Crustal Lg and upper mantle Pn attenuation structure beneath the Yangtze craton and its implications for the ancient cratonic nucleus

Cratons are traditionally considered to be long-lived and stable owing to their great thickness and rigid lithospheric roots. However, increasing evidence suggests that some cratons have experienced significant lithospheric thinning and destruction. The Sichuan basin, a cratonic basin within the Yangtze Craton, is widely regarded as the cratonic nucleus owing to its long-term tectonic stability and continuous sedimentary subsidence. However, the oldest Archean basement of the Yangtze Craton, represented by the Kongling Complex, is mainly exposed in the eastern Sichuan Basin, raising the question of the spatial location of the ancient nucleus for the Yangtze Craton. Since the Mesozoic, the Yangtze Craton has been affected by the combined influences of Paleo-Pacific subduction and Cenozoic eastward extrusion of the Tibetan Plateau, and the preservation and spatial distribution of its deep lithospheric root remain poorly constrained by geophysical observations. Here, we constructed a high-resolution crustal-upper mantle attenuation model using regional Pn and Lg phases to constrain the coupling/decoupling characteristics between crust and upper mantle beneath the Yangtze Craton. The weak crustal Lg attenuation in the Sichuan Basin does not correspond to the weak Pn attenuation in the upper mantle, indicating that the lithospheric root may mechanically migrate to the eastern Sichuan Basin. The phenomenon is likely associated with the Cenozoic eastward extrusion of the Tibetan Plateau, yet the eastern Yangtze Craton appears to have undergone overall lithospheric thinning and destruction related to Mesozoic Paleo-Pacific subduction. This study was supported by the National Natural Science Foundation of China (42474084) and Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project (2025ZD1005302).