柯树背岩体的元素地球化学特征及其成矿意义   总被引：1，自引：0，他引：1  

胡恭任  陈培荣等 《地质与勘探》2002,38(6):25-29

对柯树背岩体的岩石化学，稀土元素，微量元素及铀金成矿元素进行了系统的研究。研究结果表明：柯树背岩体F9大断裂（鹰潭－安远深大断裂）以东部分（东体）与F9大断裂以西部分（西体）在稀土分布模式，微量元素，铀金成矿元素及矿化特征上存在很大的差别，东体与寨背岩体类似，为同熔系列花岗岩，对铀成矿不利；西体为重熔再生岩浆成因的改造型花岗岩，对铀成矿有利，具有良好的成矿远景。  相似文献   

粉喷桩技术加固软土地基   总被引：3，自引：0，他引：3  

郝加和  程华龙 《安徽地质》2002,12(4):282-285,292

简介了水泥粉体喷射搅拌加固软土地基的工作机理,结合沪蓉高速公路(沪宁段)地基处理实践,论述了粉喷桩加固软土地基的计算方法.采用粉喷桩加固软基,可加快路堤填土速率,铺筑路面后的工后沉降量能得到有效地控制,保证了工程质量.  相似文献   

多年冻土地区L型挡土墙土压力(冻胀力)的分析与试验   总被引：6，自引：0，他引：6  

梁波  王家东  严松宏  黄志军  杨泉 《冰川冻土》2002,24(5):628-633

为适应多年冻土区土体冻胀过程所产生的较大变形的特性, 缩短施工进程, 减少扰动时间, 在青藏铁路格拉段选择了一个试验工点进行了L型悬臂挡墙的初步验证性试验研究. 通过对L型挡墙的受力模式分析, 确定了对粗颗粒填料不考虑冻胀力的土压力设计控制值. 通过与现场实测土压力分布规律的对比, 探讨了土压力与冻胀力的关系.  相似文献   

古—中生代之交的全球变化与生物效应   总被引：9，自引：0，他引：9  

彭元桥  殷鸿福 《地学前缘》2002,9(3):85-93

古—中生代之交是显生宙以来最大的一次生物绝灭期 ,其形成机制一直是地学界长期探讨的热点课题之一。地史重大转折期是地球内、外各圈层长期作用下 ,各种量变达到阀值 ,加之可能的外因激化 ,在短时间内以连锁反应形式相继质变 ,形成了全球变化 (包括生物绝灭 )的地球突变期。文中从可能的外因 (外星体撞击事件 )及内因 (岩石圈的变化 ,地球表层的变化和生物圈的变化 )两个方面探讨了古—中生代之交的全球变化与生物效应  相似文献   

山东金青顶金矿床和七宝山金矿床的流体包裹体REE组成   总被引：6，自引：0，他引：6  

陈绪松  徐九华  刘建明  谢玉玲  朱和平  李永兵 《矿床地质》2002,21(4):387-392

文章运用电感耦合等离子体质谱（ICP-MS）方法，研究了金青顶金矿床和七宝山金矿床的脉石英中流体包裹体REE组成特征，结果表明流体包裹体的REE均为LREE富集型，并显示Eu正异常。成矿流体REE配分模式和REE参数特征表明它们具有相当的来源。与金矿有关的成矿母岩，即昆嵛山花岗岩和七宝山次火山岩的REE特征也极为相似，反映成矿流体的REE组成都有从成岩向成矿过程演化继承的关系。矿床流体包裹体REE组成的相似特征及矿床碳氧同位素等特点表明，金青顶金矿床和七宝山金矿床是华北东部中生代同一构造热事件的产物。  相似文献   

Rare earth elements in waters from the albitite-bearing granodiorites of Central Sardinia, Italy   总被引：1，自引：0，他引：1  

Riccardo BiddauRosa Cidu  Franco Frau 《Chemical Geology》2002,182(1):1-14

With the aim of contributing to the knowledge of the geochemical behaviour and mobility of the rare earth element (REE) in the natural water systems, the ground and surface waters of the Ottana-Orani area (Central Sardinia, Italy) were sampled. The study area consists of albititic bodies included in Hercynian granodiorites. The waters have pH in the range of 6.0-8.6, total dissolved solid (TDS) of between 0.1 and 0.6 g/l, and major cation composition dominated by Ca and Na, whereas predominant anions are Cl and/or HCO₃.The pH and the major-element composition of the waters are the factors affecting the concentration of REE in solution. The concentrations of ∑REE+Y in the samples filtered at 0.4 μm vary between 140 and 1600 ng/l, with La of between 14 and 314 ng/l, and Yb of between <6 and 12 ng/l. A negative Ce anomaly, especially marked at high pH, is observed in the groundwaters. The surface waters show lower REE concentrations, which are independent of pH, and negligible Ce anomaly.Speciation calculations, carried out with the EQ3NR computer program, showed that the complexes with the CO₃²⁻ ligand are the dominant REE species at pH in the range of 6.7-8.6. The REE³⁺ ions dominate the speciation at pH <6.7 and only in the light REE (LREE).The relative concentrations of REE in water roughly reflect those in the aquifer host rocks. However, when concentrations of REE in water are normalised relative to the parent rocks, a preferential fractionation of heavy REE (HREE) into the water phase can be observed, suggesting the greater mobility and stability of HREE in aqueous solution.  相似文献   

Negative Ce Anomaly in the Indian Banded Iron Formations: Evidence for the Emergence of Oxygenated Deep-Sea at 2.9-2.7 Ga     

Yasuhiro KATO  Takashi KANO  Keitaro KUNUGIZA 《Resource Geology》2002,52(2):101-110

Abstract: Major and rare earth element contents are reported for Late Archean banded iron formations (BIFs) in the Bababudan Group of the Dharwar Craton, South India. The BIFs are mostly composed of SiO₂ (average1ρ = 54.88.1 wt%) and Fe₂O₃* (44.38.2 wt%). The Al₂O₃ and TiO₂ contents are remarkably low, suggesting that detrital components were starved during the BIF deposition. The BIFs have a LREE-enriched pattern with a relatively high (La/Yb)_N (6.644.07). Total REE concentrations (RE) vary from 5.2 to 65.3 ppm. The REE patterns are characterized by the presence of a very large negative Ce anomaly (Ce/Ce*: 0.13-0.83) and a positive Eu anomaly (Eu/Eu*: 0.96-2.45). The Eu/Eu* decreases and (La/Yb)_N increases with a increase of RE. These correlations of REE indices are similar to those of modern hydrothermal iron-rich sediments near a mid-ocean ridge (MOR). Greenstones associated with the BIFs have MORB-like geochemical features. These geochemical and geological lines of evidence indicate that the depositional site of the BIFs was remote from a continent and/or island arc and that the BIFs were in situ hydrothermal sediments near a MOR. A striking negative Ce anomaly in the BIFs indicates that oxygenated deep-sea environments emerged at 2.9-2.7 Ga. The existence of contemporaneous Mn deposits in the Dharwar Craton supports this assertion. Our scenario of oxygen in the Earth's surface of the Late Archean is different from long-held notion that the atmosphere and ocean were persistently anoxic throughout the Archean.  相似文献   

三原井水位固体潮加卸载响应比的地震异常   总被引：2，自引：0，他引：2  

邢西淳  邵辉成  毛娟  毛胜利  陈建民 《华北地震科学》2002,20(4):40-46

讨论了三原井水位在泾阳4．8级地震前的变化特征，重点是泾阳地震前水位对固体潮响应的变化，即固体潮加卸载响应率与加卸载响应比的变化，对水位观测资料的计算分析表明，震前加卸载响应率及响应比有“平稳－升高－恢复”的特征，说明水位固体潮加卸载响应比方法有可能捕捉5级左右近震的前兆信息。  相似文献   

江西瑞昌1995年ML4.9级地震前后九江地震台倾斜固体潮汐变化分析     

赵爱平  吴敏 《华南地震》2002,22(4):79-84

通过月整点值数据文件和滑动值数据文件这两种数据处理形式。对九江台地倾斜资料进行调和分析计算。分析了M2潮汐因子与瑞昌ML4.9级地震的关系。认为存在震前短临异常或震后异常，并与趋势异常得到相互印证。  相似文献   

Gravity and magnetic signatures of volcanic plugs related to Deccan volcanism in Saurashtra, India and their physical and geochemical properties   总被引：1，自引：0，他引：1  

D.V. ChandrasekharD.C. Mishra  G.V.S. Poornachandra RaoJ. Mallikharjuna Rao 《Earth and Planetary Science Letters》2002,201(2):277-292

The Bouguer anomaly and the total intensity magnetic maps of Saurashtra have delineated six circular gravity highs and magnetic anomalies of 40-60 mGal (10⁻⁵m/s²) and 800-1000 nT, respectively. Three of them in western Saurashtra coincide with known volcanic plugs associated with Deccan Volcanic Province (DVP), while the other three in SE Saurashtra coincide with rather concealed plugs exposed partially. The DVP represents different phases of eruption during 65.5±2.5 Ma from the Reunion plume. The geochemical data of the exposed rock samples from these plugs exhibit a wide variation in source composition, which varies from ultramafic/mafic to felsic composition of volcanic plugs in western Saurashtra and an alkaline composition for those in SE Saurashtra. Detailed studies of granophyres and alkaline rocks from these volcanic plugs reveal a calc-alkaline differentiation trend and a continental tectonic setting of emplacement. The alkaline plugs of SE Saurashtra are associated with NE-SW oriented structural trends, related to the Gulf of Cambay and the Cambay rift basin along the track of the Reunion plume. This indicates a deeper source for these plugs compared to those in the western part and may represent the primary source magma. The Junagadh plug with well differentiated ring complexes in western Saurashtra shows well defined centers of magnetic anomaly while the magnetic anomalies due to other plugs are diffused though of the same amplitude. This implies that other plugs are also associated with mafic/ultramafic components, which may not be differentiated and may be present at subsurface levels. Paleomagnetic measurements on surface rock samples from DVP in Saurashtra suggest a susceptibility of 5.5×10⁻² SI units with an average Koenigsberger ratio (Q_n) of almost one and average direction of remanent magnetization of D=147.4° and I=+56.1°. The virtual geomagnetic pole (VGP) position computed from the mean direction of magnetization for the volcanic plugs and Deccan basalt of Saurashtra is 30°N and 74°W, which is close to the VGP position corresponding to the early phases of Deccan eruption. Modeling of gravity and magnetic anomalies along two representative profiles across Junagadh and Barda volcanic plugs suggest a bulk density of 2900 and 2880 kg/m³, respectively and susceptibility of 3.14×10⁻² SI units with a Q_n ratio of 0.56 which are within the range of their values obtained from laboratory measurements on exposed rock samples. The same order of gravity and magnetic anomalies observed over the volcanic plugs of Saurashtra indicates almost similar bulk physical properties for them. The inferred directions of magnetization from magnetic anomalies, however, are D=337° and 340° and I=−38° and −50° which represent the bulk direction of magnetization and also indicate a reversal of the magnetic field during the eruption of these plugs. Some of these plugs are associated with seismic activities of magnitude ≤4 at their contacts. Based on this analysis, other circular/semi-circular gravity highs of NW India can be qualitatively attributed to similar subsurface volcanic plugs.  相似文献