Receiver function imaging of dense seismic array and deep dynamic mechanism beneath the eastern South China

• Published in: Science China. Earth sciences Vol. 66; no. 6; pp. 1289 - 1308
• Main Authors: Han, Rubing, Yang, Dinghui, Li, Qiusheng, Huang, Rong, Zhang, Hongshuang, Li, Jiangtao, Chen, Hao, Ye, Zhuo, Fu, Wei
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 01-06-2023; Springer Nature B.V
• Subjects: Ambient noise; Belts; Broadband; Continental margins; Cretaceous; Crustal thickness; Dynamic models; Earth and Environmental Science; Earth Sciences; Geological faults; Heat flow; Heat transmission; Igneous rocks; Image resolution; Imaging techniques; Lithosphere; Mesozoic; Ocean circulation; Plates; Plates (tectonics); Plutons; Poisson's ratio; Research Paper; Seismic arrays; Subduction; Subduction (geology); Tectonics; Thickness; Tomography; Upwelling; China; Dense seismic array; Slab breakoff; “Y-shaped” thinnest crustal belt; Eastern South China Block; Receiver function
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-022-1046-7

The Mesozoic tectonic framework of the eastern South China is mainly controlled by subduction, turning toward, and rollback of the Pacific Plate. Recent studies of receiver function imaging and ambient noise tomography have revealed the “Y-shaped” thinnest crustal belt in the eastern South China under the overall extension of the lithosphere. However, the deep dynamic environment and formation mechanisms of the thin crustal belt remain debatable. Here we obtained high-resolution images of the crustal thickness and Poisson’s ratio in the eastern South China Block applying the recently proposed
H-κ-c
receiver function method, using data recorded by 305 dense portable broadband stations and 219 permanent stations surrounding. Additionally, we discussed the deep dynamic formation mechanism of the “Y-shaped” thinnest crustal belt coupled with two common conversion point stacked images at key locations. Results show that the average crustal thickness of the study area is 33 km (thin crust) and the average Poisson’s ratio is 0.24 (low ratio). The overall crustal thinning toward the continental margin is likely because eastern South China was in a back-arc extension environment, which was induced by the rollback of the subducted plate in the Early Cretaceous. The crustal thickness of the “Y-shaped” thinnest crustal belt is <30 km, which is 3–5 km thinner than that outside the zone. The eastern branch is distributed along the trajectory of Nanchang-Ji’an-Ganzhou-Shaoguan-Guangzhou, and the western branch is around the Jianghan-Xiangzhong Basin, both of which intersect in Nanling. The eastern branch of the thin crustal zone indicates the potential location of the Pacific subduction slab breakoff, and the formation mechanism may be related to the interaction of deep-shallow processes, including the upwelling of mantle heat flow through the slab window and transtensional pre-existing faults. We developed a dynamic model that combines subduction-breakoff-rollback processes of the Paleo-Pacific Plate and accompanying deep fluid upwelling to explain the regional extension of the South China lithosphere, the formation mechanism of the thinnest crustal belt, and the distribution of granitic plutons.