Late Paleozoic retrograded eclogites from within the northern margin of the North China Craton: Evidence for subduction of the Paleo-Asian ocean

Retrograded eclogites from the central part of the northern margin of the North China Craton, Hebei Province, China occur as separate tectonic lenses or boundins within garnet–biotite–plagioclase gneisses of the Paleoproterozoic Hongqiyingzi Complex characterized by amphibolite facies paragneisses. The petrographic features and mineralogical compositions represent three main metamorphic stages: (1) the peak eclogite facies stage (P > 1.40–1.50 GPa, T = 680–730 °C), (2) the granulite facies stage and (3) the amphibolite facies stage (P = 0.67–0.81 GPa, T = 530–610 °C) formed during decompression. The major and trace element and Sm–Nd isotopic data suggest that most of the retrograded eclogite samples had protoliths of tholeiitic oceanic crust with geochemical characteristics of mid-ocean ridge basalt (MORB) or island arc tholeiite (IAT) environment, and were contaminated by crustal components during subsequent subduction. Zircon SHRIMP isotopic dating of two different textural varieties of retrograded eclogite defines a weighted mean age of 325 Ma, which is interpreted as the peak metamorphic age of the eclogites and reflects the occurrence of eclogite facies metamorphism related to subduction of Paleo-Asian Oceanic crust beneath the North China Craton during the Late Paleozoic. Finally, we show that the retrograded eclogite from Hebei Province is not related to the Baimashi retrograded eclogite at the northern foot of the Heng Mountains, approximately, 300 km to the southwest.     

Comparison of the <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis> toxic effects of three sizes of zinc oxide (ZnO) particles using flounder gill (FG) cells and zebrafish embryos

Nano-sized zinc oxide (nZnO) particles are one kind of the most commonly used metal oxide nanoparticles (NPs). This study compared the cytotoxic and embryotoxic effects of three increasing sized ZnO particles (? 30 nm, 80-150 nm and 2 μm) in the flounder gill (FG) cells and zebrafish embryos, and analyzed the contribution of size, agglomeration and released Zn²⁺ to the toxic effects. All the tested ZnO particles were found to be highly toxic to both FG cells and zebrafish embryos. They induced growth inhibition, LDH release, morphological changes and apoptosis in FG cells in a concentration-, size- and time-dependent manner. Moreover, the release of LDH from the exposed FG cells into the medium occurred before the observable morphological changes happened. The ultrasonication treatment and addition of serum favored the dispersion of ZnO particles and alleviated the agglomeration, thus significantly increased the corresponding cytotoxicity. The released Zn²⁺ ions from ZnO particles into the extracellular medium only partially contributed to the cytotoxicity. All the three sizes of ZnO particles tested induced developmental malformations, decrease of hatching rates and lethality in zebrafish embryos, but size- and concentration- dependent toxic effects were not so obvious as in FG cells possibly due to the easy aggregation of ZnO particles in freshwater. In conclusion, both FG cells and zebrafish embryos are sensitive bioassay systems for safety assessment of ZnO particles and the environmental release of ZnO particles should be closely monitored as far as the safety of aquatic organisms is concerned.     

深部找矿研究问题

中国大部分矿产资源供应的紧缺形势,要求加大中东部地区深部找矿(包括矿山和矿集区)的力度。文章在论述深部找矿的重要性、可能性和艰巨性的基础上,阐释了深部找矿的有关概念,对比了深部矿床和浅表矿床的差异,重点论述了深部探矿的4个基本科学问题,包括：①成矿系统发育的完整程度;②成矿系统发育的深度;③成矿系统网络的三维结构与矿床分带;④深部矿床的示踪标志。最后,作者对加强深部找矿提出了意见和建议。     

Climatology and trends of wet spells in China

Summary Climatological features and variations of wet spells, especially their trends over China, are investigated using a dataset of 594 meteorological stations across China from 1951 to 2003. The results show that the lower the latitude is, the longer the annual duration of wet spells is. The mean annual precipitation from wet spells is higher in southeastern coastal areas and much lower in western and northern China. The longest wet spells are found in Southwest China and the eastern Tibetan Plateau. The maximum daily precipitation of wet spells decreases from the southeast to the northwest, with the highest in southeastern coastal areas and the lowest in western China. The trends of wet spells exhibit striking regional differences. In most areas of western China, the annual number of days in wet spells has slightly increased, but significantly decreased over North China, Central China and Southwest China. The annual precipitation amount from wet spells displays significant downward trends in North China, eastern Northeast China and the eastern part of Southwest China, but upward trends in the eastern Tibetan Plateau and some southeastern coastal areas. Two clearly-contrasting regions in climatic changes of wet spells are the mid-lower reaches of the Yellow River and the eastern Tibetan Plateau, characterized by a decrease of about 24 days and an increase of about 6 days in annual wet spell days from 1953 to 2003, respectively.     

长江流域潜在蒸发量和实际蒸发量的关系

针对“蒸发悖论”科学问题,从长江流域实际蒸发量变化的原因着手,探讨实际蒸发量与潜在蒸发量之间的关系。研究结果表明：一般情况下当干燥度指数R<0.8时,实际蒸发量与潜在蒸发量为明显的正相反关系,当0.81.0时,实际蒸发量与潜在蒸发量为明显的互补关系。     

8616号台风风场非对称研究

本文对8616号台风动力学特征和能量学特征量进行了计算和分析。研究结果表明,这个台风风速分布不对称,气旋性最大切向风位于台风右前象限。风速的垂直切变随台风加强而减弱。强流入位于台风南半圆300hPa以下,流入最大值在700hPa层附近。高层最强反气旋流出在150—100hPa层附近,流出主要位于台风北半圆。在台风内区,正涡度分布近似准对称,散度分布很不对称。这个台风垂直运动分布与台风的发展及位置有密切关系。台风整个生命期均具有暖心结构,250—200hPa附近增暖最明显。扰动期500hPa以上存在干燥层,     

大别山东段反季蔬菜生产中的气候问题

在分析大别山东段 (安徽侧 )高山反季蔬菜生产的气候优势和气象条件限制的基础上 ,本着趋利避害的原则 ,就蔬菜生产的安全高度、播种适期、栽培管理等问题进行了探讨。     

中国区域成矿若干问题探讨

本文以区域大地构造演化和区域岩石圈组成为基础,将中国大陆划分为６个成矿域：天山－兴蒙成矿域,塔里木－华北成矿域。秦－祁－昆成矿域,扬子成矿域,华南成矿域,喜马拉雅－三江成矿域,并描述了它们的基本下,按照不同地质时代,简述了中国大地构造演化与主要矿床过程,并从中国近处大地构造背景和地质成矿演化历史出发,探讨了中国区域成矿特色,初步提出８点;（１）大陆边缘成矿显著;（２）发育叠加复合成矿作用;（３）壳     

关于成矿参数临界转换的探讨

在成矿过程中，普遍存在矿参数的临界转换现象。在制约成临界转换的参数和多种形式中，构造动力转换可能起着根本的作用。文章以山东焦家、阜山等矿床为例，列举剪切带构造中的临界转换现象。又以火山爆发和地震为例，说明构造动力体制转换诱发的突发地质事件及伴随的成矿作用。在说明构造动力转换的多重尺度后，重点论述了整体构造背景下的局部转换（例如总体挤压背景下的局部拉张、总体拉张盆地中的局部封闭）是一常见的矿源－运输－汇聚结构。在构造动力体制转换带动下，多种参数的联动转换是形成大型矿床的一种机制。     

一次飑线大风天气过程成因分析

利用常规气象资料、自动站资料、多普勒雷达资料及NCEP再分析资料,分析了2014年3月31日广西大风天气过程的环境背景场、层结结构、垂直风切变场、局地层结特征、物理量配置、雷达回波及地面风场特征,得到一些有意义的结论,可以为此类天气过程预报提供参考。