マントルのレオロジーに対する実験からのアプローチ
1998 年 27 巻 1 号 p. 45-56
詳細
1998 年 27 巻 1 号 p. 45-56
Experimental studies on the rheology of the Earth's mantle have been reviewed. During the past 30 years, defomation experiments of mantle minerals androcks have been conducted by constant strain-rate and constant load tests and the microstructures in recovered samples have been observed with electron microscopy and/or an oxidation decoration method in order to understand deformation mechanisms in the mantle. Rheological properties of both single crystal and polycrystal of olivine which is the major constituent in the upper mantle have been particularly investigated. The results have indicated that their plasticities are strongly influenced by water content, oxygen fugacity and grain size as well as temperature and strain rate conditions. Seismic anisotropy in the upper mantle is most certainly due to the preferred orientation of olivine which is induced by dislocation creep. Since the middle of 1980s, deformation experiments of garnet, perovskite and their analog materials have been conducted in order to clarify the dynamics in the subducting slub, mantle transition zone and lower mantle. Ordinary deformation apparatuses such as Griggs apparatus can not directly elucidatethe effect of high pressure on the plasticity in the mantle minerals due to the limitation of their generated pressure ranges. To overcome this problem, high-pressure apparatuses such as multi-anvil apparatus have been recently applied for rheological studies.
