Adjoint Tomography of the Lithospheric Structure beneath Northeastern Tibet

2020 ◽  
Vol 91 (6) ◽  
pp. 3304-3312
Author(s):  
Xingpeng Dong ◽  
Dinghui Yang ◽  
Hejun Zhu
Keyword(s):  
Tibetan Plateau ◽  
Indian Plate ◽  
Tectonic Deformation ◽  
Lithospheric Structure ◽  
The Tibetan Plateau ◽  
S Wave ◽  
Low Velocity ◽  
Northeastern Tibet ◽  
Adjoint Tomography ◽  
Indian Lithosphere

Abstract Northeastern Tibet is still in the primary stage of tectonic deformation and is the key area for studying the lateral expansion of the Tibetan plateau. In particular, the existence of lower crustal flow, southward subduction of the Asian lithosphere, and northward subduction of the Indian lithosphere beneath northeastern Tibet remains controversial. To provide insights into these issues, a high-resolution 3D radially anisotropic model of the lithospheric structure of northeastern Tibet is developed based on adjoint tomography. The Tibetan plateau is characterized as a low S-wave velocity lithosphere, in contrast with the relatively high S-wave velocities of the stable Asian blocks. Our tomographic result indicates that the low-velocity zone (LVZ) within the deep crust extends northeastward from Songpan–Ganzi to Qilian, which is interpreted as a channel flow within the crust. The upper mantle of Alxa and Qinling–Qilian are dominated by a rather homogeneous LVZ, which is inconsistent with the hypothesis that the Asian lithospheric mantle is being subducted southward beneath northeastern Tibet. Furthermore, high-velocity regions are observed in the southern Songpan–Ganzi region at depths ranging from 100 to 200 km, indicating that the northward-subducting Indian plate has probably reached the Xianshuihe fault.

Crustal structure of the Tibetan Plateau: A surface-wave study by a moving window analysis

1977 ◽  
Vol 67 (3) ◽  
pp. 735-750
Author(s):  
Kin-Yip Chun ◽  
Toshikatsu Yoshii
Keyword(s):  
Tibetan Plateau ◽  
Crustal Structure ◽  
The Tibetan Plateau ◽  
Moving Window ◽  
Low Velocity ◽  
Period Range ◽  
Window Analysis ◽  
Dispersion Data ◽  
Moving Window Analysis ◽  
Group Velocities

abstract Group velocities of fundamental-mode Rayleigh and Love waves are analyzed to construct a crustal structure of the Tibetan Plateau. A moving window analysis is employed to compute group velocities in a wide period range of 7 to 100 sec for 17 individual paths. The crustal models derived from these dispersion data indicate that under the Tibetan Plateau the total crustal thickness is about 70 km and that the crustal velocities are generally low. The low velocities are most probably caused by high temperatures. A low-velocity zone located at an intermediate depth within the crust appears to be strongly demanded by the observed dispersion data. The main features of the proposed crustal structure will place stringent constraints on future tectonic models of the Tibetan Plateau which is generally regarded as a region of active deformation due to the continent-continent collision between India and Asia.

A new crustal shear-velocity model in Southwest China from joint seismological inversion and its implications for regional crustal dynamics

2019 ◽  
Author(s):  
Yan Yang ◽  
Huajian Yao ◽  
Hanxiao Wu ◽  
Ping Zhang ◽  
Maomao Wang
Keyword(s):  
Tibetan Plateau ◽  
Rayleigh Wave ◽  
Joint Inversion ◽  
Shear Velocity ◽  
P Wave ◽  
Tectonic Deformation ◽  
Inversion Method ◽  
Low Velocity ◽  
Sw China ◽  
S Period

SUMMARY Southwest (SW) China is located in a transition site from the active Tibetan Plateau to the stable Yangtze craton, which has complicated tectonic deformation and severe seismic hazards. We combine data from ambient noise, teleseismic body and surface waves, and petroleum wells to better constrain the crustal shear-velocity structure in SW China. We jointly invert the Rayleigh wave dispersion (5–40 s period), Rayleigh wave ZH ratio (20–60 s period), and P-wave receiver function for 114 permanent stations with a stepwise linearized joint inversion method. Compared to previous tomography results, we observe higher shear velocity in the sedimentary rocks within the Sichuan Basin, which is consistent with sonic logging measurements. Our model reveals widespread low-velocity zones in the mid-lower crust, and their boundaries correlate well with major fault systems. Between two main mid-crustal low-velocity channels, a prominent high-velocity region surrounded by earthquakes is observed in the inner zone of the Emeishan large igneous province (ELIP) and around the Anninghe-Zemuhe fault zone. These observations are comparable to regional tomography results using very dense arrays. Based on the results, we suggest that mid-lower crustal ductile flow and upper-crustal rigid fault movement play equally important roles in controlling the regional deformation styles and earthquake distribution in SW China. Our results also resolve thick crust-mantle transition zones beneath the eastern Tibetan Plateau and the inner zone of the ELIP due to ‘top-down’ and ‘bottom-up’ crust-mantle interactions, respectively. Our new model can serve as a reference crustal model of future high resolution model construction in SW China.

Expanse of greater india in the cretaceous

2021 ◽  
Author(s):  
Jun Meng ◽  
Stuart Gilder ◽  
Yalin Li ◽  
Chengshan Wang
Keyword(s):  
Early Cretaceous ◽  
Plate Boundary ◽  
Vertical Axis ◽  
Indian Plate ◽  
Paleomagnetic Data ◽  
Fundamental Parameter ◽  
The Tibetan Plateau ◽  
Northern Margin ◽  
Indian Lithosphere ◽  
Tethyan Himalaya

<p>Knowing the original size of Greater India is a fundamental parameter to quantify the amount of continental lithosphere that was subducted to help form the Tibetan Plateau and to constrain the tectonic evolution of the India-Asia collision. Here, we report Early Cretaceous paleomagnetic data from the central and eastern Tethyan Himalaya that yield paleolatitudes consistent with previous Early Cretaceous paleogeographic reconstructions. These data suggest Greater India extended at least 2,675 ± 720 and 1,950 ± 970 km farther north from the present northern margin of India at 83.6°E and 92.4°E, respectively. The paleomagnetic data from Upper Cretaceous rocks of the western Tethyan Himalaya that are consistent with a model that Greater India extended ~2700 km farther north from its present northern margin at the longitude of 79.6°E before collision with Asia. Our result further suggests that the Indian plate, together with Greater India, acted as a single entity since at least the Early Cretaceous. An area of lithosphere ≥4.7 × 10<sup>6</sup> km<sup>2</sup> was consumed through subduction, thereby placing a strict limit on the minimum amount of Indian lithosphere consumed since the breakup of Gondwanaland. The pre-collision geometry of Greater India’s leading margin helped shape the India-Asia plate boundary. The proposed configuration produced right lateral shear east of the indenter, thereby accounting for the clockwise vertical axis block rotations observed there.</p>

Widespread crustal melting since 28 Ma creates the modern flat Tibet

2020 ◽  
Author(s):  
Xiu-Zheng Zhang ◽  
Qiang Wang ◽  
Wei Dan
Keyword(s):  
Tibetan Plateau ◽  
Lower Crust ◽  
Theoretical Models ◽  
Geothermal Gradient ◽  
Magma Source ◽  
The Tibetan Plateau ◽  
Crustal Melting ◽  
Low Velocity ◽  
Crustal Xenoliths ◽  
Orogenic Belts

<p>As the largest and highest plateau on Earth, the Tibetan Plateau is distinguished from most other ranges and liner continental orogenic belts (e.g., the Alps) by its broad and flat topography. According to influential numerical and theoretical models, the (former) existence of ductile and molten mid-to-lower crust was an essential contributor to the topographic smoothing process. However, the question of whether the Tibetan Plateau has undergone widespread crustal melting remains highly controversial and hard to prove due to the scarcity of direct evidence from the deep crust. Here we first report on a series of hydrous crustal xenoliths entrained in 28 Ma host lavas from central and northern Tibet. Our new results document the former existence of hydrous crust at 28 Ma as a potentially highly fertile magma source. Quantitative modeling reveals a thermal gradient reaching about 680 ℃ to 790 ℃ at a depth of 14 to 40 kilometers, which is significantly lower than that of recent (since 2.3 Ma) evidence for hot Tibetan crust. Petrological data suggest that the initial crustal melting beneath Tibet began at 28 Ma at depths of 23–40 km (and even deeper) with 0.5–9.6 vol. % melts, which would lead to a significant reduction of seismic speeds similar to the low-velocity zones observed in the present Tibetan mid-to-lower crust. As the geothermal gradient continued to rise from 28 to 2.3 Ma, wholesale crustal melting (> 20–30 vol. %) of the mid-to-lower crust beneath Tibet was inevitable and created the modern flat Tibetan Plateau.</p>

Tectonic Deformation and Surface Processes of the Tibetan Plateau Constrained by Time Series Analysis of Sentinel-1 InSAR Data

2020 ◽  
Author(s):  
Robert Zinke ◽  
Gilles Peltzer ◽  
Eric Fielding ◽  
Simran Sangha ◽  
David Bekaert ◽  
...  
Keyword(s):  
Time Series ◽  
Tibetan Plateau ◽  
Surface Deformation ◽  
Active Faults ◽  
High Rate ◽  
Surface Processes ◽  
Tectonic Deformation ◽  
The Tibetan Plateau ◽  
Data Set ◽  
Temporal Sampling

<p>We quantify deformation patterns resulting from tectonic motions and surface processes across the central Tibetan Plateau (29–45ºN, 83–92ºE) since late 2014 using ascending and descending passes of the Sentinel-1A and -1B radar satellites. The broad spatial extent of these data (> 10<sup>6</sup> km<sup>2</sup>), fine spatial resolution (originally 90 m pixels, resampled to 270 m pixels), and high rate of temporal sampling (12–24-day orbit repeat time) offer unprecedented resolution of surface deformation in space and time. To process such an extensive data set – including more than 100 dates and 300 interferograms per track thus far – we leverage the Advanced Rapid Imaging and Analysis (ARIA) standardized interferometric synthetic aperture radar (InSAR) products and toolbox. We construct time series of surface deformation constrained from our Sentinel-1 interferograms using the small baseline subset approach implemented by the Miami InSAR time series software in Python (MintPy). Our preliminary results from three Sentinel-1 orbits (two descending and one ascending; each comprising 10 frames along track) allow us to quantify deformation in the satellite lines of sight. Combinations of ascending and descending track measurements are used to approximate east-west and vertical ground velocities. The resulting velocity fields will provide a more complete and accurate picture of interseismic strain accumulation rates across active faults in the region such as the Altyn Tagh and Kunlun faults, and allow us to study surface processes such as permafrost active layer dynamics and isostatic adjustment due to lake level changes in unparalleled scope and detail.</p>

Lithospheric structure and crust–mantle decoupling in the southeast edge of the Tibetan Plateau

2012 ◽  
Vol 22 (3-4) ◽  
pp. 1060-1067 ◽  
Author(s):  
Jiafu Hu ◽  
Haiyan Yang ◽  
Xingqian Xu ◽  
Limin Wen ◽  
Guangquan Li
Keyword(s):  
Tibetan Plateau ◽  
Lithospheric Structure ◽  
The Tibetan Plateau

scholarly journals Mesozoic–Cenozoic Uplift/Exhumation History of the Qilian Shan, NE Tibetan Plateau: Constraints From Low-Temperature Thermochronology

2021 ◽  
Vol 9 ◽  
Author(s):  
Lihao Chen ◽  
Chunhui Song ◽  
Yadong Wang ◽  
Xiaomin Fang ◽  
Yihu Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Low Temperature ◽  
Tectonic Deformation ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Two Phase ◽  
Late Mesozoic ◽  
Plate Convergence ◽  
History Of ◽  
Upward Growth

The Qilian Shan, which is located along the northeastern margin of the Tibetan Plateau, plays a key role in understanding the dynamics of the outward and upward growth of the plateau. However, when and how tectonic deformation evolved into the geographic pattern which is currently observed in the Qilian Shan are still ambiguous. Here, apatite fission track (AFT) thermochronology and sedimentology were conducted to interpret the low-temperature tectonic deformation/exhumation events in well-dated Late Miocene synorogenic sediment sequences in the Xining Basin, which is adjacent to the southern flank of the Qilian Shan. These new low-temperature thermochronological results suggest that the Qilian Shan experienced four stages of tectonic exhumation during the late Mesozoic–Cenozoic. The Late Cretaceous exhumation events in the Qilian Shan were caused by the diachronous Mesozoic convergence of the Asian Plate and Lhasa Block. In the early Cenozoic (ca. 68–48 Ma), the Qilian Shan quasi-synchronously responded to the Indian–Asian plate collision. Subsequently, the mountain range experienced a two-phase deformation during the Eocene–Early Miocene due to the distal effects of ongoing India–Asia plate convergence. At ca. 8 ± 1 Ma, the Qilian Shan underwent dramatic geomorphological deformation, which marked a change in subsidence along the northeastern margin of the Tibetan Plateau at that time. Our findings suggest that the paleogeographic pattern in the northeastern Tibetan Plateau was affected by the pervasive suture zones in the entire Qilian Shan, in which the pre-Cenozoic and Indian–Asian plate motions reactivated the transpressional faults which strongly modulated the multiperiodic tectonic deformation in northern Tibet during the Cenozoic. These observations provide new evidence for understanding the dynamic mechanisms of the uplift and expansion of the Tibetan Plateau.

Late Mesozoic−Cenozoic cooling history of the northeastern Tibetan Plateau and its foreland derived from low-temperature thermochronology

2021 ◽  
Author(s):  
Chen Wu ◽  
Andrew V. Zuza ◽  
Jie Li ◽  
Peter J. Haproff ◽  
An Yin ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Low Temperature ◽  
Large Scale ◽  
Qaidam Basin ◽  
Tectonic Deformation ◽  
Formation Mechanisms ◽  
The Tibetan Plateau ◽  
Thrust Belt ◽  
The South ◽  
Late Mesozoic

The growth history and formation mechanisms of the Cenozoic Tibetan Plateau are the subject of an intense debate with important implications for understanding the kinematics and dynamics of large-scale intracontinental deformation. Better constraints on the uplift and deformation history across the northern plateau are necessary to address how the Tibetan Plateau was constructed. To this end, we present updated field observations coupled with low-temperature thermochronology from the Qaidam basin in the south to the Qilian Shan foreland in the north. Our results show that the region experienced a late Mesozoic cooling event that is interpreted as a result of tectonic deformation prior to the India-Asia collision. Our results also reveal the onset of renewed cooling in the Eocene in the Qilian Shan region along the northern margin of the Tibetan Plateau, which we interpret to indicate the timing of initial thrusting and plateau formation along the plateau margin. The interpreted Eocene thrusting in the Qilian Shan predates Cenozoic thrust belts to the south (e.g., the Eastern Kunlun Range), which supports out-of-sequence rather than northward-migrating thrust belt development. The early Cenozoic deformation exploited the south-dipping early Paleozoic Qilian suture zone as indicated by our field mapping and the existing geophysical data. In the Miocene, strike-slip faulting was initiated along segments of the older Paleozoic suture zones in northern Tibet, which led to the development of the Kunlun and Haiyuan left-slip transpressional systems. Late Miocene deformation and uplift of the Hexi corridor and Longshou Shan directly north of the Qilian Shan thrust belt represent the most recent phase of outward plateau growth.

Sign in / Sign up

Export Citation Format

Share Document