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The garnet muscovite granitic pegmatite of Um Solimate, in southern Egypt, represents a promising asset for strategic and economic metals, especially Bi–Ni–Ag–Nb–Ta as well as U and Th. The ore bodies occur as large masses, pockets and/or veins of very coarse-grained pegmatites, which consist mainly of K-feldspar, quartz and albite with subordinate muscovite, garnet, and biotite. Radiometric data revealed that eU- and eTh-contents of the pegmatites reach up to 39 ppm and 82 ppm, respectively. The studied pegmatites are enriched in primary U and Th minerals (uraninite, coffinite, thorianite and uranothorite) as well as Hf-rich zircon and monazite, which give rise to anomalous radioactive zones. Niobium-tantalium-bearing minerals (i.e. ferrocolumbite, microlite and uranopyrochlore), xenotime, barite, galena, fluorite, and apatite are ubiquitous, and, consequently, the studied pegmatites belong tothe Niobium–Yttrium–Fluorine-type (NYF) family. The noble metal mineralization includes argentite (Ag2S), native Ni and Bi as well as bismite and bismoclite. In addition, beryl and tourmaline are observed in pegmatites near the contact with metasediments and ultramafic bodies. The observed compositional variations of Ta/(Ta+Nb) and Mn/(Mn+Fe) ratios in columbite (0.08–0.45 and 0.11–0.57, respectively) and Hf contents in zircon (3.54–6.46 wt%) may reflectan extreme degree of magmatic fractionation leading to formation of the pegmatite orebody. 相似文献
64.
Elman神经网络在低渗储层敏感性预测中的应用 总被引:2,自引:1,他引:1
油气储层敏感性是制约低渗储层有效开发的重要因素之一,但在勘探开发早期储层敏感性预测及分布规律的研究受到资料不足的限制.从实验敏感性分析结果入手,对Elman神经网络预测储层敏感性的过程及方法进行了系统的分析,并提出了通过设置虚拟井来预测储层敏感性平面分布的方法.结果表明:①影响低渗储层敏感性的主要因素有蒙皂石、伊利石、高岭石、绿泥石、伊-蒙混层、石英、长石的体积分数,孔隙度和渗透率;②Elman神经网络能够很好地预测低渗储层的敏感性,预测结果与实测结果绝对误差的平均值均低于0.04,水敏性样品的预测结果与实测结果绝对误差的平均值为0.001;③通过设置虚拟井位,能够很好地预测储层敏感性的平面分布规律. 相似文献
65.
Almroth BC Sturve J Stephensen E Holth TF Förlin L 《Marine environmental research》2008,66(2):271-277
The use of fish in environmental monitoring has become increasingly important in recent years as anthropogenic substances, many of which function as prooxidants, are accumulating in aquatic environments. We have measured a battery of antioxidant defenses as a measure of oxidative status, as well as protein carbonylation as a measure of oxidative damage, in corkwing wrasse (Symphodus melops) captured near a disused copper mine, where water and sediment are contaminated with heavy metals, and an aluminum smelter, a site contaminated with PAHs. Results were compared to two different reference sites. Fish at the heavy metal site had lower glucose-6-phosphate dehydrogenase activity and elevated protein carbonyls (1.8 times) compared to fish from the reference site. At the PAH site, EROD was increased 2-fold, while total glutathione and methemoglobin reductase concentration, were decreased. No differences were seen in protein carbonyl levels at the PAH site. Measures of both antioxidant defenses and oxidative damage should be used when assessing effects of xenobiotics on oxidative stress in fish species. 相似文献
66.
Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China 总被引:1,自引:1,他引:0
L E ZHANG Lei CHEN Min QIU Yusheng XING N YANG Weifeng LI Yanping HUANG Yipu 《海洋学报(英文版)》2008,27(1):29-41
Surface water was collected from the Jiulong Estuary for determination of activity concentrations of uranium isotopes in different size fractions, namely, greater than 53, 10 -53, 2 - 10, 0.4 -2 μm, 10 000 u -0.4 μm and less than 10 000 u fractions by microfihration and cross-flow uhrafiltration technologies. Results indicated that most of the dissolved uranium ( 〈 0.4 μm) exis- ted in the low molecular mass fraction ( 〈 10 000 u), and the colloidal uranium-238 (10 000 u -0.4 μm) only contributed less than 1% of the dissolved uranium-238. The fractions of colloidal uranium in the dissolved phases decreased with the increasing sa- linity. A positive linear relationship between uranium-238 activities and salinities was observed for the dissolved, colloidal and low molecular mass fractions, indicating a conservative behavior of uranium in the Jiulong Estuary. In the particulate phases ( 〉 0.4 μm), the partitioning of uranium isotopes among different size fractions was controlled by the partitioning of particle concentrations. In the regions with salinities below 20, the partitioning of uranium-238 among different size fractions was as follows: 10 - 53 μm 〉 2 - 10 μm 〉 0.4 - 2 μm greater than above 53 μm. However, the order at the offshore station with salinities above 30 changed as follows : 0.4 - 2 μm 〉 10 - 53 μm 〉 2 - 10 μm greater than above 53 μm. The fraction of the 0.4 - 2 μm particles increased at the offshore station, suggesting the increased contribution of the authigenic uranium. The activity ratio of uranium-234 to uranium-238 in the dissolved phases, including the low molecular mass fraction and the colloidal fraction, was larger than unity, showing the occurrence of excess uranium-234. In contrast, the activity ratio of uranium-234 to uranium-238 in all size fractions of the particulate phase was close to the equilibrium value (1.0). The observed different values of the activity ratio of uranium-234 to uranium-238 in the dissolved phase and the partic 相似文献
67.
北极东部宽广的陆架展布着几个不同时期、不同走向的裂谷成因构造。利用构造纲要图,展示了上Brooksian地层单元(白垩纪-新生代)的主要构造元素,并勾画出Ellesmerian地层单元(晚泥盆世-侏罗纪)的构造轮廓,通常认为本区该期烃源岩最丰富。上地层单元发现了3个主要沉积盆地:Vil’kitskii-北楚科奇盆地,南楚科奇盆地和东楚科奇盆地,它们被楚科奇中央隆起所分隔。该隆起在EUesmerian期最活跃。通过与研究详细的陆架和陆坡区对比,概括了这3个盆地烃类的形成和聚集模式,了解可能的油气储集远景区带。 相似文献
68.
Caurant F Aubail A Lahaye V Van Canneyt O Rogan E López A Addink M Churlaud C Robert M Bustamante P 《Marine environmental research》2006,62(2):131-148
Lead concentrations and isotopic composition have been measured in bone and teeth of small cetaceans belonging to three species (Delphinus delphis, Phocoena phocoena and Stenella coeruleoalba), to evaluate the toxicological risk and to determine sources of lead in the European waters. Lead concentrations, far lower than threshold value inducing toxic effects in human, were higher in teeth than in bones, but highly correlated between the two tissues (r=0.92, p<0.001). Large variations of 206Pb/207Pb values in bone tissue showed that cetaceans must be submitted to various atmospheric influences. No geographical differences appeared which is consistent with studies on their distribution indicating seasonal movements between Brittany waters and the Bay of Biscay. The negative correlation between 206Pb/207Pb ratios and age of the individuals reflected the decrease in the production of alkyl lead in Europe, i.e., the increasing use of unleaded gasoline. 相似文献
69.
影响西太平洋台风形成的大尺度环流条件 总被引:14,自引:1,他引:14
根据全球热带气旋频率的统计[1],这些频率有明显的年际变化。在过去二十年中全球热带气旋数年变化的百分率为其平均数的-13%-+23%,最多和最少年热带气旋数差达28个,相当于全球年平均热带气旋数(79)的35%。目前认为有三个原因可能影响热带气旋频率:大尺度环流,海面温度和地球以外的因子。 相似文献
70.
Pedro S.B.REYES Mauricio E.VALAREZO Jenry CóRDOVA Fran?ois A.MICHAUD Camilo ZAPATA 《山地科学学报》2018,15(5):966-975
The longitudinal profile of a river channel can be described in function of mathematical expressions. The logarithmic fit is the most used method to describe the relative equilibrium of a channel elevation profile. Rivers showing zones of high channel gradient and convex-upward profiles can be evaluated in function of the offset distance with respect to the logarithmic curve. The Jama River profile has been constructed using differential GPS data for the downstream reach and 4-m-grid DEM data base for the remaining headward profile. The resulting longitudinal profile shows a prominent knickpoint of about 80 m in elevation characterized by sharp local convexity. The offset distance in vertical direction from the logarithmic plot is interpreted as the successive accumulation of multiple uplift episodes associated with the Jama Fault System activity. The horizontal offset is suggested to represent the remaining retreated distance for the upstream propagation of the Jama knickpoint. The highly resistant Cretaceous rocks outcropping along the Jama knickpoint reach acts as an inflection point between two subprofiles that show well-fitted logarithmic curves, thereby representing a temporary partitioned equilibrium along the Jama River profile. 相似文献