地幔柱的发生机制研究——以Ferrar为例

利用三维数值模拟方法, 根据地幔对流控制方程, 以180 Ma喷发的Ferrar大火成岩省(LIP)为例, 在模型中引入Pangea超大陆、大型横波低速带(LLSVPs)和Pangea超大陆边缘的俯冲带, 模拟地幔对流过程, 研究其对应地幔热柱从地球内部热边界层(例如核幔边界)的生成过程, 并讨论导致该地幔柱产生的相关因素。结果表明, LLSVPs的形状以及俯冲带与LLSVPs边缘的距离对地幔柱的发生位置影响巨大; 地幔柱多起源于LLSVPs边缘曲率较大的位置, 并随着俯冲带与LLSVPs边缘的距离增加逐渐向远离LLSVPs边缘的方向偏移; 俯冲带的黏度影响地幔柱发生的时间, 但不影响地幔柱的位置。

Study on the Mechanism of Mantle Plume Production:Taking Ferrar as an Example

According to the mantle convection control equations, taking the Ferrar large igneous province (LIP) erupted at 180 Ma as an example, we used the 3D numerical simulation method and introduced Pangea supercontinent, large low shear velocity provinces (LLSVPs), subductions surrounding Pangea supercontinent to simulate mantle convection process. The evolution process of Ferrar LIP from the interior thermal boundary layer of the earth (such as the core-mantle boundary) and the related factors affecting the location of mantle plumes are discussed. The results show that the shape of LLSVPs and the distance between subduction zone and LLSVPs’ edge have great influence on the location of mantle plumes. The mantle plumes often rise from the position where the curvature of the LLSVPs’ edge is large, and gradually shift away from the LLSVPs’ edge with the increase of the distance between the subduction zone and the LLSVPs’ edge. The viscosity of the subduction zone affects the timing of the mantle plume emergence, but not the location of the mantle plume production.