Abstract
The nature of upper mantle is important to understand the evolution of the South China Sea (SCS); thus, we need better constrains on its mantle heterogeneity. Magma water concentration is a good indicator, but few data have been reported. However, the rarity of glass and melt inclusions and the special genesis for phenocrysts in SCS basalts present challenges to analyzing magmatic water content. Therefore, it is possible to estimate the water variations through the characteristics of partial melting and magma crystallization. We evaluated variations in Fe depletion, degree of melt fractions, and mantle source composition along the fossil spreading ridge (FSR) using SCS basalt data from published papers. We found that lava from the FSR 116.2° E, FSR 117.7° E, and non-FSR regions can be considered normal lava with normal water content; in contrast, lava from the FSR 117° E-carbonatite and 114.9–115.0° E basalts have higher water content and show evidence of strong Fe depletion during the fractional crystallization after elimination of the effects of plagioclase oversaturation. The enriched water in the 117° E-carbonatite basalts is contained in carbonated silicate melts, and that in the 114.9–115.0° E basalts results from mantle contamination with the lower continental crust. The lava from the 117° E-normal basalt has much lower water content because of the lesser influence of the Hainan plume. Therefore, there must be a mantle source compositional transition area between the southwestern and eastern sub-basins of the SCS, which have different mantle evolution histories. The mantle in the west is more affected by contamination with continental materials, while that in the east is more affected by the Hainan mantle plume.
Highlights
The formation of the South China Sea (SCS) has always been a hot topic in research, with multiple genetic models being explored [1,2,3,4,5,6,7,8], and the key research area for the petrologist is the nature of the upper mantle
The mantle in the west is more affected by contamination with continental materials, while that in the east is more affected by the Hainan mantle plume
The details of the volcanic rock total alkali silica (TAS) classification and primary melt calculation are shown in Supplementary Materials Section S1, S3, and Figure S1
Summary
The formation of the South China Sea (SCS) has always been a hot topic in research, with multiple genetic models being explored [1,2,3,4,5,6,7,8], and the key research area for the petrologist is the nature of the upper mantle Such studies have been limited by the lack of fresh volcanic samples. Thereby, it increases the denominator in the definition of the mean extent of melting (F), and causes a decrease in the mean extent of melting [39] Based on these characteristics, it helps to identify high water mantle sources. We use SCS basalt data from published papers to evaluate variations in CA characteristics (Fe depletion), the degree of mantle melting, and mantle source composition along the FSR.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
