青藏高原的现今构造变形与地球动力过程
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本文为国家自然科学基金项目(编号42030301)和广东省珠江人才计划项目的资助成果。


Present- day deformation and geodynamic processes of the Tibetan Plateau
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    摘要:

    作为地球陆地上最高、最大、最平坦的地貌单元,青藏高原晚第四纪—现今构造变形的运动学状态是研究其深部地球动力作用的重要基础。全球卫星导航系统能够观测几十年时间尺度的地壳运动定量资料,历史记载和仪器观测获得的历史地震资料提供着数百年时间尺度的构造运动和深部变形数据,而上万年时间尺度的活动断裂定量研究数据则揭示着长期、平均构造变形状态。综合这三类不同时间尺度的地表构造变形定量数据,就能够定性推测或定量模拟驱动地表构造变形的深部地球动力作用。本文综合利用上述三类资料,发现青藏高原晚第四纪—现今的运动状态受控于统一的应变场,地表与深部一致,现今与长期一致。最大剪切应变主要分布在高原周边的主要逆冲断裂带和内部的巨型活动走滑断裂带,产生众多的强震;收缩应变和地壳缩短主要发生在周边山系及其伴随的前陆盆地,形成逆冲断裂和逆冲型强震;面膨胀应变和地壳拉张发生在高海拔的青藏高原内部,形成近南北向正断层和北东/北西向共轭剪切断裂系,并控制着正断层型地震的发生;青藏高原的所谓“向东挤出”,不是刚性岩石圈地块在走滑断裂夹持下的向东滑移,而是高原内部岩石圈物质的向东流动和绕喜马拉雅东构造结的顺时针旋转。这种运动状态只能被青藏高原之下岩石圈地幔对流剥离动力学模型很好解释。被对流剥离的岩石圈沉入中下地幔时伴随着负浮力的产生,不仅使得青藏高原发生垂向隆升,还对周边施加水平挤压应力,从而造成高原周边准同期地向外逆冲扩展,导致了起始于晚新生代并延续至今的构造变形,形成所观测到的不同时段的构造变形运动场。

    Abstract:

    As the highest, the largest, and the flattest geomorphological unit, the kinematics of presentday surface tectonic deformation of the Tibetan Plateau is a fundamental to studies of geodynamic process in the depth.GNSS observations provide quantitative data of crustal deformation in the time scale of a few decades. Earthquakes data from historical and instrumental documentation can be used to obtain both tectonic deformation in time scale of hundred years and the deformation at earthquake focal depth. Quantitative active fault studies in the millennium time scale offer information on longterm and average tectonic deformation. Comprehensive synthesizing of these three types of data would be able to infer or model the geodynamics driving the surface deformation. This paper summarizes these three types of data in the Tibetan Plateau to study late Quaternary to present tectonic deformation. We discover that the style and kinematics of contemporary surface deformation coincide with longterm deformation at depth, and the overall deformation is probably controlled by a unified strain field. The calculated GNSS maximum shear strain mainly distribute along the megathrust faults around the Tibetan margins and the major active strikeslip faults within the plateau. Contraction straining and crustal shortening take place around the marginal mountains around the plateau and their associated foreland basins in association with thrust earthquakes. The expansional strain and crustal extension occur in the plateau interior that form NStrending normal faults and conjunction strikeslip fault system. Normal faulting and strikeslip earthquakes characterized seismic activity in the plateau interior. The so called “eastward extrusion” of rigid block is in fact an eastward movement of crustal material and clockwise rotation around the Eastern Himalaya Syntax. The primary style and kinematics of presentday tectonic deformation of the Tibetan Plateau can be interpreted by geodynamic model of “convective removal of mantle lithosphere”. The convectively removed mantle lithosphere subsides to middle and lower mantle, and generates negative buoyancy to uplift the Tibetan Plateau. The uplifting of high plateau exerts horizontal contraction to the surrounding crustal blocks to form thrust faults so that the plateau grows outward.

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张培震,王伟涛,甘卫军,张竹琪,张会平,郑德文,郑文俊,王洋,王岳军,许斌斌,张逸鹏.2022.青藏高原的现今构造变形与地球动力过程[J].地质学报,96(10):3297-3313.
Zhang Peizhen, Wang Weitao, Gan Weijun, Zhang Zhuqi, Zhang Huiping, Zheng Dewen, Zheng Wenjun, Wang Yang, Wang Yuejun, Xu Binbin, Zhang Yipeng.2022. Present- day deformation and geodynamic processes of the Tibetan Plateau[J]. Acta Geologica Sinica,96(10):3297-3313.

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历史
  • 收稿日期:2022-07-13
  • 最后修改日期:2022-08-10
  • 录用日期:2022-08-12
  • 在线发布日期: 2022-11-22