Meeting room "Glova", 4 floor, Integrated Research Building
Abstract
We conducted numerical experiments of mantle convection in order to study the generation of ascending plumes in the presence of chemical heterogeneity and continental drift. In this study, we consider a convection of two-component fluid, under the extended Boussinesq approximation, in a model of a two-dimensional rectangular box of 2900km height and the aspect ratio (width/height) of 12. In addition, we impose a block of highly viscous fluid of 11600km width along the top surface, as a model of a supercontinent. We also take into account the effects of a drifting motion of supercontinent, by allowing a coherent (rigid) and horizontal motion of continental block driven by the overall convection in the mantle.
Our calculations demonstrated that the thermal and chemical state in the deep mantle is significantly affected by the presence of the continental block at the top surface. In particular, owing to a strong ``blanketing effect'', both thermally and chemically, caused by the continental block, a pile of dense and hot materials firmly develops beneath the initial position of the continent. The thermochemical pile, once it forms beneath the continental block, remains strong enough to dominate the overall convection in the mantle, causing intense ascending flows in its neighborhood. We also found that the viscosity of the bulk lower mantle is of crucial importance in controlling the behaviors of the blocks of dense materials at the base of the mantle. The blocks remain as several isolated patches when the viscosity is sufficiently high, while for low viscosity they are drawn and absorbed by the major thermochemical pile which is initially formed beneath the supercontinent. This finding highlights the potential importance of rheological properties to the development of the thermochemical structure of the deep mantle.
For inquiry：Taku Tsuchiya TEL:（089）927-8198
E-mail takut@sci.ehime-u.ac.jp
