Overtopping Discharge of Wind-Waves on Simple Slope Dikes     

Yu Kuang-ming  Zhang Jiachang  Zhou Jiabao Professor  Senior Engineer  The River  Harbour Department  Nanjing Hydraulic Research Institute  Nanjing Senior Engineer  The River  Harbour Department  Nanjing Hydraulic Research Institute  Nanjing 《中国海洋工程》1991,(4)

An empirical formula for estimating the overtopping discharge of wind-waves on a smooth-impermeable-simple slope dyke is derived through model tests in this paper, it can be adopted by related design departments in the determination of the crest elevation of the dyke.  相似文献   

桩式离岸堤保滩促淤工程消浪效果试验研究   总被引：9，自引：0，他引：9  

龚崇准  陈美发等 《海洋工程》2001,19(4):72-77

在上海奉贤南北港保滩促淤工程中，采用了一种新型结构型式－桩式离岸堤，并通过物理模式试验进行了桩式离岸堤消浪效果研究。针对离岸堤通常建于近岸水区破波带的特点，重点研究水深，堤高以及堤身结构对波浪衰减的影响，同时对桩式离岸堤堤后水域的波浪底流速 分析探讨。研究结果表明，桩式离岸堤不仅具有良好的消浪效果。而且可在较大范围内改变波态，即由引起水体剧烈紊动的破波转变为浅水推进波，从而有效地改善海滩上的动力条件，促进海滩免受侵蚀，是一种具有广泛应用前景和新型保滩促淤结构。  相似文献   

新疆库鲁克塔格地区二叠纪脉岩群岩石地球化学特征，Nd、Sr、Pb同位素组成与岩石成因   总被引：12，自引：22，他引：12       下载免费PDF全文

姜常义姜寒冰  叶书锋夏明哲 逯东霞 《地质学报》2005,79(6):823-833

库鲁克塔格地区二叠纪脉岩群非常发育,主要岩石类型是辉绿岩,并有少量的斜闪煌斑岩、斜长玢岩和花岗斑岩。花岗斑岩属高钾钙碱性系列,具有A型花岗岩的稀土元素和微量元素地球化学特征;斜长玢岩的地球化学特征与花岗斑岩相似,二者都亏损U、Nb、Ta。斜闪煌斑岩的岩石化学组成属过碱性系列,显著富集轻稀土元素和大离子亲石元素。辉绿岩的岩石化学组成以钙碱性系列为主,稀土元素总量变化较大,Cs、Rb、Ba、Th元素丰度变化大,普遍亏损U、Nb、Ta。研究证明,辉绿岩脉的这些地球化学特征都与同化混染作用有关,大离子亲石元素丰度的变化还与热液蚀变有关。辉绿岩具有富集型Nd、Sr同位素组成,且变化范围大,是岩浆源区同化混染作用的结果。它们的铅同位素组成属低U(Th)/Pb值的正常铅,主要受混染物控制,并不代表源区特征。库鲁克塔格地区岩石圈地幔Nd、Sr、Pb同位素比塔里木板块西缘岩石圈地幔的富集程度更高,且变化范围大,反映了这两个地区岩石圈地幔的演化历史存在明显差异。  相似文献   

湘东北中生代基性岩脉岩石地球化学及构造意义   总被引：8，自引：1，他引：8  

贾大成  胡瑞忠  谢桂青 《大地构造与成矿学》2002,26(2):179-184

湘东北中生代发育以辉绿岩类和煌斑岩类为代表的基性岩脉,属陆内拉斑玄武岩系,部分煌斑岩属于碱性系列。岩石富集LREE,δEu负异常不明显,其形成主要受软流圈地幔部分熔融作用制约。煌斑岩类微量元素总体上具有洋岛玄武岩(OIB)岩浆源区特征,富集Nd、P、Cs而K、Rb、Sr、U、Th等富集程度不明显,Ta、Nb略有富集。辉绿岩类表现出Ta、Nb、Ti亏损,但LILE并不富集,反映地壳混染程度的增强。基性岩脉形成于陆内拉张带的构造环境,岩浆活动未受到中生代大洋板块俯冲的影响。基性岩脉在时、空及物质组成上与湘东南玄武质岩石基本一致,属于整个湘东南岩石圈拉张-减薄带的一部分。  相似文献   

Sedimentary facies during early stages of flooding in an extensional basin: the Brèche Rouge de Carboneras (Late Miocene, Almería/SE Spain)     

Uwe M. R. Krautworst  Thomas C. Brachert 《International Journal of Earth Sciences》2003,92(4):610-623

The intramontane basins of the Betic Cordilleras (SE Spain) formed subsequent to the main phase of orogenic deformation during the middle Miocene in a close genetic relation to the Trans-Alboran Shear zone. Left lateral movements along a local branch (Carboneras fault zone, CF; strike NE–SW) of this zone played a major role in controlling the formation and dynamics of the Nijar-Carboneras Basin. To the south of the fault, a major phase of strike-slip faulting is recorded during the late Tortonian. The expression of this event is the Brèche Rouge de Carboneras (BRC), which seals a deep denudational surface on top of dislocated fault blocks formed by volcanics of the Cabo de Gata complex and early Tortonian shallow marine calcarenite. The sedimentary facies of this widely distributed unit in the Carboneras-Subbasin mirror the submarine topography and the distribution of the fault zones. Along strike-slip fault zones, autoclastic breccias and neptunian dikes preferentially oriented NW–SE and NE–SW occur, which are interpreted to represent the near-surface expression of the faults. Red limestone forms the groundmass of the autoclastic breccia and infills of neptunian dikes, which exhibit multiple phases of opening of fissures, gravitational sedimentary infill, lithification, and renewed creation of cracks. Steep relief, probably along fault scarps, was mantled by epiclastic volcanic conglomerate with a red carbonate matrix. Well-lithified coarse skeletal limestone rich in planktonic foraminifera formed pavements along sediment starved rocky surfaces in deep water. Laterally, within topographic depressions, the pavement limestone grades into thick accumulations of skeletal rudstone composed of fragmented azooxanthellate corals and stylasterid hydrozoans, which were concentrated by powerful bottom currents and gravitiy flows. Within the shallow water zone of dip slope ramps, cross-bedded calcarenite and calcirudite formed. Based on textures, fabrics and biota, rocks of the BRC were grouped into nine genetic lithofacies which document cryptic, deep-aphotic and shallow-photic environments typical of a sediment starved extensional basin.  相似文献   

Geochronology, geochemistry and tectonic implications of Xiongshan diabasic dike swarm, northern Fujian     

Shengli Ren  Jiliang Li  Xinhua Zhou  Min Sun 《中国科学D辑(英文版)》1997,40(4):411-417

Sm/Nd isotopic age determination showed that Xiongshan dike swarm was at 585.7 Ma ± 30 Ma. The trace element geochemistry and Sr/Nd/Pb isotope gemhemistry studies indicate that the dike swarm was products of back-arc basin spreading ridge and the magma originated from the depleted mantle region which was metasomatized by LILE-rich liquids/melts derived from subduction slab. Project supported by the National Natural Science Foundation of China.  相似文献   

青藏高原南羌塘基性岩墙群U-Pb和Sm-Nd同位素定年及构造意义   总被引：17，自引：0，他引：17  

李　才和钟铧  李惠民 《中国地质》2004,31(4):384-389

羌塘地区是青藏高原古特提斯研究的关键地区,羌塘南部地区基性岩墙群的侵位时代与构造背景对确定古特提斯阶段联合古陆解体的具体时间和青藏高原构造演化有重要意义。选择单颗粒锆石U-Pb法和全岩Sm-Nd等时线法对基性岩墙进行定年研究,获得了(312±4)Ma单颗锆石U—Pb谐合线年龄和(299±13)Ma和(314±5)Ma两个Sm-Nd全岩等时年龄。结合区域地质资料研究认为,基性岩墙群为羌塘地块裂离作用的产物,所获得的同位素年龄代表了基性岩墙群的侵位时间,为羌塘地块裂解提供了构造事件年龄,为重塑龙木错—双湖古特提斯洋盆的形成演化过程提供了重要信息。  相似文献   

关于倾斜脉的重力异常公式及理论曲线正误的商榷     

袁业培  金文丽 《华东地质学院学报》1986,(2)

本文着重讨论了重力勘探教材中关于倾斜脉的△g、V_(xz)、V_(zz)理论公式及二次微商理论曲线的正误问题。文中给出了无限延深倾斜脉的准确的 V_(xz)及 V_(zz)理论曲线,并且指出应该充分地利用 V_(xz)V_(zz)异常特征解释推断脉的倾向.  相似文献   

A Least-squares Window Curves Method for Interpretation of Magnetic Anomalies Caused by Dipping Dikes   总被引：1，自引：0，他引：1  

E. M. Abdelrahman  E. R. Abo-Ezz  K. S. Soliman  T. M. El-Araby  K. S. Essa 《Pure and Applied Geophysics》2007,164(5):1027-1044

We have developed a least-squares method to determine simultaneously the depth and the width of a buried thick dipping dike from residualized magnetic data using filters of successive window lengths. The method involves using a relationship between the depth and the half-width of the source and a combination of windowed observations. The relationship represents a family of curves (window curves). For a fixed window length, the depth is determined for each half-width value by solving one nonlinear equation of the form f (z) = 0 using the least-squares method. The computed depths are plotted against the width values representing a continuous curve. The solution for the depth and the width of the buried dike is read at the common intersection of the window curves. The method involves using a dike model convolved with the same moving average filter as applied to the observed data. As a result, this method can be applied to residuals as well as to measured magnetic data. Procedures are also formulated to estimate the amplitude coefficient and the index parameter. The method is applied to theoretical data with and without random errors. The validity of the method is tested on airborne magnetic data from Canada and on a vertical component magnetic anomaly from Turkey. In all cases examined, the model parameters obtained are in good agreement with the actual ones and with those given in the published literature.  相似文献   

The November 2002 eruption at Piton de la Fournaise volcano,La Réunion Island: ground deformation,seismicity, and pit crater collapse     

Marc-Antoine Longpré  Thomas Staudacher  John Stix 《Bulletin of Volcanology》2007,69(5):511-525

An eruption on the eastern flank of Piton de la Fournaise volcano started on 16 November, 2002 after 10 months of quiescence. After a relatively constant level of activity during the first 13 days of the eruption, lava discharge, volcanic tremor and seismicity increased from 29 November to 3 December. Lava effusion suddenly ceased on 3 December while shallow earthquakes beneath the Dolomieu summit crater were still recorded at a rate of about one per minute. This unusual activity continued and increased in intensity over the next three weeks, ending with the formation of a pit crater within Dolomieu. Based on ground deformation, measured by rapid-static and continuous GPS and an extensometer, seismic data, and lava effusion patterns, the eruptive period is divided into five stages: 1) slow summit inflation and sporadic seismicity; 2) rapid summit inflation and a short seismic crisis; 3) rapid flank inflation, onset of summit deflation, sporadic seismicity, accompanied by stable effusion; 4) flank inflation, coupled with summit deflation, intense seismicity, and increased lava effusion; and finally 5) little deflation, intense shallow seismicity, and the end of lava effusion. We propose a model in which the pre-intrusive inflation of Stage 1 in the months preceding the eruption was caused by a magma body located near sea level. The magma reservoir was the source of an intrusion rising under the summit during Stage 2. In Stage 3, the magma ponded at a shallow level in the edifice while the lateral injection of a radial dike reached the surface on the eastern flank of the basaltic volcano, causing lava effusion. Pressure decrease in the magmatic plumbing system followed, resulting in upward migration of a collapse front, forming a subterranean column of debris by faulting and stoping. This caused intense shallow seismicity, increase in discharge of lava and volcanic tremor at the lateral vent in Stage 4 and, eventually the formation of a pit crater in Stage 5.  相似文献