全球地表热流的产生与分布

GENERATION AND DISTRIBUTION OF GLOBAL HEAT FLOW

全球地表热流是反映地球内部热与动力学过程的一种主要能流 .本文在三维球坐标框架下 ,就几个不同的粘度模型分别研究地幔内部密度异常 (基于全球地震层析结果 )以及板块运动激发的地幔流动的热效应及其对于观测地表热流产生和分布特征的贡献 .由于地幔动力系统具有较高的Pe数 ,可以期望由板块运动激发的地幔流动将强烈地扰动地幔内部初始传导状态下的温度场以及地表热的热流分布 .结果表明 ,与地幔内部密度异常产生的热效应相比 ,运动的板块及其激发的地幔流动在全球地表观测热流的产生和分布特征上起着更为重要的作用 .观测到的大洋中脊处的高热流在很大程度上可以归因于板块激发的地幔流动的热效应 .计算的平均温度剖面较好地揭示了岩石圈和D″层的温度特征 ,即温度随深度的剧烈变化 ,这与我们目前通过其他手段对岩石圈和D″层的温度结构了解是一致的 .一个下地幔粘度比上地幔高出 30倍的粘度结构 (文中使用的粘度模型 2 )较之其余模型的拟合程度似乎更好 .

The globle heat flow is the primary energy flow responsible for the dynamic of nature of our planet. In this study we investigate in a three dimensional spherical geometry frame, the generation and distribution characteristics of global heat flow on the basis of exploring thermal effects of density anomaly and platedriven mantle flows. Results show that the thermal effect of plate motion driven mantle flow and its contribution to the observed heat flow is greater than that due to internal density anomaly (tomography based). Higher values of observed heat flow in mid ocean ridge system could be accuounted for, to a great extent, by the thermal effect generated by the plate driven mantle flow. Furthermore, the predicted average temperature as function of depth reveals the features of an isothermal core and two thermal boundary laters at the surface and the core mantle boundary. An approximate thickness of 150km for lithosphere within which the temperature rapidly varies can be obtained. A mantle viscosity model, in which viscosity in the lower mantle is 30 times than that in the upper mantle, appears to fit data better.