南海扩张期岩浆流体对洋壳厚度的影响: 数值模拟  

Influence of magmatic fluid on oceanic crustal thickness during the expansion period of the South China Sea: Numerical modeling

作　　者：张慧慧[1,3] 许鹤华 邵佳[4] 姚永坚 何丽娟 ZHANG HuiHui;XU HeHua;SHAO Jia;YAO YongJian;HE LiJuan(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 511458,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Department of Marine Science and Engineering,Southern University of Science and Technology,Shenzhen 518055,China;Key Laboratory of Submarine Mineral Resources,Ministry of Natural Resources,Guangzhou Marine Geological Survey,Guangzhou 510760,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中国科学院边缘海与大洋地质重点实验室,南海海洋研究所,南海生态环境工程创新研究院,广州511458 [2]南方海洋科学与工程广东省实验室(广州),广州511458 [3]中国科学院大学地球与行星科学学院,北京100049 [4]南方科技大学海洋科学与工程系,深圳518055 [5]广州海洋地质调查局自然资源部海底矿产资源重点实验室,广州510760 [6]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029

出　　处：《地球物理学报》2024年第2期615-629,共15页Chinese Journal of Geophysics

基　　金：NSFC-广东联合基金项目(U20A20100);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0104);中国科学院战略性先导科技专项(A类)(XDA13010303)联合资助.

摘　　要：扩张期洋中脊热液循环系统的热排出与岩浆系统的热注入共同控制着洋壳厚度的生成,而岩浆流体是热液循环系统的流体成分之一,往往与下渗海水混合参与各圈层能量和物质传递,但其能量传递对洋壳厚度的影响机制目前还不清楚.利用有限元的数值模拟手段,对扩张期热液循环系统中岩浆流体与洋壳厚度的关系进行研究.结果表明:(1)相较于只有海水参与的对流循环,含有岩浆流体的热液循环造成的洋壳厚度的减薄量更大、热液喷口温度更高.(2)岩浆流体对洋壳厚度的二次减薄作用随其含量的增大而减弱,热液喷口温度随其含量的增大而升高.(3)南海岩浆水、地幔水含量和洋壳厚度的分布具有非均质性,东部次海盆的地幔水、岩浆水含量高于西南次海盆,前者的平均洋壳厚度也大于后者,并且在海盆残余扩张脊附近存在异常薄洋壳.结合模型结果分析认为,残余扩张脊附近的薄洋壳可能受到扩张期热液循环或后期岩浆流体的影响,而东部、西南次海盆的洋壳厚度差异可能是由于前者的岩浆流体含量高于后者而造成的.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.

关 键 词：热液循环 岩浆流体 洋壳厚度 数值模拟 洋壳增生 南海 异常薄洋壳 

分 类 号：P738[天文地球—海洋地质]