The mid-ocean ridge hydrothermal circulation system of thermal discharge and the magma system thermal injection jointly controlled the generation of the oceanic crustal thickness in the expansion period.Magmatic fluid is one of the fluid compositions of hydrothermal circulation systems,often mixed with seawater participate in energy and material transfer in each sphere,but the influence mechanism of energy transfer on the shell thickness is unclear.The relationship between magma fluid and oceanic crustal thickness in the hydrothermal circulation system during expansion is studied using the finite element numerical simulation method.The results show that:(1)Compared with the convective cycle involving only seawater,the hydrothermal cycle with magmatic fluid results in greater thinning of oceanic crustal thickness and higher temperature of hydrothermal vents.(2)The secondary thinning effect of magmatic fluid on oceanic crustal thickness decreases with the increase of magmatic fluid content,and the temperature of hydrothermal vents increases with the increase of magmatic fluid content.(3)The distribution of magmatic water,mantle water,and oceanic crustal thickness in the South China Sea is heterogeneous.The content of mantle water and magma water in the eastern subbasin is higher than that in the southwest subbasin,and the average oceanic crustal thickness in the former is also higher than that in the latter.There is an abnormally thin oceanic crust near the residual spreading ridge of the basin.Combined with the model results,it is concluded that the thin oceanic crust near the residual spreading ridge may be affected by hydrothermal circulation or later magmatic fluids,while the difference in oceanic crustal thickness between the eastern and southwestern subbasins may be due to the higher magmatic fluid content in the former than in the latter.
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