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The lithospheric structure in the Southwest Subbasin, South China Sea and its geological implication
Hu LiTian1,2,3; Zhang Peizhen1,2; Hao TianYao3,4,5; Xu Ya3
AbstractThe South China Sea is the largest marginal sea in the west pacific and an important place for the geodynamic research. However, compared with crustal structure, there is little data about the lithospheric structure, which is essential to study continental breakup, seafloor spreading and marginal sea dynamics. So we present two 2. 5D lithospheric profiles across the Southwest Subbasin to study its evolution process. The lithospheric model is based on the free-air gravity, geoid, elevation, heat flow and seismic data, and under three assumptions: the density of the lithosphere mantle dependent on the temperature, thermal steady-state and local isostasy. The model is divided into a number of rectangle bodies with different material properties: density, thermal conductivity and heat production. We establish the crustal model mainly based on the seismic results and calculate initial lithospheric temperature distribution and lithosphere asthenosphere boundary (LAB) by solving the steady-state heat transport equation. Forward results of the initial model are compared with the measured values and the geometry of the lithosphere is tuned until a best-fitting lithospheric structure is found. As the formulas of every geophysical data are not the same, using diverse data can reduce the uncertainty of the final model and obtain a reliable result. In the profile A-E, the base of the lithosphere varies quickly from 105 km beneath the Pearl River Mouth Basin to 50 km beneath the Xisha Trough. It is 50 similar to 60 km deep beneath Xisha Trough, Xisha-Zhongsha Islands and Southwest Subbasin. The shallowest region along the studied profile is 50km beneath the spreading center in the Southwest Subbasin. In the profile F-I, the LAB rises from 88 km beneath Xisha Islands-Zhongjian Massif to 46 similar to 50 km beneath the Southwest Subbasin, then deepens to 64km beneath Zhenghe Massif. The resent deep tow magnetic surveys and IODP results imply the age of the subbasin in the studied profile is 22 similar to 16 Ma. According to this age, the heat flow and bathymetry values calculated from the common-used cooling model are 101 similar to 114 mW . m(-2) and 3. 9 similar to 4. 1 km, respectively, differ much with the measured values, which are 75 similar to 105 mW . m(-2) and 4. 3 similar to 4. 8 km after sediment correction, implying a much older lithosphere. Therefore, the cooling model isn't suitable in the Southwest Subbasin. By comparing the profile A-E with F-I, we conclude the profile A-E stretched for a longer time, proving the Southwest Subbasin experienced propagated rifting from northeast to southwest. Finally, according to the lithospheric structure, the range of thin crust, the distribution of carbonate platform, the lower crust ductile flow, rheological structure and sedimentary characteristics, we argue the Southwest Subbasin shows a two-stage extension. The lithospheric mantle broke up first while the continental crust was still necking during its evolution. Finally, the crust broke up and the seafloor spreading started. It shows a type II non-volcanic margin.
KeywordSouthwest Subbasin Lithospheric structure Propagated rifting Type II margin
WOS Research AreaGeochemistry & Geophysics
WOS SubjectGeochemistry & Geophysics
WOS IDWOS:000495040900019
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Document Type期刊论文
Corresponding AuthorHu LiTian
Affiliation1.Sun Yat Sen Univ, Sch Earth Sci & Engn, Guangdong Prov Key Lab Geodynam & Geohazards, Guangzhou 510275, Guangdong, Peoples R China
2.Southern Marine Sci & Engn Guangdong Lab Zhuhai, Zhuhai 519082, Guangdong, Peoples R China
3.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Petr Resources Res, Beijing 100029, Peoples R China
4.Minist Nat Resources, Key Lab Submarine Geosci, Hangzhou 310012, Zhejiang, Peoples R China
5.Univ Chinese Acad Sci, Beijing 100049, Peoples R China
First Author AffilicationKey Laboratory of Petroleum Resource Research, Chinese Academy of Sciences
Corresponding Author AffilicationKey Laboratory of Petroleum Resource Research, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
Hu LiTian,Zhang Peizhen,Hao TianYao,et al. The lithospheric structure in the Southwest Subbasin, South China Sea and its geological implication[J]. CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,2019,62(9):3464-3481.
APA Hu LiTian,Zhang Peizhen,Hao TianYao,&Xu Ya.(2019).The lithospheric structure in the Southwest Subbasin, South China Sea and its geological implication.CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,62(9),3464-3481.
MLA Hu LiTian,et al."The lithospheric structure in the Southwest Subbasin, South China Sea and its geological implication".CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION 62.9(2019):3464-3481.
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