Polymorphism of feldspars above 10 GPa

Anna Pakhomova, Dariia Simonova, Iuliia Koemets, Egor Koemets, Georgios Aprilis, Maxim Bykov, Liudmila Gorelova, Timofey Fedotenko, Vitali Prakapenka, Leonid Dubrovinsky

Research output

Abstract

Feldspars are rock-forming minerals that make up most of the Earth’s crust. Along the mantle geotherm, feldspars are stable at pressures up to 3 GPa and may persist metastably at higher pressures under cold conditions. Previous structural studies of feldspars are limited to ~10 GPa, and have shown that the dominant mechanism of pressure-induced deformation is the tilting of AlO4 and SiO4 tetrahedra in a tetrahedral framework. Herein, based on results of in situ single-crystal X-ray diffraction studies up to 27 GPa, we report the discovery of new high-pressure polymorphs of the feldspars anorthite (CaSi2Al2O8), albite (NaAlSi3O8), and microcline (KAlSi3O8). The phase transitions are induced by severe tetrahedral distortions, resulting in an increase in the Al and/or Si coordination number. High-pressure phases derived from feldspars could persist at depths corresponding to the Earth upper mantle and could possibly influence the dynamics and fate of cold subducting slabs.
Original languageEnglish
Article number2721
JournalNature Communications
Volume11
Early online date1 Jun 2020
DOIs
Publication statusPublished - 2020

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    Pakhomova, A., Simonova, D., Koemets, I., Koemets, E., Aprilis, G., Bykov, M., Gorelova, L., Fedotenko, T., Prakapenka, V., & Dubrovinsky, L. (2020). Polymorphism of feldspars above 10 GPa. Nature Communications, 11, [2721]. https://doi.org/10.1038/s41467-020-16547-4