The deep thermal structure of the lithosphere in the northwestern South China Sea and its control on the shallow tectonics  

作　　者：Xiaofang WANG Haibo HUANG Hehua XU Ziqiang REN Jiazheng ZHANG Zhongxian ZHAO 

机构地区：[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

出　　处：《Science China Earth Sciences》2021年第6期962-976,共15页中国科学（地球科学英文版）

基　　金：supported by NSFC-Guangdong Joint Fund(Grant No.U20A20100);the Major Projects for Talent Research Team Introduction of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(Grant Nos.GML2019ZD0104,GML2019ZD0204);the Fund of Youth Innovation Promotion Association CAS,the Innovative Development Fund projects of the Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences(Grant No.ISEE2018PY02);the National Natural Science Foundation of China(Grant Nos.41506063,91958212,91428205,42076077);Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2020A1515010502,2017A030312002)。

摘　　要：The northwestern sub-basin of South China Sea(SCS)is a unique tectonic unit formed in the early spreading of the SCS.The northwestern Sub-basin has a series of complex geological structures such as seamounts and fault zones surrounded by the Xisha Trough,the Zhongsha Massif,and the Pearl River Valley.These extensional structures and magmatic activity in the northwestern sub-basin are closely related to the lithospheric structure and its deformation.However,details of the deep lithosphere structure are still poorly known.Here,we obtained detailed data of water and Moho depth using sonar buoys,Extended Spread Profiles(ESP),Ocean Bottom Seismometer(OBS),both Multi-beam and land-sea joint seismic surveys in the northwestern sub-basin and its surrounding areas.Then we adopted a thermal isostasy method to calculate the depth of the Lithosphere-Asthenosphere Boundary(LAB)in the northwestern sub-basin of the SCS and its surrounding regions.Results show that the range of LAB depth is~25–110 km.The shallowest burial depth is 25–60 km occurring in the ocean basin.The depth increases to 60–110 km toward the continental margin.The lithospheric structure on the north and south sides of the Xisha Trough is symmetrical and shows the deep structure and thermal features of aborted rifts.The LAB depth in the Zhongsha Trough and the Zhongsha Massif increased from 60 to 70 km southwestwards,consistent with the trend of surface morphology.The LAB depth to the west side of the Pearl River Valley is 60–80 km,and the thinning of the lithosphere is related to the distribution of faults,depressions and the magmatic activity.The LAB depth in the northwestern sub-basin and the eastern subbasin is less than 60 km with the thinnest part being less than 46 km.Combining ocean drilling,seismic investigation,and seafloor topography,we show that the ocean basin of the northwestern sub-basin of the SCS locates within the 46 km isobath of the LAB.The formation of the rifted valleys and discrete blocks surrounding the ocean basins is both cont

关 键 词：Northwestern sub-basin of SCS Thermal isostasy Ocean-continent transition zone Thickness of lithosphere 

分 类 号：P736[天文地球—海洋地质]