长江口海域新生代地层与断裂活动性初探   总被引：7，自引：1，他引：7  

火恩杰  章振铨  刘昌森  王锋 《中国地震》2003,19(3):206-216

长江口海域通过浅层人工地震勘察查明，新生代地层可分为5个地震层。分别为第四系、上新统、中新统上段、中新统下段及始新统。第三纪地层自东北向西南依次超覆、减薄尖灭，上部被第四纪地层不整合覆盖。沉积基底主要由晚侏罗世火山岩系及燕山晚期酸性小岩体构成，未发现早第三纪及晚白垩世断陷盆地。断裂构造很发育，按展布方向大体可归为北东、北西及近东西向3组，皆为正断层。前两者数量多、延伸长、断距大，与同区的航磁异常构架吻合。北东向断裂分段明显，西南段为第四纪断裂，中段为晚第三纪断裂，东北段为早第三纪断裂；而北西向断裂分段不很清晰。两者的垂直位移速率平均在0．015mm/a。本文对该海域有关的几个地质问题进行了讨论。  相似文献   

Preliminary Study on Cenozoic Group and Fault Activity in the Sea Area Near the Yangtze River Mouth   总被引：2，自引：0，他引：2  

Huo Enjie 《中国地震研究》2004,18(1):13-26

By shallow seismic prospecting, the Cenozoic Group in the sea area near the Yangtze Rver Mouth can be divided into five seismic sequences. They correspond to the Quaternary,Pliocene, Upper Miocene, Lower Miocene and Eocene respectively. The Quaternary System covers all the detecting area. The Tertiary System overlaps and thins out from NE to SW. The sedimentary basement mainly consists of volcanic rock (J3) and acidic rock (r35). Paleogene or Late Cretaceous basins are not found there. The faults that have been detected are all normal faults. They can be divided into three groups (NE, NW, near EW) by their trend. The NE and NW-trending faults are predominant, and agree with aeromagnetic anomaly. Their length and displacement are larger than that of the EW-trending faults. The activity of the NEtrending faults is different in different segments. The SW segment is a Quaternary fault, the middle segment is a Neogene fault, The NE is Paleogene. But the segment of the NW-trending fault is not obvious. The average vertical displacement rate is about 0.015mm/a.  相似文献   

Late-Stage Ductile Deformation in Xiongdian-Suhe HP Metamorphic Unit, North-Western Dabie Shan, Central China     

SuoShutian ZhongZengqiu ZhouHanwen YouZhendong 《中国地质大学学报(英文版)》2004,15(3):262-274

New structural and petrological data unveil a very complicated ductile deformation history of the Xiongdian-Suhe HP metamorphic unit, north-western Dabie Shun, central China. The finegrained symplectic amphibolite-facies assemblage and coronal structure enveloping eclogite-facies garnet,omphacite and phengite etc., representing strain-free decompression and retrogressive metamorphism,are considered as the main criteria to distinguish between the early-stage deformation under HP metamorphic conditions related to the continental deep subduction and collision, and the late-stage deformation under amphibolite to greenschist-facies conditions occurred in the post-eclogite exhumation processes.Two late-stages of widely developed, sequential ductile deformations D3 and D4, are recognized on the basis of penetrative fabrics and mineral aggregates in the Xiongdian-Suhe HP metamorphic unit, which shows clear, regionally, consistent overprinting relationships. D3 fabrics are best preserved in the Suhe tract of low post-D3 deformation intensity and characterized by steeply dipping layered mylonitic amphibolites associated with doubly vergent folds. They are attributed to a phase of tectonism linked to the initial exhumation of the HP rocks and involved crustal shortening with the development of upright structures and the widespread emplacement of garnet-bearing granites and felsic dikes. D4 structures are attributed to the main episode of ductile extension (D^24) with a gently dipping foliation to the north and common intrafolial, recumbent folds in the Xiongdian tract, followed by normal sense top-to-the northductile shearing (D^24) along an important tectonic boundary, the so-called Majiawa-Hexiwan fault (MHF), the westward continuation of the Balifan-Mozitan-Xiaotian fault (BMXF) of the northern Dabie Shan. It is indicated that the two stages of ductile deformation observed in the Xiongdian-Suhe HP metamorphic unit, reflecting the post-eclogite compressional or extrusion wedge formation, the subhorizontal ductile extension and crustal thinning as well as the top-to-the north shearing along the high-angle ductile shear zones responsible for exhumation of the HP unit as a coherent slab, are consistent with those recognized in the Dabie-Sulu UHP and HP metamorphic belts, suggesting that they were closely associated in time and space. The Xiongdian-Suhe HP metamorphic unit thus forms part of the Triassic(250-230 Ma) collision orogenic belt, and can not connect with the South Altun-North Qaidam-North Qinline UHP metamorphic belt formed durin~ the Early Paleozoic (500-400Ma).  相似文献   

上扬子地壳区域性地层岩石物性力学参数与滑动层位关系研究   总被引：5，自引：2，他引：5       下载免费PDF全文

孙岩  刘德良  朱文斌  郭继春  李本亮  郭建  王锋  赵忠岩 《地质科学》2005,40(4):532-538

在中下扬子地区地壳区域性滑动层位岩石物性力学参数研究的基础上,对上扬子地区地壳的相应岩层进行了系统的定量测试。其滑动层位各种参量在塑性、韧性和粘性上所表现出特征的规律,在我国南方型数字地层中,具有一定的普遍性和可比性。同时,也揭示了地壳的构造分层性,并可作为上扬子板块浅层地质—地球物理特征分析的重要依据和建库信息。  相似文献   

鞍山附近“樱桃园组”的构造样式及其时代讨论          下载免费PDF全文

刘如琦  蔡一廷  张宝华 《地质科学》1987,(1):24-38

本文区分了“樱桃园组”岩石在元古主构造旋回的三幕变形,详细描述了各幕SFL组合和按区段进行了投影。主变形幕D₁的构造最发育,F₁控制着本区的岩性分布。构造序列及样式变化显示由高塑性向脆性的变形格式。本组与下伏的太古鞍山群变粒岩在构造序列、样式和变质相上都有显著差异,过去许多地质学家把二者混划为一个单位,统名“鞍山群”,属太古宙。但本组与上覆的辽河群(上元古)的构造样式和变质相却相似,故其时代相当于早元古Ferrian期。  相似文献   

瞬态瑞雷面波法在公路工程地质勘察中的应用     

刘长平  郭正言 《安徽地质》2007,17(2):124-127

结合安徽省高速公路建设工程实例,介绍瞬态瑞雷面波勘探技术在公路工程地质勘察中的应用,解决沿线高边坡、深路堑、桥梁、隧道进出口的岩土分层,给出基岩风化分带等工程地质问题,省时、省力,取得了良好的经济效益和环境效益.  相似文献   

层状侵入体的韵律层理成因     

桑祖南  金振民 《地质科技情报》2001,20(1):20-24

层状侵入体的一个典型的特征是具有隐导理和韵律层理，分析比较了前人提出的韵律层理形成的各种机制并结合对攀枝花层状侵入体的研究认为，层状侵入体的韵律层理的形成与成岩的压实作用关系密切，细粒韵律层理是由于颗粒大小的微小差别或矿物成分含量的逐渐增加和重复的再平衡所致，矿物成分含量的逐步增加和重复是通过在类似于奥斯特瓦尔德成熟的条件下循环溶解和晶体生长形成的，在影响层理形成的多种因素中，以对流作用，密度，粘度及岩浆房的几何形状等因素的研究较为详细，各研究者也存在较大分歧。  相似文献   

桩端持力层加筋作用的特性探讨     

费勤发  马海龙 《岩土力学》1995,16(4):38-45

运用弹性半空间无限体的明德林解答和浅基础中的分层总和法、桩土间滑动采用刚塑性模型，以某工程试桩资料为例，较详细地分析了桩端持力层加筋作用的特性。并通过工程实例证明本文研究结果是正确的，这对桩基的设计和研究有较大的参考价值。  相似文献   

Large-scale Mechanical Redistribution of Orthopyroxene and Plagioclase in the Basement Sill, Ferrar Dolerites, McMurdo Dry Valleys, Antarctica: Petrological, Mineral-chemical and Field Evidence for Channelized Movement of Crystals and Melt     

Bedard  Jean H. J.; Marsh  Bruce D.; Hersum  Taber G.; Naslund  H. Richard; Mukasa  Samuel B. 《Journal of Petrology》2007,48(12):2289-2326

The Jurassic Ferrar dolerite sills of the McMurdo Dry Valleys,Antarctica represent the plumbing system for flood basalt eruptionsassociated with the breakup of Gondwana. Among the Ferrar sills,the 350–450 m thick cumulate-textured Basement Sill isdifferentiated into a Lower Marginal Zone (LMZ) gabbronorite,a thick Lower Zone (LZ) orthopyroxene–plagioclase orthocumulatepyroxenite, a strongly layered mela- to leuco-gabbronorite MiddleZone (MZ), a thick Upper Zone (UZ) gabbronorite with ferrogabbroicpods, and an Upper Marginal Zone (UMZ) gabbronorite. Texturesand mineral compositions in the LZ pyroxenite and MZ–UZgabbronorites are nearly identical, the main distinction beingthe greater relative proportion of plagioclase in the MZ–UZgabbronorites, and of pigeonite in the UZ. Most orthopyroxenein the LZ, MZ and UZ occurs as sub-euhedral, normally zonedprimocrysts, commonly with rounded plagioclase inclusions. Plagioclaseis usually sub-euhedral and normally zoned, but can containsodic cores interpreted to be xenocrystic. Orthopyroxene andfeldspar compositions thoughout the sill are generally fairlyuniform, and resemble the compositions of micro-phenocrystsin the chilled margins. We infer that the sill was filled bya c. 1250°C slurry of orthopyroxene + plagioclase phenocrystsor primocrysts that subsequently unmixed in response to buoyancyforces. The LZ websterite contains numerous anorthosite to gabbronoriteschlieren, veins and pipes (< 2 m diameter), which we interpretas fossil segregation channels. Textures and mineral compositionsin these felsic channels are very similar both to UZ and MZgabbronorites, and to the groundmass separating accumulatedorthopyroxene primocrysts in the LZ and MZ. We infer that plagioclase-charged,hydrous pore melt from the pyroxenite may have segregated, pooledand ascended through these conduits to feed growth of the UZgabbronorite. Detailed mapping shows that the pipes are separatedby about 15 m on average. Calculations suggest that this numberdensity of conduits could have drained the LZ cumulates of theirinterstitial melt + plagioclase in about 8 days. Sequences (eachc. 5–10 m thick) of layered leuco-gabbronorite in theMZ could represent intra-cumulate sills that formed from plagioclase-richslurries ascending in segregation channels. Fe–Ti-richpyroxenitic veins and pods (some pegmatitic) and an unusualcoarse-grained plagioclase facies occur at the contacts betweenmassive leuco-gabbronorite layers in the MZ. Discordant ferro-pegmatitepods and dykes occur throughout the UZ. We interpret these Fe-richpegmatoidal rocks as evolved residual melts expelled from thecompacting gabbronoritic cumulates of the MZ and UZ. KEY WORDS: Ferrar; cumulates; differentiation; Antarctica; layering  相似文献   

Oxygen isotope fractionation in mantle minerals     

Yongfei Zheng  Chunsheng Wei  Gentao Zhou  Baolong Xu 《中国科学D辑(英文版)》1998,41(1):95-103

The increment method is adopted to calculate oxygen isotope fractionation factors for mantle minerals, particularly for the polymorphic phases of MgSiO₃ and Mg₂SiO₄. The results predict the following sequence of¹⁸O-enrichment:pyroxene (Mg, Fe, Ca)₂Si₂O₆>olivine (Mg, Fe)₂SiO₄ > spinel (Mg, Fe)₂SiO₄> ilmenite (Mg, Fe, Ca) SiO₃>perovskite (Mg, Fe, Ca) SiO₃. The calculated fractionations for the calcite-perovskite (CaTiO₃) System are in excellent agreement with the experimental calibrations. If there would be complete isotopic equilibration in the mantle, the spinel-structured silicates in the transition zone are predicted to be enriched in¹⁸O relative to the perovskite-structured silicates in the lower mantle but depleted in¹⁸O relative to olivines and pyroxenes in the upper mantle. The oxygen isotope layering of the mantle might result from differences in the chemical composition and crystal structure of mineral phases at different mantle depths. Assuming isotopic equilibrium on a whole earth scale, the chemical structure of the Earth’s interior can be described by the following sequence of¹⁸O-enrichment:upper crust>lower crust>upper mantle>transition zone>lower mantle>core. Project supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences.  相似文献