Dynamic Mechanism Research on the Tectonic Activation of Anninghe Rift

2014 ◽  
Vol 580-583 ◽  
pp. 851-856
Author(s):  
Jun Qi Liu ◽  
Yu Sheng Li
Keyword(s):  
Tibetan Plateau ◽  
Plastic Flow ◽  
Upper Crust ◽  
Geodynamic Environment ◽  
Mechanism Research ◽  
Constant State ◽  
Brittle Rock Mass ◽  
Shallow Crust ◽  
Narrow Area ◽  
Anninghe Fault

Anninghe rift is located on the western edge of Yangtze Block next to Tibetan Plateau, along the axis of a continental paleorift zone, Panxi paleorift. Recent studies have found that an upward mantle convection system existed since the late Pliocene in the deep lithosphere of a long and narrow area controlled by Anninghe fault. Lithospheric temperature distribution in the area has characteristics similar to that in Baikal and other modern rifts. A mantle upwelling area was in a constant state of “pull-subsidence.” Brittle rock mass of the shallow crust cracked into the new secondary subsidence blocks. A thick lacustrine sedimentary sequence of continental subsidence type developed. These all indicate that Anninghe rift is in an obvious tectonic activation state. It is believed that the tectonic activation of Anninghe rift has been produced by both horizontal squeeze from a plastic flow of the upper crust and expansion from mantle uplift. The pressure from the plastic flow of the upper crust is slightly greater than the expansion stress from the uplifting of lithosphere. Under this specific geodynamic environment, whether the tectonic activation of Anninghe rift can continue depends on the thermal motion rate of deep mantle materials and the eastward migration of the crustal materials of Tibetan Plateau.

Degassing of deep-sourced CO2 from Xianshuihe-Anninghe fault zones in the eastern Tibetan Plateau

2021 ◽  
Author(s):  
Sheng Xu ◽  
Lufeng Guan ◽  
Maoliang Zhang ◽  
Jun Zhong ◽  
Wei Liu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Fault Zones ◽  
Eastern Tibetan Plateau ◽  
Anninghe Fault

Multilayered Crustal Anisotropy in Eastern Tibet Revealed by Receiver Function Data

2020 ◽  
Author(s):  
Shaohua Qi ◽  
Qiyuan Liu ◽  
Jiuhui Chen ◽  
Biao Guo
Keyword(s):  
Tibetan Plateau ◽  
Lower Crust ◽  
Seismic Anisotropy ◽  
Receiver Function ◽  
Azimuthal Anisotropy ◽  
Strain History ◽  
The Tibetan Plateau ◽  
Anisotropy Axis ◽  
Upper Crust ◽  
Western Sichuan

<p>It is widely accepted that the ongoing India-Asia collision since approximately 50 Ma ago has resulted in the uplift and eastward expansion of the Tibetan Plateau. Yet the interpretations of its dynamic process and deformation mechanism still remain controversial. Distinct models that emphasize particular aspects of the tectonic features have been proposed, including fault-controlled rigid blocks, continuous deformation of lithosphere and lower crust flow.</p><p>One possible way to reconcile these models is to investigate crustal deformation at multiple depths simultaneously, as well as crust-mantle interaction. Seismic anisotropy is considered as an effective tool to study the geometry and distribution of subsurface deformation, due to its direct connection to the stress state and strain history of anisotropic structures and fabrics. In the eastern margin of Tibetan plateau, previous studies of seismic anisotropy have already provided useful insights into the bulk anisotropic properties of the entire crust or upper mantle, based on shear wave splitting analyses of Moho Ps and XKS phases.</p><p>In this study, we went further to extract anisotropic parameters of multiple crustal layers by waveform inversion of teleseismic receiver function (RF) data from the western-Sichuan temporal seismic array using particle swarm optimization. Instead of directly fitting the backazimuthal stacking of RFs from each station, we translated the RF data into backazimuthal harmonic coefficients using harmonic decomposition technique, which separates the signals (of planar isotropic structure and anisotropy) from the scattering noise generated by non-planar lateral heterogeneity. The constant (k=0) and k=1, 2 terms of backazimuthal harmonic coefficients were used in our inversion. We also fixed the anisotropic model to slow-axis symmetry to avoid ambiguous interpretations.</p><p>Our results show that:</p><p>(1) Anisotropy with a titled anisotropy axis of symmetry is more commonly observed than pure azimuthal anisotropy in our data, which has been also reported by other RF studies across the surrounding areas of Tibetan plateau.</p><p>(2) The trends of slow symmetry axis vary from the upper to lower part of the crust in both Chuandian and Songpan units, indicating the deformation of the upper crust is decoupled from that of the lower crust in these two regions, while the trends are more consistent throughout the crust in the Sichuan basin.</p><p>(3) In the upper crust, the trends show a degree of tendency to lie parallel to the major geological features such as the Xianshuihe and Longmenshan faults, exhibiting a fault-controlled deformation or movement. In the middle and lower crust, the trends are NS or NW-SE in Chuandian unit and NE-SW in Songpan unit, which are coincident with the apparent extension directions of the ductile crustal flow.</p>

scholarly journals Continental subductions and Tibetan plateau growth

2013 ◽  
Vol 46 ◽  
Author(s):  
Stephane Guillot ◽  
Anne Replumaz
Keyword(s):  
Tibetan Plateau ◽  
Early Growth ◽  
The Tibetan Plateau ◽  
Upper Crust ◽  
Metamorphic Petrology ◽  
Continental Lithosphere ◽  
Southern Tibet ◽  
Northern Tibetan Plateau ◽  
Northern Portion ◽  
Cenozoic Magmatism

How and when the Tibetan plateau developed has long been a puzzling question with implications for the current understanding of the behaviour of the continental lithosphere in convergent zones. We present and discuss recent data acquired in geology and geophysics and through igneous and metamorphic petrology and palaeo-altitude estimates. This research indicates that Tibet initiated from the accretion of the Gondwana continental blocks to the southern Asian margin during the Palaeozoic and Mesozoic eras. These successive accretions have potentially favoured the creation of local landforms, particularly in southern Tibet, no evidence exists in favour of the existence of a proto-Tibetan plateau prior to the Cenozoic. By the time the India-Asian collision began it was cold enough to transfer stress but that does not mean there was not a proto-plateau prior to collision. Depending on the types of Paleozoic and Mesozoic collisions, the sutures terranes could be cool enough to transfer stress, especially in the upper crust. However, these successive accretions associated with subductions have metasomatized the Tibetan lithospheric mantle and largely explain the potassium- and sodium-rich Cenozoic magmatism. Another consequence of this contamination by fluids is the softening of the Tibetan lithosphere, which favoured intra­continental subductions. The timing and the geochemical signatures of the magmatism and the palaeo-altitudes suggest the early growth of the Tibetan plateau. By Eocene time, the southern plateau and the northern portion of Himalaya were at an altitude of approximately 4000 metres, while the central and northern Tibetan plateau was at altitudes of approximately 2000 to 3000 meters at the Eocene-Oligocene transition. From all of these data, we propose a model of the formation of the Tibetan plateau coupled with the formation of Himalaya, which accounts for more than 2500 km of convergence accommodated by the deformation of the continental lithosphere.

scholarly journals Structural Heterogeneities in Southeast Tibet: Implications for Regional Flow in the Lower Crust and Upper Mantle

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Zhi Wang ◽  
Xuben Wang ◽  
Runqiu Huang ◽  
Wenli Huang
Keyword(s):  
Tibetan Plateau ◽  
Crustal Deformation ◽  
Lower Crust ◽  
Dynamic Pressure ◽  
Uppermost Mantle ◽  
Crust And Upper Mantle ◽  
Southeastern Tibetan Plateau ◽  
Regional Flow ◽  
Deep Suture ◽  
Anninghe Fault

Our seismic study together with the MT analysis reveal a “R-shape” flow existing in both the lower crust and uppermost mantle, which suggests the crustal deformation along the deep, large sutures (such as the Longmen Shan fault and the Anninghe Fault) under the southeastern Tibetan Plateau is maintained by dynamic pressure from the regional flow intermingled with the hot upwelling asthenosphere. The material in the lower crust and uppermost mantle flowing outward from the center of the plateau is buttressed by the old, strong lithosphere that underlies the Sichuan basin, pushing up on the crust above and maintaining steep orogenic belt through dynamic pressure. We therefore consider that the “R-shape” regional flow played a key role in the crustal deformation along the deep suture zones of the Bangong-Nujiang, the Longmen-Shan faults, and other local heavily faulted zones beneath the southeastern Tibetan Plateau.

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