弹性岩石层、区域重力异常和上地幔小尺度对流

在小尺度地幔对流模型的基础上 ,建立了顾及岩石层与地幔耦合的地幔对流模型。考虑到岩石层对上地幔小尺度对流的弹性响应 ,将上地幔视为一均匀的等粘滞系数的牛顿粘滞流体 ,其对流能量来源于下地幔 ,用热流体动力学基本方程得到的上地幔对流在壳幔边界处的垂向应力作为弹性板弯曲方程的垂直加载 ,来耦合弹性岩石层和可流动地幔。推导了两者耦合下区域重力异常和上地幔小尺度对流的相关方程 ,用以反演上地幔小尺度对流流场模式和岩石层底部拖曳力场格局。对比了有、无弹性岩石层影响的模型之间的差异 ,并对模型应用范围 ,特别是板块边界水平构造力可能产生的影响 ,作了进一步探讨。

ELASTIC LITHOSPHERE, REGIONAL ISOSTATIC GRAVITY ANOMALY AND SMALL SCALE CONVECTION IN THE UPPER MANTLE

Because of the elastic lithosphere's overlapping the uppermost mantle, the elastic lithosphere and the convection in the upper mantle together affect boundary deformations and the gravity anomaly. On the basis of the model of small scale convection in upper mantle, a new convection model which give consideration to the coupling of lithosphere with mantle is set up.This work assumes that the lithosphere is homogeneous elastic thin board, the upper mantle is homogeneous newtonian viscous fluid, and that the energy of the thermal convection current comes from the lower mantle. In accordance with basic fluid dynamic equations we establish a thermal convection model, which is constrained on the regional isostatic gravity anomaly. Considering the stresses of both the convection and the elastic lithosphere at the LM boundary, we get a new boundary deformation condition, deduce the gravity anomalies of the density heterogeneity and the boundary deformations and draw a conclusion about the correlative equation of regional isostatic anomaly and the small scale convection model in the upper mantle.Comparing the old model with the new one, we find that the new model is similar to the old one in the patterns of mantle convection and stress distribution, and that the convective velocity of new one is close to the old one's. It is shown that the mantle convection from the new model is more stable than the old one.