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Si-rich Mg-sursassite Mg4Al5Si7O23(OH)5 with octahedrally-coordinated Si: a new ultra-high-pressure hydrous phaseстатья
Информация о цитировании статьи получена из
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 19 октября 2022 г.
- Авторы: Bindi L., Welch M.D., Bendeliani A.A., Bobrov A.V.
- Журнал: American Mineralogist
- Том: 105
- Год издания: 2020
- Издательство: Mineralogical Society of America
- Местоположение издательства: United States
- DOI: 10.2138/am-2020-7533
- Аннотация: The crystal structure of a new high-pressure hydrous phase, Si-rich Mg-sursassite, of composition Mg4Al5Si7O23(OH)5, that was produced by sub-solidus reaction at 24 GPa and 1400 °C in an experiment using a model sedimentary bulk composition, has been determined by single-crystal X-ray diffraction. The phase was found to be topologically identical to Mg-sursassite, Mg5Al5Si6O21(OH)7, and has space group P21/m and lattice parameters a = 8.4222(7), b = 5.5812(3), c = 9.4055(9) Å, β = 106.793(8)°, V = 423.26(6) Å3 and Z = 1. The empirical formula determined by electron microprobe analysis of the same crystal as was used in the X-ray experiment is [Mg3.93Fe0.03]Σ3.96 [Al4.98Cr0.04]Σ5.02 Si7.02O23(OH)5, with hydroxyl content implied by the crystal structure analysis. The most significant aspect of the structure of Si-rich Mg-sursassite is the presence of octahedrally-coordinated Si. Its structural formula is M1,VIIMg2 M2,VIMg2+2 M3,VI(Al0.5Si0.5)2 M4,VIAl2 M5,VIAl2 T1,IVSi2 T2,IVSi2 T3,IVSi2 O23(OH)5. Si-rich Mg-sursassite joins the group of hydrous ultra-high-pressure phases with octahedrally-coordinated Si that have been discovered by experiment, and that may play a significant role in the distribution and hosting of water in the deep mantle at subduction zones. The reactions defining the stability of Si-rich Mg-sursassite are unknown, but are likely to be fundamentally different from those of Mg-sursassite, and involve other ultra-high-pressure dense structures such as Phase D, rather than Phase A.
- Добавил в систему: Бобров Андрей Викторович