日時 ： ２００９年１２月２５日（金）※16：30～
場所 ： 愛媛大学総合研究棟Ⅰ 4F 共通会議室（理学部構内）
要 旨
We are conducting numerical simulations of mantle convection in order to study the generation of plumes in the presence of chemical heterogeneity in the mantle and continental drift. In this study we employ a model of a two-dimensional rectangular box with a periodic boundary condition along the side walls. The mantle materials are modeled by a mixture of two components with different density. The convecting motion of fluid is driven by not only a thermal but also a chemical buoyancy coming from the variation in the content of denser component. In addition, we impose a block of highly viscous fluid along the top surface as a model of continent. We also assumed that the continental block horizontally moves along with the overall convection in the mantle. Our preliminary calculations showed that, when the effect of negative chemical buoyancy is sufficiently large, a dome-like structure of the dense material develops at the base of the mantle which survives for more than 0.5 gigayears. This is consistent with the inference by Burke et al. (2008) on the fixity of the plume generation zones at least over 0.3 gigayears. We also found that the long-lived dome-like structure forms a broad region of high temperature which is similar to the superplumes or the large low shear velocity provinces (LLSVPs) observed in the lower mantle. In the seminar, we will discuss the details of our present numerical results and future directions.
問い合わせ先：土屋 卓久 TEL （089）927-8198
E-mail takut@sci.ehime-u.ac.jp
