滇黔桂岩溶地区农业地域类型分区之研究

本文针对滇黔桂岩溶地区农业自然环境特征、农村社会经济条件及其岩溶对农业生产发展和农业生态环境建设影响等的显著地域差异和显著地域分异规律,根据分区指标选择原则,建立起以地貌类型、岩溶地貌景观类型、农民人均纯收入为内容的分区指标体系,把全区划分为三大类、九个农业地域类型区。对三大类型区作了简述。     

基于空间几何原理的北斗三频IF-PPP建模和验证

利用空间几何原理推导三频消电离层参数和最小噪声直线空间表达式,采用5个静态观测站和1组实测跑车北斗三频观测数据,对比分析北斗三频消电离层模型与双频消电离层模型PPP精度和收敛速度。结果表明,静态条件下,三频PPP的位置误差为3.75 cm,标准差为2.06 cm,收敛时间为109.6 min,较双频PPP性能分别提升22.3%、19.8%、22.1%;动态条件下,三频PPP的位置误差为15.21 cm,标准差为12.89 cm,较双频PPP性能分别提升42.4%和26.8%,且收敛速度也更优。     

西藏北冈底斯扎独顶A型花岗岩锆石U-Pb年代学、地球化学及其地质意义

西藏北冈底斯早白垩世花岗岩分布广泛;扎独顶岩体作为其中的一个典型代表,其分布广泛,呈岩基型式产出,在岩性上属二长花岗岩。在岩石化学上扎独顶岩体具有富Si O2(70.05%~74.97%)和K2O(4.09%~5.35%),贫Ca O(0.93%~2.19%)、Ti O2(0.22%~0.52%)和Al2O3(12.81%~14.24%)的特征;属于准铝质-弱过铝质(A/CNK=0.99~1.0)高钾钙碱性系列。岩体稀土元素总量偏高(∑REE=199.36×10-6~247.91×10-6),相对富集轻稀土元素(LREE/HREE=5.82~6.88),Eu负异常明显(δEu=0.30~0.45),球粒陨石标准化分布模式呈向右缓倾的V型。微量元素显示其富集Rb、Th、K、Zr和Hf,亏损Nb、Ta、Sr、Ba、P和Ti,(Zr+Nb+Ce+Y)平均值为427.63。全岩锆石饱和温度(828~838°C)表明岩浆形成温度高。上述岩石地球化学特征表明扎独顶岩体为A型花岗岩。扎独顶岩体LA-ICP-MS锆石U-Pb年龄为(103.8±1.0)Ma,表明其形成于早白垩世晚期;在构造判别图解上位于碰撞后的A2型花岗岩区,是在碰撞后岩石圈伸展背景下,由于软流圈物质上涌导致岩石圈地幔与壳源熔体部分熔融并经历过一定程度的混合作用而形成的。     

REE, Mn, Fe, Mg and C, O Isotopic Geochemistry of Calcites from Furong Tin Deposit, South China: Evidence for the Genesis of the Hydrothermal Ore-forming Fluids

The Furong tin deposit in the central Nanling region, South China, consists of three main types of mineralization ores, i.e. skarn-, altered granite- and greisen-type ores, hosted in Carboniferous and Permian strata and Mesozoic granitic intrusions. Calcite is the dominant gangue mineral intergrown with ore bodies in the orefield. We have carried out REE, Mn, Fe, and Mg geochemical and C, and O isotopic studies on calcites to constrain the source and evolution of the ore-forming fluids. The calcites from the Furong deposit exhibit middle negative Eu anomaly (Eu/Eu*= 0.311–0.921), except for one which has an Eu/Eu* of 1.10, with the total REE content of 5.49–133 ppm. The results show that the calcites are characterized by two types of REE distribution patterns: a LREE-enriched pattern and a flat REE pattern. The LREE-enriched pattern of calcites accompanying greisen-type ore and skarn-type ore are similar to those of Qitianling granite. The REE, Mn, Fe, and Mg abundances of calcites exhibit a decreasing tendency from granite rock mass to wall rock, i.e. these abundances of calcites associated with altered granite-type and greisen-type ores are higher than those associated with skarn-type ores. The calcites from primary ores in the Furong deposit show large variation in carbon and oxygen isotopic compositions. The δ¹³C and δ¹⁸O of calcites are −0.4 to −12.7‰ and 2.8 to 16.4‰, respectively, and mainly fall within the range between mantle or magmatic carbon and marine carbonate. The calcites from greisen and altered granite ores in the Furong deposit display a negative correlation in the diagram of δ¹³C versus δ¹⁸O, probably owing to the CO₂-degassing of the ore-forming fluids. From the intrusion to wall-rock, the calcites display an increasing tendency with respect to δ¹³C values. This implies that the carbon isotopic compositions of the ore-bearing fluids have progressively changed from domination by magmatic carbon to sedimentary carbonate carbon. In combination with other geological and geochemical data, we suggest that the ore-forming fluids represent magmatic origin. We believe that the fluids exsolved from fractionation of the granitic magma, accompanying magmatism of the Qitianling granite complex, were involved in the mineralization of the Furong tin polymetallic deposit.     

沙三中亚期东营三角洲前缘滑塌浊积岩定量预测

东营凹陷沙三中亚段广泛发育三角洲-浊积体系沉积。根据砂层组沉积的垂向变化特征,将沙三中亚段沉积时期东营三角洲自上而下划分为1～9期次,自东向西向湖盆中心进积。与三角洲有关的前缘浊积体包括滑动浊积岩、滑塌浊积岩及远源浊积岩3种类型,其中滑塌浊积岩发育的规模、数目最为稳定,是前缘浊积体定量研究的重要类型。笔者采用控制变量的方法对单因素关系进行探讨,进而分析多因素综合关系,对沙三段中亚段沉积时期东营三角洲前缘浊积体进行定量研究,从而探讨三角洲沉积结构与前缘滑塌浊积体发育的定量关系。研究发现,三角洲沉积结构特征(三角洲前缘地层厚度H、砂岩百分含量x等)、浊积岩滑移距离s以及三角洲前缘斜坡坡角的大小α,可以定量地确定,并且三角洲前缘滑塌浊积体发育的厚度h与前缘厚度H、前缘砂岩百分含量x成正相关,与浊积体滑移距离s呈负相关,并且得到预测三角洲前缘浊积体厚度h的数学模型。     

The Asymmetrical Eruption of a Quiescent Filament and Associated Halo CME

We will present detailed observations of the asymmetrical eruption of a large quiescent filament on 24 November 2002, which was followed by a two-ribbon flare, three coronal dimmings, endpoint brightenings, and a very fast halo-type coronal mass ejection (CME). Before the eruption, the filament lay along the main neutral line (MNL) underneath a single-arcade helmet streamer with a simple bipolar configuration. However, photospheric magnetic fields on both sides of the filament showed an asymmetrical distribution, and the filament and MNL were not located just at the center of the streamer base but were closer to the eastern leg of the streamer arcade. Therefore, instead of erupting along the streamer’s symmetrical axis, the filament showed a nonradial and asymmetrical eruption. It lifted from the eastern flank of the streamer arcade to impact the western leg directly, leading to an asymmetrical CME that expanded westward; eventually the streamer was disrupted significantly. Accordingly, the opposite-polarity coronal dimmings at both sides of the filament forming in the eruption also showed an asymmetrical area distribution. We thus assume that the streamer arcade could guide the filament at the early eruption phase but failed to restrain it later. Consistent with previous results, these observations suggest that the global background magnetic field can impose additional action on the initial eruption of the filament and CME, as well as the dimming configuration.     

北大西洋秋季“三极子”海温结构对冬季大气环流场的影响

利用NCEP再分析资料、Hadley中心的海表面温度(SST)资料等,从北大西洋秋季海表面温度异常(SSTA)变化入手,对其影响后期冬季大气环流场的机制进行了分析。研究结果如下:(1)北大西洋SST异常与大气环流异常之间存在着相互作用;(2)秋季北大西洋SSTA具有较好的持续性,"正负正"海温异常空间分布导致12月巴伦支海上空500hPa位势高度异常偏高;(3)异常环流形势对应的海表面风异常场(SSWA)通过阶段性风-蒸发-SST异常反馈机制(WES机制)利于海温异常分布的持续及对上空异常大气环流的反馈;(4)三极子海温结构中负异常海温自10月份开始有自西向东的移动,风作用下蒸发加大,伴随上升运动自欧洲西部爱尔兰群岛出现自西向东移动的降水正异常区,潜热释放有利于冬季巴伦支海上空的异常高压脊发展。研究表明,北大西洋秋季SSTA通过阶段性海气相互作用机制影响海洋温度分布和大气环流异常,对后期冬季中国东北部的气候变化产生影响。     

地铁隧道地震反应非线性分析

本文对动力有限元法中的一系列问题进行了讨论,对土体动力本构模型和土-结构接触面模型的设定提出了建议．在此基础上以天津地铁1、2号线工程为实例,分别对水平地震作用下圆形盾构隧道的动位移、动应力与动应变以及地表位移等动力反应进行了非线性分析,得出了一些有益的规律和结论,从而为地铁隧道的抗震设计与研究提供参考和依据。     

Variability of soil moisture and its relationship with surface albedo and soil thermal parameters over the Loess Plateau

Data from July 2006 to June 2008 observed at SACOL(Semi-Arid Climate and Environment Observatory of Lanzhou University,35.946°N,104.137°E,elev.1961 m),a semi-arid site in Northwest China,are used to study seasonal variability of soil moisture,along with surface albedo and other soil thermal parameters, such as heat capacity,thermal conductivity and thermal diffusivity,and their relationships to soil moisture content.The results indicate that surface albedo decreases with increases in soil moisture content,s...     

低涡过程对流云和降水结构特征及其环境条件分析

利用遥感及加密观测资料详细分析了2005年6月25～26日一次低涡过程对流云和降水的结构特征,并利用NCEP再分析资料以及实况风场资料分析了其形成的有利条件。分析表明：此次低涡过程中出现的中尺度对流云团（MCC）经历了十几小时的发展演变,云顶亮温低达-90℃,导致了局地暴雨出现,对流云和降水的分布有很好的对应但同时具有显著的时空分布不均匀性。对流云内部高空存在冰晶的大值区,云水含量也比周围环境丰富,冰晶下落过程中通过碰粘其它冰晶、碰冻云水导致了云内的可降水增多,播撒-供应机制起主要作用。而对流降水的“双峰“廓线结构表明暖雨过程非常强。此次过程有形成强对流非常有利的环境：强西南低空急流水汽输送和水汽辐合与高空偏西风急流的相互作用为对流云团和强降水的形成提供水汽和不稳定条件;低层不稳定区域上强垂直上升运动则提供了不可缺少的动力条件;中尺度辐合系统的形成是此次强对流产生的直接原因。