Karato S, Li P
Science. 1992 Mar 6;255(5049):1238-40. doi: 10.1126/science.255.5049.1238.
High-temperature creep experiments on polycrystalline perovskite (CaTiO(3)), an analog of (Mg,Fe)SiO(3) perovskite of the lower mantle, suggest that (grain size-sensitive) diffusion creep is important in the lower mantle and show that creep rate is enhanced by the transformation from the orthorhombic to the tetragonal structure. These observations suggest that grain-size reduction after a subducting slab passes through the 670-kilometer discontinuity or after a phase transformation from orthorhombic to tetragonal in perovskite will result in rheological softening in the top portions of the lower mantle.
对多晶钙钛矿（CaTiO₃）进行的高温蠕变实验表明，下地幔中（对晶粒尺寸敏感的）扩散蠕变很重要。多晶钙钛矿是下地幔中（Mg,Fe）SiO₃钙钛矿的类似物，实验还表明，从正交结构转变为四方结构会提高蠕变速率。这些观察结果表明，俯冲板块穿过670公里间断面后，或者钙钛矿从正交结构转变为四方结构后，晶粒尺寸减小将导致下地幔顶部的流变软化。
