构造成矿的一些基本规律   总被引：5，自引：0，他引：5  

李德威 《矿产与地质》1993,7(4):267-272

系统论述了构造与成矿的一些基本规律:构造背景与成矿;构造形式与成矿;构造边界与成矿;构适演化与成矿;构造动力与成矿等;并建立动力成矿模式.  相似文献   

宁夏地质梗要   总被引：2，自引：0，他引：2  

霍福臣 《甘肃地质》1993,(Z1):101-133

宁夏位于中朝准地台和昆仑秦岭地槽褶皱区两大地质构造单元的衔接部位。区内各时代地层均有出露;岩浆岩不发育;构造运动活跃。该区地质构造的演化大致经历了4个阶段。  相似文献   

华南地台盖层和上覆盆地层的褶皱时代   总被引：4，自引：0，他引：4       下载免费PDF全文

郭福祥 《地球科学》1993,18(5):581-588

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Theory and applicability of a recrystallized grain size paleopiezometer   总被引：16，自引：0，他引：16  

Robert J. Twiss 《Pure and Applied Geophysics》1977,115(1-2):227-244

An approximate theoretical relation is derived which relates stress during steady state creep to both subgrain size and dynamically recrystallized grain size. The relation results from equating the dislocation strain energy in the grain boundary to that in the enclosed volume. Available data on metals and silicates are in excellent agreement with the theory. For paleopiezometry, the recrystallized grain size must be preserved by quenching, by cooling under stress, or by inhibition of grain growth by intimate mixture of two or more phases. In general, stress may be underestimated using rocks in which grain size has been reduced by dynamic recrystallization, especially if the grain size is very small. Stress may be overestimated using coarse grained rocks in which the grain size has increased toward the steady state value. Quantitative limits remain to be established. The theoretical relation can in principle be applied to any metal or mineral if only the effective isotropic elastic moduli and the Burgers vector are known. When used as a paleopiezometer, the technique indicates that high stresses on the order of 100 MPa are not infrequently associated with mantle diapirism and with large scale thrust faulting. Consideration of the Mt. Albert ultramafic body suggests that texturally inferred stresses from peridotite massifs and from ultramafic xenoliths in alkali olivine basalts might reflect either horizontal variations in stress across a rising diapir or else a vertical variation in stress as defined by the pyroxene geobarometer (Mercier et al. 1977). In either case the stresses are probably characteristic of local diapirism. Stresses characteristic of global upper mantle flow might be inferred from xenoliths originating from above kimberlite-producing diapirs.  相似文献   

Vertical soil water movement in a tropical rainforest catchment in northeast queensland     

M. Bonell  D. S. Cassells  D. A. Gilmour 《地球表面变化过程与地形》1983,8(3):253-272

In a tropical rainforest catchment, shallow piezometers respond almost instantaneously to rainfall, but the dominant ground water recharge mechanisms are not well understood. To improve understanding, the downward movement of soil water on a runoff plot was traced using tritiated water injected at 0·20 m below the surface which marks the lower boundary of active subsurface storm flow. The tritium pulse was translated slowly down the profile, apparently dominated by interstitial piston flow on the lines described by Zimmermann's theoretical model. This recharge mechanism accounted for about 35 per cent of rainfall or 50 per cent of throughfall. The pulse's advance may have also been delayed by the upward movement of soil water indicated by the distribution of hydraulic potential under different hydrological conditions. The result was an increase in soil water transit time particularly below 1·0 m. There was also evidence in the tracer profiles for rapid by-pass flow but the volumes concerned could not be quantified in this experiment.  相似文献   

Discriminant analysis as a possible tool in landslide investigations     

James P. Reger 《地球表面变化过程与地形》1979,4(3):267-273

As part of an investigation of mass movement on outslopes of contour surface-mines in West Virginia, discriminant analysis was used to determine whether selected spoil properties could statistically distinguish failed and unfailed embankments. The analysis utilized the variables degree of saturation, liquid limit, and shrinkage limit, and the a priori assignment of samples into either actively failing, unfailed, or regraded categories. Results were encouraging, with seventy-four percent of the samples being correctly classified. All misclassifications involved samples from active or regraded landslides, suggesting the method was conservative. Performance of discriminant analysis could probably be improved by modifying the sampling plan.  相似文献   

PROGRESS IN APPLICATION OF GNSS TO DIVISION OF ACTIVE TECTONIC BLOCKS IN CONTINENTAL CHINA          下载免费PDF全文

HAO Ming  WANG Qing-liang 《地震地质》1979,42(2):283-296

Chinese scientists proposed that large earthquakes that occurred in mainland China are controlled by the movement and deformation of active tectonic blocks. This scientific hypothesis explains zoned phenomenon of seismicity in space. The active tectonic blocks are intense active terranes formed in late Cenozoic and late Quaternary, and the tectonic activity of block boundaries is the intensest. Global Navigation Satellite System(GNSS)has advantages of high spatio-temporal resolution, broad coverage, and high accuracy, and is utilized to monitor contemporary crustal deformation. High accuracy and resolution of GNSS velocity field within mainland China and vicinities provided by previous studies clearly demonstrate that different active tectonic blocks behave as different patterns of movement and deformation, and block interaction boundaries have intense tectonic deformation. The paper firstly introduces the GPS networks operated by the Crustal Movement Observation Network of China(CMONOC)since 1999, and GNSS data processing methods, including GAMIT, BERNESE and GIPSY/OASIS, and discusses the advantages of using South China block as a regional reference frame for GNSS velocity field, then proposes three strategies of block division, F-test, quasi-accurate detection(QUAD), and clustering analysis. Furthermore, we introduce rigid and non-rigid block motions. Rigid block motion can be denoted by translation and rotation, while non-rigid block motion can be described by rigid motion and internal strain deformation. Internal strain deformation can be divided into uniform and linear strains. We also review the usage of F-test to distinguish whether the block acts as rigid deformation or not. In addition, combining with recent GNSS velocity results, we elaborate the characteristics of present movement of rigid block, such as the South China, Tarim, Ordos, Alashan, and Northeast China, and that of non-rigid block, such as the Tibetan plateau, Tian Shan, and North China plain. Especially, the Tibetan plateau and Tian Shan seem to deform continuously with significant internal deformation. In order to enrich and perfect the active tectonic block hypothesis, we should carefully design dense GNSS networks in inner blocks and block boundaries, optimize utilizing other space geodesy technologies such as InSAR, and strengthen combining study of geodesy, seismogeology and geophysics. Through systematic summary, this paper is very useful to employing GNSS to investigate characteristics of block movement and dynamics of large earthquakes happening in block interaction boundaries.  相似文献   

PRESENT-DAY KINEMATICS OF THE ORDOS BLOCK AND ITS SURROUNDING AREAS FROM GPS OBSERVATIONS          下载免费PDF全文

LI Zhang-jun  CHAI Xu-chao  GAN Wei-jun  HAO Ming  WANG Qing-liang  ZHUANG Wen-quan  YANG Fan 《地震地质》1979,42(2):316-332

Located among the South China block, Tibetan plateau, Alxa block and Yinshan orogenic belt, the Ordos block is famous for its significant kinematic features with stable tectonics of its interior but frequent large earthquakes surrounding it. After the destruction of the North China Craton, the integrity, rotation movement and kinematic relations with its margins are hotly debated. With the accumulation of active tectonics data, and paleomagnetic and GPS observations, some kinematic models have emerged to describe rotation movement of the Ordos block since the 1970's, including clockwise rotation, anticlockwise rotation, clockwise-anticlockwise-alternate rotation, and sub-block rotation, etc. All of these models are not enough to reflect the whole movement of the Ordos block, because the data used are limited to local areas.
In this study, based on denser geophysical observations, such as GPS and SKS splitting data, we analyzed present-day crustal and mantle deformation characteristics in the Ordos block and its surrounding areas. GPS baselines, strain rates, and strain time series are calculated to describe the intrablock deformation and kinematic relationship between Ordos block and its margins. SKS observations are used to study the kinematic relationship between crust and deeper mantle and their dynamic mechanisms, combined with the absolute plate motion(APM)and kinematic vorticity parameters. Our results show that the Ordos block behaves rigidly and rotates anticlockwise relative to the stable Eurasia plate(Euler pole: (50.942±1.935)°N, (115.692±0.303)°E, (0.195±0.006)°/Ma). The block interior sees a weak deformation of~5 nano/a and a velocity difference of smaller than 2mm/a, which can be totally covered by the uncertainties of GPS data. Therefore, the Ordos block is moving as a whole without clear differential movement under the effective range of resolution of the available GPS datasets. Its western and eastern margins are characterized by two strong right-lateral shearing belts, where 0.2°~0.4°/Ma of rotation is measured by the GPS baseline pairs. However, its northern and southern margins are weakly deformed with left-lateral shearing, where only 0.1°/Ma of rotation is measured. Kinematics in the northeastern Tibetan plateau and western margin of the Ordos block can be described with vertical coherence model with strong coupling between the crust and deeper mantle induced by the strong extrusion of the Tibetan plateau. The consistency between SKS fast wave direction and absolute plate motion suggests the existence of mantle flow along the Qinling orogenic belt, which may extend to the interior of the Ordos block. SKS fast wave directions are consistent with the direction of the asthenosphere flow in Shanxi Rift and Taihang Mountains, indicating that the crustal deformation of these areas is controlled by subduction of the Pacific plate to North China. The week anisotropy on SKS in the interior of Ordos block is from fossil anisotropy in the craton interior. After comparing with the absolute plate motion direction and deformation model, we deem that anisotropy in the interior of Ordos block comes from anisotropy of fossils frozen in the lithosphere. In conclusion, the Ordos block is rotating anticlockwise relative to its margins, which may comes from positive movement of its margins driven by lithospheric extrusion or mantle flow beneath, and its self-rotation is slight. This study can provide useful information for discussion of kinematics between the Ordos block and its surrounding tectonic units.  相似文献   

Some applications of a backpropagation neural network in geo-engineering     

K.?NeaupaneEmail author  S.?Achet 《Environmental Geology》2004,45(4):567-575

A MATLAB based backpropagation neural network (BPNN) model has been developed. Two major geo-engineering applications, namely, earth slope movement and ground movement around tunnels, are identified. Data obtained from case studies are used to train and test the developed model and the ground movement is predicted with the help of input variables that have direct physical significance. A new approach is adopted by introducing an infiltration coefficient in the network architecture apart from antecedent rainfall, slope profile, groundwater level and strength parameters to predict the slope movement. The input variables for settlement around underground excavations are taken from literature. The neural network models demonstrate a promising result predicting fairly successfully the ground behavior in both cases. If input variables influencing output goals are clearly identified and if a decent number of quality data are available, backpropagation neural network can be successfully applied as mapping and prediction tools in geotechnical investigations.  相似文献   

Observations of several characteristics of aeolian sand movement in the Taklimakan Desert   总被引：2，自引：0，他引：2  

HAN Zhiwen  DONG Zhibao  WANG Tao  CHEN Guangting  YAN Changzhen & YAO ZhengyiKey Laboratory of Desert  Desertification  Cold  Arid Regions Environmental  Engineering Research Institute  Chinese Academy of Sciences  Lanzhou  China Correspondence should be addressed to Han Zhiwen 《中国科学D辑(英文版)》2004,47(1):86-96

With both sides of the Taklimakan Desert highway line as the study area, three typical aeolian sand landforms, i.e. complex dune ridge, barchan dune and flat sand land, were selected as sand beds for the observation, analysis and research of the characteristics of aeolian sand movement such as aeolian sand stream structure, sand transport intensity, etc. in the Taklimakan Desert. The results show that there is a linear relation between the height and the log of sand transport rate over transverse dune chain, longitudinal dune ridge and flat sand land, i.e. the sand transport percentage decreases exponentially with increasing height. Sand transport rate within the 10 cm height above the bed surface accounts for 80%-95% of the total sand transport rate of the observed height (40 cm), while the sand transport rate in 20 cm occupies 98% of the total amount. Sand transport rate (g·cm-1·min-1) differs greatly with respect to different landform types and different topographic positions. Based on the investig  相似文献