Geochemistry and tectonic environment of amphiholites of the Zanhuang metamorphic complex北大核心

Amphibolites, one of the kinds of Precambrian basement rocks, are exposed in the south-middle Zanhuang Metamorphic Complex, central-south segment of the Trans-North China Orogen. These metamorphic rocks were carefully studied through field investigations and petrographical and geochemical analyses. It was found that protoliths of the Zanhuang amphibolites are calc-alkaline and tholeiitic rocks with a large range of ΣREE (41.38 × 10-6 -232.55 × 10-5 ) and weak LREE enrichment. The multi-element variation results showed that K, Rb and Ba were relatively concentrated, Nb and Ta were of evident depletion while Ti was of weak depletion. Geochemical characteristics and various relevant geochemical discrimination diagrams showed that the Zanhuang amphibolites were formed in volcanic arcs of continental margin similar to the current continental margin, which was resulted from the subduction between the Western Block and the Eastern Block.     

RAMS模式在山谷城市模拟性能的检验

 利用2005年冬季兰州边界层试验的观测数据,分别从边界层结构、近地面温度和风速、地表通量等几个方面检验了RAMS在山谷城市的模拟性能。RAMS模式能很好地捕捉边界层结构特征,模拟的白天混合层高度和夜间稳定边界层高度和观测值非常一致。模式能较好地模拟近地面温度和地表通量的日变化特征。对模拟偏差进行统计分析,结果显示RAMS对近地面温度和风速的模拟结果是可以接受的:近地面温度的平均偏差为-1.73 ℃,RMSE为2.16 ℃,风速的平均偏差为0.35 m·s-1,RMSE和RMSVE分别为1.61 m·s-1和3.15 m·s-1。研究表明,RAMS适合作为研究兰州山谷城市大气边界层的工具。     

定向剪切应力路径下冻结黏土变形特性试验

为研究复杂应力路径下冻土的强度与变形特征,采用冻土空心圆柱仪（FHCA-300）对不同负温状态下的饱和冻结黏土开展定向剪切试验,基于不同剪切方向下冻结黏土的轴向和扭剪分量的应力-应变关系,探讨土样的剪切变形特征、各向异性属性以及剪切带的演变规律,并考察温度、大主应力方向角、平均主应力以及中主应力系数等因素对冻结黏土强度的影响。结果表明：平均主应力p值对冻结黏土的应力-应变关系影响显著,尤其是p=4.5 MPa时具有较高的剪切强度,且该值可能为压融临界p值;大主应力方向变化会诱发冻结黏土的各向异性,随着大主应力方向角的增加,冻结黏土剪切强度逐渐降低,并有明显的剪切带产生;中主应力系数的增加使得轴向强度有逐渐降低的趋势,但对剪切强度影响不明显;随着温度的降低,冻结黏土强度逐渐增大,试样发生脆性破坏并出现剪切破裂面,其剪切强度主要取决于冰颗粒和土颗粒的胶结力。     

锆石微量元素及其揭示的深部过程

近十年来对锆石研究已从早期的U-Pb放射性同位素定年和锆石同位素分析,发展到大量研究锆石的微量元素。锆石微量元素不仅可以作为锆石Ti温度计估算岩浆温度,也可以用来识别锆石及其母岩的岩石类型和成因,区分岩浆熔体或者流体控制的岩浆作用、变质作用、成矿作用等深部作用过程。文中在归纳总结岩浆锆石、变质锆石、热液锆石、碎屑锆石等不同类型锆石的微量元素成分基础上,以青藏高原碰撞后超钾质岩石中产出的锆石为例,系统介绍了超钾质岩石中各类锆石的结构、年龄和微量元素特征,并应用于解释超钾质岩石成因、岩浆源区成分、岩浆演化和上部地壳物质的混染、下地壳加厚和高原隆升之间的关系。     

冲绳海槽中部沉积物物质来源和沉积环境分析

本文基于AMS14C高精度测年,通过对柱状沉积物HOBAB2-S2的粒度、微量元素和稀土元素的分析,对冲绳海槽中部区5 300 a以来的物质来源和沉积环境进行了研究。通过对该孔的稀土元素与微量元素的研究发现研究区沉积物质具有陆源属性,并且通过不同物源区沉积物的稀土元素散点图表明5 300 a以来沉积物主要来自于台湾。文中将粒度特征作为研究区域沉积环境,尤其是水动力（黑潮）强弱的指示参数,根据粒度变化曲线,可将沉积过程分为4个阶段:第一阶段（5.30~3.81 ka BP）,粒径由粗变细,黑潮强度逐渐减小;第二阶段（3.81~2.70 ka BP）,粒径波动较大,无明显增大或减小趋势,表明沉积环境处于相对波动状态,水动力强弱不稳定;第三阶段（2.70~0.97 ka BP）,粒径变化较小,表明沉积环境处于相对稳定状态,研究区的水动力条件较稳定;第四阶段（从0.97 ka BP至今）,粒径逐渐变粗,水动力条件增强。     

高压密闭消解-电感耦合等离子体光谱和质谱联合测定海洋地质样品中52种元素

An improved analytical method to determine the content of 52 major, minor and trace elements in marine geological samples, using a HF-HCl-HNO_3 acid system with a high-pressure closed digestion method(HPCD), is studied by an inductively coupled plasma optical emission spectrometry(ICP-OES) and an inductively coupled plasma mass spectrometry(ICP-MS). The operating parameters of the instruments are optimized, and the optimal analytical parameters are determined. The influences of optical spectrum and mass spectrum interferences, digestion methods and acid systems on the analytical results are investigated. The optimal spectral lines and isotopes are chosen, and internal standard element of rhodium is selected to compensate for matrix effects and analytical signals drifting. Compared with the methods of an electric heating plate digestion and a microwave digestion, a high-pressure closed digestion method is optimized with less acid, complete digestion,less damage for digestion process. The marine geological samples are dissolved completely by a HF-HCl-HNO_3 system, the relative error(RE) for the analytical results are all less than 6.0%. The method detection limits are 2–40μg/g by the ICP-OES, and 6–80 ng/g by ICP-MS. The methods are used to determine the marine sediment reference materials(GBW07309, GBW07311, GBW07313), rock reference materials(GBW07103, GBW07104,GBW07105), and cobalt-rich crust reference materials(GBW07337, GBW07338, GBW07339), the obtained analytical results are in agreement with the certified values, and both of the relative standard deviation(RSD) and the relative error(RE) are less than 6.0%. The analytical method meets the requirements for determining 52 elements contents of bulk marine geological samples.     

科学合作地域倾向性研究——以中国雾霾研究为例

科学合作是促进知识传播和共享的重要途径,已有研究表明,地理因素是影响科学合作的主要因素之一。然而,目前针对该问题的研究大多只是从科学计量学的角度,对科学合作强度与地理距离的函数关系进行描述,无法揭示科学合作在空间上的分布特征和内部差异性。因此,本文从地理学的角度,以中国雾霾研究的合作网络为例,通过对文献题录中的位置信息进行解析,将虚拟的科学合作网络映射到地理合作网络。在此基础上,提出了一种考虑地理距离的科学合作网络社区发现方法,挖掘科学合作网络中蕴含的空间聚类特征,从而对科学合作的地域倾向性进行反映。通过比较发现,基于合作频次与地理距离的社区发现算法,能够使社区内部的平均地理距离最小而合作强度最大,既反映了科学合作在地理上的近似性,又体现了科学合作强度特征。该方法能够直观地揭示科学合作中隐含的空间分布模式和联系,对其他复杂网络的地理社区划分也有一定的借鉴意义。     

云南都龙超大型锡锌多金属矿床中闪锌矿微量及稀土元素地球化学特征

云南马关都龙锡锌多金属矿床位于滇东南老君山锡锌钨多金属成矿区南部,是我国三大锡石硫化物矿床之一,目前对其矿床成因认识存在较大分歧。本文采用ICP-MS对都龙矿床中闪锌矿微量元素及稀土元素组成进行分析,以探讨该矿床成矿作用,为甄别已有成因观点提供证据。结果表明,矿床中闪锌矿以富集Fe、Mn、In、Co、Sn和贫Cd、Ga、Ge、Ni等元素为特征,成矿温度属于中—高温,其微量元素组成与白牛厂矿床(与燕山晚期花岗岩有关的矽卡岩型矿床)中的闪锌矿非常相似,和远源矽卡岩型铅锌矿床(核桃坪和芦子园)中闪锌矿存在一定差异,明显有别于喷流沉积型铅锌矿床(云南澜沧老厂和广东大宝山)中闪锌矿。此外,该矿床闪锌矿稀土配分模式多为轻稀土元素富集中等的向右倾斜曲线,以LREE/HREE值高、Eu负异常明显和Ce异常不明显为特征,与矿区燕山晚期隐伏花岗岩稀土元素特征基本一致,成矿物质来源以矿区燕山晚期隐伏花岗岩为主。结合近期矿山开采和地质勘探所揭露的矿化和矽卡岩蚀变的垂向分带等矿床地质特征,认为云南马关都龙锡锌多金属矿床属于与燕山晚期花岗岩有关的矽卡岩型多金属矿床,其中层状矽卡岩的形成应为成矿流体顺层交代的结果,矿化类型和围岩蚀变的分带与隐伏岩体的距离有关。     

Glaciokarst landforms and processes of the southern Dinaric Alps

Glaciokarst is a landscape which combines karst features and hydrology as well as inherited glacial features. It is a result of glaciation upon a karst geomorphological system. The relationship between glaciers and karst is rather poorly known and inadequately recognized. This research focuses on three distinct karst areas along the Adriatic coast in the southern Dinaric Alps that were affected by the Quaternary glaciations. An insight into specific glaciokarst processes and surface features was provided through the study of the areas of the Lov?en, Orjen and Vele? Mountains. A glaciokarst geomorphology is in general well preserved due to the prevailing vertically oriented chemical denudation following de‐glaciation and almost the entire absence of other surface processes. Typical glacial erosional features are combined by a variety of depressions which are the result of a karstic drainage of sub‐glacial waters. The majority of glacial deposits occur as extensive lateral‐terminal moraine complexes, which are often dissected by smaller breach‐lobe moraines on the external side of the ridge. Those moraine complexes are likely to be a product of several glacial events, which is supported by complex depositional structures. According to the type of glacial depositional features, the glaciers in the study areas were likely to have characteristics of moraine‐dammed glaciers. Due to vertical drainage ice‐marginal fluvial processes were unable to evacuate sediment. Fluvial transport between glacial and pro‐glacial systems in karst areas is inefficient. Nevertheless, some sediment from the glacier margin is washed away by the pro‐glacial streams, filling the karst depressions and forming piedmont‐type poljes. Copyright © 2015 John Wiley & Sons, Ltd.     

考虑挤土效应时楔形桩纵向振动阻抗研究

基于复刚度传递多圈层平面应变模型,研究考虑桩周土挤土效应时成层地基中楔形桩的纵向振动问题。首先根据桩周土体的纵向成层情况并考虑楔形桩的变截面特性,将桩土系统沿纵向划分为有限个微元段,对每个微元段的桩周土体建立复刚度传递多圈层平面应变模型,并通过剪切复刚度递推方法求得桩周土作用在桩身的剪切复刚度;然后将求得的剪切复刚度代入桩身纵向振动控制方程,运用Laplace变换技术和阻抗函数递推方法,推导得到考虑桩周土挤土效应时成层地基中楔形桩纵向振动时桩顶复阻抗的解析解;最后,采用参数研究方法在低频范围内分析挤土效应对桩顶复阻抗的影响及其规律。