HR: 0830h
AN: V21D-0545    [PDF]
TI: Condition of Development of Channeled Flow in Analogue Partially Molten Medium
AU: * Takashima, S
EM: takasima@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, Univ. of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032 Japan
AU: Kumagai, I
EM: kumaton@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, Univ. of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032 Japan
AU: Kurita, K
EM: kurikuri@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, Univ. of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032 Japan
AB: Melt migration in partially molten medium is conceptually classified into two contrasting models; homogeneous permeable flow and localized channeled flow. The transition from homogeneous flow to localized one is promoted with advance of melting and deformation of the medium, but the physics behind this transition is not yet clarified well. Here we show two kinds of experimental results which are mutually related. One is a development of the channeled flow in a so-called Rayleigh-Taylor Instability experiments. Dense viscous fluid is poured at the top of the matrix fluid; homogeneous mixture of soft transparent gel and viscous fluid having equal density. Liquid fraction is varied for this matrix fluid to see how the fraction controls the development. At the intermediate gel fraction (between70% to about 40%) the dense fluid at first migrates through the grain boundary as permeable flow. But local heterogeneity in the gel fraction induces relative movement of solid phase, which in turns enhances the localization of the flow and deformation. We measured the motion of fluid phase and solid phase separately by PIV/PTV methods. Estimated relative motion and divergence of velocity field of the solid phase show that the state in the relative movement of the solid phase could cause heterogeneous distribution of the solid fraction. The deformation-induced compaction plays an important role. The second experimental result is rheology of the dense suspension of soft gel and viscous fluid. Deformation experiment with concentric cylinders shows that the mixture system has yield strength at the intermediate gel fraction. In the stress state above the yield strength the region where deformation rate is large has low viscosity and its internal structure evolves to the state in heterogeneous distribution of viscosity. We would like to show that this nature is critical in the development of flow from homogeneous one to localized one.
DE: 8145 Physics of magma and magma bodies
DE: 8160 Rheology--general
DE: 8434 Magma migration
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting