Asthenospheric Flow Channel From Northeastern Tibet Imaged by Seismic Tomography Between Ordos Block and Yangtze Craton. Issue 17 (8th September 2021)

• Record Type: Journal Article
• Authors: Yu, Yong; Chen, Yongshun John; Feng, Yongge; An, Meijian; Liang, Xiaofeng; Guo, Zhen; Qu, Wulin; Li, Shilin; Dong, Shuwen
• Is Part Of: Geophysical research letters. Volume 48:Issue 17(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-08
• Subjects: the northeastern Tibetan Plateau -- asthenospheric flow -- finite‐frequency tomography -- the Ordos block -- the Qinling‐Dabie orogenic belt; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL093561
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The collision between India and Eurasia forming the Tibetan Plateau since the early Cenozoic had led to the crustal and upper‐mantle (asthenospheric) extrusion from the plateau to the east. However, the Ordos and Yangtze cratonic keels next to the northeastern and eastern Tibetan Plateau obstruct this eastward asthenospheric extrusion. With a dense seismic array, for the first time, we imaged a narrow low P‐wave and S‐wave velocity anomaly characterized with higher Vp / Vs between these two Archean cratons at depths ranging from 150 to 300 km using finite‐frequency tomography. We interpret this low‐velocity anomaly as a channel of the eastward asthenospheric flow from the Tibetan Plateau. We provide solid seismic observations for a pathway of the Tibetan asthenospheric extrusion due to the ongoing collision of the Indian and Eurasian continents. This asthenospheric extrusion from the Tibetan Plateau could influence the lithospheric reworking in the central and eastern North China Craton. Plain Language Summary: The Tibetan Plateau is formed due to the continuous collision between the Indian and Eurasian continents over the past 50 Ma. Both the crust and upper mantle beneath the plateau are squeezed outwards and primarily to the east. By analyzing seismic signals emitted by earthquakes and recorded by temporary and permanent seismometers near the northeastern Tibetan Plateau, we perform a tomographic study to estimate seismic wave speed variations beneath the study region. We find a continuous channel‐shaped structure of low seismic velocity between two ancient and rigid tectonic units, the Ordos block and Yangtze craton. Our observation suggests that hot and viscous materials deep beneath the Tibetan Plateau might flow through this narrow channel to the eastern Chinese continent. This study's results indicate that the formation of the Tibetan Plateau could affect the lithospheric destruction of the eastern Chinese continent far to the east. Key Points: A low P‐wave and S‐wave velocity anomaly with a higher Poisson's ratio is imaged in the upper mantle between the Ordos block and Yangtze craton Such anomalous feature is interpreted as a narrow channel for the eastward Tibetan asthenospheric flow The continental collision at Tibet could have a far effect on the cratonic lithosphere rejuvenation in the central North China craton