大别山造山带核部九资河-天堂寨花岗岩的成因和时代

近十余年来,众多国内外著名学者、专家对大别山造山带进行了深入研究,一些长期争论不休的问题逐渐取得了一致意见。如大别山造山带是华北地块与扬子地块于印支期陆—陆碰撞的产物［１～３］,但是,仍有相当多的重大地质问题还未取得共识。如伴随造山带形成的“天堂寨混...     

实验变形煤结构演化的电子顺磁共振研究

通过１４件高温高压实验样品及其原样的电子顺磁共振研究,论述了温度、压力、应力、应变速率和应变强度等是影响变形煤化学结构演化的重要因素,但在不同的煤级中和不同的实验条件下,各因素所起的作用是不同的。变形煤ＥＰＲ参数的演化与镜质组反射率的变化密切相关,并且具有较好的规律性。说明镜质组反射率是煤化学结构演化的外在反映,是煤田构造研究中极为重要的标志物之一。     

阿拉善高原地下水的稳定同位素异常

1987～1995年对降水、黑河水和古日乃草原地下水作了定位观测,在巴丹吉林沙漠水文探险中采集了沙漠和戈壁地下水及湖水.降水同位素组成δD～δ18O与Craig线相同,但发现了地下水的δD～δ18D关系平行于降水线且有氘盈余为负且达-22‰的异常,其成因不明.由地表、地下水环境同位素组成,分析了黑河治理规划实施后可能对地下水资源产生的工程影响,它近期不会成为古日乃草原沙漠化进程的因素,但对额济纳绿洲的影响却不容忽视.     

大地测量在研究青藏地壳运动及其机制中的作用

基于对GPS和重力测量数据的分析,扼要地介绍了重力与内部构造关系,大地水准面的场源与其动力效应等方面的研究内容和方法。总结了利用重力与形变资料研究青藏地区的现代地壳运动及其动力机制的研究结果。     

The numerical simulation on the PBL structure and its evolution over small-scale concave terrain

A high-resolution, nonhydrostatic, three-dimensional diagnostic PBL model over small-scale concave terrain was established in this paper. A two-dimensional prognostic model was developed based on the diagnostic model. The hydrostatic approximation was abandoned and the simple energy (E-ε) closure scheme was used in both mod-els. Using the two models, characteristics of PBL structure and its evolution were fully studied. The main characteris-tic of the PBL is the circulation, and it fairly affects the distribution of the pollutant in the pit.     

Computational microstructure modeling to estimate progressive moisture damage behavior of asphaltic paving mixtures

This paper presents a computational microstructure model to estimate the progressive moisture damage of multiphase asphaltic paving mixtures. Moisture damage because of water transport is incorporated with mechanical loading through a finite element method. To simulate nonlinear damage evolution in the mixtures, the model includes Fickian moisture diffusion, a cohesive zone model to simulate the gradual fracture process, and a degradation characteristic function to represent the reduction of material properties because of moisture infiltration. With the model developed, various parametric analyses are conducted to investigate how each model parameter affects the material‐specific moisture damage mechanism and damage resistance potential of the mixtures. Analysis results clearly demonstrate the significance of physical and mechanical properties of mixture components and geometric characteristics of microstructure for the better design of asphaltic paving mixtures and roadway structures. Copyright © 2012 John Wiley & Sons, Ltd.     

A sub-surface eddy at inertial current layer in the Canada Basin,Arctic Ocean

An Arctic Ocean eddy in sub-surface layer is analyzed in this paper by use of temperature,salinity and current profiles data obtained at an ice camp in the Canada Basin during the second Chinese Arctic Expedition in summer of 2003.In the vertical temperature section,the eddy shows itself as an isolated cold water block at depth of 60 m with a minimum temperature of-1.5℃,about 0.5℃ colder than the ambient water.Isopycnals in the eddy form a pattern of convex,which indicates the eddy is anticyclonic.Although maximum velocity near 0.4 m s-1 occurs in the current records observed synchronously,the current pattern is far away from a typical eddy.By further analysis,inertial frequency oscillations with amplitudes comparable with the eddy velocity are found in the sub-surface layer currents.After filter the inertial current and mean current,an axisymmetric current pattern of an eddy with maximum velocity radius of 5 km is obtained.The analysis of the T-S characteristics of the eddy core water and its ambient waters supports the conclusion that the eddy was formed on the Chukchi Shelf and migrated northeastward into the northern Canada Basin.     

地理学本科生科研训练体系的构建与实践

大学本科阶段是创新性人才培养的关键时期。北京师范大学地理学基地一直在努力探索本科生早期科研训练的机制、模式与途径,以研究性教学和教学科研互动的新理念,依托基地所拥有的国家、教育部和北京市重点实验室、国家一级重点学科、国家级科学研究和教学研究项目等丰富的科研资源和院士、长江学者、杰出青年基金获得者、教学名师等高水平的首席导师+教学团队师资,建立并完善本科生科研立项制度,构建多学科平台、多元模式、多阶段的阶段-学科-能力三维体系的因材施教的科研训练体系。     

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??10???????FG5-112?????????????й???????????????????о?????嶯??????????????????????68??????????ι????????????С??2??10 ^-8 ms ^-2???????????????????????С?????????????;????????????????????????????????????仯?????1??10 ^-8 ms ^-2 /a??????????λ???????-0.38 cm/a;??????????λ?仯??????????????????????????????     

In situ LA-ICP-MS zircon U-Pb age of ultrahigh-pressure eclogites in the Yukahe area,northern Qaidam Basin

Zircon grains were selected from two types of ultrahigh-pressure (UHP) eclogites, coarse-grained phengite eclogite and fine-grained massive eclogite, in the Yukahe area, the western part of the North Qaidam UHP metamorphic belt. Most zircon grains show typical metamorphic origin with residual cores in some irregular grains and sector, planar or misty internal textures on the cathodoluminescence (CL) images. The contents of REE and HREE of the core parts of grains range from 173 to 1680 μg/g and 170 to 1634 μg/g, respectively, in phengite eclogite, and from 37 to 2640 μg/g and 25.7 to 1824 μg/g, respectively, in massive eclogite. The core parts exhibit HREE-enriched patterns, representing the residual zircons of protolith of the Yukahe eclogite. The contents of REE and HREE of the rim parts and the grains free of residual cores are much lower than those for the core parts. They vary from 13.1 to 89.5 μg/g and 12.5 to 85.7 μg/g, respectively, in phengite eclogite, and from 9.92 to 45.8 μg/g and 9.18 to 43.8 μg/g, respectively, in massive eclogite. Negative Eu anomalies and Th/U ratios decrease from core to rim. Positive Eu anomalies are shown in some grains. These indicate that the presence of garnet and the absence of plagioclase in the peak metamorphic mineral assemblage, and the zircons formed under eclogite facies conditions. LA-ICP-MS zircon U-Pb age data indicate that phengite eclogite and massive eclogite have similar metamorphic age of 436±3Ma and 431±4Ma in the early Paleozoic and magmatic protolith age of 783–793 Ma and 748–759 Ma in the Neo-proterozoic. The weighted mean age of the metamorphic ages (434±2 Ma) may represent the UHP metamorphic age of the Yukahe eclogites. The metamorphic age is well consistent with their direct country rocks of gneisses (431±3 Ma and 432±19 Ma) and coesite-bearing pelitic schist in the Yematan UHP eclogite section (423–440 Ma). These age data together with field observation and lithology, allow us to conclude that the Yukahe eclogites were Neo-proterozoic igneous rocks and may have experienced subduction and UHP metamorphism with continental crust at deep mantle during the early Paleozoic, therefore the metamorphic age of 434±2 Ma of the Yukahe eclogites probably represents the continental deep subduction time in this area.