中国北方大陆下的地幔热柱与岩石圈运动

本文首次提出中国北方大陆下存在一个地幔热柱的论证,并提出亚热柱(sub—plume)的新概念。热柱的中心与边缘部分的隙间熔浆分别为苦橄质玄武岩与碱性玄武岩。在渐新世到中新世约18.4 Ma内,北方大陆以3.26cm/a的速率向东南飘移了约600km,使日本海、渤海—华北平原等脱离热柱。导致晚第三纪日本海扩张的停止,渤海—华北平原等早第三纪火山喷发的突然中止。火山喷发期间,在热柱头部若干个亚热柱的形成,好似若干个“铆钉”穿入岩石圈,有效地阻止了岩石圈的飘移(这时的飘移速率只有0.05cm/a),我们把火山喷发称为固定岩石圈的“铆钉效应”。     

Kinematics and timing of continental block deformation from margins to interiors

During the deformation of continental blocks, the magnitude of tectonic stress generally decreases with increasing distance from the margin of the block. However, the timing and kinematics of stress transmission from the margins to the interiors of continents are poorly resolved, even though this information is critical to our understanding of the dynamics of continental deformation. Here, we present a case study of Mesozoic deformation of the North China Craton (NCC). Field investigations of Mesozoic thrust faults and folds, granitic intrusions and dykes, combined with zircon SHRIMP and LA–ICP–MS dating and muscovite ⁴⁰Ar/³⁹Ar plateau ages, reveal the age of the NE–SW‐trending tectonic belts as ~180–155 Ma, where the deformation of the craton margin occurred 10–20 Ma earlier than that of the craton's interior. Although the kinematics of deformation are similar for the interior and the margin of the NCC, strain decreases with increasing distance from the margin. Notably, the bulk of the strain in the cratonic interior was focused in zones of pre‐existing weakness. Overall, we determined that the NCC deformed under conditions of uniaxial compression, a conclusion that is compatible with simple rheological models, and that the stress magnitude attained in the cratonic interior was much less than that along its margin.     

Nitrate in groundwater of China: Sources and driving forces

Identifying the sources of reactive nitrogen (N) and quantifying their contributions to groundwater nitrate concentrations are critical to understanding the dynamics of groundwater nitrate contamination. Here we assessed groundwater nitrate contamination in China using literature analysis and N balance calculation in coupled human and natural systems. The source appointment via N balance was well validated by field data via literature analysis. Nitrate was detected in 96% of groundwater samples based on a common detection threshold of 0.2 mg N L^?1, and 28% of groundwater samples exceeded WHO's maximum contaminant level (10 mg N L^?1). Groundwater nitrate concentrations were the highest beneath industrial land (median: 34.6 mg N L^?1), followed by urban land (10.2 mg N L^?1), cropland (4.8 mg N L^?1), and rural human settlement (4.0 mg N L^?1), with the lowest found beneath natural land (0.8 mg N L^?1). During the period 1980–2008, total reactive N leakage to groundwater increased about 1.5 times, from 2.0 to 5.0 Tg N year^?1, in China. Despite that the contribution of cropland to the total amount of reactive N leakage to groundwater was reduced from 50 to 40% during the past three decades, cropland still was the single largest source, while the contribution from landfill rapidly increased from 10 to 34%. High reactive N leakage mainly occurred in relatively developed agricultural or urbanized regions with a large population. The amount of reactive N leakage to groundwater was mainly driven by anthropogenic factors (population, gross domestic product, urbanization rate and land use type). We constructed a high resolution map of reactive N source appointment and this could be the basis for future modeling of groundwater nitrate dynamics and for policy development on mitigation of groundwater contamination.     

2006年9月秭归泄滩极微震群初步研究

2006年 9月17～22日在秭归泄滩镇西侧发生了一次极微震群活动,其中最大地震为9月20日21时10分 ML1.8级.分析结果表明:本次震群的震中主要集中于泄滩镇老石门村至老泄滩一线,震源深度为海平面以上0.5 km范围内,为正倾滑机制解;该震群频谱最佳频率主要集中在2 Hz左右,初步推断该震群为地表层重力作用下矿塌型地震并伴有几次浅层微滑坡.     

����ˮ��ˮ���շ������䷢չ����̽��

?????????????????????????????????з???????????????????????????????????????????????????? ???????о???????? 1996??4??21???????ML4.1????????????????????????????????????3????????????????????С??     

Source of and potential bio-indicator for the heavy metal pollution in Ny-(A)lesund, Arctic

Three kinds of tundra plant samples including Dicranum angnstum(a type of boreal bryophyte) , PuccineUia phryganodes (a type of fringy p/ant),Salix polaris (a type of vascular plant) and surface soil were samples in 200 at Ny-Alesund of the Arctic.The levels of eight heavy metal elements (Hg, Pb, Cd, Cu, Zn, Ni, Fe and Mn) and three metal-like dements (As, Se, Sr) in the plant and soil samples of the areas within previous coal mining activities are significantly higher than those of other areas.The relative accumulation of these elements in these tundra plant samples is consistent with the one in the soft samples, especially in the areas affected by previous coal-mining activities.Thus, the pollution is apparently from local coal mining activity.Dicranum angustum has the highest concentrations among those elements, and it can be a good bio-indicator for heavy metal pollution in Ny(A)lesund.Though Ny(A)lesund is less polluted by heavy metal than nearby Northern European human living areas, but much more than the tundras of the Alaska, Greenland and the Antarctic.     

从世界各地“地理考察”现况看我国中学地理教学

地理学是研究地球表层事物空间分布的科学,实地考察在地理学科中尤为重要。本文分析了英格兰、澳大利亚新南威尔士州及新加坡中学地理课程,发现其普遍重视地理考察,并且在公开考试中考核学生的地理考察技能。随着新一轮课程改革提出对核心素养的培养,应系统地加强中学地理考察活动的课程开发、实施与评价。     

Sanxicun landslide: an investigation of progressive failure of a gentle bedding slope

Natural Hazards - A gentle bedding slope (16° dip angle) failure at Sanxicun (SXC) village in Dujiangyan city was triggered by heavy rainfall in 2013. The landslide has a sliding distance of...     

Evaluating effectiveness of mitigation measures for large debris flows in Wenchuan,China

Landslides - To cope with frequent debris flow hazards, many cascade check dams and diversion channels have been adopted in Wenchuan, Sichuan, China, on the eastern margin of the Tibetan plateau....