Aluminum Components in Bridgmanite Coexisting With Corundum and the CF‐Phase With Temperature
Aluminum Components in Bridgmanite Coexisting With Corundum and the CF‐Phase With Temperature
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DOI：
10.1029/2022jb025739
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发表时间：
2023-01
期刊：
影响因子：
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通讯作者：
Lin Wang;Zhaodong Liu;S. Koizumi;T. B. Ballaran;T. Katsura
中科院分区：
文献类型：
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作者：
Lin Wang;Zhaodong Liu;S. Koizumi;T. B. Ballaran;T. Katsura
利用多砧实验装置在27 GPa和2000-2600 K下研究了MgSiO 3-MgAl 2 O 4-Al 2 O3系统的相关系。在2000 ~ 2600 K的温度范围内，硼镁石中AlAlO 3的含量随温度的升高而从8.6摩尔%增加到20.0摩尔%，而MgAlO2.5的含量几乎保持不变，即在这些温度下为3-4摩尔%。因此，额外的含Al相的存在抑制了氧空位对桥镁石中Al 3+的取代。相反，大量的Al 8/3 O 4组分可以溶解到钙铁氧体型MgAl 2 O 4-Mg 2SiO 4-Al 8/3 O 4相（CF-相）中，这意味着CF-相可能含有一定量的空位。因此，CF相也可能是将挥发分输送到下地幔的候选矿物。我们的研究结果，结合先前对含铝的硼镁石的研究，表明一旦硼镁石中每个分子式单元的Al超过0.12，MgAlO2.5的含量几乎保持不变，AlAlO 3组分占主导地位。
Phase relations in the MgSiO3–MgAl2O4–Al2O3 system are investigated at 27 GPa and 2000–2600 K using a multi‐anvil apparatus. The AlAlO3 content in the bridgmanite increases from 8.6 to 20.0 mol% with increasing temperature from 2000 to 2600 K, while the MgAlO2.5 content remains nearly constant, that is, 3–4 mol% at these temperatures. Therefore, the presence of an additional Al‐bearing phase suppresses the oxygen vacancy substitution for Al3+ in bridgmanite. Conversely, significant amounts of the Al8/3O4 component can be dissolved into the calcium‐ferrite type MgAl2O4–Mg2SiO4–Al8/3O4 phase (CF‐phase), implying that the CF‐phase likely contains some amount of vacancies. Therefore, the CF‐phase could also be a candidate mineral for transporting volatiles into the lower mantle. Our results, combined with previous studies on Al‐bearing bridgmanite, indicate that, once the Al per formula unit exceeds 0.12 in bridgmanite, the MgAlO2.5 content remains nearly constant and the AlAlO3 component becomes dominant.