Phase transition of Ca-perovskite and stability of Al-bearing Mg-perovskite in the lower mantle
Phase transition of Ca-perovskite and stability of Al-bearing Mg-perovskite in the lower mantle
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DOI：
10.2138/am-2004-1016
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发表时间：
2004-10
影响因子：
3.1
通讯作者：
S. Ono;Y. Ohishi;K. Mibe
中科院分区：
文献类型：
--
作者：
S. Ono;Y. Ohishi;K. Mibe
摘要 本文采用原位 X 射线衍射技术，结合高温高压激光加热金刚石砧座，研究了 38 至 106 GPa、300 至 2600 K 范围内 KLB-1 橄榄岩成分样品的相关系，以确定下地幔中相的稳定性。我们观察到含铝镁钙钛矿和镁方石在高达 106 GPa 的压力下仍保持稳定，这对应于 2400 km 的下地幔深度。相比之下，观察到钙钛矿从立方结构到四方结构的相变。在 300 K 时，这种材料的变形量随着压力的增加而增加。因此，四方结构向立方结构转变的温度似乎随着压力的增加而增加。这种卡普罗夫斯基相变有可能导致下地幔中未识别的地震异常。
Abstract Here, using in situ X-ray diffraction combined with a laser-heated diamond anvil cell at high temperatures and high pressures, a phase relationship in KLB-1 peridotite composition samples was investigated from 38 to 106 GPa, and 300 to 2600 K, in order to determine the stability of phases in the lower mantle. We observed that Al-bearing Mg-perovskite and magnesiowüstite remained stable up to 106 GPa, which corresponds to a lower mantle depth of 2400 km depth. By contrast, a phase transition in Ca-perovskite from a cubic to a tetragonal structure was observed. The amount of distortion in this material increases as pressure increases at 300 K. The temperature of the tetragonal to cubic structure transition, therefore, appears to increase with increasing pressure. There is a possibility that this Caperovskite phase transition contributes to unidentified seismic anomalies in the lower mantle.