中国科学院大学计算地球动力学重点实验室

The geoid, one of the most important geophysical observations, has been well explained in mantle flow models with the buoyancy inferred from seismic models that in turn place constraints on mantle viscosity structure. These models often assume a simple whole-mantle convection with uniform composition and 1-D viscosity. However, seismic and geochemical observations suggest possible existence of chemically distinct piles under Africa and Pacific which extends hundreds of kilometers above the CMB (i.e., LLSVPs).  We formulate a thermochemical mantle model with chemically distinct and stable piles. This models can reconcile the geoid observation with the interpolation of LLSVPs as long-term stable chemical piles. The viscosity structure as well as density anomalies in the thermochemical mantle are inferred.