藏南罗布莎蛇绿岩成因:壳层熔岩的Sr-Nd-Pb同位素制约

罗布莎蛇绿岩是雅鲁藏布江蛇绿岩带东段出露较好,也是研究程度较高的(蛇绿岩片之一,其壳层熔岩的S r,N d,Pb同位素组成具有较高的ISr值,较低的IN d值,大的Nεd(t)值和富集放射性成因铅的特征。ISr值偏高可能是存在富集型地幔源区和蛇绿岩形成过程中经受了地幔流体的交代作用引起的。N d同位素及S r-N d同位素图解表明罗布莎蛇绿岩壳层玄武岩源区有N-M ORB的特征,又有EMⅡ型富集地幔组分的贡献。Pb-Pb图解上样品均投影在NHRL上方,ΔS r为47.4~73.0(平均为58.4),Δ7/4Pb为0.69~12.20(平均为5.87),Δ8/4Pb为12.78~58.39(平均为35.23),表明存在Dupa l同位素异常。根据S r-N d,Pb-Pb和N d-Pb同位素相关特征,判明罗布莎蛇绿岩壳层熔岩是由具亏损地幔端员(DMM)性质的岩浆和具EMⅡ型富集地幔端员性质的岩浆在源区混合形成的。     

城市地下管线信息化建设框架研究

目前,我国各城市相继展开地下管线普查、地下管线信息系统的建设工作,力求建立科学、准确、完整、动态的综合管线信息管理系统,但也都普遍存在一些问题。本文针对管线信息化过程中普遍存在的这些问题,提出站在城市的高度,统筹规划管线信息系统的建设工作。并通过对现代城市发展过程中城市管线信息需求的分析,给出了城市地下管线信息化建设的一种框架。     

基于DVB-S数据共享平台的NOAA/ATOVS资料获取、处理与显示系统

充分利用国家科技部大力推行的DVB-S共享数据平台,加强气象卫星遥感数据的广泛应用,特别是发挥卫星垂直探测器(ATOVS)资料在我国数值天气预报以及监测重大灾害性天气系统中的作用。该文介绍了基于DVB-S系统的NOAA/ATOVS资料的处理、分析与显示系统的概况及主要功能,并以2005年7月人们关注的台风“海棠”为个例,展示了利用该系统在监测和分析台风或强对流天气时的独特优势。该系统的建立,将解决省、地气象部门不能实时获取ATOVS资料的问题,并将推动ATOVS资料在气象以及相关部门的实际应用。     

Variable resolution on quasi-uniform grids: linear advection experiments

Summary A couple of different techniques for implementing the variable resolution within numerical models of the atmosphere that use quasi-uniform grids are estimated and compared based on their merit in the simple linear advection experiments. These techniques are: grid stretching, Schmidt transforming and grid overlapping. The quasi-uniform grids are: a conformal cubic and an octagonal grid. The techniques for the variable resolution are evaluated from the perspective of their effects on numerical solution and the practicality of their application. Our analysis suggests that the grid stretching is for now the most optimal choice. However, a special form of grid overlapping is presented that has potential to become a viable alternative in the future.     

A method for generating uniform size-segregated pyrite particle fractions

Background  

Standardized sample preparation techniques allow comparison of pyrite dissolution experiments under diverse conditions. Our objective was to assess dry and wet sieving preparation methodologies, and to develop a reproducible technique that yields uniformly size-distributed material within a limited size range of interest.     

加密自动气象站蓄电池使用及维护

1引言加密自动气象站投入运行以来,由于蓄电池原因引起的故障占了较大比例,为保证加密自动气象站正常运行,就如何对蓄电池进行正确的使用和维护进行论述。     

Genesis of the Changba–Lijiagou Giant Pb-Zn Deposit, West Qinling, Central China: Constraints from S-Pb-C-O isotopes

The extensive Changba-Lijiagou Pb-Zn deposit is located in the north of the Xihe–Chengxian ore cluster in West Qinling. The ore bodies are mainly hosted in the marble, dolomitic marble and biotite-calcite-quartz schist of the Middle Devonian Anjiacha Formation, and are structurally controlled by the fault and anticline. The ore-forming process can be divided into three main stages, based on field geological features and mineral assemblages. The mineral assemblages of hydrothermal stage I are pale-yellow coarse grain, low Fe sphalerite, pyrite with pits, barite and biotite. The mineral assemblages of hydrothermal stage II are black-brown cryptocrystalline, high Fe shalerite, pyrite without pits, marcasite or arsenopyrite replace the pyrite with pits, K-feldspar. The features of hydrothermal stage III are calcite-quartz-sulfide vein cutting the laminated, banded ore body. Forty-two sulfur isotope analyses, twenty-five lead isotope analyses and nineteen carbon and oxygen isotope analyses were determined on sphalerite, pyrite, galena and calcite. The δ34 S values of stage I(20.3 to 29.0‰) are consistent with the δ34 S of sulfate(barite) in the stratum. Combined with geological feature, inclusion characteristics and EPMA data, we propose that TSR has played a key role in the formation of the sulfides in stage I. The δ34 S values of stage II sphalerite and pyrite(15.1 to 23.0‰) are between sulfides in the host rock, magmatic sulfur and the sulfate(barite) in the stratum. This result suggests that multiple S reservoirs were the sources for S2-in stage II. The δ34 S values of stage III(13.1 to 22‰) combined with the structure of the geological and mineral features suggest a magmatic hydrothermal origin of the mineralization. The lead isotope compositions of the sulfides have 206 Pb/204 Pb ranging from 17.9480 to 17.9782, 207 Pb/204 Pb ranging from 15.611 to 15.622, and 208 Pb/204 Pb ranging from 38.1368 to 38.1691 in the three ore-forming stages. The narrow and symmetric distributions of the lead isotope values reflect homogenization of granite and mantle sources before the Pb-Zn mineralization. The δ13 CPDB and δ18 OSMOW values of stage I range from-0.1 to 2.4‰ and from 18.8 to 21.7‰. The values and inclusion data indicate that the source of fluids in stage I was the dissolution of marine carbonate. The δ13 CPDB and δ18 OSMOW values of stage II range from-4 to 1‰ and from 12.3 to 20.3‰, suggesting multiple C-O reservoirs in the Changba deposit and the addition of mantle-source fluid to the system. The values in stage III are-3.1‰ and 19.7‰, respectively. We infer that the process of mineralization involved evaporitic salt and sedimentary organic-bearing units interacting through thermochemical sulfate reduction through the isotopic, mineralogy and inclusion evidences. Subsequently, the geology feature, mineral assemblages, EPMA data and isotopic values support the conclusion that the ore-forming hydrothermal fluids were mixed with magmatic hydrothermal fluids and forming the massive dark sphalerite, then yielding the calcite-quartz-sulfide vein ore type at the last stage. The genesis of this ore deposit was epigenetic rather than the previously-proposed sedimentary-exhalative(SEDEX) type.     

灰色理论在预应力锚索优化设计中的应用

简要介绍了灰色理论的局势决策和线性规划方法,并以实例说明该方法的预应力锚索加固优化设计中的具体应用过程。     

Sediment transport for desert watersheds in erodible materials

Sediment transport for five small watersheds in arid southern Israel, eroded into shales, chalks, anhydrites and alluvium is studied. Analysis includes data from three large watersheds in the southern United States. Results indicate that floodwater heavily laden with suspended load (10-60 per cent, by weight) is characteristic of watersheds cut in erodible materials. No correlation was found between environmental characteristics such as lithology, catchment area, angle of slope or rainfall intensity and suspended-sediment concentration or texture. The carrying capacity for sands, derived both from hillslopes and channel alluvium is greatly increased by high suspended silt concentration, the trend being (where R = ratio, % fines/% sand; C_s = suspended load concentration, per cent by weight). The high concentration of fine sediment effectively causes more sand transport than would normally occur. This is also true for transport of coarser clastics; higher velocities, typical of highly concentrated silt suspensions, increased competence for transporting pebbles and boulders. The action of a large variety of processes (splash, wash, rilling, gullying, sliding, mudflow) combine with low infiltration and high credibility to render every rainstorm erosionally effective, and high concentrations of washload increase both the capacity and competence of coarse clastic transport. Whole basins are thus subjected to high rates of denudation (2-10 mm/yr).     

青藏高原古高度重建方法研究进展

青藏高原隆升对亚洲及全球气候变化有着深刻的影响,因而地质时期青藏高原古高度定量化恢复对于理解高原隆升历史、隆升机制及其环境效应都具有非常重要的意义.通过近十余年的发展,反演高原古高度方法有了很大的发展,这些方法包括气泡法、古植物学、稳定同位素和陆地宇宙核素方法等,这些研究为恢复古高度提供了新的思路和手段.综述并简要介绍了这些方法的基本原理,同时讨论了应用各种方法的局限性,希望能进一步促进我国在高原古高度恢复方面的研究.