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Microstructural and seismic characteristics of oriented mantle xenoliths from Damaping area, and their geodynamic implications of North China Craton destruction
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  • Yilun Shao,
  • Cai Liu,
  • Rui Gao,
  • Shan Li,
  • Tianshuo Zhao
Yilun Shao
Jilin University

Corresponding Author:[email protected]

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Cai Liu
College of Geoexploration Science and Technology, Jilin University
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Rui Gao
Sun Yat-sen University
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Shan Li
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences
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Tianshuo Zhao
College of Geoexploration Science and Technology, Jilin University
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Abstract

The large-volume lithospheric mantle xenoliths around the Damaping area provides valuable insights into the detailed destruction progression of the North China Craton (NCC). This paper presents a quantitative analysis of the microstructural and seismic properties of oriented mantle xenoliths (with distinct foliation and lineation). The selected peridotites have either coarse-grained (CG) or coarse-grained and elongated (CGE) textures. The olivine crystallographic preferred orientations (CPOs) are predominantly B-type in CG samples and AG-type in CGE samples, with all xenoliths have girdled olivine [100] and [001] characteristics. Analysis of crystallographic vorticity axis (CVA) projections indicates that the majority of Damaping xenoliths have CVA maxima (sub)parallel to the lineation. These microstructure characteristics suggest that B-type CPOs were formed before the onset of pure shear-based transpression, which significantly influenced the lithospheric mantle evolution. The upwelling asthenosphere beneath Eastern Block of the NCC not only delaminated its lithospheric mantle but also experienced rollback and flowed along the NWW-SEE direction. This progression likely serves as the primary driving force of transpression. If foliation were vertical and lineation were horizontal, the valid S-wave anisotropies range is 5-12%. All selected samples are spinel facies, resulting in a maximum in-situ depth of 90 km, and the calculated SKS splitting delay times (0.5-1.3 s) align with previous seismological observations. The SKS direction in the research area is predominantly oriented perpendicular (NNE-SSW) to the flow direction of nearby asthenosphere. These characteristics are likely attributed to transpression. Therefore, the “fossil” anisotropy may have developed after the cessation of transpression.