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Amorphous Materials. An experimental study of phosphorous and aluminosilicate speciation in and partitioning between aqueous fluids and silicate melts determined in-situ at high temperature and pressure

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Published/Copyright: April 2, 2015
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American Mineralogist
From the journal American Mineralogist Volume 96 Issue 10

Abstract

The structure of phosphorus-bearing, H2O-saturated silicate melts, silicate-saturated aqueous fluids, and silicate-rich single phase (supercritical) liquids has been characterized in situ to 800 °C and 1486 MPa in an Ir-gasketed hydrothermal diamond-anvil cell (HDAC) with the aid of both confocal microRaman and FTIR spectroscopy. Temperature and pressure in the HDAC were recorded with thermocouples (±1 °C uncertainty) and pressure- and temperature-dependent Raman shift of 13C diamonds (±40 MPa uncertainty). Starting materials were aluminum-free Na2O·4SiO2 (NS4) and with 10 mol% Al2O3 (NA10) substituting for SiO2, both with 5 mol% P2O5.

Aluminosilicate species of Q0, Q1, Q2, and Q3 type exist in coexisting fluid and melt and in single phase liquid together with phosphate species, PO4, P2O7, and QnP. In the QnP species, n O atoms bridge between Si4+ and P5+, whereas there is no Si-to-P linkage in the PO4 and P2O7 species. In melts, the abundance of the most depolymerized silicate species, Q0, is positively correlated with temperature and pressure, whereas that of the most polymerized species, Q3, decreases with temperature and pressure. In the silicate solute of aqueous fluids, the opposite relationship exists with Q0 abundance decreasing and Q3 (and Q1 and Q2) abundance increasing with increasing temperature and pressure. The silicate melts, therefore, become increasingly depolymerized and the silicate solute in aqueous fluids decreasingly depolymerized because increasing H2O solubility in melts causes melt depolymerization, whereas increasing silicate solute abundance in fluids results in silicate polymerization. The P2O7 and QnP are the dominant phosphate species in fluid, melt, and single phase liquid with orthophosphate, PO4, playing a subordinate role. The fluid/melt partition coefficients for P2O7 and QnP species are in the 0.15-0.7 range with that of QnP being greater than that of P2O7. The PO4 fluid/melt partition coefficients are <0.2. In all cases, the partition coefficients increase with increasing temperature and pressure. There is no clear influence of Al2O3 on partition coefficients. Hence, it appears that P-bearing complexes in fluids and melts are associated with Na+ that becomes available as silicate species polymerize. The mobility of phosphorus during metamorphic processes is principally governed by the availability of alkali metals (and perhaps alkaline earths).

Keywords : Phosphate solution; melt structure; aqueous fluid; fluid/melt partitioning
Received: 2010-10-26
Accepted: 2011-5-3
Published Online: 2015-4-2
Published in Print: 2011-10-1

© 2015 by Walter de Gruyter Berlin/Boston

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  17. Quantum-mechanical calculations of the Raman spectra of Mg- and Fe-cordierite
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  24. The development of shape- and crystallographic-preferred orientation in CaPtO3 post-perovskite deformed in pure shear
  25. Amorphous Materials. An experimental study of phosphorous and aluminosilicate speciation in and partitioning between aqueous fluids and silicate melts determined in-situ at high temperature and pressure
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https://doi.org/10.2138/am.2011.3728
Keywords for this article
Phosphate solution; melt structure; aqueous fluid; fluid/melt partitioning

Articles in the same Issue

  1. Compressional wave velocity measurements through sandy sediments containing methane hydrate
  2. The turquoise-chalcosiderite Cu(Al,Fe3+)6(PO4)4(OH)8·4H2O solid-solution series: A Mössbauer spectroscopy, XRD, EMPA, and FTIR study
  3. Variability in sepiolite: Diffraction studies
  4. Rankamaite from the Urubu pegmatite, Itinga, Minas Gerais, Brazil: Crystal chemistry and Rietveld refinement
  5. Zeolitic-type Brønsted-Lowry sites distribution imaged on clinochlore
  6. Thermodynamic properties of alloys of gold-74/palladium-26 with variable amounts of iron and the use of Au-Pd-Fe alloys as containers for experimental petrology
  7. first-principles investigation of hydrous defects and IR frequencies in forsterite: The case for Si vacancies
  8. Estimating compositions of natural ringwoodite in the heavily shocked Grove Mountains 052049 meteorite from Raman spectra
  9. Phase stability and compression study of (Fe0.89,Ni0.11)3S up to pressure of the Earth’s core
  10. The compression pathway of quartz
  11. Experimental investigations into the silicification of olivine: Implications for the reaction mechanism and acid neutralization
  12. The effect of polymorphic structure on the structural and chemical stability of yttrium disilicates
  13. Diffusion in yttrium aluminium garnet at the nanometer-scale: Insight into the effective grain boundary width
  14. Elasticity and anisotropy of Fe3C at high pressures
  15. Raman spectroscopy of titanomagnetites: Calibration of the intensity of Raman peaks as a sensitive indicator for their Ti content
  16. Experimental determination of stability relations between monazite, fluorapatite, allanite, and REE-epidote as a function of pressure, temperature, and fluid composition
  17. Quantum-mechanical calculations of the Raman spectra of Mg- and Fe-cordierite
  18. Coarsening kinetics of coexisting peristerite and film microperthite over 104 to 105 years
  19. Local structure variations observed in orthoenstatite at high pressures
  20. Static disorders of atoms and experimental determination of Debye temperature in pyrope: Low- and high-temperature single-crystal X-ray diffraction study
  21. Effect of hydration on the single-crystal elasticity of Fe-bearing wadsleyite to 12 GPa
  22. Early Proterozoic weathering processes under low O2 conditions reconstructed from a 2.45 Ga paleosol in Pronto, Canada
  23. Eliseevite, Na1.5Li[Ti2Si4O12.5(OH)1.5]∙2H2O, a new microporous titanosilicate from the Lovozero alkaline massif (Kola Peninsula, Russia)
  24. The development of shape- and crystallographic-preferred orientation in CaPtO3 post-perovskite deformed in pure shear
  25. Amorphous Materials. An experimental study of phosphorous and aluminosilicate speciation in and partitioning between aqueous fluids and silicate melts determined in-situ at high temperature and pressure
  26. Letter. Differential degassing of H2O, Cl, F, and S: Potential effects on lunar apatite
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