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Polymorphism of feldspars above 10 GPa.

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.

SUBMITTER: Pakhomova A

PROVIDER: S-EPMC7264230 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Polymorphism of feldspars above 10 GPa.

Pakhomova Anna A Simonova Dariia D Koemets Iuliia I Koemets Egor E Aprilis Georgios G Bykov Maxim M Gorelova Liudmila L Fedotenko Timofey T Prakapenka Vitali V Dubrovinsky Leonid L

Nature communications 20200601 1

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 AlO<sub>4</sub> and SiO<sub>4</sub> tetrahedra in a tetrahedral framework. Herein, based on results of in situ single-cryst ...[more]

PMID: 32483171

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Polymorphism of feldspars above 10 GPa.

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Polymorphism of feldspars above 10 GPa.

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