Lithogeochemistry of the Mid-Ocean Ridge Basalts near the Fossil Ridge of the Southwest Sub-Basin, South China Sea

Mid-ocean ridge basalts (MORB) in the South China Sea (SCS) record deep crust-mantle processes during seafloor spreading. We conducted a petrological and geochemical study on the MORBs obtained from the southwest sub-basin of the SCS at site U1433 and U1434 of the International Ocean Discovery Progr...

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Bibliographic Details
Published in:Minerals (Basel) 2020-05, Vol.10 (5), p.465
Main Authors: Sun, Kai, Wu, Tao, Liu, Xuesong, Chen, Xue-Gang, Li, Chun-Feng
Format: Article
Language:English
Subjects:
Age
Basalt
Chemical analysis
Continental crust
Crystallization
Expeditions
Fossils
Fractional crystallization
geochemistry
Isotopes
Lava
Lithogeochemistry
Magma
magma source
magmatism
Mass spectrometry
Melting
mid-ocean ridge basalt
Mid-ocean ridges
Mineralogy
Minerals
Ocean floor
Oceanic crust
Olivine
Peridotite
Plagioclase
Potassium
Scientific imaging
Sea floor spreading
Seafloor spreading
Seawater
South China Sea
Tholeiitic basalt
Trace elements
Water analysis
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Summary:Mid-ocean ridge basalts (MORB) in the South China Sea (SCS) record deep crust-mantle processes during seafloor spreading. We conducted a petrological and geochemical study on the MORBs obtained from the southwest sub-basin of the SCS at site U1433 and U1434 of the International Ocean Discovery Program (IODP) Expedition 349. Results show that MORBs at IODP site U1433 and U1434 are unaffected by seawater alteration, and all U1433 and the bulk of U1434 rocks belong to the sub-alkaline low-potassium tholeiitic basalt series. Samples collected from site U1433 and U1434 are enriched mid-ocean ridge basalts (E-MORBs), and the U1434 basalts are more enriched in incompatible elements than the U1433 samples. The SCS MORBs have mainly undergone the fractional crystallization of olivine, accompanied by the relatively weak fractional crystallization of plagioclase and clinopyroxene during magma evolution. The magma of both sites might be mainly produced by the high-degree partial melting of spinel peridotite at low pressures. The degree of partial melting at site U1434 was lower than at U1433, ascribed to the relatively lower spreading rate. The magmatic source of the southwest sub-basin basalts may be contaminated by lower continental crust and contributed by recycled oceanic crust component during the opening of the SCS.
ISSN:2075-163X
2075-163X
DOI:10.3390/min10050465