Molecular water in beryl, VIAl2 [Be3Si6O18]·nH2O, as a function of pressure and temperature: An experimental study
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Rainer Pankrath
Abstract
The incorporation of molecular water into the c-parallel structural channels in end-member beryl VIAl2[Be3Si6O18]·nH2O, where nH2O = 1.00 corresponds to 3.24 wt% H2O, was studied experimentally in the temperature-pressure range 400-950 °C and 1-14.5 kbar (PH2O= Ptot). Time-dependent studies ensured that the incorporation of water by beryl had reached the equilibrium nH2O values in the hydration experiments.
Increasing water contents were found to enhance the refractive indices of beryl as follows:
nε = 1.5585 + 0.0080·wt% H2O (r = 0.986)
nω = 1.5616 + 0.0086·wt% H2O (r = 0.978)
These relations were used to determine the water contents attained in the equilibrium experiments, and were calibrated using synthetic beryls, the water contents of which had been determined gravimetrically with an accuracy of ±0.06 wt% H2O. The incorporation of water into the structural channels of beryl leaves the hexagonal a-axis unchanged, a = 9.2110(10) Å, c and V increase as:
c (Å) = 9.1893 + 0.0020·wt% H2O (r = 0.974)
V (Å3) = 674.98 + 0.203·wt% H2O (r = 0.936)
Two isobars at 3.4 and 10.8 kbar with PH2O = Ptotal could be modeled as:
wt% H2O (P) = a - bT (°C) + cT2 (°C)
3.4 kbar: a = 4.10, b = 5.90·10-3, c = 0.31·10-5 (r = 0.963)
10.8 kbar: a = 3.31, b = 0.514·10-3, c = 0.00 (r = 0.941)
Similarly, the two isotherms at 600 and 900 °C could be modeled as:
wt%H2O (T) = a + bP (kbar) - cP2 (kbar)
500 °C: a = 0.94, b = 0.261, c = 0.0075 (r = 0.949)
900 °C: a = 0.19, b = 0.331, c = 0.0092 (r = 0.964)
These relations together with data points from additional experiments were used to construct a (PH₂O = Ptot) - T field of isohydrons for the system end-member beryl-H2O. Comparing nH₂O-P sections at 600 °C for beryl obained in this study with data for Mg-cordierite obtained from the literature, proves nearly the same equilibrium contents of water in both minerals.
© 2015 by Walter de Gruyter Berlin/Boston
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- Effect of sonic and ultrasonic frequencies on the crystallization of basalt
- Sulfur saturation limits in silicate melts and their implications for core formation scenarios for terrestrial planets
- Molecular water in beryl, VIAl2 [Be3Si6O18]·nH2O, as a function of pressure and temperature: An experimental study
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- X-ray spectroscopic investigations of fluids in the hydrothermal diamond anvil cell: The hydration structure of aqueous La3+ up to 300 °C and 1600 bars
- Fibrous nanoinclusions in massive rose quartz: HRTEM and AEM investigations
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- Ordering of hydroxyl defects in hydrous wadsleyite (β-Mg2SiO4)
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- Raman spectroscopy of Fe2O3 to 62 GPa
- Study of the (010) olivine surface by Rutherford backscattering spectrometry in channeling geometry
- Equation of state of dense hydrous magnesium silicate phase A, Mg7Si2O8(OH)6
- Si-F bonding in aluminosilicate glasses: Inferences from ab initio NMR calculations
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Articles in the same Issue
- Presidential Address. Scales of disequilibrium and rates of equilibration during metamorphism
- Characterization of coexisting NH4- and K-micas in very low-grade metapelites
- Effect of sonic and ultrasonic frequencies on the crystallization of basalt
- Sulfur saturation limits in silicate melts and their implications for core formation scenarios for terrestrial planets
- Molecular water in beryl, VIAl2 [Be3Si6O18]·nH2O, as a function of pressure and temperature: An experimental study
- Fluid-induced nucleation of (Y + REE)-phosphate minerals within apatite: Nature and experiment. Part I. Chlorapatite
- X-ray spectroscopic investigations of fluids in the hydrothermal diamond anvil cell: The hydration structure of aqueous La3+ up to 300 °C and 1600 bars
- Fibrous nanoinclusions in massive rose quartz: HRTEM and AEM investigations
- Polysomatism in högbomite: The crystal structures of 10T, 12H, 14T, and 24R polysomes
- Ordering of hydroxyl defects in hydrous wadsleyite (β-Mg2SiO4)
- The crystal structure and cation ordering of Phase-X-(K1–x–n)2(Mg1–n[Al,Cr]n)2Si2O7H2x: A potential K- and H-bearing phase in the mantle
- Feasibility of determining the quantitative OH content of garnets with Raman spectroscopy
- Raman spectroscopic study of garnet inclusions in diamonds from the mantle transition zone
- Raman spectroscopy of Fe2O3 to 62 GPa
- Study of the (010) olivine surface by Rutherford backscattering spectrometry in channeling geometry
- Equation of state of dense hydrous magnesium silicate phase A, Mg7Si2O8(OH)6
- Si-F bonding in aluminosilicate glasses: Inferences from ab initio NMR calculations
- Monoclinic nearly stoichiometric wüstite at low temperatures
- On the nature of tincalconite
- Letters. Chloride ion sites in silicate and aluminosilicate glasses: A preliminary study by 35Cl solid-state NMR
- Nuclear magnetic resonance and infrared spectroscopic study of excess-boron olenite from Koralpe, Styria, Austria
