STRUCTURAL CHARACTERISTICS OF THE NIUSHOU MOUNTAIN AND ITS GEOLOGICAL SIGNIFICANCE IN CENTRAL NINGXIA     

ZHANGJin MAZongjin RENWenjun LEIYongliang 《大地构造与成矿学(英文版)》2003,27(1):165-178

There are many thrust-related structures occurring in the Paleozoic strata of the Niushou Mountain in the central part of Ningxia Hui Autonomous Region. The fault-related folds are the typical structures in this area. Based on the analysis about these structures and their relationships, the processes by which these structures of the Miboshan Formation were formed are reconstructed, and the strata underwent about three stages of deformation: (1) horizontal shortening, (2) folding, and (3) thrusting. And the fact that the Niushou Mountain is the leading edge of an old thrust sheet was proved, the Niushou Mountain, the Daluo Mountain and the Xiaoluo Mountain together constitute the front part of this old thrust zone, so the Niushou Mountain and the Ordovician strata in the central and southern parts of Ningxia now are likely allochthons. In the period from middle Ordovician to Devonian, the areas of the central and southern Ningxia belonged to the back-arc foreland basin of North Qilianshan orogen, which was adjacent to the continent in the north. In the later part of the early Paleozoic period, the Niushou Mountain was formed after the closure of the back-arc foreland basin.  相似文献   

Middle Paleozoic paleomagnetism of east Kazakhstan: post-Middle Devonian rotations in a large-scale orocline in the central Ural–Mongol belt     

Natalia M. Levashova  Kirill E. Degtyarev  Mikhail L. Bazhenov  Adam Q. Collins  Rob Van der Voo   《Tectonophysics》2003,377(3-4):249-268

In order to test different hypotheses concerning the Paleozoic evolution of the Ural–Mongol belt (UMB) and the amalgamation of Eurasia, we studied Middle Devonian basalts from two localities (11 sites) and Lower Silurian volcanics, redbeds, and intra-formational conglomerates from three localities (20 sites) in the Chingiz Range of East Kazakhstan. The Devonian rocks prove to be heavily overprinted in the late Paleozoic, and a high-temperature, presumably primary, southerly, and down component is isolated at only four sites from a homoclinal section. Most Silurian redbeds are found to be remagnetized in the late Paleozoic; in contrast, a bipolar near-horizontal remanence, isolated from Silurian volcanics, is most probably primary as indicated by positive tilt and conglomerate tests. Analysis of paleomagnetic data from the Chingiz Range shows that southward-pointing directions in Ordovician, Silurian, and Devonian rocks are of normal polarity and hence indicate large-scale rotations after the Middle Devonian. The Chingiz paleomagnetic directions can be compared with Paleozoic data from the North Tien Shan and with the horseshoe-shaped distribution of subduction-related volcanic complexes in Kazakhstan. Both paleomagnetic and geological data support the idea that today's strongly curved volcanic belts of Kazakhstan are an orocline, deformed mostly before mid-Permian time. Despite the determination of nearly a dozen new Paleozoic paleopoles in this study and other recent publications by our team, significant temporal and spatial gaps remain in our knowledge of the paleomagnetic directions during the middle and late Paleozoic. However, the paleomagnetic results from the Chingiz Range and the North Tien Shan indicate that these areas show generally coherent motions with Siberia and Baltica, respectively.  相似文献   

华北地台北缘东段多期褶皱及构造置换对鞍山群铁矿床的控制作用     

张宝华  屈奋雄 《地质与勘探》1996,(6)

多期褶皱和构造置换是华北地台北缘太古宙鞍山群岩石中的主要变形特征，也是对太古宙鞍山群铁矿的形态、规模、产状和分布规律的主要控制因素。  相似文献   

褶皱分形分布的岩石力学机制研究          下载免费PDF全文

侯贵廷 《地球科学》1996,21(1):53-56

在褶皱形态的分形分析基础上，利用分形理论和褶皱的岩石力学成因理论推导出了褶皱的分数维（Ｄ）与岩层厚度（ｈ）和粘度（μ）的关系式，即找到了褶皱分形分布的岩石力学成因机制，在相同的构造应力场条件下，岩层的厚度和粘度越小，则越易产生较复杂的褶皱，即褶皱的分数维越大，因此，利用褶皱的分形测量，可以定量了分析褶皱形成的岩石力学性质，这是分形研究从形态研究到机制研究的一种探索。  相似文献   

初论陆内造山带的造山模式──以四川龙门山为例   总被引：3，自引：1，他引：3  

林茂炳 《四川地质学报》1996,(3)

四川龙门山造山带是陆内造山带的一个典型实例。陆内造山带经历了漫长的发展演化历史。前寒武纪时期的环境是属于古板块俯冲、碰撞的历史。具活动性大陆边缘性质，岩浆变质作用强烈，构造混杂明显。古生代以来转入地台环境，形成台相沉积。中生代早期转入陆内造山阶段。由早期的褶皱造山进而转化为推覆造山。两类不同性质的造山运动伴随了两类不同性质的前陆沉积盆地的形成和两类不同性质的沉积体系的形成。最终的区域构造特征不同程度地保留了陆内造山各阶段的地质记录，而以最后一次的推覆造山作用的影响最深刻。陆内造山的动力机制是与区域性的板块构造活动的大环境密切相关的。  相似文献   

赣北修水观音阁砾岩特征及其构造意义   总被引：3，自引：0，他引：3  

熊清华  曾佐勋 《江西地质科技》1997,24(1):11-19

有关赣北地区双桥山群内角度不整合和地壳运动存在与否问题,一直争论不休。论文以较丰富的详细野外调查资料为基础,并结合前人研究成果和室内各类样品测试结果,围绕这个赣北地区重要的基础地质问题进行了讨论。作者认为“修水运动”不能成立,并提出了砾岩的沉积模式。  相似文献   

Detection of major geological structures in the Eastern offshore of India using Geosat altimeter data     

T. J. Majumdar  K. K. Mohanty  A. K. Srivastava 《Journal of Earth System Science》1997,106(1-2):27-32

Satellite altimetry can be used to infer subsurface geological structures analogous to gravity anomaly maps generated through ship-borne survey. The Eastern offshore was taken up for analysis using Geosat Exact Repeat Mission (ERM) altimeter data. A methodology is developed to use altimeter data as an aid to offshore hydrocarbon exploration. Processing of altimeter data involves corrections for various atmospheric and oceanographic effects, stacking and averaging of repeat passes, cross-over correction, removal of deeper earth and bathymetric effects, spectral analysis and conversion into free-air gravity anomaly. The final processed results were derived for Eastern offshore in the form of prospecting geoid and gravity anomaly maps and their spectral components. The highs and lows observed in those maps were derived in terms of a number of prominent megastructures e.g., gravity linears, 85°E and 90°E ridges, the Andaman trench complex etc. Satellite-derived gravity profiles along 12°N latitude match well with the existing structures.  相似文献   

赣西北地区修水县联测图组1：5万区调主要进展与体会   总被引：3，自引：0，他引：3  

章泽军  印纯清 《江西地质》1997,11(2):74-80

本文重点总结赣西北地区修水县联测图１∶５万区调取得的主要进展与区调方法上的创新。其中，在中元古界双桥山群浅变质岩系中所识别、填绘出的近东西向紧闭同斜倒转褶皱，叠加近南北向开阔圆滑褶皱，在中小型陆相红盆中探索出的运用数理统计与沉积学研究相结合确定冲积扇体，并用扇体与岩性段双重方法予以图面表达以及第四纪研究成果等取得的重要进展。此外，就有关提高区调质量等问题浅谈其体会。  相似文献   

长江三峡狮子口重力滑动构造          下载免费PDF全文

杨森楠  任建业 《地质学报》1997,71(1):27-35

围绕着长江三峡库处区狮子口ＮＮＷ向线性影像带的构造性及其地壳稳定性评价问题进行了专题研究，以区域地质调查为基础，运用构造解析方法，采用多学科，多手段的综合研究，确认该影像带影像特征最明显的地段乃是一个滑褶型多层式得力滑动构造，本文还分析了该系统形成的介质条件，斜坡构造及动力环境。  相似文献   

Frequency domain modal analysis of earthquake input energy to highly damped passive control structures     

Izuru Takewaki 《地震工程与结构动力学》2004,33(5):575-590

A new complex modal analysis‐based method is developed in the frequency domain for efficient computation of the earthquake input energy to a highly damped linear elastic passive control structure. The input energy to the structure during an earthquake is an important measure of seismic demand. Because of generality and applicability to non‐linear structures, the earthquake input energy has usually been computed in the time domain. It is shown here that the formulation of the earthquake input energy in the frequency domain is essential for deriving a bound on the earthquake input energy for a class of ground motions and for understanding the robustness of passively controlled structures to disturbances with various frequency contents. From the viewpoint of computational efficiency, a modal analysis‐based method is developed. The importance of overdamped modes in the energy computation of specific non‐proportionally damped models is demonstrated by comparing the energy transfer functions and the displacement transfer functions. Through numerical examinations for four recorded ground motions, it is shown that the modal analysis‐based method in the frequency domain is very efficient in the computation of the earthquake input energy. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献