Oct 16, 2013
NAL phase in K-rich portions of the lower mantle
Geophysical Research Letters
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- Volume
- 40
- Number
- 19
- First page
- 5085
- Last page
- 5088
- Language
- English
- Publishing type
- Research paper (scientific journal)
- DOI
- 10.1002/grl.50966
The stability of the K-rich new aluminous (NAL) phase was examined on the join Na1.00Mg2.00Al4.80Si1.15O 12-K1.00Mg2.00Al4.80Si 1.15O12 (Na100-K100) up to 144 GPa by X-ray diffraction in a laser-heated diamond anvil cell. Single-phase K100 and Na50K50 NAL were formed up to the lower mantle conditions, and the NAL phase coexisted with the calcium ferrite-type (CF) phase at 120 GPa and 2300 K for the Na75K25 bulk composition. This is a striking contrast to the K-free (Na100) NAL that becomes unstable above 27 GPa at 1850 K, which suggests that potassium stabilizes NAL at significantly higher pressures. K-rich NAL may host potassium in the lower mantle that contains K2O more than 0.09 wt %. In addition, the NAL phase likely formed owing to partial melting in the ultralow-velocity zone or because of a basal magma ocean. Future seismological observations may clarify whether NAL is a radiogenic heat source above the core-mantle boundary. Key Points Potassium expands the stability of the NAL phase dramatically K-rich NAL is stable o the lowermost mantle conditions NAL forms in the whole lower mantle where the K2O content is higher than 900 ppm ©2013. American Geophysical Union. All Rights Reserved.
- Link information
- ID information
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- DOI : 10.1002/grl.50966
- ISSN : 0094-8276
- ISSN : 1944-8007
- SCOPUS ID : 84884998125