Mantle Geochemical Geodynamics

Abstract

Geochemical observations offer one of the most important constraints on mantle structure and evolution, yet interpretations of these have often been in apparent contradiction with geophysical constraints. Thus, a major focus of research has been to understand the interaction between geodynamical processes, particularly mantle convection, and chemical variations, and thus what controls the resulting observed geochemical signatures. Here is presented a review of this field of research. The chapter first covers the mechanisms by which chemical heterogeneities originate, and geochemical observations and constraints. Then, the physics of the stirring and mixing of passive heterogeneities is presented, including both mathematical theory and experimental results. Chemical layering of the mantle features in many conceptual models, so the dynamics and evolution of layered convection is then discussed. Next, the chapter turns to dynamical models that track specific trace elements, and finally new concepts that may result in a revision of traditional geochemical interpretations, and the outlook for the future.