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1.
The Kamieniec Metamorphic Belt comprises a volcano-sedimentary succession exposed within a collision zone between the Saxothuringian and Brunovistulian crustal domains of the European Variscides. The studied rocks recorded two metamorphic episodes. The first episode, M1, occurred at conditions of c. 485 ± 25 °C and 18 ± 1.8 kbar related to burial within a subduction zone. The subsequent episode, M2, was linked to the final phases of exhumation to mid-crustal level, associated with pressure and temperature (P–T) conditions ranging from c. 520 ± 26 °C and 6 ± 0.6 kbar through 555 ± 28 °C and 7 kbar ± 0.7 to ~590 ± 30 °C and 3–4 ± 0.4 kbar. The documented deformation record is ascribed to three events, D1 to D3, interpreted as related to the burial and subsequent exhumation of the Kamieniec Metamorphic Belt. The D1 event must have witnessed the subduction of the Kamieniec Metamorphic Belt rock succession whereas the D2 event was associated with the exhumation and folding of the Kamieniec Metamorphic Belt in an E-W-directed shortening regime. A subsequent folding related to the D2 event was initiated at HP conditions, however, the planar fabric produced during a late stage of the D2 event, defined by a low-pressure mineral assemblage M2, indicates that the D2 final stage was synchronous with the onset of the M2 episode. Consequently, the entire D2 event seems to have been associated with the exhumation of the Kamieniec Metamorphic Belt to mid crustal level. The third deformation event D3, synchronous with the M2 episode, marked the last stage of the exhumation, and was linked to emplacement of granitoid veins and lenses. The latter resulted in heating and rheological weakening of the entire rock succession and in the formation of non-coaxial shear zones.  相似文献   
2.
冯建伟  戴俊生  秦峰  宋永 《地质学报》2019,93(11):2729-2741
针对前陆冲断带的特殊构造位置及沉积特征的复杂性,本文在地层剥蚀厚度恢复和层序划分的基础上,通过对准噶尔盆地西缘乌夏前陆冲断带沉降史分析,在海西运动晚期准噶尔地块与西伯利亚板块发生碰撞挤压,形成一系列冲断推覆构造,前缘岩石圈挠曲下陷发育周缘前陆盆地,并夹杂大规模的短暂伸展火山喷发活动,接受了巨厚的二叠系沉积层序;随着板块俯冲在二叠纪末的逐渐消亡,三叠纪进入印支期陆内坳陷继承性挤压活动阶段,周边受南北向挤压和左旋构造应力场影响,前陆冲断带古断裂再次逆冲,哈拉阿拉特山急剧抬升,后缘和什托洛盖盆地形成;进入侏罗纪—白垩纪(燕山运动早中期),为陆内坳陷的填充消亡阶段,但有继承性活动,构造活动强度较二叠纪大为减弱,在燕山运动Ⅲ幕晚期最终被覆盖定型。整个过程受地体碰撞和板内挤压影响,冲断带发生幕式构造活动,从而导致盆地沉降也发生幕式变化,而且冲断带每次挤压逆冲均导致相应的沉降和沉积物充填,并直接控制前陆盆地和陆内坳陷的沉积充填特征。  相似文献   
3.
The special interest produced by near-field directivity records and their effect on structural response has given a new significance in the velocity time history, its pulse-like content, and relevant parameters and indices. Recent research has shown that directivity pulses inherent in these records govern the linear and the nonlinear response of a wide range of structures. Based on this observation, it is suggested in this paper that a truncated ground motion, limited to the duration of the predominant velocity pulse, can be efficiently used to predict the structural response, instead of the base motion with the total duration, reducing significantly the required runtimes. The proposed methodology is verified for a series of medium to high rise reinforced concrete buildings, for which nonlinear time-history analyses are performed for a vast suite of pulse-like near-field records applied as base excitations with their total duration and the proposed truncated one. Comparison of the results for the response displacements and forces shows very good agreement, permitting the acceptance of the pulse duration as the efficient strong motion time interval of the original record, which determines the response and, thus, it can be used for nonlinear structural analyses.  相似文献   
4.
花海断裂位于河西走廊西段花海盆地内,总体走向NNW-SSE,长约38 km,为一条隐伏断裂,研究其空间展布、运动性质和活动历史对于理解青藏高原北缘的构造变形和扩展方式有重要意义.基于卫片解译、野外实地和槽探,结合光释光测年和地球物理资料,发现沿双泉子、大泉至小泉一带,发育一段长约8 km的地形陡坎,代表断裂控制下褶皱作用的地形表现.沿陡坎走向向南,断裂一直隐伏延伸至宽滩山和黑山以北.现有资料分析表明,断裂经历了早白垩世的正断、晚白垩的逆冲运动.新生代以来,断裂继承了之前的逆冲运动并一直持续至全新世中晚期.高原北缘的侧向扩展,使得作为三危山与阿尔金断裂之间块体边界的三危山、干峡山、宽滩山和塔尔湾-登登山-池家刺窝断裂发生以左旋走滑为主兼有逆冲的变形,导致了边界断裂控制山体的隆升,而内部的块体受压剪作用向北东运动.花海断裂的逆冲运动即是该次构造活动事件的响应.   相似文献   
5.
Alluviation and sedimentation of the Yellow River are important factors influencing the surface soil structure and organic carbon content in its lower reaches. Selecting Kaifeng and Zhoukou as typical cases of the Yellow River flooding area, the field survey, soil sample collection, laboratory experiment and Geographic Information System(GIS) spatial analysis methods were applied to study the spatial distribution characteristics and change mechanism of organic carbon components at different soil depths. The results revealed that the soil total organic carbon(TOC), active organic carbon(AOC) and nonactive organic carbon(NOC) contents ranged from 0.05–30.03 g/kg, 0.01–8.86 g/kg and 0.02–23.36 g/kg, respectively. The TOC, AOC and NOC contents in the surface soil layer were obviously higher than those in the lower soil layer, and the sequence of the content and change range within a single layer was TOCNOCAOC. Geostatistical analysis indicated that the TOC, AOC and NOC contents were commonly influenced by structural and random factors, and the influence magnitudes of these two factors were similar. The overall spatial trends of TOC, AOC and NOC remained relatively consistent from the 0–20 cm layer to the 20–100 cm layer, and the transition between high-and low-value areas was obvious, while the spatial variance was high. The AOC and NOC contents and spatial distribution better reflected TOC spatial variation and carbon accumulation areas. The distribution and depth of the sediment, agricultural land-use type, cropping system, fertilization method, tillage process and cultivation history were the main factors impacting the spatial variation in the soil organic carbon(SOC) components. Therefore, increasing the organic matter content, straw return, applying organic manure, adding exogenous particulate matter and conservation tillage are effective measures to improve the soil quality and attain sustainable agricultural development in the alluvial/sedimentary zone of the Yellow River.  相似文献   
6.
The pattern of resource allocation into multiple life‐history traits can vary with the environment; for example, high temperatures generally facilitate growth. Changes in investment in growth due to temperature may alter the allocation to other traits that are in trade‐off with that. Here, we investigated the trade‐off between growth and reproduction and whether the proportion of allocation to these varies with increasing seawater temperature in the lancelet Branchiostoma japonicum. We reared the lancelets of early adult stage under three different temperature treatments (control, + 1°C and + 2°C treatments) for 427 days in the laboratory. Although the total body length at initiation did not differ between treatments, the length was influenced by the interaction between elapsed days and temperature treatments, suggesting that growth rate was temperature‐dependent; the lancelets under higher temperature conditions showed a more rapid growth rate than did those under the control conditions. The frequency of individuals with gonads did not differ between treatments throughout their reproductive season. The monthly growth increments were also not significantly affected by the interaction between the presence/absence of gonads and temperature treatments, although the presence of gonads caused the growth increments to decrease. In addition, the effect of temperature treatments was significant. These results suggest that changes in temperature did not alter the pattern of allocation between growth and reproduction that were in a trade‐off, whereas high temperature would solely result in an increase in resource intake, at least in the early adult stage of this species.  相似文献   
7.
2020年中国科学院地理科学与资源研究所建所80周年。回眸80年,从1940年重庆北碚成立的中国地理研究所,到1953年重新组建的中国科学院地理研究所和1956年成立的中国科学院自然资源综合考察委员会,再到1999年地理研究所和自然资源综合考察委员会整合形成现在的地理科学与资源研究所,几经变迁,历经三代人努力,研究所始终如一,求真务实,开拓进取,推动着地理科学与资源科学的创新发展,为国家建设发展和生态文明进步做出了重要贡献。适逢建所80周年,本文回顾地理资源所发展历程,总结取得的重要科研成果,并展望未来发展。  相似文献   
8.
To provide better access to thermochronological data and understand the long‐term denudation history of the Japanese Islands, we compiled a low‐temperature thermochronological dataset of fission‐track (FT) and (U–Th–Sm)/He (He) ages for apatite and zircon in bedrocks. These thermochronometric ages are compiled from 90 literature sources and 1,096 localities, and include 418 apatite FT ages, 851 zircon FT ages, 42 apatite He ages, and 30 zircon He ages. Many FT ages have been reported previously; however, the number of He ages is limited in the Japanese Islands. The compiled data are spatially biased; for instance, more data are reported for the Chubu and Kinki districts and the Pacific coast of the Shikoku Island, whereas less data were available for the Tohoku and Chugoku districts. For better understanding arc‐scale uplift‐denudation history, further thermochronological research in the lesser‐studied regions and more He thermochronometric measurements are desired. This compilation will be updated and provided on the website of the Fission‐Track Research Group in Japan ( http://ftrgj.org/index.html ).  相似文献   
9.
大跨刚构桥结构桥跨较长和受力复杂。为提高抗震性能,需要对加固前后的桥梁进行抗震性能研究。以某双肢薄壁型高墩大跨度刚构桥为背景,采用ANSYS程序APDL语言,对结构进行合理的参数选取、网格划分和边界约束,结合抗震等级和桥梁规范等有关规定,研究整体结构在地震作用下的变化规律。通过沿墩高方向获取节点的方法,确定在地震作用下,各节点的最大位移从下到上逐渐增大。选取桥墩双肢相同部位各节点进行横向比较,总结得出双肢薄壁桥墩具有平分荷载和延长寿命的特点。为提高桥梁整体抗震性能,采取联结桥墩增大截面的方式进行加固,对比加固前后两模型在同一地震作用下的结构响应,得出该方法在提高结构整体刚度方面,效果显著。  相似文献   
10.
为了研究钢筋-沥青隔震层的材料与几何非线性震动特性,对钢筋-沥青隔震结构进行了振动台试验,分析了结构在不同加速度幅值输入时的隔震性能。同时,在钢材的应力-应变关系基础上,考虑构件竖向力的二次矩效应,提出了钢筋-沥青隔震层骨架曲线的计算方法,并结合双线型恢复力模型的滞回规则,建立了相应的恢复力模型。利用建立的恢复力模型,编制程序进行了弹塑性时程分析,并与试验结果作对比。结果表明:当钢筋-沥青隔震层的受力钢筋进入弹塑性阶段时,隔震层能够吸收大部分地震能量,显著降低上部结构的地震反应;弹塑性时程分析结果与试验结果吻合较好,由此建立的恢复力模型准确并且适用,可为钢筋-沥青隔震层的工程设计与非线性地震反应分析提供参考。  相似文献   
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