A flat lithosphere-asthenosphere boundary (∼60 km depth) in central Eastern China: Implications for lithospheric destruction and evolution

• Published in: Journal of Asian earth sciences 2024-03, Vol.263, p.106035, Article 106035
• Main Authors: Li, Xinfu, He, Xiaobo, Xu, Shuo, Li, Hongyi, Jiang, Guoming
• Format: Article
• Language: English
• Subjects: Central Eastern China; Lithosphere-asthenosphere boundary; Lithospheric thinning; Sp receiver functions
• ISSN: 1367-9120; 1878-5786
• DOI: 10.1016/j.jseaes.2024.106035

•A thin and flat LAB is observed in Central Eastern China, suggesting uniform destruction.•We attribute the destruction to lithospheric delamination along a mid-lithospheric discontinuity.•After the destruction, slab rollback and trench retreat further stretched the lithosphere. Detailed knowledge of the lithospheric thickness is important for understanding the tectonic evolution in central Eastern China, characterized by ore deposits in the Middle-Lower Yangtze Metallogenic Belt (MLYMB). We realize this goal by applying the common conversion point (CCP) stacking to Sp receiver functions (SRF) computed from 234 broadband seismic stations in central Eastern China. Distinct negative signals are identified below the Moho in all the CCP stacking profiles, which we interpret as the S-to-P conversions from the lithosphere-asthenosphere boundary (LAB). The imaged LAB is as shallow as ∼60 km with a standard deviation of ∼5 km in the whole region, in contrast to the typical cratonic lithosphere root down to 200 km depth or more, indicating the widespread lithospheric thinning in the study region. Such a flat LAB indicates that the regional lithosphere has been destructed uniformly, shedding light on its destructive mechanism, which we attribute to lithospheric delamination along a mid-lithospheric discontinuity (MLD). Compared to the MLD (∼80–100 km) observed in the western North China Craton, our observations suggest that the destructed lithosphere probably has been further stretched due to slab rollback and trench retreat. In contrast, lithospheric cooling-induced accretion plays a minor role in the lithospheric evolution after destruction.