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西秦岭是青藏高原构造域在东北缘向东西向展布的祁连-秦岭-大别构造带转换的重要地区.作为印度-欧亚大陆碰撞及青藏高原隆升的响应,西秦岭地区自中生代以来火山作用非常强烈. 相似文献
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《地学前缘》2017,(5):230-244
西秦岭北缘断裂带新生代以来挤压逆冲变形起始于何时?挤压逆冲变形之前是否经历过伸展拉张过程?北缘断裂带北侧的新生代红层盆地到底是类前陆压陷挠曲盆地还是拉张断陷盆地?上述问题对西秦岭新生代盆-山构造格局重建和印度-欧亚板块碰撞汇聚的远程构造响应的时间与方式等科学问题的认识具有重要的地质约束。本文通过对西秦岭北缘构造带内漳县渐新世—中新世含盐红层盆地沉积序列和沉积旋回特征以及盆地边界断裂之间的几何学-运动学关系分析,认为西秦岭北缘构造带内漳县含盐红层盆地具有拉张伸展动力学背景下形成的断陷盆地的地质特征。西秦岭北缘构造带内渐新世—中新世断陷盆地的确定,指示了印度板块与欧亚板块碰撞汇聚而导致的青藏高原构造挤压缩短作用至少在盆地沉积充填阶段尚未扩展到西秦岭北缘及以北地区。而漳县含盐红层盆地沉积地层褶皱缩短变形以及之后角度不整合在漳县含盐红层盆地之的上新统韩家沟粗砾岩,可能记录了西秦岭北缘由伸展边界向挤压缩短逆冲边界的转换过程。因此,青藏高原东北缘真正成为青藏高原体系组成部分是在上新世的漳县含盐红层盆地封闭-构造反转之后。这一认识对地学界长期以来认为印度板块与欧亚板块碰撞汇聚而导致的高原隆升和构造挤压早在渐新世就已经波及西秦岭北缘的观点提出了挑战。 相似文献
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西秦岭位于青藏高原东北缘重力梯度带内,是高原物质向北、向东扩展的前缘,其新生代以来地质构造 地貌过程应该是印度板块-欧亚板块的碰撞造山过程和高原隆升过程的一部分。通过对西秦岭内部中-新生代沉积、变形及地貌记录的初步综合分析,得出如下初步认识:(1)根据西秦岭中-新生代红层沉积岩石组合和构造变形特征,可以分为晚侏罗世-早白垩世、晚白垩世-古近纪和新近纪三个构造层,分别对应于西秦岭新生代3个构造演化阶段。(2)西秦岭晚白垩世-古近纪构造层的褶皱缩短和区域断裂带的逆冲推覆发生在古近纪末期-新近纪初期,与整个青藏高原主要逆冲推覆构造事件同步,说明印度板块与欧亚板块碰撞的构造应力在古近纪末已波及至西秦岭。(3)西秦岭新近纪以来经历了一个构造相对稳定的侵蚀夷平期,于36 Ma之前形成了以晚白垩世-古近纪构造层侵蚀面、前新生代碳酸盐地层的岩溶夷平面为标志的主夷平面以及夷平面发育过程中形成新近纪近水平的、以红色粘土岩为主要特征的细碎屑沉积。这一夷平面可以作为高原组成部分的西秦岭隆升的基准面。该夷平面现今高程自西向东逐渐降低,反映了西秦岭隆升呈现自西向东连续的扩展。(4)青藏高原南部构造变形方式在中新世发生了由逆冲推覆 褶皱缩短向伸展走滑的构造转换,而在西秦岭内部却并未发生这样的构造转换,仍然以逆冲构造为主,只是西秦岭北缘的边界断层在中-晚更新世才发生逆冲 左旋走滑作用,这可能指示了青藏高原东北缘晚新生代构造变形的走滑作用只是构造块体边界与构造挤压应力方向下非正交的应力分解所致,同时也可能反映了作为西秦岭块体整体滑移和块体内部的收缩变形并行不悖。(5)由GPS观测数据确定的区域位移场应该指示了现今西秦岭块体的整体缓慢的向东移动,地震机制解确定的构造应力是下地壳向东蠕动拖曳脆性上地壳的整体运动,西秦岭地壳厚度由西向东逐渐增厚是西部由于南北向缩短增厚的下地壳向东扩展流动的结果,增厚地壳的均衡抬升是西秦岭地貌面高度变化的内在原因。 相似文献
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西秦岭位于青藏高原东北缘由挤压走滑向走滑伸展构造的转换地带,成为研究青藏高原晚新生代构造扩展过程的重要构造部位。在西秦岭地区发育的一系列新近纪盆地作为高原物质向外扩展的载体,记录了扩展过程中不同阶段的构造活动和演化信息。文中选择位于成县-太白山断裂内的安化-成县盆地,通过对该盆地沉积过程与构造变形方面的详细研究,确定了盆地在新近纪晚期的两阶段构造演化历史。早期受迭部-白龙江、成县-太白山弧形断裂左行走滑的影响,在弧顶及以东位置发生走滑伸展,形成长条形的地堑半地堑盆地。同期沿青川断裂、西秦岭北缘断裂、礼县-罗家堡断裂以及西和断裂分别形成了汉中盆地、武山盆地、天水盆地以及西和盆地。这些走滑断裂向东扩展可能控制了渭河地堑约9 Ma以来的NWSE向伸展,并伴随华山、太白山以及西秦岭东段10~4 Ma的快速隆升。在4.2~2.5 Ma期间,受断裂运动学调整的影响,西秦岭地区新近纪盆地遭受挤压而发生构造反转。新近纪盆地的形成与反转历史清楚地记录了青藏高原东北缘新近纪晚期向东构造挤出的过程。 相似文献
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新生代以来印度-欧亚板块持续碰撞汇聚形成号称世界第三极的青藏高原。青藏高原的扩展生长和构造变形系统形成的动力学过程是地球科学研究的重大科学问题。青藏高原东北缘新生代以来构造演化过程及其与印度-欧亚板块碰撞汇聚的动力学耦合关系研究对于揭示青藏高原扩展生长过程具有重要地质意义。尽管前人已经开展了大量研究探索,提出各种构造-隆升模型,但青藏高原东北缘何时卷入印度-欧亚碰撞汇聚的青藏高原构造系统尚未达成共识。作为青藏高原东北缘组成部分的西秦岭北缘构造带漳县地区不仅新生代地层记录齐全,而且断裂构造发育,构造变形现象丰富,是研究青藏高原东北缘新生代构造演化及印度-欧亚碰撞汇聚远程构造响应的良好区域。通过对西秦岭北缘构造带漳县地区新生代沉积盆地地层构造格架、沉积地层序列和沉积旋回等详细野外观测研究,结合区域断裂带几何学-运动学及变形历史分析,取得如下认识:(1)西秦岭北缘漳县地区新生代沉积地层主要由为不整合分隔的两套构造性质完全不同的构造地层单元组成,即渐新世—中新世伸展断陷盆地沉积和上新世再生前陆磨拉石盆地沉积;(2)渐新世—中新世时期的地壳伸展拉张构造环境与印度-欧亚碰撞汇聚的挤压环境相悖,指示了西秦岭北缘在渐新世—中新世尚未卷入现今的印度-欧亚碰撞汇聚构造系统;(3)上新世磨拉石盆地的发育标志着西秦岭北缘构造带从伸展到挤压的构造体制转换,可能指示了印度-欧亚碰撞汇聚的挤压构造作用这时才波及西秦岭北缘;(4)上新世粗砾岩、西秦岭造山带地层和中生代沉积地层共同经历了抬升剥蚀作用,形成了西秦岭北缘广泛发育的夷平面。第四纪以来夷平面的抬升和解体、现代河流侵蚀系统和多级河流阶地的出现,指示了青藏高原东北缘整体的不均匀大规模抬升而进入现今青藏高原构造系统。 相似文献
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松潘地块若尔盖盆地与西秦岭造山带岩石圈尺度的构造关系——深地震反射剖面探测成果 总被引：19，自引：2，他引：17
若尔盖盆地和西秦岭造山带作为青藏高原东北缘典型的新生代盆山构造,其接合部位的岩石圈结构及其深部构造关系为青藏高原东北缘板块碰撞的深部过程等研究奠定基础。横过盆山结合部位的深地震反射剖面长约63km,记录时间30s(TWT),探测深度超过莫霍面深达岩石圈地幔。该剖面首次揭露出青藏高原东北缘的盆山结合部位地壳和上地幔盖层的结构,发现了若尔盖盆地和西秦岭造山带下地壳以北倾为主的强反射特征,这种北倾的反射特征提供了若尔盖盆地俯冲到西秦岭造山带之下,而西秦岭造山带逆冲推覆到若尔盖盆地之上的地震学证据,初步揭示出若尔盖盆地和西秦岭造山带在挤压构造体系下形成的岩石圈尺度的构造关系,近于平坦的Moho反射特征反映两者在造山后期又经历了强烈的伸展作用。 相似文献
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松潘地块与西秦岭造山带下地壳的性质和关系——深地震反射剖面的揭露 总被引：28，自引：1，他引：28
松潘地块位于青藏高原的东缘，处于中国大陆东西向构造与南北向构造的结合部位，特殊的构造环境使其长期控制并影响着中国大陆的形成与演化。探测松潘地块的岩石圈细结构，揭示其与东昆仑-西秦岭造山带的关系，既可为研究青藏高原东北缘板块碰撞的深部过程奠定基础，同时又关联着松潘地块的油气远景评价。2004年完成了第一条横过松潘地块北缘若尔盖盆地和西秦岭造山带的长约257km的深地震反射剖面，首次揭露出若尔盖盆地和西秦岭造山带岩石圈的细结构。发现若尔盖盆地和西秦岭造山带同属统一的稳定的大陆地块，并且下地壳均以北倾的强反射为主要特征。这种北倾的反射为松潘地块向西秦岭下地壳俯冲提供了地震学证据。近于平坦的Moho反射特征反映出西秦岭造山带在造山后又经历了强烈的伸展作用。 相似文献
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豫西地区中上三叠统主要出露在济源、义马、伊川和南召一带。印支期秦岭造山运动控制和影响着邻区中上三叠统盆地属性和沉积地层展布。通过观察研究区野外露头剖面,发现中上三叠统发育一系列典型的软沉积变形构造,包括液化底辟、枕状构造、液化柱、液化卷曲变形、负载、球-枕、火焰状构造、液化角砾岩。这些软沉积变形在垂向上表现出明显的复现性,在侧向上表现为沿地层连续展布,表明该时期研究区内地层受到频繁强烈的地震影响。通过对这些软沉积现象的识别和形成机制解释,判定其触发因素为秦岭造山过程中伴生的地震。区内地层中震积岩的存在即是对秦岭造山过程中构造活动的响应。 相似文献
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对西秦岭北缘漳县地区上新统韩家沟砾岩的地貌特征、高程分布、沉积特征、构造变形等研究表明：1）该套砾岩分布受西秦岭北缘断层系F2逆冲断层控制,主要由巨砾-中砾砾岩组成,有近源快速磨拉石沉积的特征,代表了上新世以来西秦岭地块沿北缘断层向北逆冲挤出形成的再生前陆磨拉石盆地,指示了西秦岭地块上新世以来的一次强烈的构造隆升。2）这套砾岩出露高程及宏观地貌特征指示了其形成之后又与西秦岭地块一起经历了侵蚀夷平,形成了现今海拔2 600 m 左右统一的夷平面。该夷平面的整体隆升和解体、韩家沟砾岩雅丹地貌形成和发育六级侵蚀阶地或基座阶地的漳河水系形成才真正标志着西秦岭及北缘区域的整体隆升。现今海拔1 800 m 漳河河床与2 600 m 山顶夷平面之间的高差反映了西秦岭及其北缘第四纪以来至少相对隆升了800 m。3）西秦岭北缘漳县韩家沟砾岩下伏的渐新统-中新统红层盆地沉积序列具有伸展断陷盆地充填特征,指示了这个时期西秦岭北缘处于拉张伸展构造状态,也就是说以构造挤压缩短为动力学背景下的青藏高原隆升和构造变形在渐新世-中新世时期尚未扩展至西秦岭北缘区域。尽管该断陷盆地最上部河流相-洪泛相粗碎屑沉积增多和之后地层掀斜及褶皱缩短有可能反映了中新世末或上新世初西秦岭北缘由伸展到挤压的构造转换和构造隆升,但这并不是西秦岭及北缘区域的一次强烈隆升。综上所述,我们认为西秦岭北缘上新统韩家沟砾岩出现标志着西秦岭地块向北强烈逆冲和构造隆升,但西秦岭的这次强烈隆升仅持续到上新统韩家沟砾岩沉积结束,之后西秦岭地块和北部的再生前陆磨拉石盆地一起经历了整体隆升和侵蚀夷平,形成了上新世末或第四纪初的统一夷平面。该山顶夷平面是西秦岭及其北缘区域最后整体强烈隆升的起点。韩家沟砾岩雅丹地貌形成、发育六级侵蚀阶地或基座阶地的漳河水系形成真正指示了西秦岭及北缘区域的整体隆升过程。如果西秦岭及其北缘新生代以来隆升过程在青藏高原东北缘具有代表性,那么就说明青藏高原东北缘真正隆升成为现今青藏高原系统组成部分只是上新世末期或第四纪以来地质事件。 相似文献
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GPS观测的活动断裂滑动速率及其对现今大陆动力作用的制约 总被引：51，自引：2，他引：51
活动断裂的滑动速率是晚第四纪构造变形的定量描述 ,是制约和研究现今大陆动力过程的重要基础数据。地震地质学研究给出主要活动断裂的长期和平均运动水平 ,横跨断裂的GPS观测能够提供断裂的现今滑动速率。文中利用重大科学工程“中国地壳运动观测网络”的 10 0 0多个GPS观测站的复测数据 ,计算中国大陆主要活动断裂的现今滑动速率。发现主要活动断裂的GPS滑动速率与晚第四纪滑动速率在运动方式和运动量上是大体一致的。从GPS观测到的断层滑动速率来看 ,中国大陆的大多数活动断裂的速率都在 10mm/a之下 ,而没有类似于板块边界的大于 2 0 30mm/a的滑动速率。这种现象意味着整个中国大陆的构造变形可能是分布式的 ,而不是仅仅集中在少数几条大型活动构造带上 ,沿主要活动断裂的刚性块体滑移可能不是构造变形的主要方式。现今构造变形的分块运动图像可能只是脆性上地壳的变形方式 ,中下地壳和上地幔的运动则以连续变形为特征 ,从下部驱动脆性上地壳的变形和运动 ,使得上部地壳的变形既表现出分块特征 ,又发生块内的变形。“连续变形”理论模型能够更好地描述大陆内部的构造变形。 相似文献
12.
Active Faulting Pattern,Present‐day Tectonic Stress Field and Block Kinematics in the East Tibetan Plateau 总被引：9，自引：1，他引：8
Abstract: This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region. It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field, except for the west Qinling range where it parallels the striking of the major strike-slip faults. Active tectonics in the East Tibetan Plateau is characterized by three faulting systems. The left-slip Kunlun-Qinling faulting system combines the east Kunlun fault zone, sinistral oblique reverse faults along the Minshan range and two major NEE-striking faults cutting the west Qinling range, which accommodates eastward motion, at 10–14 mm/a, of the Chuan-Qing block. The left-slip Xianshuihe faulting system accommodated clockwise rotation of the Chuan-Dian block. The Longmenshan thrust faulting system forms the eastern margin of the East Tibetan Plateau and has been propagated to the SW of the Sichuan basin. Crustal shortening across the Longmenshan range seems low (2–4 mm/a) and absorbed only a small part of the eastward motion of the Chuan-Qing block. Most of this eastward motion has been transmitted to South China, which is moving SEE-ward at 7–9 mm/a. It is suggested from geophysical data interpretation that the crust and lithosphere of the East Tibetan Plateau is considerably thickened and rheologically layered. The upper crust seems to be decoupled from the lower crust through a décollement zone at a depth of 15–20 km, which involved the Longmenshan fault belt and propagated eastward to the SW of the Sichuan basin. The Wenchuan earthquake was just formed at the bifurcated point of this décollement system. A rheological boundary should exist beneath the Longmenshan fault belt where the lower crust of the East Tibetan Plateau and the lithospheric mantle of the Yangze block are juxtaposed. 相似文献
13.
The north–south trending Xiaojiang fault system accommodates ～10–12 mm/yr sinistral motions between southeastern Tibet and south China. In the south segment, the fault system composes mainly of four parallel strike-slip faults, namely from west to east, the Luzhijiang fault, the Yimen fault, the Puduhe fault, and the Xiaojiang fault. Geological and Seismological observations have shown that these strike-slip faults are all of active, while the slip rates of the Luzhijiang, the Yimen, and the Puduhe faults are much less than that of the Xiaojiang fault. We use finite element modeling to explore the mechanical relation between crustal rheology, effective fault friction and long-term slip rate partitioning among the four parallel faults. The individual faults are simplified as vertical discontinuities embedded in the crust as geophysical explorations have predicted. A large number of models are tested, associating with variations of the crustal rheolohy and the effective fault friction of individual faults. Result shows that if crust bounding the faults trends to behave like rigid blocks and decoupled mechanically from underlying layer, the modeled result is hard to approximate slip rates of the individual faults. To better fit slip rates of the individual faults, viscous deformation of the lower crust should be included. With a heterogeneously viscous lower-crust model that is built upon thermal structure of the heat flow data, associating with relatively low effective friction of the Xiaojiang fault, the modeled results fit the geological slip rates well, with ～1–1.5 mm/yr for the Luzhijiang, the Yimen and the Puduhe faults, and ～6–6.5 mm/yr for the Xiaojiang fault. Thus, in the southward movement of the Tibetan plateau around the eastern Himalayan syntaxis, slip partitioning among the Xiaojiang fault system should be related to viscous deformation of the lower crust associated with different strength of the individual faults, highlighting that deformation of this fault system is coupled mechanically between the frictional upper crust and the viscous lower crust. 相似文献
14.
Active Faulting Pattern,Present-day Tectonic Stress Field and Block Kinematics in the East Tibetan Plateau 总被引：1，自引：0，他引：1
ZHANG Yueqiao DONG Shuwen YANG Nong Key Laboratory of Neotectonic Movement Geohazard Ministry of L Resources Beijing China Institute of Geomechanics Chinese Academy of Geological Sciences China Chinese Academy of Geological Sciences Beijing China 《《地质学报》英文版》2009,83(4)
This paper examines major active faults and the present-day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region.It shows that the East Tibetan Plateau is dominated by strike-slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field,except for the west Qinling range where it parallels the striking of the major strike-slip... 相似文献
15.
《Gondwana Research》2014,25(3-4):946-957
In addition to crustal thickening, distinctly different mechanisms have been suggested to accommodate the huge convergences caused by the continental collision between India and Eurasia. As the transition zone between the two grand tectonic domains of Asia, the Tethys and the Pacific, east Tibet and its surrounding regions are the ideal places to study continental deformation. Pervasive rock deformation may produce anisotropy on the scale of seismic wavelengths; thus, seismic anisotropy provides insight into the deformation of the crust and mantle beneath tectonically active domains. In this study, we calculated receiver function pairs of radial- and transverse-components at 98 stations located in Sichuan and Yunnan provinces, China. We selected 7423 pairs with high signal-to-noise ratio (SNR) and unambiguous Moho converted Ps phases (Pms) to measure the Pms splitting owing to the crustal anisotropy. Both the crustal thickness and the average crustal Vp/Vs ratio were calculated simultaneously by the H–k stacking method. The geodynamic implications were also investigated in relation to surface geological features, GPS velocities, absolute plate motion (APM), SKS/SKKS splitting, and other seismological observations. In addition to the fast polarization directions (FPDs) of the crustal anisotropy, we observed a conspicuous sharper clockwise rotation around the eastern Himalayan syntaxis than was revealed by GPS velocities. The distributed FPDs within and near the main active fault zones also favored the directions parallel to the faults. This implied that the deformation of a continuous medium revealed by GPS motions is a proxy for the deformation of the brittle shallow crust only, while the main active faults and the deep crustal interiors both play important roles in the deep deformation. Our results suggest that the deformation between the crust and upper mantle within the northernmost section of the Indochina block is decoupled due to the large difference in the directions between the observations related to the crust (GPS and crustal anisotropy) and mantle (APM and mantle anisotropy). Focusing on the transition zone between the plateau and the South China and Indochina blocks, we suggest that the motion of the Central Yunnan sub-block is a southeastward extrusion by way of tectonic escape. There is less deformation in the deep crust and the motion is controlled by the active boundary faults of the Ailaoshan–Red River shear zone to the west and the Xianshuihe–Xiaojiang fault to the east; the lower crustal flow within the plateau southeastward reached the Lijiang–Xiaojinhe fault, but further south it was obstructed by the Central Yunnan sub-block. 相似文献
16.
东昆仑、玉树、汶川地震的发生规律和形成机理:兼论大陆地震成因与预测 总被引：6，自引：3，他引：3
青藏高原东北部东昆仑、汶川、玉树等强震的同震地表破裂不对称发育,伴随余震有规律地分别向东、南东和北北东方向迁移,很可能是源于恒河盆地流经亚东、当雄、安多、库赛湖、治多、玉树、甘孜、汶川的弧形下地壳“热河”的流速和流向变化形成的,下地壳热流物质正在向云南及邻区汇聚形成下地壳“热海”,导致长时间跨季度构造热干旱,其影响超过大气环流的作用。地表破裂不一定受断层控制,震源也不在断层面上,下地壳流动导致中地壳发震并进一步影响上地壳形成同震脆性破裂系统。大陆板内盆山过渡带地震密集,大陆板内地震是在下地壳层流的热动力作用下导致活动地壳分层变形的产物。在大陆盆山耦合、圈层耦合的非线性开放系统中,从大洋底部的软流圈层流进入大陆底部使得地幔软流圈加厚,底辟上升为大陆下地壳流动,为地震活动提供了巨量热能;热软化的下地壳缓慢的韧性流动孕育了大陆板内地震;中地壳韧 脆性剪切带易于积累能量,发生热能与应变能的转化,产生地震,形成震源层;上地壳脆性断层活动和地表破裂是地震释放深部能量的载体和方式之一。地壳稳定性评价的依据应当是地壳的活动性而不是断层的活动性。大陆活动构造区地震活跃期与平静期交替实际上是下地壳地震能量的聚散过程,体现在下地壳热主导的韧性流动构造与上地壳应力主导的脆性破裂构造之间的相互作用。下地壳热软化物质流动过程中流速、流向等突然改变触发地震,并产生共振波。大陆下地壳流层在厚度、温度、粘度、流速、流向上的变化产生一定程度的温度异常、流体异常及与其相关的大气层、电场、磁场、重力场、地球化学场、应力场、应变场、生物场等异常。合理布置天空网、地面网、地下网,综合立体监测有效的地震前兆,系统地开展长期、中期和短临地震预测,能够不断地提高地震预测水平。 相似文献
17.
大陆构造变形与地震活动——以青藏高原为例 总被引：5，自引：0，他引：5
大陆内部构造变形和地震活动往往突显出复杂的、区域性的特征,很难用板块构造理论来解释。青藏高原是大陆构造变形的典型实例,具有不同构造变形的分区特征,不仅表现在物质组成、地形地貌和断裂组合等方面的不同,而且还表现出不同的地震活动特征。东昆仑断裂带以北的青藏高原北部地块,主要发育一系列挤压环境下的盆岭构造,表现为以连续变形为特征的上地壳挤压缩短变形;高原中北部巴颜喀拉地块,具有整体向东运动的特点,变形主要集中在其边缘,表现为刚性块体运动特征。在东部,由于稳定的四川盆地(扬子地块)的阻挡,位于龙日坝和龙门山断裂带之间相对坚硬的龙门山地区受到东西向强烈挤压,西部边界为伸展变形;在高原中央腹地羌塘地块西部,由于上地壳物质在向东挤出的驱动下不断变形,沿一系列小型正断层和走滑断层以伸展变形为主,表现为弥散型变形特征。相比之下,羌塘地块的东部向东-南东方向挤出,在大型走滑断层之间形成一个刚性块体;高原南部地块以东西向伸展的南北向裂谷系为主要变形特征,高原南缘以南北向挤压的大型逆冲断裂系为特征。历史地震和仪器记录的大地震(M≥8)只发生在高原东北和东南部的大型走滑带,以及东部和南部边缘的大型逆冲断裂上,沿后者更为频发。到目前为止,高原其他地区只发生了8级以下地震。青藏高原这种分区域的地壳变形形式和地震活动分布是大陆构造变形的重要特征。 相似文献
18.
T. V. Romanyuk 《Geotectonics》2009,43(4):305-323
The presented model of the Late Cenozoic geodynamic evolution of the central Andes and the complex tectonic, geological, and geophysical model of the Earth’s crust and upper mantle along the Central Andean Transect, which crosses the Andean subduction zone along 21°S, are based on the integration of voluminous and diverse data. The onset of the recent evolution of the central Andes is dated at the late Oligocene (27 Ma ago), when the local fluid-induced rheological attenuation of the continental lithosphere occurred far back of the subduction zone. Tectonic deformation started to develop in thick-skinned style above the attenuated domain in the upper mantle and then in the Earth’s crust, creating the bivergent system of the present-day Eastern Cordillera. The destruction of the continental lithosphere is correlated with ore mineralization in the Bolivian tin belt, which presumably started at 16° S and spread to the north and to the south. Approximately 19 Ma ago, the gently dipping Subandean Thrust Fault was formed beneath the Eastern Cordillera, along which the South American Platform began to thrust under the Andes with rapid thickening of the crust in the eastern Andean Orogen owing to its doubling. The style of deformation in the upper crust above the Subandean Thrust Fault changed from thick- to thin-skinned, and the deformation front migrated to the east inland, forming the Subandean system of folds and thrust faults verging largely eastward. The thickening of the crust was accompanied by flows at the lower and/or middle crustal levels, delamination, and collapse of fragments of the lower crust and lithospheric mantle beneath the Eastern Cordillera and Altiplano-Puna Plateau. As the thickness of the middle and lower crustal layers reached a critical thickness about 10 Ma ago, the viscoplastic flow in the meridional direction became more intense. Extension of the upper brittle crust was realized mainly in gliding and rotation of blocks along a rhombic fault system. Some blocks sank, creating sedimentary basins. The rate of southward migration estimated from the age of these basins is 26 km/Ma. Tectonic deformation was accompanied by diverse magmatic activity (ignimbrite complexes, basaltic flows, shoshonitic volcanism, etc.) within the tract from the Western Cordillera to the western edge of the Eastern Cordillera 27–5 Ma ago with a peak at 7 Ma; after this, it began to recede westward; by 5 Ma ago, the magmatic activity reached only the western part of the Altiplano-Puna Plateau, and it has been concentrated in the volcanic arc of the Western Cordillera during the last 2 Ma. 相似文献
19.
《China Geology》2020,3(2):314-338
The Yangtze River Economic Belt (YREB) spans three terrain steps in China and features diverse topography that is characterized by significant differences in geological structure and present-day crustal deformation. Active faults and seismic activity are important geological factors for the planning and development of the YREB. In this paper, the spatial distribution and activity of 165 active faults that exist along the YREB have been compiled from previous findings, using both remote-sensing data and geological survey results. The crustal stability of seven particularly noteworthy typical active fault zones and their potential effects on the crustal stability of the urban agglomerations are analyzed. The main active fault zones in the western YREB, together with the neighboring regional active faults, make up an arc fault block region comprising primarily of Sichuan-Yunnan and a “Sichuan-Yunnan arc rotational-shear active tectonic system” strong deformation region that features rotation, shear and extensional deformation. The active faults in the central-eastern YREB, with seven NE-NNE and seven NW-NWW active faults (the “7-longitudinal, 7-horizontal” pattern), macroscopically make up a “chessboard tectonic system” medium-weak deformation region in the geomechanical tectonic system. They are also the main geological constraints for the crustal stability of the YREB. 相似文献
20.
板块构造基本理论（特别是其刚性块体假设）能否应用于大陆，是大陆动力学研究所面临的主要问题之一，不同的理论模型给出不同的回答。缺乏完整、可靠的构造变形运动学图像使得无法对不同的理论模型给予约束和检验，以至于无法回答上述基本问题。本文以中国大陆及其周边近年来的1350个GPS观测资料为主，结合活动断裂和地震活动性资料，研究中国大陆现今构造变形的运动学特征。中国大陆的现今构造变形既有刚性地块的运动，如塔里木、鄂尔多斯、华南等地块；又有非刚性的连续变形，如青藏高原和天山。在大陆构造变形过程中，由于岩石圈性质的不同而造成变形的分区差异和上部脆性地壳的分块运动，不仅有整体性好的刚性地块运动，也有刚性很差的连续变形。以粘塑性流变为特征的下地壳和上地幔在周边板块作用下发生连续流动，从底部驱动着上覆脆性地块的运动，而不同活动地块本身的性质决定着地块的整体性和变形方式，中国大陆的现今构造变形可以用耦合的地块运动和连续变形模式来描述。 相似文献