动态地幔柱尾管结构

动态地幔柱模式被广泛用于讨论地球科学中的一些重要课题，如巨大火成区的成因，冈瓦纳古陆解体的原因，板块内中小尺度动力过程的驱动因素等．但是这个基于实验研究而建立的模式中，忽略了地幔柱尾管特征及其作用．地幔柱尾管内温度和速度分布是研究地幔柱上升过程的必要条件．本文从控制尾管结构的基本方程出发，给出了一个定常轴对称地幔柱温度和速度分布的近似分析解．从而得到尾管结构的基本特征：影响尾管内温度分布的主导因素是地幔柱的热流通量，而尾管内上涌速度的大小则不仅取决于热流通量，主要是取决于地幔粘度随深度的变化方式．结果表明，对弱地幔柱，尾管的热损失可能是不可忽略的，而对强地幔柱，径向质量传递可能是不可忽略的.

STRUCTURE OF TRAILING CONDUITS OF STARTING PLUMES IN THE EARTH'S MANTLE

The model of starting plumes in the earth's mantle has been widely usedto discuss some important questions in geoscience, such as the reasons of formation oflarge igneous provinces, cause for disintegration of old Gondwanaland, driving factorsfor dynamical processes which occur in intraplates and have moderate or small spacescale, and so on. But in the model derived from laboratory experiments characteristicsand effects of a trailing conduit of starting plumes in the earth's mantle has beenneglected. In a study of the uprising of a mantle plume it is necessary to find outdistribution of temperature and upwelling velocity within the trailing conduit of plumes.In the present paper an approximate analytic solution for distributions of temperatureand velocity within a steady axisymmetric plume has been obtained from the basicequations which govern the structure of the trailing conduit of mantle plumes, andthen we obtain the basic characteristics for the structure of the trailing conduits: thedominant factor for determining the distribution of temperature within the trailingconduits is the heat flux of mantle plumes, whereas the magnitude of upwellingvelocity in the trailing conduits depends not only on heat flux, and mainly on thepattern of depth dependent of viscosity in the mantle. The results demonstrate thatheat losses from the trailing conduits may not be neglected for weak plumes in theearth's mantle and radial mass transfer could not be neglected for strong plumes.