夹皮沟金矿田成矿模式     

王光奇  武贵禄 《吉林地质》1991,10(4):45-54

本文以岩性—构造—事件法论述了夹皮沟金矿田地质演化历史,并建立了夹皮沟金矿田成矿模式,对金矿田成矿理论和金矿预测提出了新的见解。研究认为,该矿田金的物质来源具多源性,金矿形成具多期多阶段性。区内北西向弧形韧性剪切带是金的主要控矿构造。总结出该矿田具有“一型三式”的特点,即花岗—绿岩型,包括板庙子式、大线沟式和三道岔式。  相似文献   

Tectonic framework of the Precambrian of Madagascar and its Gondwana connections: a review and reappraisal     

B. F. Windley  A. Razafiniparany  T. Razakamanana  D. Ackermand 《International Journal of Earth Sciences》1994,83(3):642-659

The Precambrian of Madagascar is divided into two sectors by the north-west trending sinistral Ranotsara shear zone, which continues in the Mozambique belt, probably as the Surma shear zone, and in Southern India as the Achankovil shear zone. South of Ranotsara six north-south trending tectonic belts are recognized that consist largely of granulite and high amphibolite facies paragneisses, phlogopite diopsidites, concordant granites and granulites. North of Ranotsara the central-northern segment is traversed by a north-trending axial 100–150 km wide dextral shear zone of probable Pan-African age, which was metamorphosed under granulite and high amphibolite facies conditions and which has reworked older basement. This shear zone continues across southern India as the Palghat-Cauvery shear zone. Major stratiform basic -ultrabasic complexes occur in the axial zone and in the basement to the west. Well preserved low grade continental margin-type sediments (quartzites, mica schists and stromatolitic marbles) of Kibaran age are present in western Madagascar. Two partly greenschist grade sedimentary groups lie unconformably on high grade basement in north-east Madagascar. Isotopic age data suggest the presence in Madagascar of Archaean, Early and Mid-Proterozoic crustal material that was extensively reworked in Pan-African times.  相似文献   

Effects of temperature and sliding rate on frictional strength of granite   总被引：10，自引：0，他引：10  

D. A. Lockner  R. Summers  J. D. Byerlee 《Pure and Applied Geophysics》1986,124(3):445-469

Layers of artificial granite gouge have been deformed on saw-cut granite surfaces inclined 30° to the sample axes. Samples were deformed at a constant confining pressure of 250 MPa and temperatures of 22 to 845°C. The velocity dependence of the steady-state coefficient of friction (^ss) was determined by comparing sliding strengths at different sliding rates. The results of these measurements are consistent with those reported bySolberg andByerlee (1984) at room temperature andStesky (1975) between 300 and 400°C. Stesky found that the slip-rate dependence of (^ss) increased above 400°C. In the present study, however, the velocity dependence of (^ss) was nearly independent of temperature.  相似文献   

伊通地堑上地幔剪切带   总被引：3，自引：1，他引：3  

张小鸥 《地震地质》1995,17(2):167

通过研究糜棱岩型幔源包体的变形显微构造、位错亚构造及组构特征，确定它是上地幔剪切带的代表物质。该带形成温度为７２９～８２８℃、压力为１．１０～１．３８ＧＰａ、差异应力为９７～１５０ＭＰａ、应变速率为ＩＯ￣（－１４）～１Ｏ￣（－１２）ｓ￣（－１）、等效粘滞度为１０～１０００ＥＰａ·ｓ和深度为３７～４５ｋｍ。这是一种与地幔底辟作用有关的规模较小的缓倾斜剪切带，也是应变集中带，能导致上地幔地震波速各向异性，并与地震活动有关  相似文献   

Direct Measurement Of Shear Stress During Snow Saltation     

M. Nemoto  K. Nishumura 《Boundary-Layer Meteorology》2001,100(1):149-170

Wind-tunnel experiments were carried out to measure the shear stressduring snow saltation. Shear stress acting on the snow surface, measured directly with a newly developed drag meter system, revealedthat the shear stress increased with the development ofsaltation. This result supports Owen's hypothesis that the saltationlayer acts as an increased roughness to the flow above the saltationlayer, leading to an increase in surface shear stress. To investigate the contribution of the grain borne shear stress_g and the fluid shear stress _f to the increment of the total shear stress _total, _g was calculated from the loss of horizontal momentum of saltating snowparticles. Since _g is the largest contribution to theincrement of _total, the collision of thesaltating particles is dominant for the shear stressmodification. The results qualitatively support the numericalsimulation reported by McEwan and Willetts.  相似文献   

Influence of initial density of cohesionless soil on evolution of passive earth pressure     

J. Tejchman  E. Bauer  S. F. Tantono 《Acta Geotechnica》2007,2(1):53-63

This paper focuses on the influence of the initial void ratio on the evolution of the passive earth pressure and the formation of shear zones in a dry sand body behind a retaining wall. For the numerical simulation a rigid and very rough retaining wall undergoing a horizontal translation against the backfill is considered. The essential mechanical properties of cohesionless granular soil are described with a micro-polar hypoplastic model which takes into account stresses and couple stresses, pressure dependent limit void ratios and the mean grain size as a characteristic length. Numerical investigations are carried out with an initially medium dense and initially loose sand using a homogeneous and random distribution of the initial void ratio. The geometry of calculated shear zones is discussed and compared with a corresponding laboratory model test.  相似文献   

Non-stationary random vibrations of a shear beam under high frequency seismic effects     

Zbigniew Zembaty   《Soil Dynamics and Earthquake Engineering》2007,27(11):1000-1011

Band-limited, non-stationary random vibrations of a shear beam are studied in order to investigate high frequency seismic effects on building structures. A solution for the evolutionary spectral density of the shear beam response to a time segment of band-limited white noise is given in a closed form. The root mean square (rms) and peak response of the shear beam are studied for two characteristic frequency bands: the conventional 1–4 Hz and higher frequency 4–16 Hz, characteristic for rockburst ground motion. Applying the criterion of equal excitation intensity with constant rms velocity, both responses are analyzed in detail and compared. The “switching off” fundamental mode for high frequency excitations results in characteristic overshoot of the stationary response level by the non-stationary rms response and an amplification of the response in the upper part of the shear beam.  相似文献   

In situ measurements of surficial mud strength: A new vane tester suitable for soft intertidal muds     

P. Bassoullet  P. Le Hir 《Continental Shelf Research》2007

A vane fitted to a standard shear vane tester is described, the purpose of which is to obtain better measurements of the rheological properties of soft, surficial, intertidal muds (and consequently, variations in their erodability). Specifications and geometry of this vane are presented. The computation procedure is detailed, so that the methodology can be applied to any vane tester. The main improvement is a greater vertical resolution, typically less than 1 cm. Sets of direct measurements with this equipment and correlation with dry densities for three intertidal mudflats (estuaries and bay) are presented.  相似文献   

水平切变线上涡层不稳定理论   总被引：25，自引：4，他引：25  

高守亭  周玉淑 《气象学报》2001,59(4):393-404

文中打破了传统的 Kelvin- Helmholtz研究切变不稳定的观点 ,考虑了强涡度切变存在时切变线已构成了一个涡层 ,这时切变线的不稳定问题就变为涡层的不稳定问题。同时考虑由涡层所产生的诱导速度 ,从理论上得到了水平切变线上涡层不稳定必要条件的判据 ,即必须满足 (1 - Rv Rid) >0 ,且有 U(y,t) >U(A(t) )与之相配合。这表明环境场的配置制约着切变线上扰动的发展 ,这种中尺度扰动同环境场存在着相互作用。文中还用具体个例对如何计算不稳定必要条件做了解释和说明。  相似文献   

An Evaluation Of Local Similarity At The Top Of The Mixed Layer Based On Large-Eddy Simulations     

Zbigniew Sorbjan 《Boundary-Layer Meteorology》2001,101(2):183-207

Local similarity, referred to as type II similarity,in the interfacial, stably-stratified layer at thetop of the atmospheric (or oceanic) mixed layer isdiscussed. Type II scales for scalars are based onthe local values of scalar gradients. Similaritypredictions are derived from the second-orderclosure model of Yamada and Mellor, and also fromsimilarity arguments. The obtainedformulation is verified for active and passive scalarsbased on the large-eddy simulation model.  相似文献