Lithosphere and asthenosphere of the Tien Shan imaged by S receiver functions

2002 ◽  
Vol 29 (8) ◽  
pp. 32-1-32-4 ◽  
Author(s):  
Serge Oreshin ◽  
Lev Vinnik ◽  
Dmitry Peregoudov ◽  
Steve Roecker
Keyword(s):  
2018 ◽  
Author(s):  
Lev Vinnik ◽  
Yangfan Deng ◽  
Grigoriy Kosarev ◽  
Sergey Oreshin ◽  
Larissa Makeyeva

Abstract. Receiver functions for the central Tien Shan and northern Tarim in central Asia reveal a pronounced depression on the 410-km discontinuity beneath the Permian basalts in Tarim. The depression may most likely be caused by elevated temperature. The striking spatial coherence between the anomaly of the MTZ and the Permian basalts suggests that both may be effects of the same plume. This relation can be reconciled with reconstructed positions of paleo-continents since the Permian by assuming that the mantle layer which translated coherently with the Tarim plate extended to a depth of 410 km or more. Alternatively, lithosphere and the underlying mantle are decoupled at a depth of ~ 200 km, but a cumulative effect of the Tarim plate motions since the Permian is by an order of magnitude less than predicted by the paleo-reconstructions. A similar explanation is applicable to the Siberian traps.


Solid Earth ◽  
2018 ◽  
Vol 9 (5) ◽  
pp. 1179-1185
Author(s):  
Lev Vinnik ◽  
Yangfan Deng ◽  
Grigoriy Kosarev ◽  
Sergey Oreshin ◽  
Larissa Makeyeva

Abstract. Receiver functions for the central Tien Shan and northern Tarim in central Asia reveal a pronounced depression on the 410 km discontinuity beneath the Permian basalts in Tarim. The depression may be caused by elevated temperature. The striking spatial correlation between the anomaly of the MTZ and the Permian basalts suggests that both may be effects of the same plume. This relation can be reconciled with the possible motion of Tarim on the order of 1000 km by assuming that the mantle layer, which has moved coherently with the plate since the Permian, extends to a depth of 410 km or more. Alternatively, the lithosphere and underlying mantle are decoupled at a depth of  ∼ 200 km, but a cumulative effect of the Tarim plate motion since the Permian is less by an order of magnitude. A similar explanation is applicable to the Siberian traps.


2019 ◽  
pp. 16-27
Author(s):  
L. P. Vinnik

The application results of the receiver function technique are briefly outlined. The topography of the main seismic boundaries in the mantle transition zone is evaluated with resolution of about 3 km in depth and about 200 km laterally. The maximal amplitudes of depth variations of the main boundaries reach tens of kilometers. The mantle transition zone thinning in the hot spots and the respective increase in temperature by ~100 °C is established. In several regions, two low-velocity layers are revealed in the mantle transition zone, one directly above the 410-km seismic discontinuity and another at a depth of 450 to 500 km. The origin of the first layer is associated with dehydration in the mantle plumes during olivine – walesite phase transformation. The increase in the S-wave velocity at the base of the second layer can explain the observations of the so-called 520-km boundary. The traditional approach to studying the structure of the crust and upper mantle is from surface waves. Receiver functions can provide higher resolution at the same depths when a combination of P- and S-wave receiver functions is used. This type of results was obtained for Fennoscandia, Kaapvaal craton, Indian shield, Central Tien Shan, Baikal rift zone, the Azores, Cape Verde Islands, and the western Mediterranean. S-receiver functions were used in the studies of the lunar crust. The joint P- and S-receiver function inversion provides robust estimates of the parameters of seismic boundaries including weak discontinuities such as the lithosphere – asthenosphere interface of cratons. The parameters determined from receiver functions include the P- to S-wave velocity ratio. In a few regions, a very high (> 2.0) velocity ratio is observed in the lower crust, probably indicating the presence of a fluid with high pore pressure. Receiver functions allow estimating the parameters of azimuthal anisotropy as a function of depth. The changes of the parameters with depth make it possible to distinguish the active anisotropy associated with recent deformations from the frozen anisotropy – the effect of the past tectonic processes.


2020 ◽  
Author(s):  
Xuewei Bao ◽  
Bingfeng Zhang ◽  
Yixian Xu

<p>Uplifting mechanisms for the Tien Shan, an active intracontinental orogenic belt, have been under debate for decades, a key issue being how the convergence has been accommodated at depth. Here we investigate the Moho structure across the central Tien Shan by common-conversion-point imaging and H-k-c stacking of receiver functions from a dense array. The observed Moho exhibits distinct characteristics among sub-blocks. Southward-dipping diffuse Moho is imaged in the Southern Tien Shan (STS), in contrast with the relatively flat and sharp Moho beneath the Tarim Basin. This feature along with the large Moho offset beneath the South-Boundary Fault suggests that the shortening and thickening of Tien Shan crust rather than the underthrusting of the Tarim Basin are responsible for the uplift of the STS. In the Northern Tien Shan, however, the imaged Moho doublet provides direct evidence for the underthrusting of the Kazakh Shield accommodating the convergence there.</p>


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