Volume behavior of the 10 Å phase at high pressures and temperatures, with implications for H2O content
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Alison R. Pawley
,
Mark D. Welch
Abstract
The 10 Å phase is a high-pressure hydrous magnesium silicate whose composition appears to depend on synthesis conditions. We have measured the compressibility to 10.5 GPa and thermal expansivity to 400 °C of samples of 10 Å phase synthesized in long experiments (400 and 169 h, respectively) designed to maximize compositional equilibrium. The structure was refined using a metrically trigonal unit cell. Compression is highly anisotropic, especially over the first 2 GPa of compression, indicating weak bonding across the interlayer. There is an inflection in the compression curve of c at 8 GPa, suggesting a change in compression mechanism or the onset of non-hydrostaticity in the pressure medium. Fitting the compression data collected below 8 GPa to a Murnaghan equation-of-state gives V0 = 734.8(7) Å3, K0 = 25(1) GPa, K′ = 18(1). Thermal expansion is also strongly anisotropic: coefficients for data up to 200 °C are αa = 0.15(5) × 10-5 K-1, αc = 3.1(2) × 10-5 K-1, αV = 3.4(2) × 10-5 K-1. Above 200 °C, the expansivity of c decreased, and all parameters showed a contraction after the experiment, suggesting partial dehydration at high temperatures. Comparison of our compressibility data with those of previous studies suggests that 10 Å phase synthesized in short experiments does not retain all of its interlayer H2O during quenching and decompression. In contrast, samples annealed for many hours at high pressure and temperature are stabilized by small amounts of hydrogarnet-type substitution and consequent hydrogen bond strengthening.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Characterization of cation environments in polycrystalline forsterite by 25Mg MAS, MQMAS, and QCPMG NMR
- Structure of nanocrystalline phyllomanganates produced by freshwater fungi
- First-principles study on variation of lattice parameters of mullite Al4+2xSi2–2xO10–x (x = 0.125, 0.250, 0.375)
- Natrolite may not be a “soda-stone” anymore: Structural study of fully K-, Rb-, and Cs-exchanged natrolite
- Metal retention, mineralogy, and design considerations of a mature permeable reactive barrier (PRB) for acidic mine water drainage in Northumberland, U.K.
- A relationship between d104 value and composition in the calcite-disordered dolomite solid-solution series
- XRD, micro-XANES, EMPA, and SIMS investigation on phlogopite single crystals from Mt. Vulture (Italy)
- Volume behavior of the 10 Å phase at high pressures and temperatures, with implications for H2O content
- Interfacial tension between immiscible liquids in the system K2O-FeO-Fe2O3-Al2O3-SiO2 and implications for the kinetics of silicate melt unmixing
- H2O and the dehydroxylation of phyllosilicates: An infrared spectroscopic study
- Effects of intermediate range structure on the 29Si NMR chemical shifts of framework silicates: Results for analcime
- High-temperature Mössbauer spectroscopy: A probe for the relaxation time of Fe species in silicate melts and glasses
- The thermal equation of state of FeTiO3 ilmenite based on in situ X-ray diffraction at high pressures and temperatures
- OH species, U ions, and CO/CO2 in thermally annealed metamict zircon (ZrSiO4)
- Crystallographic and chemical constraints on the nature of the proustite–pyrargyrite solid-solution series
- Accurate μRaman characterization of reaction products at the surface of (bio)oxidized pyrite
- Determination of manganese valence states in (Mn3+, Mn4+) minerals by electron energy-loss spectroscopy
- AFM study of the epitaxial growth of brushite (CaHPO4·2H2O) on gypsum cleavage surfaces
- Compressibility of protoamphibole: A high-pressure single-crystal diffraction study of protomangano-ferro-anthophyllite
- Crystal structure of hydrous wadsleyite with 2.8% H2O and compressibility to 60 GPa
- Dehydration and rehydration processes in gmelinite: An in situ X-ray single-crystal study
- Characteristics of emission centers in alkali feldspar: A new approach by using cathodoluminescence spectral deconvolution
- Mechanism of metamorphic zircon growth in a granulite-facies quartzite, Adirondack Highlands, Grenville Province, New York
- Speciation and mixing behavior of silica-saturated aqueous fluid at high temperature and pressure
- A critical comment on Thy et al. (2009b): Liquidus temperatures of the Skaergaard magma
