Na2MgSiO4 is a mineralogical phase known in the literature as N2MS and reported in several high-pressure experiments (13.6 < P < 22 GPa) to coexist with wadsleyite, garnet and pyroxene. Although the crystal structure of room-PT Na2MgSiO4 is known, a structural study of the phase recovered in high-pressure experiments has not been done yet. Here we present a chemical and structural study of a crystal of Na2MgSiO4 synthesised in the model system Na2MgSiO4–Mg2SiO4 at 22 GPa and 1800 °C. The compound was found to crystallize with the orthorhombic cristobalite-type structure previously described at room conditions, space group Pna21, with lattice parameters a = 10.8193(8), b = 5.2702(3), c = 7.0598(4) Å, V = 402.55(4) Å3, and Z = 4. The structure was refined to R1 = 0.0184 using 644 observed reflections [Fo > 4σ(Fo)] and 73 parameters. The unit-cell of the phase studied here is nearly identical to that of Na2MgSiO4 synthesised at room conditions, thus indicating that it likely relaxed during the pressure release occurring during quenching.
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Research Article|
May 01, 2018
X-ray single-crystal structural characterization of Na2MgSiO4 with cristobalite-type structure synthesised at 22 GPa and 1800 °C
Ekaterina A. Sirotkina;
Ekaterina A. Sirotkina
1
Vernadsky Institute of Geochemistry and Analytical Chemistry of Russian Academy of Sciences
, Moscow119991, Russia
2
Geological Faculty, Moscow State University
, Moscow119991, Russia
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Luca Bindi;
3
Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4
, 50121Florence, Italy
4
CNR – Istituto di Geoscienze e Georisorse, Sezione di Firenze, Via La Pira 4
, 50121Florence, Italy
Corresponding author, e-mail: luca.bindi@unifi.it
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Andrey V. Bobrov;
Andrey V. Bobrov
1
Vernadsky Institute of Geochemistry and Analytical Chemistry of Russian Academy of Sciences
, Moscow119991, Russia
2
Geological Faculty, Moscow State University
, Moscow119991, Russia
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Anastasia Tamarova;
Anastasia Tamarova
2
Geological Faculty, Moscow State University
, Moscow119991, Russia
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Dmitry Yu. Pushcharovsky;
Dmitry Yu. Pushcharovsky
2
Geological Faculty, Moscow State University
, Moscow119991, Russia
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Tetsuo Irifune
Tetsuo Irifune
5
Geodynamics Research Center, Ehime University
, Matsuyama790-8577, Japan
6
Earth-Life Science Institute, Tokyo Institute of Technology
, Tokyo152-8550, Japan
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European Journal of Mineralogy (2018) 30 (3): 485–489.
Article history
received:
11 Jul 2017
rev-recd:
29 Jul 2017
accepted:
08 Aug 2017
first online:
26 Apr 2018
Citation
Ekaterina A. Sirotkina, Luca Bindi, Andrey V. Bobrov, Anastasia Tamarova, Dmitry Yu. Pushcharovsky, Tetsuo Irifune; X-ray single-crystal structural characterization of Na2MgSiO4 with cristobalite-type structure synthesised at 22 GPa and 1800 °C. European Journal of Mineralogy 2018;; 30 (3): 485–489. doi: https://doi.org/10.1127/ejm/2017/0029-2687
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Index Terms/Descriptors
- alkali metals
- chain silicates
- characterization
- chemical composition
- crystal structure
- crystal systems
- experimental studies
- garnet group
- high pressure
- high temperature
- magnesian silicates
- majorite
- mantle
- metals
- nesosilicates
- olivine group
- orthorhombic system
- orthosilicates
- pressure
- pyroxene group
- refinement
- silicates
- sodium
- synthesis
- temperature
- unit cell
- wadsleyite
- X-ray diffraction data
- cristobalite-type structure