首页|Deformation and seismic anisotropy in the SE Tibetan Plateau lithospheric mantle inferred from Maguan peridotite xenoliths

Deformation and seismic anisotropy in the SE Tibetan Plateau lithospheric mantle inferred from Maguan peridotite xenoliths

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  • NSTL
  • Elsevier
SKS wave splitting measurements revealed strong and complex seismic anisotropy in the upper mantle beneath the southeastern Tibetan Plateau. To better understand lithospheric deformation and upper mantle anisotropy observed in this region, we performed studies on microstructures, seismic anisotropy and chemical compositions of the mantle peridotite xenoliths collected from Maguan, Yunnan Province, in the SE Tibetan Plateau. The mantle xenoliths show two types of olivine crystal preferred orientation (CPO), AG-type and A-type. AG-type fabric is characterized by a concentration of [010]-axis normal to the foliation and a large circle girdle of the [100] and [001] axes in foliation. A-type fabric shows point concentrations of [100] and [010] axes subparallel to lineation and subnormal to foliation, respectively. Orthopyroxene and clinopyroxene align their [001]-axis sub-parallel to the [100]-axis of olivine. Seismic anisotropy calculated from the fabric of xenoliths displays moderate to strong polarization anisotropy (AV(s)) ranging from 3.1% to 7.0%, with 4.6% on average. Based on the seismic properties of xenoliths, we propose that, in SE Tibetan Plateau (south of 26 degrees N), the SKS wave splitting is attributed to melt-enhanced anisotropy with a vertical structural frame lithosphere. Under this structural configuration, the large delay time could be expected with the fast wave polarization direction (FPD) in E-W direction. Our study also supports the model of double anisotmpic layers in this area. The fast orientation of lower layer caused by lithospheric mantle anisotropy is in E-W direction, while the upper one with the NNW-SSE FPD is related to the frozen anisotropy in the middle-lower crust.

Seismic anisotropyCPOPeridotite xenolithsLithospheric deformationSE Tibetan PlateauYunnan ProvinceLATTICE-PREFERRED ORIENTATIONOLIVINE FABRIC TRANSITIONREACTIVE MELT TRANSPORTCRUSTAL ANISOTROPYB-TYPEGARNET PERIDOTITESVOLCANIC FIELDWATER CONTENTSCENTRAL-ASIASHEAR ZONE

Shang, Yongmei、Yang, Yu、Yang, Xiaosong

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China Earthquake Adm

Nanjing Univ

2022

10.1016/j.tecto.2021.229152

Tectonophysics

Tectonophysics

EISCI
ISSN：0040-1951
年,卷(期)：2022.822
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