。  相似文献   

北京区域成矿规律综述   总被引：1，自引：0，他引：1  

方同明  高学泉  刘林生  刘旭东  李莉  程新彬  何付兵  张晓亮  董静  林天懿  郭高轩 《地质学报》2020,94(1):36-49

2013～2019年开展的"中国矿产地质志·北京卷"项目是全面总结北京地区现代地质矿产工作,特别是新中国成立以来北京地区矿产勘查与研究成果,旨在全面反映北京市矿产全貌及重要成矿规律。本文是对该项工作部分成果的概括总结。系统收集了北京市铁、金、煤、石灰岩等各类矿产资料,划分了矿种矿床类型,重点对铁、金、煤、石灰岩等矿种成矿地质特征进行了阐述。在全国Ⅰ-Ⅲ级成矿区带划分基础上,结合北京市地质构造演化和成矿特点,提出北京市区域成矿区带划分方案,划分了怀柔北金萤石成矿区、八达岭金铜钼铅锌成矿区、京西煤石灰岩成矿区、密云-怀柔铁金成矿区、密云-平谷金石灰岩成矿区5个Ⅴ级成矿区,总结了不同区带各矿种规律特征。从矿产时空演化、岩浆岩控矿、构造控矿角度进行了区域成矿规律总结,提升了北京地区矿产地质研究水平,填补了北京区域成矿规律多矿种综合性研究的空白。  相似文献   

徐闻南山镇红树林沉积物及红树植物中重金属的累积特征与迁移规律     

罗松英  梁艺琼  陈碧珊  林梦婷  梁家新  邱锦坤 《热带地理》2019,39(3):347-356

为探究重金属在红树林沉积物及红树植物中的分布累积及迁移规律，选取了徐闻南山镇红树林为研究对象，通过测定红树林沉积物及红树植物不同部位（根、茎、叶）的重金属质量分数，运用富集因子、生物富集系数、转移系数及相关性分析等方法进行分析。结果表明：1）红树林沉积物重金属质量分数表现为铬（Cr）＞锌（Zn）＞镍（Ni）＞铜（Cu）＞铅（Pb）＞砷（As）＞汞（Hg）＞镉（Cd），为中等变异程度；除了镍（Ni）元素外，其余7种重金属未超过国家一级标准，除了铅（Pb）元素外，其余7种重金属均超过广东省土壤环境背景值，说明研究区沉积物中重金属具有一定的积累效应。2）沉积物中砷（As）、铜（Cu）、锌（Zn）、汞（Hg）、镍（Ni）、铬（Cr）富集因子值均＞1.5，说明受到轻微人为活动影响；各站位镍（Ni）富集因子值均＞5，结合研究区背景，反映了镍（Ni）受到自然和人为输入的共同影响。3）白骨壤体内重金属主要集中在根部，而红海榄体内重金属在根茎叶中分布相对均匀。白骨壤根茎叶部位的大多数重金属质量分数远高于红海榄，说明白骨壤对重金属的吸附能力比红海榄强。汞（Hg）集中分布在植物的叶片部位，且与其他重金属之间相关性不明显；推测汞（Hg）主要通过叶片吸收进入植物体内，与交通运输污染有关。4）不同红树植物对不同重金属富集能力各异，白骨壤对重金属的富集能力表现为：镉（Cd）＞砷（As）＞铜（Cu）＞锌（Zn）＞汞（Hg）＞铅（Pb）＞镍（Ni）＞铬（Cr），红海榄表现为：镉（Cd）＞铜（Cu）＞汞（Hg）＞锌（Zn）＞铅（Pb）＞砷（As）＞镍（Ni）＞铬（Cr）。白骨壤和红海榄对汞（Hg）的运移能力都较强；红海榄对镉（Cd）的富集能力和转运能力都较强，而白骨壤对镉（Cd）富集能力较强，转运能力却较弱，这说明红树植物对重金属元素的富集能力与转运能力不存在正比关系。  相似文献   

Land Resource Carrying Capacity in Xilin Gol Grassland Transects: A Perspective on Food Nutritional Demand     

YANG Wanni  ZHEN Lin  LUO Qi 《资源与生态学报(英文版)》2019,10(6):614-620

Food safety is an important issue for the development of the national economy and society. Studying regional food supply and demand from the perspective of land resource carrying capacity can provide new references for regional resource sustainability. This study uses the data from farmer and herdsmen household questionnaires, statistical data, land use data, and other sources to construct a land resource carrying capacity (LCC) assessment framework, targeting the food supply and demand of residents in representative areas, specifically the typical grassland pastoral areas, sandy pastoral areas and agro-pastoral areas on the Xilin Gol grassland transects. The three food nutritional indicators of calories, protein and fat were selected for analyzing the balance of land resource carrying capacity. We found that: 1) Along the Xilin Gol grassland, the main local food supply showed a shift from meat and milk to grains, vegetables and fruits. 2) From north to south along the grassland transects, the calorie intake increased gradually, while the intake of protein and fat was highest in pastoral areas and lowest in agricultural areas. 3) The overall land resource carrying capacity of the Xilin Gol grassland transects was in a surplus state, but the land carrying capacity of typical grassland pastoral area was higher than the two other types of areas. This study provides an empirical reference for the sustainable development of regional food nutrition.  相似文献   

Environmental changes in the north‐east Sunda region over the last 40 000 years     

Chuanxiu Luo  Simon Haberle  Zhuo Zheng  Rong Xiang  Chixin Chen  Gang Lin  Kumar Sazal 《第四纪科学杂志》2019,34(3):245-257

  相似文献   

水平低周往复位移下单桩-土相互作用试验研究     

黄福云  陈汉伦  董锐  单玉麟 《岩土力学》2020,41(5):1625-1634

整体式桥台无伸缩缝桥梁（以下简称整体桥）桩基应设计为柔性桩，以保证较好的抗水平变形能力。但是，我国相关规范中判别柔性桩的算法主要应用于单向水平受荷桩，可否沿用至整体桥桩基还有待验证。为此，根据一种特殊设计的桩身变形测量方法，对3根埋深不同的混凝土模型桩进行了低周水平往复位移下的拟静力试验，研究单桩-土体系的抗震性能和相互作用机制。研究表明，水平往复位移下混凝土桩在埋深为3D～6D（D为桩径）范围内开裂；桩的埋深越大，桩身挠曲程度越大、变形特征点位置也越深、桩-土体系的抗弯刚度也越大、水平极限承载力也越高、抗震性能也越强。研究还表明，桩-土体系进入弹塑性阶段后，柔性桩的水平工作性状将逐渐向刚性桩退化。另外，在判别整体桥桩基的水平工作性状时，我国相关规范中的规定偏不安全。实际工程中，建议以Broms方法进行参考计算。  相似文献   

A Revisited Purification of Li for ‘Na Breakthrough’ and its Isotopic Determination by MC‐ICP‐MS     

Lin Xu  Chongguang Luo  Hanjie Wen 《Geostandards and Geoanalytical Research》2020,44(1):201-214

The accurate and precise determination of Li isotopic composition by MC‐ICP‐MS suffers from the poor performance of traditional column chromatography. Previously established chromatographic processes cannot completely remove Na in complex geological samples, which is currently interpreted to be a result of Na breakthrough. In this study, Na breakthrough during single‐column purification was found to differ between simply artificial Na‐containing sample solutions, where a little Na residue was found, and silicate rocks, where a large amount of breakthrough occurred. A revised two‐step column purification for Li using 0.5 and 0.3 mol l^?1 HCl as eluents was designed to remove the Na. This modified method achieves high‐efficiency Li purification from Na and consequently avoiding high Na/Li ratio interference for subsequent MC‐ICP‐MS analyses. The proposed method was validated by the analysis of a series of reference materials, including Li₂CO₃ (IRMM‐016, ‐0.10‰), basalt (BCR‐2: 2.68‰; BHVO‐2: 4.39‰), andesite (AGV‐2: 6.46‰; RGM‐2: 2.59‰), granodiorite (GSP‐2: ?0.87‰) and seawater (CASS‐5, 30.88‰). This work reports early Na appearance prior to the elution curves in chromatography and emphasises its influence for subsequent Li isotope measurement. Based on the findings, the established two‐step method would be more secure than single‐column chemistry for Li purification.  相似文献   

基于条件平差的卫星双向时间传递链路性能优化方法          下载免费PDF全文

王翔  宋会杰  王威雄  高喆  张继海  武文俊  董绍武 《天文学报》2020,61(3):25

卫星双向时间传递(Two-Way Satellite Time and Frequency Transfer, TWSTFT)是目前精度最高的时间传递方法之一,同时也是参与国际原子时计算的守时实验室之间比较原子时尺度的一种主要方法.提高TWSTFT链路的短期稳定度,降低周日效应对链路时间传递结果的影响,对优化TAI (International Atomic Time)的性能具有现实意义.提出了一种基于条件平差的TWSTFT链路性能优化方法,先依据TWSTFT链路测量噪声水平与谱分析结果建立TWSTFT链路性能优化网络(简称优化网络),再根据优化网络中各链路测量噪声分析结果设置权系数阵,建立条件平差模型.选取亚太地区的中国计量科学研究院(National Institute of Metrology, NIM)-中国科学院国家授时中心(National Time Service Center, NTSC)卫星双向时间传递链路作为待优化链路,以NTSC、NIM以及德国联邦物理技术研究所(Physikalisch-Technische Bundesanstalt,PTB)之间的TWSTFT链路组成优化网络,对优化网络的组网方法和条件平差模型进行实验验证.结果表明,平差后待优化链路短期稳定度得到了改善,同时其受周日效应的影响降低了约24.6%.使用该方法,能够有效提高待优化链路的时间传递性能.  相似文献   

Carboniferous integrative stratigraphy and timescale of China     

Wang  Xiangdong  Hu  Keyi  Qie  Wenkun  Sheng  Qingyi  Chen  Bo  Lin  Wei  Yao  Le  Wang  Qiulai  Qi  Yuping  Chen  Jitao  Liao  Zhuoting  Song  Junjun 《中国科学:地球科学(英文版)》2019,62(1):135-153

The Carboniferous period lasted about 60 Myr, from ～358.9 Ma to ～298.9 Ma. According to the International Commission on Stratigraphy, the Carboniferous System is subdivided into two subsystems, i.e., Mississippian and Pennsylvanian, including 6 series and 7 stages. The Global Stratotype Sections and Points(GSSPs) of three stages have been ratified, the Tournaisian, Visean, and Bashkirian stages. The GSSPs of the remaining four stages(i.e., the Serpukhovian, Moscovian,Kasimovian, and Gzhelian) have not been ratified so far. This paper outlines Carboniferous stratigraphic subdivision and correlation on the basis of detailed biostratigraphy mainly from South China, and summarizes the Carboniferous chronostratigraphic framework of China. High-resolution biostratigraphic study reveals 37 conodont zones, 24 foraminiferal(including fusulinid) zones, 13 ammonoid zones, 10 brachiopod zones, and 10 rugose coral zones in the Carboniferous of China. The biostratigraphic framework based on these biozones warrants the precise correlation of regional stratigraphy of China(including2 subsystems, 4 series, and 8 stages) to that of the other regions globally. Meanwhile, the Carboniferous chemo-, sequence-,cyclo-, and event-stratigraphy of China have been intensively studied and can also be correlated worldwide. Future studies on the Carboniferous in China should focus on(1) the correlation between shallow-and deep-water facies and between marine and continental facies,(2) high-resolution astronomical cyclostratigraphy, and(3) paleoenvironment and paleoclimate analysis based on geochemical proxies such as strontium and oxygen isotopes, as well as stomatal indices of fossil plants.  相似文献   

轨道交通沿线土地溢价归公的政策与实践——以东莞市为例     

林雄斌  余筱琪  陈伟劲 《热带地理》2019,39(5):732-741

轨道交通周边土地开发和溢价归公有助于缓解城市财政压力,推动公交都市建设。结合国外实施溢价归公的政策和实践模式,以东莞市为例,在资料收集、政策分析、文本和案例解读的基础上,探讨了中国城市政府在规划和建设轨道交通中,以土地溢价归公反哺轨道交通融资的政策安排和实施效果。结果表明：1）溢价归公的本质是以特定方式实现正外部效应的内部化,由于土地制度和税收体系的差异,欧美地区溢价归公主要依赖多样化的土地税收体系,而中国城市的实践主要借鉴了“轨道+物业”的联合开发模式;2）东莞市溢价归公策略的形成是综合开发规划编制和审批、沿线土地控制和储备、土地发展权转移、土地增值分配等核心环节有效协调的结果;3）东莞轨道交通沿线土地开发能形成可观的财政收益,潜在土地收益占轨道资金总需求的比例超过20%,但在实施过程中仍面临较大困难。东莞市案例能为其他城市轨道交通融资、土地开发和溢价归公的政策体系编制和有效实施提供一定的参考。  相似文献