Gold Occurrence and Ore Genesis,Yata Micro—Disseminated Gold Deposit,Guizhou,Southwest China     

朱笑青  王中刚 《中国地球化学学报》2002,21(4):370-373

The mode of occurrence of gold in the Yata micro-disseminated gold deposit is ap-proached through chemical phase studies coupled with ore-dressing monitoring and micro-beam analysis.The results showed that gold occurred for the most part as ultra-microscopic particles adsorbed on the surfaces or fracture planes of pyrite and other sulphides.The proportions of gold of different occurrences were estimated solutions containing nanometer-sized gold particles were prepared following the hydrolysis-reduction procedure and the adsorption of nanometer-sized gold on ordinary sulphides and rocks was experimentally determined.It is evident that sulphides are good adsorbents of gold and this is consistent with geological observations.  相似文献   

Structure sismique du socle paléozoı̈que du bassin des Doukkala,Môle côtier,Maroc occidental. Indication en faveur de l'existence d'une phase éo-varisqueSeismic structure of the Doukkala basin,Palaeozoic basement,western Morocco: a hint for an Eovariscan fold-and-thrust belt     

Hassan Echarfaoui  Mohamed Hafid  Abdallah Aı̈t Salem 《Comptes Rendus Geoscience》2002,334(1):13-20

Seismic profiles and well data from the Doukkala basin unravel the structure of the Palaeozoic basement and suggest that this coastal zone of western Morocco was affected by a compressive phase during the Frasnian. This resulted in the formation of upright, plurikilometric folds associated with reverse faults (North Doukkala), and of asymmetrical folds associated with mostly west verging ramps (South Doukkala). Folding involved all pre-Upper Frasnian formations and caused partial or total hiatus of Upper Frasnian–Strunian strata. This event can be correlated with the orogenic phase reported from more internal domains of the Morocco Hercynian belt, where it is referred to as the ‘Bretonne’ or ‘Eovariscan’ phase. To cite this article: H. Echarfaoui et al., C. R. Geoscience 334 (2002) 13–20  相似文献   

Simulation of artificial random field considering the temporal-spatial variation     

倪永军  朱晞 《地震学报(英文版)》2002,15(4):425-430

Introduction For the seismic design of special structures such as nuclear power station, marine platform, long-span bridge and dam, generally the time-history response analysis of the structure under seismic excitation is imperative, which was coded in most seismic design codes. The earthquake records suitable for the seismic situation and site condition are necessary to be used as the seismic input in the dynamic analysis of structures. As a result of the limited observational condition of st…  相似文献   

X线侧位片与高分辨率CT对鼻骨骨折的对比研究   总被引：17，自引：0，他引：17  

王惠芝  孙璐  闫罡  曾庆玉 《CT理论与应用研究》2002,11(3):33-38

目的　通过86例鼻骨骨折的鼻骨X线侧位片与高分辨率CT(HRCT）对比研究，确定HRCT检查对鼻骨骨折的诊断价值。材料与方祛　86例鼻外伤或/和He、面外伤的患者均进行了鼻骨X线侧位摄影、HRCT扫描检查，经集体讨论，由有经验的放射医师对全部影像资料进行分析并进行统计学处理。结果HRCT显示所有的86例鼻骨骨折，但在此86例骨折中X线平片只显示了35例阳性，包括15例鼻骨汇合部骨折，7例双侧鼻骨骨折，3例复合骨折(鼻骨汇合部及双侧鼻骨骨折)，l0例鼻区骨折。X线平片显示5l例为阴性。结论　对鼻骨骨折的诊断，HRCT明显优于鼻骨X线侧位片，HRCT扫描检查可提高X线隐性鼻骨骨折的诊断，并可明确鼻骨骨折的类型、范围和程度，为临床诊断和治疗提供可靠的依据。  相似文献   

Screening model for volatile pollutants in dual porosity soils     

Mohamed M. Hantush  Rao. S. Govindaraju  Miguel A. Marioand Zhonglong Zhang 《Journal of Hydrology》2002,260(1-4):58-74

This paper develops mass fraction models for transport and fate of agricultural pollutants in structured two-region soils. Mass fraction index models, based on a semi-infinite domain solution, are derived that describe leaching at depth, vapor losses through soil surface, absorption, and degradation in the dynamic- and stagnant-water soil regions. The models predict that leaching is the result of the combined effect of the upward vapor-phase transport relative to downward advection, residence time relative to half-life, dispersion, and lateral diffusive mass transfer. Simulations show that leached fraction of volatile compounds does not always decrease monotonically with increased residence time relative to the pollutant half-life, as a result of complex interactions among the different physical and biochemical processes. The results show that leaching, volatilization, and degradation losses can be affected significantly by lateral diffusive mass transfer into immobile-water regions and advection relative to dispersion (i.e. Peclet number) in the mobile-water regions. It is shown that solute diffusion into the immobile phase and subsequent biochemical decay reduces leaching and vapor losses through soil surface. Potential use of the modified leaching index for the screening of selected pesticides is illustrated for different soil textures and infiltration rates. The analysis may be useful to the management of pesticides and the design of landfills.  相似文献   

Melting of β-quartz up to 2.0 GPa and thermodynamic optimization of the silica liquidus up to 6.0 GPa     

Pierre Hudon  In-Ho Jung  Don R. Baker 《Physics of the Earth and Planetary Interiors》2002,130(3-4):159-174

Melting relations of β-quartz were experimentally determined at 1.0 GPa (1900±20 °C), 1.5 GPa (2033±20 °C), and 2.0 GPa (2145±20 °C) using a new high-pressure assembly in a piston–cylinder apparatus and substantial differences were found with data previously reported. The new melting data of β-quartz were combined and optimized with all available thermodynamic, volumetric, and phase equilibria data for β-cristobalite, β-quartz and coesite to produce a P–T liquidus diagram for silica valid up to 6.0 GPa. Using the new optimized thermodynamic parameters, the invariant point β-cristobalite+β-quartz+liquid and β-quartz+coesite+liquid were determined to lie at 1687±17 °C and 0.457 GPa, and 2425±25 °C and 5.00 GPa, respectively.  相似文献   

The experimental studies on electrical con-ductivities and P-wave velocities of anortho-site at high pressure and high temperature   总被引：1，自引：0，他引：1  

白利平  杜建国  刘巍  周文戈 《地震学报(英文版)》2002,15(6):667-676

Introduction The measurements of the compressional wave velocity and electrical conductivity of minerals and rocks are of fundamental importance to look into the earths interior, including composition, geotherm, generation and distribution of fluids and melts. Hydrous minerals formed by metamatu-siom are abundant within the earth. Previous studies have been carried out on the dehydration effect on the electrical conductivity and wave velocity of rocks such as serpentine, amphibole, most of whi…  相似文献   

滇池农村固体废物和化肥流失治理试验研究   总被引：5，自引：1，他引：5  

戴丽  郭慧光  汤承彬  罗丽 《云南地理环境研究》2002,14(2):70-79

怎样合理处置农村固体废物和减少农田化肥流失一直是农村面源污染控制的难题之一。该研究将农村固体废物的处理与减少化肥施用措施有机结合，利用微生物复合发酵剂和农村固体废物生产活性肥料，开展了一系列农业种植试验和数据监测，在此基础上，提出了一套实用性强、效果好的控制农业固体废物和化肥流失污染的对策措施。  相似文献   

Offset on the Main Recent Fault of NW Iran and implications for the late Cenozoic tectonics of the Arabia–Eurasia collision zone     

Morteza Talebian  James Jackson 《Geophysical Journal International》2002,150(2):422-439

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The effect of scattering in surface wave tomography   总被引：6，自引：1，他引：6  

Jesper Spetzler  Jeannot Trampert  Roel Snieder 《Geophysical Journal International》2002,149(3):755-767

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