皖南宁国竹溪岭钨银矿床及相关岩体的同位素地质年龄

皖南宁国竹溪岭钨银矿床是近年来发现的一个与花岗岩类有关的矽卡岩型矿床,准确厘定其成矿年龄及相关侵入岩体的年龄有利于深入认识区域岩浆作用与成矿作用的规律。本文在矿床地质调查的基础上,应用现代同位素定年技术开展地质年代学研究,获得矿床矿石中的辉钼矿Re-Os模式年龄为142.7±2.1 Ma和142.9±2.1 Ma,相关侵入岩体花岗闪长岩、花岗斑岩和花岗闪长斑岩的LA-ICP-MS锆石U-Pb年龄分别为139.8±1.8 Ma、143.3±1.9 Ma、140.2±1.7 Ma,显示矿床的成矿年龄与侵入岩体的成岩年龄基本一致,为燕山晚期早白垩世。矿床矿石中的辉钼矿的Re含量指示成矿物质来源于地壳和地幔的混合;与成矿相关侵入岩的稀土元素和Hf同位素组成特征指示成岩物质也具有壳幔混源特征,显示成矿物质来源与成岩物质来源具有一致性。区域岩浆岩和矿床的对比表明,与之相邻的长江中下游地区、浙西地区和赣东北地区乃至整个华南地区这一时期发生了大规模的岩浆作用和钨锡多金属成矿作用,显示扬子板块在此阶段处于岩浆–成矿大爆发时期,皖南地区的成矿时代对应于华南中生代三次大规模岩浆作用和成矿作用的第二阶段。     

新疆二红洼镁铁—超镁铁岩体橄榄石成因及其对硫化物熔离的指示

二红洼岩体位于新疆东天山黄山镁铁—超镁铁岩带的西段,地表由南、北两个小岩体组成,北岩体出露面积约1.42km2,呈北东—南西向展布;南岩体在呈椭圆形,出露面积约为6.25km2。岩体可分为两个侵入期次:第一侵入期次岩性为(含长)二辉橄榄岩和橄榄辉长岩,第二侵入期次岩性为辉长苏长岩和淡色辉长岩,辉长苏长岩侵入于第一期次形成的含长二辉橄榄岩和橄榄辉长岩中。岩体橄榄石Fo值在80.9~89.7之间,为贵橄榄石;Ni含量变化范围较大,主要集中在102.19×10-6~4319.66×10-6之间。岩体母岩浆MgO含量为10.3%,FeO含量为10.8%;回归计算结果显示二红洼岩体的原始岩浆中MgO含量为15.73%,FeO含量为10.71%。在橄榄石的结晶过程中母岩浆达到硫饱和,并发生有硫化物的熔离作用;橄榄石与硫化物的晶出质量比(橄榄石:硫化物)为50~100∶1。通过岩石学、矿物学特征以及模拟计算结果表明,二红洼岩体具有形成铜镍矿床的基本条件,但是岩体在深部岩浆房已经达到硫饱和并发生了硫化物的熔离作用,导致母岩浆中亏损Ni、Cu等成矿元素,未能形成工业矿体;在以后找矿勘探中,需要寻找早期硫化物熔离所形成的那部分硫化物熔体,并进一步寻找成矿富集的有利地段。     

层状侵入体韵律层理形成过程的定量模拟——以四川攀枝花层状岩体为例

层状侵入体的韵律层理是一种特殊的岩石构造,长期以来其成因倍受关注,成因假说很多。本文在综合这些观点关于岩浆物理,化学性质的研究,尤其是在岩浆房地对流特征研究成果的基础上,提出了新的成因解释,认为固化带前锋处矿物的结晶,熔浆组分的扩散及固化带前锋本身的推进等３个因素的相互耦合是形成韵律层理的主要机制,这个过程是发生在一定过冷却条件下的,在这种定性认识基础上,笔者提出了旨在对韵律层理形成过程进行模拟计     

可视化地层模型信息系统在水文地质环境地质中的应用

可视化地层模型信息系统是基于GMS平台上建立的,可直观地显现不同性质的空间展布形态和空间组合特征,实现了研究区地层的拆分与组合,剖面的任意切割与显示,指定深度切割水平剖面,任意视角观测地层等信息的三维可视化直观表达,近年来已成为研究地质方面的一个新的亮点,为地质研究人员提供了方便快捷的资料信息。本文以洮儿河扇形地为例介绍可视化地层模型信息系统在水文地质环境地质中的应用。     

玄武质岩石的单颗粒锆石U-Pb年龄谱

报道了托云、东浮山、羊角、雪花山和山旺5处新生代玄武岩的SHRIMP锆石U-Pb测年结果。位于西南天山造山带的托云新生代玄武岩的14个测点年龄值十分发散,最大值与最小值分别为857.1和203.4Ma,它们与其余4件玄武岩样品49个SHRIMP锆石测点年龄一同构筑了涵盖各个地质时期几乎贯穿整个地质时间的复杂年龄谱。位于华北克拉通中部区域南太行山造山带的东浮山、羊角和雪花山新生代玄武岩3件样品累计36个锆石测点形成的锆石年龄谱相对简单,其中35个测点的年龄集中在1719.9～2641.6Ma,唯一的古生代年龄(311.3Ma)出现在雪花山玄武岩7.1测点。位于华北克拉通东部裂谷带内山旺玄武岩6件样品27个测点的单颗粒锆石年龄构筑的锆石年龄谱形成3个集中时间段,分别为新太古代—古元古代(2595.4～1852.2Ma)、古生代(385.8～271.1Ma)和中生代(109.4Ma)。3个年龄谱中大部分单颗粒锆石U-Pb年龄均能在各自所处区域内发现与之对应的岩浆-热事件,部分单颗粒锆石年龄可能暗示所在区域至今未发现的岩浆热事件,托云、东浮山-羊角-雪花山、山旺新生代玄武岩的复杂单颗粒锆石年龄谱再造了各自所处区域的地质演化史。3个锆石年龄谱的复杂程度与各自区域地表出露岩浆岩的规模和期次复杂程度相关,天山造山带内岩浆岩发育,托云玄武岩锆石年龄普最复杂,记录了天山造山带的演化,而华北克拉通中部区域南太行山造山带地表零星出露岩浆岩,东浮山-羊角-雪花山玄武岩的锆石年龄普最简单。处于后期遭受破坏改造的华北克拉通东部裂谷带内的山旺玄武岩的单颗粒锆石年龄谱,其复杂程度明显低于托云玄武岩的年龄谱,而又高于东浮山-羊角-雪花山玄武岩的年龄谱。鉴于玄武质岩浆同化混染围岩过程中能量消耗和地球化学印记以及玄武质岩浆上升的耗时限制,认为托云、东浮山、羊角、雪花山和山旺新生代玄武岩中具有复杂年龄信息的锆石捕掳晶不是玄武质岩浆在快速上升过程中从围岩中捕获的,而是在岩石圈拆沉过程中进入软流圈地幔中,随着具原生岩浆性质的玄武质岩浆喷发到达地表。     

对铁路客运专线穿越采空区场地的稳定性检算分析

就主采空区地表塌陷对铁路客运专线的危害性按照《建筑物、水体、铁路及主要井巷煤柱留设与压煤开采规程》及相关规范技术要求,对线路与主采空区之间的安全距离进行了量化评价,之后就小窑采空区场地对高等级铁路稳定性运用浅埋采空平衡拱的理论量化评价。以上两种量化评价的结果是可以保障线路与主采空区之间的安全距离,该小窑采空区顶板不受力,顶板地基稳定性差,最后文中对场地地基稳定性差的线路基础提出处理措施与建议。     

Diagnostics of subseasonal prediction biases of the Asian summer monsoon by the NCEP climate forecast system

Biases of subseasonal prediction of the Asian summer monsoon are diagnosed using daily data from the hindcasts of 45-day integrations by the National Centers for Environmental Prediction Climate Forecast System version 2. The retrospective forecasts often show apparent systematic biases, which are mostly represented by the underestimation of the whole Asian monsoon. Biases depend not only on lead time, but also on the stage of monsoon evolution. An abrupt turning point of bias development appears around late June and early July, when ensemble spread and bias growth of winds and precipitation show a significant change over the northwestern Pacific (NWP) and the South Asian summer monsoon (SASM) region. The abrupt turning of bias development of winds, precipitation, and surface temperature is also captured by the first two modes of multivariate empirical orthogonal function analysis. Several features appear associated with the abrupt change in bias development: the western Pacific subtropical high (WPSH) begins its first northward jump and the surface temperature over the Tibetan Plateau commences a transition from warm bias to cold bias, and a reversal of surface temperature biases occurs in the eastern tropical Indian Ocean and the SASM region. The shift of WPSH position and the transition of surface thermal bias show close relationships with the formation of bias centers in winds and precipitation. The rapid growth in bias due to the strong internal atmospheric variability during short leads seems to mainly account for the weak WPSH and SASM in the model. However, at certain stages, particularly for longer-lead predictions, the biases of slowly varying components may also play an important role in bias development of winds and precipitation.     

Monitoring severe aquifer-system compaction and land subsidence in Taiwan using multiple sensors: Yunlin,the southern Choushui River Alluvial Fan

During 1992–2007, excessive pumping of groundwater caused large-scale aquifer-system compaction and land subsidence in the Choshui River Alluvial Fan, especially in the area of Yunlin county. The subsidence impedes surface-water runoff and endangers the operation of Taiwan High Speed Rail. Leveling, Global Positioning System (GPS), multi-level compaction monitoring well, and Differential Interferometric Synthetic Aperture Radar (DInSAR) are used to study the extent of subsidence in Yunlin and its mechanism. These sensors complement each other in spatial and temporal resolutions. A leveling network totaling 434 km in length was deployed to derive subsidence at every 1.5 km along the routes, and the result is accurate to few mm and shows a basin-like subsidence pattern centering at Tuku Township. Four multi-level compaction monitoring wells, co-located with GPS pillars, detect compactions at different depths, showing that the aquifer-system compaction (the cause of subsidence) occurs mostly below depths >200 m, where reduction of groundwater pumping is most needed. The vertical displacements from GPS and leveling agree to within 1 cm, and are larger than the cumulative compaction detected by the compaction-monitoring wells, suggesting that compaction also occurs below 300 m (the depth of the wells). The vertical displacements derived using DInSAR and 8 ENVISAT SAR images agree with the leveling result to 1–2 cm.     

Effects of natural and calcined oyster shells on Cd and Pb immobilization in contaminated soils

In Korea, soils adjacent to abandoned mines are commonly contaminated by heavy metals present in mine tailings. Further, the disposal of oyster shell waste by oyster farm industries has been associated with serious environmental problems. In this study, we attempted to remediate cadmium (Cd)- and lead (Pb)-contaminated soils typical of those commonly found adjacent to abandoned mines using oyster shell waste as a soil stabilizer. Natural oyster shell powder (NOSP) and calcined oyster shell powder (COSP) were applied as soil amendments to immobilize Cd and Pb. The primary components of NOSP and COSP are calcium carbonate (CaCO₃) and calcium oxide (CaO), respectively. X-ray diffraction, X-ray fluorescence and scanning electron microscope analyses conducted in this study revealed that the calcination of NOSP at 770°C converted the less reactive CaCO₃ to the more reactive CaO. The calcination process also decreased the sodium content in COSP, indicating that it was advantageous to use COSP as a liming material in agricultural soil. After 30 days of incubation, we found that the 0.1 N HCl-extractable Cd and Pb contents in soil decreased significantly as a result of an increase in the soil pH and the formation of metal hydroxides. COSP was more effective in immobilizing Cd and Pb in the contaminated soil than NOSP. Overall, the results of this study suggest that oyster shell waste can be recycled into an effective soil ameliorant.     

Assessing adaptability of planted trees using leaf traits: A case study with Robinia pseudoacacia L. in the Loess Plateau, China

Leaf trait patterns and their variations with climate are interpreted as an adaptive adjustment to environment.This study assessed the adaptability of planted black locust (Robinia pseudoacacia L.) based on the analysis of leaf traits and the comparison of its leaf traits with inter-specific ones existing in the same area.We measured some water and N use related leaf traits: leaf dry mass per unit area (LMA) and N,P and K concentrations based on both leaf area (Narea,Parea and Karea) and leaf mass (Nmass,Pm...