Phase Transitions in the Earth's Mantle: Implications for the Nature of the 410-km and 670-km Discontinuities

9418945菲拟议的研究将通过使用补充的高压技术(高温钻石顶盒和多砧板装置)来确定与410公里和670公里地震不连续有关的震相关系。用高温金刚石池进行同步辐射X射线原位测量，可以确定在Mg_2SiO_4-Fe_2SiO_4系统中橄榄石改性的尖晶石和尖晶石=钙钛矿+镁硅铁矿的转变。用高温金刚石池可精确测定尖晶石向钙钛矿+镁闪锌矿的转变斜率和钛铁矿向钙钛矿的转变斜率。首次在多压头装置中采用高分辨率、高效率的多室样品室设计，考察了α-β相变压力和两相区宽度的组成效应。预期结果将用于评估两个不连续面的性质，410公里不连续面的尖锐程度是否与两个相区的宽度一致，以及是否可以根据与670公里不连续面有关的过渡的斜率来评估整个地幔对流是否可以发生。

9418945 Fei The proposed research will determine phase relations relevant to the 410-km and 670-km seismic discontinuities by using complementary high-pressure techniques (high- temperature diamond-anvil cell and multi-anvil apparatus). The olivine-modified spinel and the spinel = perovskite + magnesiowustite transitions in the system Mg2SiO4-Fe2SiO4 will be determined by in situ synchrotron x-ray measurements with a high temperature diamond cell. The slopes of the transformations of spinel to perovskite plus magnesiowustite and of ilmentie to perovskite will be precisely determined with the high temperature diamond cell. The compositional effect of the alpha-beta transition pressure and width of the two-phase region will be examined for the first time by using high-resolution and high-efficiency multi-cell sample chamber design in multi-anvil apparatus. The expected results will be used to evaluate the nature of the two discontinuities,whether the sharpness of the 410-km discontinuity is consistent with the width of the two phase region, and whether whole mantle convection can occur based on the slope of the transitions related to the 670-km discontinuity.