岩质边坡设计坡角和锚固方案的确定   总被引：3，自引：0，他引：3  

郭映忠 《工程地质学报》1996,4(2):1-6

本文运用赤平极射投影、块体理论和岩体力学的基本原理, 试探求一种可供边坡工程设计采用的确定人工岩质边坡最大安全设计坡角和锚固方案的简易方法。  相似文献   

Palaeomagnetic evidence for southward displacement of the Chuan Dian fragment of the Yangtze Block   总被引：5，自引：0，他引：5  

Masato Tamai  Yuyan Liu  Lian Zhong Lu  Masahiko Yokoyama  Nadir Halim  Haider Zaman  Yo-ichiro Otofuji 《Geophysical Journal International》2004,158(1):297-309

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The Spherical Block Model: Dynamics of the Global System of Tectonic Plates and Seismicity     

V. L. Rozenberg  P. O. Sobolev  A. A. Soloviev  L. A. Melnikova 《Pure and Applied Geophysics》2005,162(1):145-164

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华北地块东部晚中生代至新生代岩石圈不均一减薄与改造模式     

闫峻  陈江峰 《地质论评》2005,51(1):16-26

本文综合运用不同时代幔源包体平衡温压对比、玄武岩地球化学性质对岩石圈厚度的反演以及不同时代岩石圈地幔地球化学性质的对比的方法，把华北地块东部岩石圈的减薄时间限定在晚中生代至新生代之间。减薄的机制可能是华北东部地区晚白垩世以来大陆岩石圈的拉张作用。由于机械性拉薄和热、机械和化学侵蚀作用，岩石圈厚度最终减薄到70km以下。但古老的岩石圈地幔并没有完全因减薄而消失，残留部分受到了来自软流圈物质的强烈改造，使其Sr、Nd同位素组成类似于软流圈，但Os同位素没有受到明显的改变。改造后的岩石圈地幔成为华北地块东部新生代岩石圈地幔的主体。在时空上，岩石圈的减薄具有不均一的性质。  相似文献   

下扬子南黄海沉积盆地构造地质特征   总被引：6，自引：0，他引：6  

庞玉茂  张训华  肖国林  温珍河  郭兴伟  侯方辉  朱晓青 《地质论评》2016,62(3):604-616

南黄海盆地作为下扬子块体之上的大型叠合盆地,海相构造层保存完整,陆相断拗构造层也较为发育,盆地地质结构复杂,构造变形强烈,利用最新的地质地球物理资料和解释成果,对低勘探程度的南黄海盆地进行了研究,认为盆地演化大致经历了克拉通被动陆缘初始发育阶段—南缘前陆北缘被动陆缘过渡阶段—南北对冲前陆定型阶段—滨太平洋弧后陆内调整四个阶段。南黄海盆地属于台地—断拗复合地质结构,中、新生代为具有盆内隆起带的断陷箕状结构,且中、新生代多期构造运动在盆地原型改造和后期沉积发育上起着至关重要的作用,尤其印支—燕山早期运动、燕山中期黄桥运动和喜马拉雅期盐城运动与盆地地层变形、沉积发育、断裂发育及构造样式等盆地要素演化密切相关,进而导致盆地垂向地质结构和构造变形的层次性极为显著,而中生代燕山期和新生代喜马拉雅期两期构造岩浆活动则与滨太平洋域的动力学背景相关。  相似文献   

Paleomagnetism of the Carboniferous Rouchel Block,Tamworth Belt,and pole path revision for the New England Orogen,eastern Australia     

C. Klootwijk 《Australian Journal of Earth Sciences》2016,63(5):513-549

Structural, magnetic and gravity trends of the southern New England Orogen (SNEO) indicate four oroclinal structures, none conclusively confirmed paleomagnetically. Curved structures of the Tamworth Belt (TB)—a continental forearc exposed across six tectono-stratigraphic blocks with interlinked Carboniferous stratigraphies and extensive ignimbritic rocks known to retain primary magnetisations despite prevalent overprinting—are prospective to oroclinal testing through comparison of Carboniferous pole paths for individual blocks. Pole paths (a) have been established for the Rocky Creek and Werrie blocks (northwestern/western TB), (b) are described herein for the Rouchel Block (southwestern TB), and (c) are forthcoming for the Gresford and Myall blocks (southern/southeastern TB). The Rouchel path derives from detailed paleomagnetic, rock magnetic and magnetic fabric studies. Thermal, alternating field and liquid nitrogen demagnetisations show a low-temperature overprint, attributed to late Oligocene weathering, and high-temperature (HT) primary and overprint components in both magnetite and hematite carriers, showing slight, systematic, directional differences with hematite providing the better cleaned site poles. Seven primary mean-site poles of Tournaisian and mainly Visean age and three overprint poles show six positive fold tests, five at 95% or higher confidence levels. Two dispersed groupings of intermediate (IT) and HT overprint site poles of Permian and Permo-Triassic age are attributed to early and late phases in oroclinal evolution of the SNEO. HT and IT/HT overprint site poles of mid-Carboniferous age are attributed to Variscan Australia–Asia convergence. Individual pole paths for the Rocky Creek, Werrie and Rouchel blocks show no noticeable rotation between them, indicating primary curvature for the southwestern TB. Their integrated SNEO pole path establishes a reference frame for determining rotations of the southern and southeastern TB.  相似文献   

History of faulting in the Northern Hastings Block,southern New England Orogen     

J. Yan  R. Offler 《Australian Journal of Earth Sciences》2016,63(7):821-841

Brittle failure is common in the Devonian to Permian rocks in the Northern Hastings Block (NHB) and is manifested by faults of different orientation and kinematic histories, but the timing of fault movement is not well defined. In this study, faults in the NHB were analysed with the map pattern of cross-cutting faults used to estimate the relative time of movement and relationship to other faults. We defined five episodes of faulting or fault reactivation that affected the NHB. The Yarras Fault System on the southwestern side of the NHB and the Parrabel Fault and related faults on the eastern side of the NHB are the two major fault systems responsible for transporting and rotating the NHB in the late Carboniferous. Faults on the eastern, northeastern and northern part of Parrabel Dome started and stopped moving after emplacement of the Hastings Block and before the intrusion of the Werrikimbe Triassic granitoids. We suggested that the movement on the major bounding faults is related to the accommodation of the NHB to the folding and cleavage development in the adjoining Nambucca Block, and is associated with the earliest part of the Hunter–Bowen Orogeny. Limited dextral movement on the extensions of the Taylors Arm Fault System caused minor displacements in the northeastern part of the NHB during the Late Triassic. Some small faults cut the Triassic granitoids or Triassic Lorne Basin sediments indicating tectonic activity continued post-Triassic.  相似文献   

Possible spatial variability in the Selwyn Block of Central Victoria: evidence from Late Devonian felsic igneous rocks   总被引：2，自引：0，他引：2  

J. D. Clemens  M. A. Elburg 《Australian Journal of Earth Sciences》2016,63(2):187-192

The Neoproterozoic to Cambrian Selwyn Block in Central Victoria forms the mainly unexposed basement to the Paleozoic metasediments, granitic rocks and felsic volcanic complexes of the Melbourne Zone of the Lachlan Orogen. The Late Devonian felsic rocks are largely products of partial melting of the Selwyn Block, and their chemistry implies that their sources were most probably arc-related andesite, dacite, volcaniclastic greywackes and some pelites. When plotted against the median longitudes of the plutons and volcanic complexes, the average values for ⁸⁷Sr/⁸⁶Sr_t and ?Nd_t (at 370 Ma) reveal broad trends interpreted to reflect possible compositional and/or age structure in the Selwyn Block. Assuming that the trends are real, from W to E, I-type sources are progressively less crustally evolved, probably younging eastward. The S-type sources show no trend in ?Nd_t, suggesting that there was efficient sediment mixing. The ⁸⁷Sr/⁸⁶Sr_t values, however, become more evolved eastward (opposite in sense to the apparent variation in the I-type sources). This is interpreted as the original Selwyn Block sediments having been more pelitic eastward, perhaps suggesting a deepening of the basin in this direction, as well as structurally upward in the succession. The opposite senses of variation highlights the spatial separation of the S- and I-type sources and suggest that the granitic magmas here are unlikely to represent any sort of mixing continuum.  相似文献   

Magnetic properties of the remagnetized Middle-Ordovician limestones of the Ponón Trehué Formation (San Rafael Block,central-western Argentina): Insights into the Permian widespread Sanrafaelic overprint     

《Journal of South American Earth Sciences》2016

The widespread Sanrafaelic remagnetization reset most of the early Cambrian to mid-Ordovician carbonate platform of the Argentine Precordillera and the calcareous units of the San Rafael Block. We conducted a detailed rock-magnetic study on the Middle-Ordovician limestones of the Ponón Trehué Formation at both limbs of a tight anticline exposed in the San Rafael Block (Mendoza province, central-western Argentina) that are carriers of a syntectonic magnetization of Permian age. We found that the magnetic overprint in the Ponón Trehué Formation is carried by both pyrrhotite and magnetite, with goethite and subordinate haematite likely related to weathering. Hysteresis parameters, frequency dependence of magnetic susceptibility, Cisowski and modified Lowrie-Fuller tests suggest the presence of ultrafine particles of chemical origin. Demagnetization of natural remanent magnetization and of three-axis isothermal remanence confirm pyrrhotite and magnetite as important contributors to the remanence. Both minerals carry the same magnetic syntectonic component suggesting a coeval or nearly coeval remanence acquisition and therefore mineral formation. This and the results of the magnetic fabric analyses indicate an authigenic origin of the magnetic minerals during folding associated with the Sanrafaelic tectonic phase (ca. 280 Ma). Although the chemically active (oxidizing?) fluids expelled from the orogen as it developed in the early Permian is a viable explanation for the Sanrafaelic remagnetization, the role of the nearly coeval magmatism in Precordillera and the San Rafael Block remains to be properly evaluated.  相似文献   

拉萨地块林芝杂岩体石榴角闪岩的地球化学特征和年代学研究     

黄杰  张聪  杨经绥  李鹏  王舒 《地球学报》2016,37(6):711-722

本文对位于青藏高原拉萨地体东南缘林芝杂岩中的两类石榴角闪岩进行了详细的地球化学和锆石U-Pb年代学研究。这两类石榴角闪岩分别为硅不饱和的含十字石石榴角闪岩和硅饱和的含石英石榴角闪岩。含十字石石榴角闪岩矿物组合为十字石、石榴子石、角闪石、钠云母、绿泥石、斜长石。石英石榴角闪岩矿物组合为石榴子石、角闪石、石英、斜长石、黑云母。岩石学及变质相平衡研究表明两类石榴角闪岩均经历了高压角闪岩相变质作用。含十字石石榴角闪岩和石英石榴角闪岩具有MORB的地球化学特征,锆石U-Pb年代学分析获得了800~200 Ma的206Pb/238U年龄范围,出现了~430 Ma、~268 Ma和~216 Ma年龄峰值。~430 Ma年龄可能和拉萨地体岩浆活动有关,~268 Ma变质年龄和~216 Ma变质年龄和拉萨地块经历的高压变质作用有关。其中~268 Ma年龄和拉萨地块内部松多高压带榴辉岩的峰期变质年龄一致,而~216 Ma年龄和榴辉岩的围岩含石榴子石片岩年龄一致。对比该区域的年代学研究成果,这表明林芝杂岩体不仅经历了中新生代的变质和岩浆再造活动,还经历了古特提斯洋闭合,南北拉萨地块发生碰撞的晚二叠世的高压变质作用和三叠纪的中压变质作用。  相似文献