The paleo-lithospheric structure and rifting-magmatic processes of the northern South China Sea passive margin

Zhao，Zhongxian1,3; Sun，Zhen1,2; Qiu，Ning1,2; Zhao，Minghui1,2; Zhang，Jiazheng1,2; Li，Fucheng1,2; Lin，Jian1,2,3,4; Young Lee，Eun5

2022

10.1016/j.gr.2022.06.015

GONDWANA RESEARCH   Impact Factor & Quartile

1342-937X

1878-0571

The northern South China Sea has complex rifting-magmatic styles, which are significantly distinct from the Atlantic end-member passive margins that initiated rifting in a craton, and was argued to originate from a subducted setting. Here we propose a new kinematic method to calculate the paleo-lithospheric structure and reconstruct the rifting processes along a ∼ 400 km seismic line in the northern South China Sea margin. The detailed paleo-tectonic setting and its linkage with the rifting-magmatic processes are explored. Seismic-gravity analysis reveals a “boudin-type” passive margin with a wide distal domain (>200 km) comprising discrete hyperextended zones of the Baiyun Sub-basin, Liwan Sub-basin and a narrow continent-ocean transition (<30 km). The calculated pre-rift lithospheric thickness declines abruptly from ∼ 100–80 km in the proximal margin to ∼ 40 km in the distal margin, implying that the pre-rift margin was affected by a flat to steep slab of the subducted paleo-Pacific. The steep slab lying beneath the proximal margin formed an arc where the high-density lower crust probably has a pre-rift age. The flat slab beneath the Baiyun Sub-basin to the southern conjugate margin formed a forearc. As the slab steepened and retreated to beneath the Baiyun Sub-basin in rift phase 1 (∼56–38 Ma) and Liwan Sub-basin in rift phase 2 (∼38–33 Ma), the mantle convection and slab dehydration weakened the above lithosphere successively, promoting seaward migration and younging of strong faulting, magmatic underplating, intrusion, and eruption. When slab broke suddenly at ∼ 33 Ma in the continent-ocean transition, the deep hot asthenosphere upwelled to rupture the lithosphere abruptly and induced intense magmatism. Modelling results further show that the paleo-crustal thickness and basement erosion are both fundamentally important in assessing and understanding the crustal thinning.

Boudin-type passive margin Paleo-crustal thickness Paleo-lithospheric thickness South China Sea Subducted slab setting

SCI

English

Others

Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)["GML2019ZD0205","2019BT02H594"] ; Guangzhou Municipal Science and technology program["201904010285","202102020896"] ; National Natural Science Foundation of China["42076077","U2244221","41730532","41890813"] ; China Geological Survey[DD20190378] ; Chinese Academy of Sciences["Y4SL021001","QYZDY-SSWDQC005","133244KYSB20180029","131551KYSB20200021","ISEE2021PY03"] ; Hainan Provincial Natural Science Foundation of China[422MS161] ; Guangdong Basic and Applied Basic Research Foundation: Natural Science Foundation of Guangdong Province["2021A1515011526","2022A1515011921"]

Geology

Geosciences, Multidisciplinary

WOS:001040308200001

ELSEVIER

GEOSCIENCES

2-s2.0-85134776956

Scopus

1.Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou,511458,China
2.Southern Marine Science and Engineering Guangdong Laboratory,Guangzhou,511458,China
3.Department of Ocean Science and Engineering,Southern University of Science and Technology,Shenzhen,518055,China
4.Department of Geology and Geophysics,Woods Hole Oceanographic Institution,Massachusetts,Woods Hole,02543,United States
5.University of Vienna,Department of Geology,Vienna,Austria

Zhao，Zhongxian,Sun，Zhen,Qiu，Ning,et al. The paleo-lithospheric structure and rifting-magmatic processes of the northern South China Sea passive margin[J]. GONDWANA RESEARCH,2022,120.

Zhao，Zhongxian.,Sun，Zhen.,Qiu，Ning.,Zhao，Minghui.,Zhang，Jiazheng.,...&Young Lee，Eun.(2022).The paleo-lithospheric structure and rifting-magmatic processes of the northern South China Sea passive margin.GONDWANA RESEARCH,120.

Zhao，Zhongxian,et al."The paleo-lithospheric structure and rifting-magmatic processes of the northern South China Sea passive margin".GONDWANA RESEARCH 120(2022).