Open AccessVelocity Anomalies Around the Mantle Transition Zone Beneath the Qiangtang Terrane, Central Tibetan Plateau From Triplicated P Waveforms
Author(s) -
Li Guohui,
Bai Ling,
Zhang Heng,
Xu Qiang,
Zhou Yuanze,
Gao Yuan,
Wang Mujiangshan,
Li Zihao
Publication year - 2022
Publication title -
earth and space science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.843
H-Index - 23
ISSN - 2333-5084
DOI - 10.1029/2021ea002060
Subject(s) - geology , terrane , downwelling , upwelling , lithosphere , mantle (geology) , asthenosphere , plateau (mathematics) , transition zone , seismology , geophysics , crust , oceanography , tectonics , mathematical analysis , mathematics
The Qiangtang terrane exhibits many unique features compared with surrounding areas in the Tibetan plateau. It has been largely remodeled by the northward downwelling of the Indian lithosphere and the vertical upwelling of the Eurasian asthenosphere. Here, we investigate the P ‐wave velocity around the mantle transition zone (MTZ) beneath the Qiangtang terrane using high‐frequency triplicated waveforms recorded by the China Digital Seismic Network. We found a low‐velocity layer (LVL) atop the MTZ and a high‐velocity anomaly (HVA) in the lower part of the MTZ. They are characterized by thickness of 36 km with velocity drop of −2.0% and 155 km with velocity increment of 1.2%, respectively. The 410 and 660 km discontinuities are depressed by different depths of 12 and 30 km, suggesting a thickened MTZ. In combination with previous multi‐disciplinary observations, we infer that the LVL is a hydrous partial melt affected by dehydration and high temperature, and the HVA is due to water and low temperature conditions. The downwelling cold continental lithosphere may have accumulated in the lower MTZ and induced the hydrous hot MTZ materials to upwelling until the shallow depths of the upper mantle beneath the Qiangtang terrane.