地幔对流的实验研究:非立柱状幔柱和地幔涡旋

EXPERIMENTAL STUDY OF MANTLE CONVECTION: NON COLUMNAR PLUME AND MANTLE VORTEX

地幔对流的物理模拟实验结果表明 ,在地幔介质和温度非均匀分布的复杂条件下 ,热卷流 (地幔柱 )往往由立柱状转变为非立柱状 (含斜柱状、涡旋状等 )。在忽略科里奥利力的情况下 ,板块的下插和滞积下沉、岩石圈根的存在以及地幔介质粘度的非均匀分布等都可能构成不同形状的障碍 -导流体 ,导致地幔的涡旋运动。软流圈中的水平涡旋环带属于对数螺线型 ,环带旋转半径及线速度逐渐减小 ,最终在旋转中心处下沉 。

The physical modeling of mantle convection based on the theory of similarity provides an approach to understanding the origin and mechanism of mantle vortex. The results of the experiments indicate that: thermal plumes in the mantle (i.e. mantle plumes) should be divided into two types, vertical plumes, as mentioned traditionally, and non vertical plumes, including those of inclined columns, vortexes, etc., and the former may be only a particular case of the latter; under the condition of the Coriolis force to be ignored. Vortex like plume can result from a variety of flow guides, such as those formed by the subduction, stagnancy and flush of lithospheric slab, the existence of lithospheric roots, and the inhomogeneous viscosity distribution in the mantle; the mantle vortex in the asthenosphere flows along a logarithmic spiral trajectory with its rotating radius and linear velocity decreasing gradually while its angular velocity roughly to be constant.