Aluminum Components in Bridgmanite Coexisting With Corundum and the CF‐Phase With Temperature
DOI: https://doi.org/10.1029/2022JB025739
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11126
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11126
Supplement: https://doi.org/10.5281/zenodo.7512647
Wang, Lin; Liu, Zhaodong; Koizumi, Sanae; Ballaran, Tiziana Boffa; Katsura, Tomoo, 2023: Aluminum Components in Bridgmanite Coexisting With Corundum and the CF‐Phase With Temperature. In: Journal of Geophysical Research: Solid Earth, Band 128, 1, DOI: 10.1029/2022JB025739.
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Abstract
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. Plain Language Summary:
Bridgmanite, the most abundant mineral in the Earth's mantle, can contain Al3+ in the forms of MgAlO2.5 and AlAlO3. To constrain the substitution mechanism of Al3+ in bridgmanite, we investigate the MgAlO2.5 and AlAlO3 contents in bridgmanite coexisting with a calcium‐ferrite type phase and corundum at different temperatures. Our results demonstrate that the MgAlO2.5 content reaches saturation (3–4 mol%) when an additional Al‐bearing phase exists in the system. Key Points:
The MgAlO2.5 content in bridgmanite remains constant with temperature when bridgmanite coexists with corundum and the CF‐phase.
The MgAlO2.5 content in bridgmanite reaches a solubility of 3–4 mol% when bridgmanite coexists with an additional Al‐bearing phase.
A significant amount of the Al8/3O4 component can be dissolved into the CF‐phase.
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