Pervasion degree of convective mixing and investigations of mantle mixing

Abstract

Geodynamic studies have shown that mantle convection is like a giant blender to make the original heterogeneous mantle mixing and homogenizing. However, some models, especially from geochemical data show that the modern mantle may still contain a number of reservoir bodies with different chemical composition. Then, the modern mantle is homogeneous? Authors have defined a box replacement degree of convective mantle mixing and pervasion degree of convective mantle mixing (that equals to initial density of tracing elements divided by final density of tracing elements) to investigate the mantle mixing. The previous results have shown that after four billion years the mantle is basic uniform and the box replacement of the convective mantle is more than 80% in steady-state convection models. This paper calculates and discusses the pervasion degree of convective mantle mixing in detail. For the initial state we will set some 10°×10° (spacing 0.25°) tracing boxes, which includes 1 681 tracer, at the top and bottom of the mantle, and then track the motions of these tracers, and investigate the convective mixed pervasions. The results show that at the initial stage though the convective mixing pervasions are very different from mode to mode, after running for some time, the convective mixing pervasions for most modes are going to be a constant and the tracers are more evenly distributed in the whole mantle.