Mantle Heterogeneity and Melting Processes in the South China Sea: Thermal and Melting Models Constrained by Oceanic Crustal Thickness and Basalt Geochemistry

Zhang，Xubo1,2,3,4,5; Lin，Jian1,2,3,5,6; Behn，Mark D.5,7

2021-02-01

10.1029/2020JB020735

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH   影响因子和分区

2169-9313

2169-9356

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 NaO 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.

SCI

英语

通讯

WOS:000631921200033

GEOSCIENCES

2-s2.0-85101532195

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,China
2.Southern Marine Science and Engineering,Guangdong Laboratory (Guangzhou),Guangzhou,China
3.China-Pakistan Joint Research Center on Earth Sciences,CAS-HEC,Islamabad,Pakistan
4.State Key Laboratory of Marine Geology,School of Ocean and Earth Science,Tongji University,Shanghai,China
5.Department of Geology and Geophysics,Woods Hole Oceanographic Institution,Woods Hole,United States
6.Department of Ocean Science and Engineering,Southern University of Science and Technology,Shenzhen,China
7.Department of Earth and Environmental Sciences,Boston College,Chestnut Hill,United States

Zhang，Xubo,Lin，Jian,Behn，Mark D.. Mantle Heterogeneity and Melting Processes in the South China Sea: Thermal and Melting Models Constrained by Oceanic Crustal Thickness and Basalt Geochemistry[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,2021,126(2).

Zhang，Xubo,Lin，Jian,&Behn，Mark D..(2021).Mantle Heterogeneity and Melting Processes in the South China Sea: Thermal and Melting Models Constrained by Oceanic Crustal Thickness and Basalt Geochemistry.JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,126(2).

Zhang，Xubo,et al."Mantle Heterogeneity and Melting Processes in the South China Sea: Thermal and Melting Models Constrained by Oceanic Crustal Thickness and Basalt Geochemistry".JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 126.2(2021).