Abstract
In situ, high-pressure single-crystal X‑ray diffraction experiments were performed on a feldspar with composition SrAl2Si2O8 (space group I2/c). The measurements were performed at 19 different pressures up to 7.9 GPa. The unit-cell parameters and the unit-cell volume show a strong discontinuity at 6.6 GPa indicating a first-order phase transition. The systematic absences clearly show that the transition occurs from I2/c to P21/c space group symmetry, as for the transition recently reported for a feldspar with composition Sr0.8Ca0.2Al2Si2O8.
Our results suggest that the P21/c phase is softer than the I2/c one. Moreover, within the I2/c symmetry two pressure-volume trends are evident due to a volume softening above 4.2 GPa. The softening did not allow fitting the data to a single equation of state, and only the data up to 3.67 were fitted with a third-order Birch-Murnaghan equation of state.
Based on our and previous experimental results we propose a possible composition-pressure stability field for the Sr-rich side along the CaAl2Si2O8-SrAl2Si2O8 join.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Needs and opportunities in mineral evolution research
- Rutile inclusions in quartz crystals record decreasing temperature and pressure during the exhumation of the Su-Lu UHP metamorphic belt in Donghai, East China
- A first-principles study of the phase transition from Holl-I to Holl-II in the composition KAlSi3O8
- Sejkoraite-(Y), a new member of the zippeite group containing trivalent cations from Jáchymov (St. Joachimsthal), Czech Republic: Description and crystal structure refinement
- Thermoelastic and thermodynamic properties of plagioclase feldspars from thermal expansion measurements
- Quantitative determination of chrysotile in massive serpentinites using DTA: Implications for asbestos determinations
- In situ observation of the crystallization pressure induced by halite crystal growth in a microfluidic channel
- Microstructures of the larval shell of a pearl oyster, Pinctada fucata, investigated by FIB-TEM technique
- Magnesium quantification in calcites [(Ca,Mg)CO3] by Rietveld-based XRD analysis: Revisiting a well-established method
- The effect of Fe on olivine H2O storage capacity: Consequences for H2O in the martian mantle
- Kinetics of thermal transformation of partially dehydroxylated pyrophyllite
- Dehydration of the natural zeolite goosecreekite CaAl2Si6O16·5H2O upon stepwise heating: A single-crystal and powder X-ray study
- Incorporation mechanisms of Ta and Nb in zircon and implications for pegmatitic systems
- Variable-temperature 27Al and 29Si NMR studies of synthetic forsterite and Fe-bearing Dora Maira pyrope garnet: Temperature dependence and mechanisms of paramagnetically shifted peaks
- Calibrating Ti concentrations in quartz for SIMS determinations using NIST silicate glasses and application to the TitaniQ geothermobarometer
- Crystal structure of Na3Fe(SO4)3: A high-temperature product (∼400 °C) of sideronatrite [Na2Fe(SO4)2OH⋅3H2O]
- Evidence for boron incorporation into the serpentine crystal structure
- Structure refinement of Ag-free heyrovskýite from Vulcano (Aeolian Islands, Italy)
- Microtextures, microchemistry, and mineralogy of basaltic glass alteration, Jeju Island, Korea, with implications for elemental behavior
- Orientation of channel carbonate ions in apatite: Effect of pressure and composition
- Thermoelastic property and high-pressure stability of Fe7C3: Implication for iron-carbide in the Earth’s core
- Yttriaite-(Y): The natural occurrence of Y2O3 from the Bol’shaya Pol’ya River, Subpolar Urals, Russia
- Identification and characterization of nanosized tripuhyite in soil near Sb mine tailings
- Letter. High-pressure I2/c-P21/c phase transformation in SrAl2Si2O8 feldspar
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