Paleoproterozoic Granitoids on Liaodong Peninsula,North China Craton     

ZHU Kai  LIU Zhenghong  XU Zhongyuan  LIU Jiexun  WANG Xing’an 《《地质学报》英文版》2019,93(5):1377-1396

Paleoproterozoic granitoids are an important constituent of the Jiao–Liao–Ji Belt(JLJB). The spatial-temporal distribution and types of Paleoproterozoic granitoids are closely related to the evolution of the JLJB. In this paper, we review the field occurrence, petrography, geochronology, and geochemistry of Paleoproterozoic granitoids on Liaodong Peninsula, northeast China. The Paleoproterozoic granitoids can be divided into pre-tectonic(～2.15 Ga; peak age=2.18 Ga) and post-tectonic(～1.85 Ga) granitoids. The pre-tectonic granitoids are magnetite and hornblende–biotite monzogranites and granodiorites. Pre-tectonic monzogranites are widespread in the JLJB and have A_2-type affinities. In contrast, pretectonic granodiorites are only present in the Simenzi area and have adakitic affinities. The post-tectonic granitoids consist of porphyritic monzogranite, syenite, diorite, granodiorite, quartz monzonite, monzogranite, and granitic pegmatite, which are adakitic rocks and I-, S-, and A_2-type granitoids. The assemblage of pre-tectonic A_2-type granitoids and adakitic rocks indicates the initial tectonic setting of the JLJB was a continental back-arc basin. The assemblage of post-tectonic adakitic rocks and I-, S-, and A_2-type granitoids indicates a post-collisional setting. The 2.20–2.15 Ga A_2-type granitoids and adakitic rocks were associated with the initial stage of back-arc extension, and the peak of back-arc extension is inferred from the subsequent(2.15–2.10 Ga) mafic intrusive activity. The ～1.90 Ga adakitic rocks mark the beginning of the postcollisional stage, which was followed by the intrusion of low-temperature S-and I-type granitoids. High-to low-pressure granitoids(S-type) were generated during the peak of post-collisional lithospheric delamination and asthenospheric upwelling. The emplacement of later granitic pegmatites occurred during the waning of the orogeny.  相似文献   

超高压变质带的全球分布及其大地构造意义     

游振东 《高校地质学报》2007,13(3):383-391

对全球28个超高压变质岩产地的地质对比研究发现,超高压变质带的发育,与弧-陆和陆-陆碰撞造山带关系密切。碰撞造山带多发育于活动的大陆边缘。在那里,冷的陆壳物质可以深俯冲到另一个相对稳定的未俯冲的板块之下,其深度可以超过90~120 km,在高压达>2.5 GPa和温度约600℃或更高条件下,导致超高压特征矿物如,柯石英、金刚石等的生成。在空间分布上,超高压变质带集中于欧亚大陆及其周缘,澳洲和北美目前尚未有报道。从时代上看,超高压变质带多出现于显生宙,前寒武纪只有晚元古代（泛非运动期）少数两例。说明以超高压变质带为特征的碰撞造山作用,是显生宙以来,陆壳增生达到一定的规模后,才出现的构造体制;Rodinia和Pangea古大陆的裂解,使地温梯度降低,从而有利于超高压变质带的生成。  相似文献   

动扭剪试验中砂土液化后流动特性分析   总被引：2，自引：0，他引：2  

刘汉龙  陈育民 《岩土力学》2009,30(6):1537-1541

土体在初始液化后仍然可能承受动荷载作用发生大变形。引入流体力学中的剪应变率和表观黏度的概念,对振动扭剪试验中饱和砂土液化后的流动特性进行了分析。分析中将砂土的状态分为0有效应力状态和非0有效应力状态。结果表明,砂土在0有效应力状态下表现出与静扭剪试验类似的“剪切稀化”非牛顿流体的特征,表观黏度随着剪应变率的增大而减小。加载周数对“剪切稀化”状态下的剪应变率幅值有影响,随着加载周数的增加,剪应变率幅值逐渐增大,而对流动曲线的形状没有影响。在非0有效应力状态下,砂土的表观黏度随应变的增大而增大,随孔压比的减小而增大,且所有的试验得到的表观黏度与孔压比具有一致关系。  相似文献   

Seismic design procedure and seismic response of post‐tensioned self‐centering steel frames     

Hyung‐Joon Kim  Constantin Christopoulos 《地震工程与结构动力学》2009,38(3):355-376

Post‐tensioned (PT) self‐centering moment‐resisting frames (MRFs) have recently been developed as an alternative to welded moment frames. The first generation of these systems incorporated yielding energy dissipation mechanisms, whereas more recently, PT self‐centering friction damped (SCFR) moment‐resistant connections have been proposed and experimentally validated. Although all of these systems exhibited good stiffness, strength and ductility properties and stable dissipation of energy under cyclic loading, questions concerning their ultimate response still remained and a complete design methodology to allow engineers to conceive structures using these systems was also needed. In this paper, the mechanics of SCFR frames are first described and a comprehensive design procedure that accounts for the frame behavior and the nonlinear dynamics of self‐centering frames is then elaborated. A strategy for the response of these systems at ultimate deformation stages is then proposed and detailing requirements on the beams in order to achieve this response are outlined. The proposed procedure aims to achieve designs where the interstory drifts for SCFR frames are similar to those of special steel welded moment‐resisting frames (WMRFs). Furthermore, this procedure is adapted from current seismic design practices and can be extended to any other PT self‐centering steel frame system. A six‐story building incorporating WMRFs was designed and a similar building incorporating SCFR frames were re‐designed by the proposed seismic design procedure. Time‐history analyses showed that the maximum interstory drifts and maximum floor accelerations of the SCFR frame were similar to those of the WMRF but that almost zero residual drifts were observed for the SCFR frame. The results obtained from the analyses confirmed the validity of the proposed seismic design procedure, since the peak drift values were similar to those prescribed by the seismic design codes and the SCFR frames achieved the intended performance level under both design and maximum considerable levels of seismic loading. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

太阳射电IV型爆发及伴随现象与白光耀斑的关系     

谢瑞祥  汪敏 《中国天文和天体物理学报》2000,20(1)

通过1991年6月6日共生太阳白光耀斑（WLF）的射电运动IV型爆发及其伴随现象（包括耀斑后环、爆发衰减相的射电脉动、多波段射电辐射和太阳物质抛射等）观测资料的分析,定性地探讨了WLF的起源、加热机制和发射地点的问题．假设了WLF和射电运动IV型射电爆发可能有共同起源的低日冕电子加速区,讨论了WLF的能量传输可能是通过二步加速过程,即来自低日冕的非热电子沉降能量于色球层,产生色球层的压缩波或向下的辐射场进而使上光球层温度增加导致WLF此外,提出WLF可能会伴有耀斑后环和射电精细结构的对应物．  相似文献   

西华山钨矿床晶洞中水晶与黑钨矿流体包裹体显微测温与特征元素测定   总被引：2，自引：0，他引：2  

黄惠兰  常海亮  李芳  谭靖  张春红  周云  杨科  闫芬 《地学前缘》2013,20(2):205-212

摘要：西华山钨矿床晶洞中水晶与黑钨矿以及晶洞外部块状石英与共生黑钨矿中流体包裹体对比研究结果表明,后期应力作用和流体改造是造成共生石英与黑钨矿包裹体均一温度出现重大差异的主要原因。一般来说,在后期应力作用和流体改造下,黑钨矿有较好的稳定性,能较好地保存原生包裹体和较少出现次生包裹体,而与之共生石英中的原生包裹体几乎破坏殆尽,现在所看到的包裹体绝大部分是后来形成的次生包裹体,且很难确切区别原生与次生关系。当后期应力作用和流体改造很微弱时,石英中可保存较多原生包裹体,并且原生与次生关系较易区分。当完全未受应力作用改造时,共生石英(水晶)与黑钨矿中都只有原生包裹体,其Th值和盐度值基本相同或完全一致,且石英(水晶)流体包裹中富含W、Mn、Fe等成矿元素,表明石英与黑钨矿是由同一流体在相同时间和相同条件下沉淀的。鉴于一般金属矿床皆在一定程度上经受了后期应力作用和流体改造,因此在有关流体包裹体研究中应该结合不透明矿物进行全面对比,并且切实加强岩相学研究。  相似文献   

Retrofit of reinforced concrete frames with buckling‐restrained braces          下载免费PDF全文

Christoph Mahrenholtz  Pao‐Chun Lin  An‐Chien Wu  Keh‐Chyuan Tsai  Shyh‐Jiann Hwang  Ruei‐Yan Lin  Muhammad Y. Bhayusukma 《地震工程与结构动力学》2015,44(1):59-78

Damage to buildings observed in recent earthquakes suggests that many old reinforced concrete structures may be vulnerable to the effects of severe earthquakes. One suitable seismic retrofit solution is the installation of steel braces to increase the strength and ductility of a building. Steel bracings have some compelling advantages such as their comparatively low weight, their suitability for prefabrication, and the possibility of openings for utilities, access, and light. The braces are typically connected to steel frames that are fixed to the concrete structure using post‐installed concrete anchors along the perimeter. However, these framed steel braces are not without some disadvantages such as heavier steel usage and greater difficulties during the installation. Therefore, braces without steel frames appear to be an attractive alternative. In this study, braces were connected to gussets furnished with anchor brackets, which were fixed by means of a few post‐installed concrete anchors. The clear structural system and the increased utilization of the anchors allowed the anchorage to be designed precisely and economically. The use of buckling‐restrained braces (BRBs) provides additional benefits in comparison with conventional braces. BRBs improve the energy dissipation efficiency and allow the limitation of the brace force to be taken up by the highly stressed anchorage. Cyclic loading tests were conducted to investigate the seismic performance of BRBs connected with post‐installed anchors used to retrofit reinforced concrete frames. The tests showed that the proposed design method is feasible and increases strength as well as ductility to an adequate seismic performance level. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Evaluation of displacement‐based vulnerability assessment methodology using observed damage data from Christchurch          下载免费PDF全文

S. R. Uma  Rajesh P. Dhakal  Mostafa Nayyerloo 《地震工程与结构动力学》2014,43(15):2319-2339

On 22 February 2011, Christchurch City experienced a destructive magnitude (Mw) 6.2 aftershock following the main event of magnitude (Mw) 7.1 on the 4 September 2010. Severe damage was inflicted on the building stock, particularly within the central business district (CBD) of Christchurch. The strong motion stations around the CBD region and extensive building damage survey information from the Christchurch City Council provided a unique opportunity to calibrate a theoretical regional vulnerability assessment model developed and refined to be applicable for New Zealand (NZ) buildings. In this study, data from the building safety evaluation survey conducted by Christchurch City Council are synthesised and processed to extract details on building typologies in the CBD region and the colour tagging assigned to each building depending on the degree of damage. A displacement‐based framework is used to carry out vulnerability assessment for Christchurch buildings to estimate damage sustained under the recorded ground motions in the February event. As the damage survey indicators were ‘colour tags’, a mapping scheme has been explored to link the observed colour tagging damage statistics with ‘drift‐based damage limit states’ adopted in the theoretical approach. A sensitivity analysis is carried out to calibrate the mapping scheme, which can provide estimates of proportions of buildings likely to fall in different colour regimes when used in conjunction with the proposed vulnerability assessment methodology. It is shown that the methodology is reasonably robust, thereby increasing the confidence in using this approach to predict seismic vulnerability of building stock in NZ. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Seismic performance evaluation of high‐voltage disconnect switches using real‐time hybrid simulation: II. Parametric study          下载免费PDF全文

Selim Günay  Khalid M. Mosalam 《地震工程与结构动力学》2014,43(8):1223-1237

This paper presents the results of a parametric study that consists of real‐time hybrid simulation tests of electrical insulator posts on a smart shaking table. A companion paper presents the details of the development and validation of the real‐time hybrid simulation system used for conducting the tests of this parametric study. The purpose of the parametric study presented in this paper is to evaluate the effect of support structure damping and stiffness on the response of disconnect switches with two different insulator materials, namely porcelain and polymer insulator posts. Various global and local response parameters including accelerations, forces, displacements, and strains are considered in this evaluation. The data obtained from the conducted tests show that the maximum insulator response corresponds to the case where the support structure frequency is close to the insulator frequency. An incorporated evaluation of all the response parameters indicates that the stiff support structures constitute the most suitable configuration for both material types of the tested insulator posts. It is also observed that support structure damping has an effect on the response of both insulator types. However, this effect is secondary compared with the effect of support structure stiffness. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Impacts of post‐glacial rebound on landslide spatial distribution at a regional scale in northern Iceland (Skagafjörður)          下载免费PDF全文

Etienne Cossart  Denis Mercier  Armelle Decaulne  Thierry Feuillet  Helgi Páll Jónsson  Þorsteinn Sæmundsson 《地球表面变化过程与地形》2014,39(3):336-350

In de‐glaciated areas, para‐glaciation (i.e. the conditioning of landscapes by prior glaciation) has often been considered a major predisposing factor in landslide occurrence; its consequences have been particularly well identified at a fine scale (especially on bedrock jointing). Hitherto, the relative impacts of para‐glaciation on hillslope dynamics at a regional scale had nevertheless not been quantified statistically. We examine Skagafjörður area (northern Iceland) where landslides are widespread (at least 108 were mapped in an area of c. 3000 km²). We compare the role of para‐glaciation (debuttressing, influence of post‐glacial rebound) with that of classic factors (topography, lithology, etc.) in landslide occurrence and location, using a spatial analysis based on a chi‐square test. On the one hand, the results highlight that landslides are over‐represented in areas where post‐glacial rebound was at its maximum, with a stronger concentration of landslides in the northern part of the fjord. On the other hand, the distribution of landslides did not show any clear relationship with the pattern of glacial debuttressing. Tschuprow coefficient highlights that the influence of post‐glacial rebound on landslide location is higher than the combined influence of slope gradient, curvature or geological structure. This result is supported by our initial evidence for the timing of landslides in the area: most landslides occurred during the first half of the Holocene, and a period of hillslope instability was initiated when the post‐glacial uplift was at its maximum. Finally, the mechanisms that link post‐glacial rebound and landsliding as well as the geomorphic impacts of landslides, are discussed. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献