The process and driving forces of eco-geo-environmental evolution of the Songnen Plain in northeast China since the Quaternary     

Dianfa Zhang  S. Wang 《Environmental Geology》2001,40(11-12):1362-1366

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Disintegration and age of basement metamorphic rocks in Qiangtang,Tibet, China     

Wang  Guozhi  Wang  Chengshan 《中国科学:地球科学(英文版)》2001,44(1):86-93

Comprehensive studies on lithologic association, provenance of metacongelometre, characteristics of metamorphism and deformation, and²⁰⁷Pb/²⁰⁶Pb-dating of single-zircon for metamorphic rocks distributed in Chabu-Chasang areas in Qiangtang block indicate that most of them belong to Middle Proterozoic metamorphic basement except silicilith member ascribed to Triassic. Disintegrated basement strata are called Gemuri group and Guoganjianianri group; they are different in histories of metamorphism and deformation. The single-zircon²⁰⁷Pb/²⁰⁶Pb-ages provide excellent evidence for the existence of an Archean continent nucleus around study areas. Some thermal event ages such as 929–1016 and 509–548 Ma are recorded in Gemuri group.

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Statistical analysis of surface hydrography and circulation variations in northern South China Sea     

吴玲娟  崔茂常 《中国海洋湖沼学报》2005,23(4):383-392

1 INTRODUCTIONThe South China Sea (SCS) is a semi-enclosedmarginal sea in western North Pacific Ocean withvery complex topography and is the important pas-sage connecting the Pacific and Indian Oceans. Ithas great impact to the global climate and a greatinterest of many oceanography researchers. Twodominant surface hydrographic and circulation fea-tures in the northern SCS are a strong fresh waterexpansion and a warm and high-salinity seawaterintrusion such as the SCS Diluted Water…  相似文献   

青藏块体东北缘地壳水平运动状态   总被引：10，自引：6，他引：4  

崔笃信  王庆良  王文萍 《大地测量与地球动力学》2004,24(3):29-34

应用青藏块体东北缘1999～2003年多期GPS观测资料，计算了不同时段GPS点水平运动速率。通过分析发现：甘青块体可分为东部块体和西部块体，东、西部块体的运动状态存在明显的差异；受2001年11月14日昆仑Ms8．1地震的影响，震后地壳运动状态发生了明显的改变。  相似文献   

元岭金矿蚀变破碎带特征及其找矿意义     

刘红樱  周顺之  胡受奚  王群昌 《河南国土资源》1996,(2)

根据对元岭金矿三条蚀变破碎带一般地质特征、微量元素特征的对比研究，并借鉴邻近矿区蚀变破碎带的矿化特征，本文阐明了元岭蚀变破碎带矿化的有利构造部位，总结了蚀变破碎带特征与矿化强度之间的关系，指出蚀变破碎带的矿化蚀变元素为中低温组合，矿化蚀变愈强则参与元素的种类愈多、数量愈大。围岩性质对矿化蚀变有一定影响，围岩中的易迁移亲铜元素和亲硫铁族无素对矿化有利。据此，为进一步成矿预测、评价蚀变破碎带的含矿性提供依据。  相似文献   

ANALYSES OF VECTOR MAGNETOGRAMS IN FLARE-PRODUCTIVE ACTIVE REGIONS     

Wang  Haimin 《Solar physics》1997,174(1-2):163-173

This paper reviews studies of the relationship between the evolution of vector magnetic fields and the occurrence of major solar flares. Most of the data were obtained by the video magnetograph systems at Big Bear Solar Observatory (BBSO) and Huairou Solar Observatory (HSO). Due to the favorable weather and seeing conditions at both stations, high-resolution vector magnetograph sequences of many active regions that produced major flares during last solar maximum (1989–1993) have been recorded. We have analyzed several sequences of magnetograms to study the evolution of vector magnetic fields of flare productive active regions. The studies have focused on the following three aspects: (1) processes which build up magnetic shear in active regions; (2) the pre-flare magnetic structure of active regions; and (3) changes of magnetic shear immediately preceding and following major flares. We obtained the following results based on above studies: (1) Emerging flux regions (EFRs) play very important roles in the production of complicated photospheric flow patterns, magnetic shear and flares. (2) Although the majority of flares prefer to occur in magnetically sheared regions, many flares occurred in regions without strong photospheric magnetic shear. (3) We found that photospheric magnetic shear increased after all the 6 X-class flares studied by us. We want to emphasize that this discovery is not contradictory to the energy conservation principle, because a flare is a three-dimensional process, and the photosphere only provides a two-dimensional boundary condition. This argument is supported by the fact that if two initial ribbons of a flare are widely separated (which may correspond to a higher-altitude flare), the correlation of the flare with strong magnetic shear is weak; if the two ribbons of a flare are close (which may correspond to a lower-altitude flare), its correlation with the strong shear is strong. (4) We have analyzed 18 additional M-class flares observed by HSO in 1989 and 1990. No detectable shear change was found for all the cases. It is likely that only the most energetic flares can affect the photospheric magnetic topology.  相似文献   

ENERGY FLOW OF BELIAMYA AERUGINOSA IN A SHALLOW ALGAL LAKE, HOUHU LAKE （WUHAN, CHINA）     

Yan Yun-jun  Liang Yan-ling  Wang Hong-zhu 《中国海洋湖沼学报》2001,19(3):243-248

The energy budget ofBellamya earuginosa in a shallow algal lake, Houhu Lake (Wuhan, China) was investigated by the measurement of flesh production (32.8 kJ/(m²·a)), egestion (337.7 kJ/(m²·a)), metabolism (246.7 kJ/(m²·a)), and estimation of excretion (21.4kJ/(m²·a)). The net growth efficiency of the species is about 10.9%, which accords with the generally reported value for gastropods. In addition, the relationships between starvation respiration (R, mgO₂/(Ind·d)), body weight (Wd, mg in dry wt) and temperature (T, °C) were also determined. The regression equationR=0.044Wd ^0.537 e ^0.061T was obtained by the least square method, The measured SDA of the species is 26.51% of its gross metabolism. Project No. 3960019 and 39430101 supported by NSFC and also a granted for the East Lake Ecological Experimental Station, CAS, Wuhan.  相似文献   

The elastodynamic near field     

Ru-Shan Wu  Ari Ben-Menahem† 《Geophysical Journal International》1985,81(3):609-621

Summary. The elastodynamic fields of point forces and shear dislocations of finite source duration are analysed with the aim of establishing the frequency and time-domain characteristics of the field in the near-source region. Criteria are obtained for amplitude dominance in regions where the source–sensor distance is much smaller than the wavelength.
It is shown that in the frequency domain , the Green's tensor (and hence the displacement field of a single point force) attenuates like R ⁻¹ in the near-source region and there exists no region in which the 'near-field' term becomes dominant such that the 'far-field' term can be neglected. Hence, there is no real 'near-field' term for the elastodynamic Green's tensor. The near-field terms of the displacements, velocities and accelerations excited by a shear dislocation attenuate like R ⁻², since the R ⁻³ and R ⁻⁴ terms tend to be eliminated due to mutual cancellation of P and S motions in the near-source region.
In the time domain , the corresponding near field of the displacement field is defined for the steady amplitude interval (away from transients) R /β < t < R /α+ T by the condition R ≤βT where β is the shear velocity and T is the source's duration. The relative strengths of all other arrivals will depend on the particular time window under consideration.
The particle motion patterns due to a single force in the near-source region are shown to be similar to rotating hyperbolas with an axis along the force direction, which are quite different from the 'smoke ring' motion patterns of the so-called 'near-field' term itself.  相似文献   

石英砂扫描电镜在漓江“泥砾”成因中的应用     

吴枝坦  王壬林  姚若飞 《南方国土资源》1992,(4)

本文根据扫描电镜对从漓江河谷钻孔中的泥砾层取得的481粒石英砂表面形态特证研究结果:石英砂多数颗粒保持棱角状外形并遭受不同程度的磨蚀,具阶状贝壳断口,平直或弧形刮削面和多向擦痕,沿解理面破碎呈“V”字形沟和撞击碟形坑,以及微溶蚀孔、隙、蜂窝状溶孔群和SiO_2再沉积等表面形态结构特征。认为它是在第四纪古地理湿热气候条件下泥石流沉积的产物,物源可能来自境内或周边的泥盆系砂岩和境外的花岗岩。  相似文献   

介绍一个新建立的岩石地层单位——陈刘组     

张继淹  唐娟红 《南方国土资源》1997,(2)

陈刘组为新建立的岩石地层单位，代表广西早三叠世盆地滨岸相带沉积类型。层型剖面位于贵港市陈刘村附近。层型定义指位于龙潭组与板纳组之间的沉积序列，岩性为灰绿、紫红色泥岩、粉砂细砂岩夹少量火山岩及碳酸盐岩，含菊石、双壳类、牙形石等化石，厚３５９ｍ。  相似文献