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洋中脊与地幔柱相互作用诱发的洋脊抽吸作用,被认为是产生富集型洋中脊玄武岩以及某些洋岛和海山的重要地质过程。但是,对于边缘海扩张是否同样会产生洋脊抽吸作用并控制其周边的玄武质岩浆活动,目前仍不清楚。南海海盆是世界上最大的边缘海海盆之一,它的扩张时间为~32~16 Ma。由于其周边分布有大量的软流圈来源的玄武岩,因而是讨论这一问题的理想研究区。文章对相对远离南海扩张中心的浙江省新生代玄武岩进行了K-Ar定年工作,发现浙江余姚的新生代玄武岩主要形成于渐新世至早中新世(32.2~21.7 Ma),属于南海扩张期的玄武岩。前人研究发现,南海周边的新生代玄武岩主要是形成于南海盆地扩张结束之后。结合前人数据和此次研究的年龄结果发现,越远离南海扩张中心,中国东南部的南海扩张期玄武质岩浆活动越密集。洋脊抽吸作用可以很好的解释这一时空分布规律,因为上涌的地幔流会汇聚在南海扩张中心的区域。而在浙江地区发现了南海扩张期玄武岩,则表明该区域深部的地幔流并没有受到南海洋脊抽吸作用的显著影响。
The mid-ocean ridges and mantle plume-induced ocean ridge pumping are thought to be important geologic processes that produce enriched mid-oceanic ridge basalts and some oceanic and seamounts. However, it remains unclear whether the marginal sea expansion will also produce the ocean ridge suction and control the surrounding basaltic magmatic activity. The South China Sea basin is one of the largest marginal sea basins in the world and its expansion time is ~ 32-16 Ma. Due to the abundance of basalt from the asthenosphere, it is an ideal research area for discussing this issue. In this paper, the K-Ar dating of Cenozoic basalts in Zhejiang Province, which is relatively far away from the South China Sea expansion center, was found. The Cenozoic basalts of Yuyao, Zhejiang Province, were mainly formed from Oligocene to Early Miocene (32.2 ~ 21.7 Ma) Basalt. Previous studies have found that the Cenozoic basalts around the South China Sea were formed mainly after the expansion of the South China Sea basin was over. Based on previous data and the age of the study, we found that the farther away from the South China Sea expansion center, the more intensive the South China Sea expansion phase basaltic magmatism in southeastern China. Ridge aspiration can explain this spatial-temporal distribution well because the upwelling mantle flow converges in the area of the South China Sea expansion center. The discovery of the Nanhai expansion basalts in Zhejiang Province indicates that the deep mantle flow in the area is not significantly affected by the suction of the South China Sea Ridges.