Sodium silicates at the boundary between the transition zone and the lower mantle: compositional and structural patterns

database, nuove specie, discrediti,
ridefinizioni, classificazioni, ecc.
Rispondi
Avatar utente
Marco E. Ciriotti
Messaggi: 26747
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Sodium silicates at the boundary between the transition zone and the lower mantle: compositional and structural patterns

Messaggio da Marco E. Ciriotti » gio 21 mag, 2020 20:32

Referenza:
▪ Matrosova, E.A., Bobrov, A.V., Tamarova, A.P., Bindi, L., Pushcharovsky, D.Yu., Irifune, T. (2020): Sodium Silicates at the Boundary between the Transition Zone and the Lower Mantle: Compositional and Structural Patterns. Doklady Earth Sciences, 491, 150–154.

Abstract:
The new results of experimental study of the Na2MgSiO4–Mg2SiO4 section of the SiO2–MgO–Na2O model system at 22–24 GPa and 1600–1900°C are discussed in this paper. An association of Na-bearing ringwoodite (up to 0.42 wt % Na2O) and the phase with the composition Na2MgSiO4 with a cristobalite-type structure was obtained at 22 GPa. Incorporation of Na in ringwoodite occurs through the mechanism Mg2+ → 2/3Na+ + 1/3Si4+ and results in an increase in the cell parameter in relation to that of pure Mg2SiO4 ringwoodite. A paragenesis of Na-bearing bridgmanite (up to 0.67 wt % Na2O), periclase, and anhydrous sodium phase X (Na2Mg2Si2O7) is formed at 23–24 GPa. Based on the data obtained, high-pressure Na–Mg silicates, Na2MgSiO4 and Na2Mg2Si2O7, may be considered as mineralogically probable mantle phases within the locally metasomatized mantle regions, although their finds as inclusions in diamond crystals are unlikely.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

Rispondi

Chi c’è in linea

Visitano il forum: Bing [Bot] e 3 ospiti