Publication Date:
2022-05-27
Description:
Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 126(2), (2021): e2020JB020735, https://doi.org/10.1029/2020JB020735.
Description:
We simulate mantle flow, thermal structure, and melting processes beneath the ridge axis of the South China Sea (SCS), combining the nominally anhydrous melting and fractional crystallization model, to study mantle heterogeneity and basin evolution. The model results are constrained by seismically determined crustal thickness and major element composition of fossil ridge axis basalts. The effects of half-spreading rate, mantle potential temperature, mantle source composition, and the pattern of melt migration on the crustal thickness and magma chemical composition are systematically investigated. For the SCS, the east and southwest (SW) subbasins have comparable crustal thickness, but the east subbasin has higher FeO and Na2O contents compared to the SW subbasin. The estimated best fitting mantle potential temperatures in the east and SW subbasins are 1,360 ± 15 °C and 1,350 ± 25 °C, respectively. The mantle in the east subbasin (site U1431) prior to the cessation of seafloor spreading is composed primarily of the depleted mid-ocean ridge basalt mantle (DMM), and is slightly contaminated by eclogite/pyroxenite-rich component. However, the mantle source composition of the SW subbasin (sites U1433 and U1434) contains a small percentage (2–5%) of lower continental crust. Basalt samples at the northern margin of the east subbasin (site U1500) shows similar chemical characteristics with that of the SW subbasin. We suggest that the basin-scale variability in the mantle heterogeneity of the SCS can be explained by a single model in which the contamination by the lower continental crust is gradually diluted by melting of DMM as the ridge moves away from the rifted margin.
Description:
This work is supported by National Natural Science Foundation of China (41890813, 91628301), Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0205), Chinese Academy of Sciences (Y4SL021001, QYZDY-SSW-DQC005, 133244KYSB20180029), International Exchange Program for Graduate Students of Tongji University (201502, 201801337), Chinese Scholarship Council (201606260207), and US National Science Foundation (OCE-14-58,201). A special acknowledgement should be expressed to China-Pakistan Joint Research Center on Earth Sciences that supports the implementation of this study.
Description:
2021-07-13
Repository Name:
Woods Hole Open Access Server
Type:
Article
