Complex Crustal Deformation Beneath the Cathaysia Block in South China: Evidence From Receiver Function Analysis.

By harmonically fitting the arrival times of the P‐to‐S converted phases from the Moho, we systematically investigate the crustal anisotropy beneath the Cathaysia Block (CaB) and the surrounding areas in South China for the first time. The measured anisotropy parameters show strong lateral variations with an average splitting time of 0.35 ± 0.12 s. The resulting fast directions exhibit clear geographic variations with two possible boundaries that separate the CaB into three parts. The inconsistent fast direction of crustal anisotropy among each part, and the comparisons with teleseismic XKS splitting measurements indicate that the mechanisms of crustal deformation vary between distinct regions. The crust deforms coherently with the upper mantle in the western CaB, which is possibly driven by mantle flow. The fast directions of crustal anisotropy in the central CaB exhibit a radial pattern and show large discrepancies with XKS splitting measurements. We suggest that the crust has a complex deformation mechanism in this region. We propose a new scenario that emphasizes the interaction of the crust and upper mantle for interpreting the radial‐patterned crustal anisotropy, which involves the processes of subduction plate rollback, asthenospheric upwelling, crustal melting and lithospheric mantle intrusion. The fast directions of crustal anisotropy in the eastern CaB are dominantly parallel to the continental margin, suggesting subduction‐controlled crustal deformation in this region. Plain Language Summary: The Cathaysia Block (CaB) is an important part of the South China Block, which has experienced multistage tectono‐thermal events and a complex tectonic evolution. Previous studies focused on upper mantle deformation and rarely involved crustal deformation. We systematically measure the crustal anisotropy from receiver function analysis beneath the CaB for the first time. The results show that crust at different parts of the CaB have different deformation mechanisms. The crust of the western CaB deforms coherently with lithospheric mantle, which may be driven by deep mantle flow. The central CaB has a complex crustal deformation mechanism involving a series of processes like plate rollback, asthenospheric upwelling, crustal melting and lithospheric mantle intrusion. The crust deformation of the eastern CaB is likely controlled by oceanic plate subduction. Key Points: We investigate the crustal anisotropy beneath the Cathaysia Block (CaB) from receiver function analysis for the first timeThe fast directions of crustal anisotropy exhibit geographic variations with two clear tectonic boundariesThe complex features of crustal anisotropy reveal different deformation mechanisms beneath different parts of the CaB [ABSTRACT FROM AUTHOR]