[M-GI35] 計算科学が拓く宇宙の構造形成・進化から惑星表層環境変動まで

[MGI35-P05] 対流する固体のマントルにおけるマグマの生成・移動・集中・再固結の三次元モデリング

*柳澤 孝寿¹、亀山 真典²、小河 正基³ (1.国立研究開発法人海洋研究開発機構 海域地震火山部門、2.愛媛大学地球深部ダイナミクス研究センター、3.東京大学大学院総合文化研究科)

キーワード：マントル対流、火成活動、三次元モデル

Magmatism in rocky mantle of terrestrial planets is one of the most important factors for surface tectonics and volcanic activities. It is also an essential mechanism for the evolution of internal structure of planets. Melting in mantle induces differentiation of the composition resulting a formation of crust. We treat a series of process of magma ascent in a numerical simulation including magma generation, migration, concentration, and re-solidification in a simplified setting. The background is a slowly convecting mantle of solid phase. Melting and solidification, that is phase changes of the material, occur depending on the thermodynamics. We set an idealized solidus curve depending on the depth; the generated melt is slightly lighter than the solid material. In the model, migration of melt is modeled as a permeable flow driven by the density difference. When a relative motion between the melt and solid occurs, the porosity of mantle rock changes and the permeability is reduced or increased. There is also a feedback process from the existence of melt to the convective motion of the solid mantle. The important parameters in this modeling are Rayleigh number for solid mantle convection and non-dimensional permeability relating to magma migration. We succeeded in the three-dimensional treatment of this calculation in horizontally wide geometries. Though this model does not include such as crust and lithospheric plate at present, it will help quantifying spatial scales of magmatic activities and time scales of structural evolution in rocky mantle.