Long-Term Variations in the Vertical Thermohaline Structure in Deep-Water Zones of the Caspian Sea     

Tuzhilkin  V. S.  Kosarev  A. N. 《Water Resources》2004,31(4):376-383

Long-term variability in water temperature and salinity in August has been determined for deep-water segments of standard profiles in the Central and Southern Caspian Sea based on data of on-board observations carried out in 1956–2000. Estimates of parameters of the vertical thermohaline structure of waters were obtained for four time intervals. These estimates have been compared to the variability in the main external factors governing the formation of thermohaline regime. Appreciable long-term variations in the vertical thermohaline structure of waters, caused by a nonperiodic alternation of two main types of hydrological processes in the Caspian Sea are revealed. Qualitative characteristics of these two types are presented.  相似文献   

具有空间分布裂缝岩石的随机介质模型     

曾新吾  张光莹  秀明王 《应用地球物理》2004,1(1):50-55

利用随机过程的谱展开理论以及Hudson等人的裂纹介质模型构造一种裂纹数密度是空间平稳随机过程的随机介质模型。这个模型可以将裂纹的微观参数(裂纹数密度)与裂纹介质的宏观性质(弹性常数)联系起来,能灵活、有效地描述实际非均匀裂纹介质。模型算例表明,弹性常数的空问分布特征与裂纹数密度的有差别,而且对不同的弹性常数影响不同。通过改编自相关长度的大小,可以模拟裂缝在两个坐标轴方向上具有不同分布尺度的情况。最后,利用高阶的交错网格有限差分方法,我们模拟了地震波在具有随机分布裂缝岩石中的传播特征。  相似文献   

Differential retardation of organic matter maturation by overpressure   总被引：2，自引：1，他引：2  

HAO Fang    JIANG Jianqun  ZOU Huayao  FANG Yong & ZENG Zhiping . Key Lab for Hydrocarbon Accumulation Mechanism in the Ministry of Education  Petroleum University  Beijing  China  . Department of Petroleum Geology  China University of Geosciences  Wuhan  China 《中国科学D辑(英文版)》2004,47(9)

Thetraditionalhydrocarbongenerationmodeldoesnottakeintoaccounttheeffectofpressure[1].Astotheroleofpressureinorganicmattermaturationandpetroleumgeneration,threeconflictingopinionshaveeverbeenproposed:(1)Increasingpressurehasnodetectableeffectonorganic-mattermaturation[1,2];(2)increasingpressureenhanceshydrocarbon-thermaldestruction[3];(3)increasingpressuresignificantlyretardsorganic-mattermaturationandhydrocarbongeneration[4,5].Therearemorethan180overpressuredbasinsintheworld.Theroleofoverpress…  相似文献   

An automated seamless mosaicing system of multi-charge coupled devices of panchromatic data     

R. Ramakrishnan  S. Manthira Moorthi  N. Padmanabhan  P. Gupta 《Journal of the Indian Society of Remote Sensing》2004,32(1):103-111

Panchromatic data of pixel resolution 5.8 m obtained from IRS-1C and IRS-1D satellites proved to be very useful for mapping purposes. One of the popular data product is the 70 km swath mosaic which is covered by a combination of 3 CCD line sensors, each with 4096 pixels. Each CCD-line sensor with different imaging times causes geometric problems of mosaicing three strips data together. In this paper, we propose the details of the design elements of system that caters to the need for accurate and automatic multi strip image registration without any second resampling of the data. The systematic geometric correction grid mapping is improved to facilitate accurate mosaicing by automatic image registration task that makes use of the overlap data within image strips and image registration is achieved up to sub-pixel level.  相似文献   

安徽铜陵矿集区海底喷流沉积体系的流体包裹体微量元素对比   总被引：7，自引：3，他引：7  

徐九华  谢玉玲  杨竹森  蒙义峰  曾普胜 《矿床地质》2004,23(3):344-352

铜陵矿集区与铜-金(多金属)矿床有关的热液活动主要有两大体系。即与海西期海底喷流沉积有关的热液体系和与矽卡岩矿化有关的燕山期岩浆热液体系。查明这两类热液体系的流体包裹体特征对区域找矿和矿床成因研究都有实际意义。在包裹体岩相学研究基础上，应用ICP-MS技术和热爆提取方法，研究了新桥、冬瓜山、峙门口、铜官山、朝山等矿床具代表性的热液石英中流体包裹体的微量元素、稀土元素特征。结果表明，两类热液体系在流体包裹体特征上有较大的区别，在流体的微量元素和稀土元素特征方面也很不相同。海底喷流沉积体系的热液石英中流体包裹体与岩浆热液体系的相比。稀土总量较高，LREE／HREE比值较大，δEu不明显。且Mo／(W Sn)比值较高，反映流体中成矿物质的深源特征；Ga／T1、Rb／Cs大。Zr／Hf低，也不同于岩浆热液体系。  相似文献   

长江中下游地区地下水中Mn元素的背景特征及其形成   总被引：3，自引：0，他引：3  

曾昭华 《上海国土资源》2004,(1):9-12

该文论述了长江中下游地区地下水锰元素的背景特征及其与地下水的含水介质成分、上覆岩土性质、氧化还原环境、地下水的迳流条件、地下水及土壤酸碱度的关系.研究结果表明,长江中下游地区地下水中Mn元素含量,在区域上分布特点为江汉平原东部区〉长江三角洲南部区〉鄱阳湖区.  相似文献   

中国2010年上海世博会场址区地质环境条件分析与评价     

张鹏飞  史玉金  曾正强  严学新 《上海国土资源》2004,(4):1-6

文章在简要介绍世博会场址地质条件的基础上，分别分析了场址区流砂、软土和地下水等不良地质现象对工程建设的影响，然后评价了场址区天然地基工程、桩基工程以及地下工程建设的适宜性，为世博会场址区工程建设提供必要的地质依据。  相似文献   

Problems of Siderite Formation and Iron Ore Epochs: Communication 1. Types of Siderite-Bearing Iron Ore Deposits     

V. N. Kholodov  G. Yu. Butuzova 《Lithology and Mineral Resources》2004,39(5):389-411

It is shown that siderite is unstable during sedimentation, diagenesis, and metamorphism of sedimentary and volcanosedimentary rocks. Regularities in the distribution of siderite in Precambrian jaspilites (iron formations), metasomatic ores of the Bakal type, continental–marine coaliferous formations, and oolitic iron ores are discussed. The genesis of the Precambrian iron formations and Riphean–Lower Paleozoic elisional–hydrothermal deposits is considered. The genetic relation of nodular siderites from coaliferous formations and oolitic iron ores with lowmoor coal-forming peat deposits is noted.  相似文献   

New geochemical data from the Nigerian sector of the Chad basin: implications on hydrocarbon prospectivity     

N.G Obaje  H Wehner  H Hamza  G Scheeder 《Journal of African Earth Sciences》2004,38(5):339

Organic geochemical studies have been carried out to assess the qualities of source rocks penetrated by four wells (Kemar-1, Murshe-1, Tuma-1 and Ziye-1) in the Nigerian sector of the Chad basin. The Chad basin is a large intracratonic basin in Central West Africa. Commercial hydrocarbon accumulations have been discovered in some sectors of the basin outside the Nigerian border in a structurally related contiguous basin. Fair to poor quality source rocks are inherent in the sequences penetrated by the studied wells. About 80% of all samples have their total organic carbon (TOC) contents more than 0.5 wt.%, the minimum limit for hydrocarbon generation. Juxtaposition of the hydrogen indices against the TOC and T_max indicates that the source rocks are entirely gas-prone. However, biomarker chromatograms and extract vs. TOC plots indicate the presence of oil shows in Ziye-1 well at a depth of 1210 m. Although generated hydrocarbons (wherever they have accumulated) would be overwhelmingly gaseous, gas is the energy of the future. The gas resources of this part of Nigeria's inland basins can be economically exploited through policies that will increase the tempo of gas-utilization projects and the construction of a national grid of gas pipelines with nodal points of input and output.  相似文献   

Reversibility of radiocaesium sorption on illite     

Arjan de Koning  Rob N.J Comans 《Geochimica et cosmochimica acta》2004,68(13):2815-2823

Adsorption of trace amounts of radiocaesium on NH₄-, K-, and Na-saturated Fithian illite and subsequent desorption by 1 M NH₄ showed that a substantial amount of radiocaesium (44%, 46%, and 91% for NH₄-, K-, and Na-illite, respectively) cannot be desorbed after only 5 min of adsorption. Our results suggest that this instantaneous fixation is caused by the collapse of the frayed edges of the clay mineral and the relatively high concentration of radiocaesium building up in solution in the batch desorption experiments. Consequently, commonly applied high-NH₄ extractions underestimate truly exchangeable amounts of radiocaesium in soils and sediments containing illitic clay minerals. The rate of desorption of trace amounts of radiocaesium from the solids using high NH₄ or Cs concentrations has a half-life of about 2 yr, reflecting radiocaesium desorption from (partially) collapsed interlayers. Extraction of radiocaesium from illite after 5 min of contact time with a Cs-selective adsorbent or a 1 × 10^-6 M CsCl solution shows that 100% of the bound radiocaesium is readily available. The desorption rate in the presence of a Cs-selective adsorbent has a half-life of about 0.2 yr. Desorption of radiocaesium from illite using different ammonium concentrations shows that radiocaesium partitioning follows reversible ion-exchange theory if the NH₄ concentration is below 1 × 10^-4 M, and sufficient time (weeks) is allowed for the reaction to proceed. Thus, radiocaesium sorption reversibility in the natural environment is much higher than generally assumed, and equilibrium solid/liquid partitioning may be assumed for the long-term modelling of radiocaesium mobility in the natural environment. In the particular case of anoxic freshwater sediments with very high NH₄ concentrations in the pore waters (up to several mmol.L^-1), collapse of the frayed edges of illite may occur, influencing radiocaesium partitioning. If collapse occurs before radiocaesium adsorbs to illite, high caesium sorption reversibility as measured by high-NH₄ extraction can be expected because further collapse of the frayed edges during the extraction procedure will be limited. This effect has indeed been observed earlier in the extraction of radiocaesium from anoxic freshwater sediments with high-NH₄ solutions and was as yet unexplained.  相似文献