冰雷达探测研究南极冰盖的进展与展望   总被引：3，自引：0，他引：3  

崔祥斌  孙波  田钢  蒋芸芸  张向培  郭井学  唐学远 《地球科学进展》2009,24(4):392-402

南极冰盖是地球上最大的陆缘冰体,其物质收支和稳定性对全球气候变化和海平面升高有重要的影响。冰雷达,或称无线电回波探测,是冰川学家调查南极冰盖冰下特征的主要方法。在过去的50年里,冰雷达被广泛用于测量冰盖厚度、内部构造和冰下地貌,这些参数是计算冰盖体积和物质平衡、重建过去冰雪积累和消融率以及冰盖动力和沉积过程的基础。现在,冰雷达测量覆盖了南极绝大部分区域,极大地提升了人们对南极冰盖和全球系统间相互作用的理解。首先,简要介绍了冰雷达及其技术发展,然后着重评述了冰雷达在探测研究南极冰盖厚度和冰下地形、内部反射层、冰下湖和冰下水系、冰床粗糙度以及冰晶组构上的进展。最后,对未来冰雷达探测研究南极冰盖的前景进行了展望,并给出我国的现状。
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Two-stage collision-related extrusion of the western Dabie HP–UHP metamorphic terranes, central China: Evidence from quartz c-axis fabrics and structures     

Sanzhong Li  Timothy M. Kusky  Xiaochun Liu  Guowei Zhang  Guochun Zhao  Lu Wang  Yuejun Wang 《Gondwana Research》2009,16(2):294

The western Dabie orogen (also known as the Hong'an block) forms the western part of the Dabie–Sulu HP–UHP belt, central China. Rocks of this orogen have been subjected to pervasive ductile deformation, and include numerous quartz schists and felsic mylonites cropping out in ductile shear zones. Quartz textures in these mylonites contain important clues for understanding the movement sense of late-collisional extrusion and exhumation of high-pressure–ultrahigh-pressure (HP–UHP) rocks from the lower crustal level to the upper crustal level during Middle Triassic and Early Jurassic. The orientation and distribution of quartz crystallographic axes were used to confirm the regional shear sense across the orogen. The asymmetry of c-axis patterns consistently indicates top-to-the-southeast thrusting across the orogen in early structural stages. Later stages of deformation show different senses of movement in northern and southern parts of the orogen, with top-to-the-northwest sinistral shearing recorded in rocks north of the Xinxian HP–UHP eclogite-facies belt, and top-to-the-southeast dextral shearing south of the same unit.Based on our study on quartz c-axis fabrics and marco- to micro-scale structures, simultaneous southeastward shearing within a large part of the orogen and normal faulting north of the Xinxian HP–UHP unit is explained by upward extrusion in early stages of deformation. The extrusion process has been attributed to syn- and late-collisional processes, accounting for some earlier deformation in the western Dabie orogen such as metamorphic sequences around the core of the Xinxian HP–UHP eclogite-facies unit. Much higher pressure of deformation is also indicated in the aligned glaucophane and omphacite from blueschist and eclogite in the field. An orogen-parallel eastward extrusion of the Xinxian HP–UHP eclogite-facies unit, however, occurred diachronously in later stages of deformation. Therefore, a tectonic model combining an early upward extrusion with a later eastward extrusion is presented. Two different stages and types of extrusion for exhumation of HP–UHP rocks are suitable to all of east central China. Geochronological data shows that the first, upward extrusion occurred during Middle Triassic, the second, eastward extrusion occurred during Late Triassic to Early Jurassic. These two extrusions are correlative with two stages of rapid exhumation of the Dabie HP–UHP rocks, respectively. These two-stage late-collisional (Middle Triassic to Early Jurassic) extrusion events bridge the gap between syn-collisional (Early to Middle Triassic) vertical extrusion and post-collisional (Cretaceous) eastward-directed lateral escape and provide vital clues to understanding the more detailed processes of exhumation of HP–UHP rocks.  相似文献   

Deformation temperatures and flow vorticities near the base of the Greater Himalayan Series,Sutlej Valley and Shimla Klippe,NW India     

《Journal of Structural Geology》2013

We report new deformation temperature and flow vorticity data from the base of the Greater Himalayan Series (GHS) exposed in the Sutlej Valley and Shimla Klippe of NW India. We focus on three groups of transects across the hanging wall of the Main Central Thrust (MCT). In order of relative foreland – hinterland positions, they are the Shimla Klippe, Western and Eastern Sutlej transects. Deformation temperatures indicated by quartz c-axis fabric opening-angles increase both from foreland to hinterland at a given structural distance above the MCT and up structural section from the MCT within individual transects. Deformation temperatures in the immediate hanging wall to the MCT are estimated at ∼510–535, 535–550 and 610 °C on the Shimla, Western Sutlej and Eastern Sutlej transects, respectively. The steepest inferred field gradients in deformation temperatures are recorded adjacent to the MCT and progressively decrease up structural section following a power law relationship. Comparison with temperature estimates based on multi-mineral phase equilibria data suggests that penetrative shearing occurred at close to peak metamorphic conditions. Vorticity analyses indicate that shearing along the base of the GHS occurred under sub-simple shear conditions (Wm values of 0.9–1.0) with a minor component of pure shear.  相似文献   

Quartz fabrics and recumbent folds in the Sierra de Los Filabres (SE-Spain)     

Willem Arend Zevenhuizen 《Geodinamica Acta》2013,26(1):95-105

Abstract

An important generation of recumbent folds can be recognized in the Nevado-Filabride nappe complex in the Sierra de los Filabres in SE Spain.

Folding post-dates an initial phase of flattening and is prior to the main phase of non-coaxial deformation and thrusting in the upper part of the complex, involved in a large-scale movement zone with dominant sense of shear to the northwest.

Axial planes and axes of these folds are aligned sub-parallel to the plastic flow plane in quartz and the shear direction respectively. Relict quartz fabrics can be found however, which strongly suggest that some fold axes originated in this position and did not rotate towards parallelism with the shear direction. This apparently contradicts the generally accepted model of development of folds in mylonite zones.

The redistribution of linear structures of the older flattening fase over the folds, confirms that the original orientation of fold axes was close to the present and indicates that an important component of flexural slip was involved in fold formation.  相似文献   

差应力与石英组构关系的实验研究     

马瑞  田海民  张刚 《吉林大学学报(地球科学版)》2009,39(1):89

为了探讨柯石英的形成条件,利用河北省平山县西柏坡地区太古代阜平群中的黑云母片麻岩进行高温高压条件下的岩石变形实验。实验的温度为800 ℃,围压为0.2 GPa,应变量为10%,应变速率为10^-5/s。实验结果表明,变形后样品中不同部位石英颗粒的激光拉曼光谱与标准的石英光谱相比较发生了明显的变化,具体表现为：挤压带中,石英颗粒的光谱出现了9个峰,而标准石英光谱为6个峰;在剪切带中,石英颗粒的谱线只有一个清晰的峰,在拉伸带中,石英颗粒的谱线无论峰的数目还是出现的位置都与标准石英光谱有着显著的区别,说明导致岩石变形的差应力对石英晶格结构的改造具有一定的影响。  相似文献   

龙门山飞仙关断层传播褶皱磁组构特征及构造意义   总被引：3，自引：0，他引：3  

胡潜伟  贾东  陈竹新  罗良  贾秋鹏 《高校地质学报》2005,11(4):649-655

沿龙门山南段冲断前锋带飞仙关断层传播褶铍剖面钻取了270个磁组构定向岩芯样品,对其进行了磁性矿物与磁组构分析。通过等温剩磁和三轴热退磁实验确定了样品中的主要载磁矿物为赤铁矿。磁组构测试结果显示27个采样点的磁组构为中间组构与构造组构两种类型。通过对各点磁组构特征及各项磁组构参数进行详细分析,再结合断层传播褶皱运动学模型,得出断层传播褶皱形成过程中岩石应变及磁组构演化：断层扩展前的平行层缩短作用把原始的沉积组构改造成为中问组构;在断层扩展过程中,两翼地层的旋转抬升产生的简单剪切作用对地层磁化率各向异性产生影响,使得校正的磁化率各向异性度Pj值局部升高,以及在剪切变形强烈的区域形成构造磁组构。  相似文献   

Emplacement of the Ardara pluton (Ireland): new constraints from magnetic fabrics, rock fabrics and age dating     

S. Siegesmund  J. K. Becker 《International Journal of Earth Sciences》2000,89(2):307-327

The Ardara pluton as part of the Donegal batholith was intruded into Neoproterozoic metasediments and metadolerites at mid-crustal levels. The emplacement mechanism of the Ardara granite is very controversial, and mechanisms ranging from diapirism, ballooning and stoping followed by nested diapirism have been proposed. Magnetic fabrics, rock fabrics and K/Ar dating of micas are used here to constrain the emplacement history. The compositional zoning of the Ardara pluton is clearly reflected in the different bulk magnetic susceptibilities between the outer quartz monzodiorite and the central granodiorite, whereas the intervening tonalite is of intermediate nature. The magnetic carriers are characterized by the anisotropy of the magnetic susceptibility (AMS), thermomagnetic measurements and through high field analyses (HFA). The separation of the ferrimagnetic and paramagnetic contributions revealed that biotite and magnetite control the AMS in the quartz monzodiorite. Both minerals are oriented in such a way that their summed contribution is constructive and originates from the shape fabric of magnetite and the texture of biotite. Biotite is responsible mainly for the AMS in the tonalite and granodiorite. The magnetic foliation can be directly related to the macroscopic foliation and also to the D4 structures in the country rocks. The foliation is consistent with the geometry of the roughly circular shape and has a mostly steep to vertical dip. Towards the central granodiorite the magnetic foliation dies out, although plagioclase texture measurements indicate a weak magmatic shape fabric. With the exception of the tail, the K_max axes (magnetic lineation) vary from steeply to gently plunging. The so-called lineation factor is approximately 1.01 and therefore points to a less significant axial symmetry. These observations coincide with strain estimates on mafic enclaves that show a very consistent pattern of K ∼0 flattening strain. Texture analyses of biotite and quartz additionally support the observations made by the strain analyses and the magnetic fabric data. Microstructural investigations give evidence that the fabrics are associated with the emplacement over a range of temperatures from truly magmatic to high-temperature solid-state conditions. The age of the intrusion is still under discussion, but a new cooling age was determined by K/Ar dating of biotite at 403.7±8 Ma corresponding to a temperature range between 450 and 300°C. For a mylonite along the southern contact between the Ardara pluton and the country rock a K/Ar muscovite age of 378.8±7 Ma indicates a minimum age for the shear zone when the Ardara pluton must have already been cooled down below 350±50°C. Received: 28 January 1999 / Accepted: 28 December 1999  相似文献   

凤凰山花岗岩体构造系统分析及侵位机制   总被引：7，自引：1，他引：6  

李东旭  张达  刘文灿  杜子图 《地质力学学报》1996,2(2):55-65

本文从宏观上对凤凰山岩体的区域构造位置、岩体侵位前后的构造演化过程及岩浆侵位时的动力学条件进行了论述;对岩体内部及接触带的面理、线理进行了磁组构测量、显微构造观察、包体应变测量及X光组构分析等系统研究,最终获得如下结论:该岩体侵位除有膨胀作用外,在岩体侵位后期还有过旋转运动,而且岩体侵位受到NNE向左旋剪切作用控制。   相似文献   

华北南缘古元古代末岩墙群侵位的磁组构证据   总被引：7，自引：3，他引：4  

侯贵廷  王传成  李乐 《岩石学报》2010,26(1):318-324

华北克拉通南缘的中条山及邻区广泛发育元古宙放射状基性岩墙群,与五台山-恒山和大同地区的北北西向基性岩墙群以及熊耳中条拗拉谷的火山岩在时空分布和地球化学方面均具有密切的相关性。中条山及邻区放射状基性岩墙群的宏观和微观流动构造(包括捕虏体、冲痕构造、矿物线理和定向斑晶)指示岩墙群以一定的仰角向北西侵位。通过该区岩墙群磁化率各向异性(AMS)测量得到磁组构的最大磁化率长轴优势方位分布图和磁组构各向异性特征分析进一步指示华北南缘古元古代末岩墙群从熊耳中条拗拉谷的底部向北西侵位。岩墙群的流动构造和磁组构的统计成果夯实了华北克拉通古元古代末基性岩墙群与熊耳中条拗拉谷的成生联系。  相似文献   

河南西南部典型白垩纪剖面的岩石磁组构特征及其构造意义   总被引：3，自引：0，他引：3  

李震宇  黄宝春  张春霞 《岩石学报》2010,26(11):3418-3430

对河南西南部西峡盆地阳城-丹水上白垩统岩石磁学、磁组构的研究表明,该陆相沉积地层磁性矿物以及特征剩磁载体以赤铁矿为主,并含少量磁铁矿,且磁铁矿与赤铁矿相对含量比例随剖面由老到新显示出逐渐增加的趋势。岩石磁组构主要受顺磁性矿物以及反铁磁性矿物的控制。全剖面磁化率椭球结果显示在原生沉积组构基础上叠加了最早期阶段的弱变形组构;同时,全剖面以及各岩石地层单元磁化率椭球体主轴方向的变化揭示了两个不同方向及大小的构造挤压作用导致磁化率最大轴从NNW-SSE向转至NW-SE向,后又到NNW-SSE向的变化模式,一方面是由于华南、华北板块NE-SW向的构造挤压导致;另一方面是由两板块构造挤压而引起的桐柏-大别造山带上地壳物质相对下地壳发生东向构造逃逸和挤出过程中与东部块体物质间发生的挤压作用引起,这两种不同的挤压应力作用在盆地发展的不同阶段各占主要地位。  相似文献