Home Physical Sciences Mg/Si ratios of aqueous fluids coexisting with forsterite and enstatite based on the phase relations in the Mg2SiO4-SiO2-H2O system
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Mg/Si ratios of aqueous fluids coexisting with forsterite and enstatite based on the phase relations in the Mg2SiO4-SiO2-H2O system

  • Tatsuhiko Kawamoto EMAIL logo , Kyoko N. Matsukage , Kenji Mibe , Maiko Isshiki , Koshi Nishimura , Naoki Ishimatsu and Shigeaki Ono
Published/Copyright: March 28, 2015
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American Mineralogist
From the journal American Mineralogist Volume 89 Issue 10

Abstract

Direct observation of aqueous fluids coexisting with MgSiO3 (enstatite) and/or Mg2SiO4 (forsterite) was performed at 0.5-5.8 GPa and 800-1000 °C with an externally heated diamond-anvil cell and synchrotron X-rays. At 1000 °C in the MgSiO3 -H2O system, forsterite crystallizes below 3 GPa but not above that pressure. At 1000 °C in the Mg2SiO4 -H2O system, forsterite congruently dissolves into the aqueous fluids up to 5 GPa. These observations suggest that the aqueous fluids coexisting with enstatite and forsterite have Mg/Si < 1 below 3 GPa and 1 < Mg/Si < 2 above that pressure.

Comparison with the previous studies reporting Mg/Si ratios of the aqueous fluid coexisting with enstatite and forsterite indicates that the Mg/Si ratios change rapidly from SiO2-rich to MgO-rich at around 3 GPa and 1000 °C. This change can be related to possible structural changes of liquid water under these conditions. The aqueous fluids coexisting with enstatite and forsterite do have Mg/Si ratios similar to those found in the partial melts of H2O-saturated peridotite. Somewhere within the upper mantle, these two fluids unite to form a single regime and cannot be distinguished from each other.

Received: 2003-7-17
Accepted: 2004-3-23
Published Online: 2015-3-28
Published in Print: 2004-10-1

© 2015 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.2138/am-2004-1010

Articles in the same Issue

  1. The origin of the color of pearls in iridescence from nano-composite structures of the nacre
  2. “Invisible„ gold revealed: Direct imaging of gold nanoparticles in a Carlin-type deposit
  3. Behavior of cation vacancy in kenotetrahedral Cr-spinels from Albanian eastern belt ophiolites
  4. Displacement and strain fields around a [100] dislocation in olivine measured to sub-angstrom accuracy
  5. Kiglapait mineralogy IV: The augite series
  6. Metasomatic formation of kosmochlor-bearing diopside in peridotite xenoliths from North Island, New Zealand
  7. Determination of standard thermodynamic properties of sulfides in the Ag-Au-S system by means of a solid-state galvanic cell
  8. Hydroxyl ordering in igneous apatite
  9. Accommodation of the carbonate ion in apatite: An FTIR and X-ray structure study of crystals synthesized at 2–4 GPa
  10. Mg/Si ratios of aqueous fluids coexisting with forsterite and enstatite based on the phase relations in the Mg2SiO4-SiO2-H2O system
  11. The activity of silica, water, and the equilibration of intermediate and silicic magmas
  12. The CO2–H2O system: IV. Empirical, isothermal equations for representing vapor-liquid equilibria at 110–350 °C, P ≤ 150 MPa
  13. Repercussions of size heterogeneity on the measurement of specific surface areas of colloidal minerals: Combination of macroscopic and microscopic analyses
  14. The crystal-structure of synthetic NaNa2Mg5Si8O21(OH)3, a triclinic C1̄ amphibole with a triple-cell and excess hydrogen
  15. High-pressure phase transitions in Ca0.2Sr0.8Al2Si2O8feldspar
  16. Phase transition of Ca-perovskite and stability of Al-bearing Mg-perovskite in the lower mantle
  17. Mineralogy and petrology of a mullite-bearing pseudotachylyte: Constraints on the temperature of coseismic frictional fusion
  18. New developments in two-feldspar thermometry
  19. Ordered distribution of Au and Ag in the crystal structure of muthmannite, AuAgTe2, a rare telluride from Sacarîmb, western Romania
  20. Polytypism of cookeite in low-grade metapelites of the Cameros Basin, Spain: Lack of correlation of well-ordered polytypes with pressure
  21. Evolution of mineral compositions during eclogitization of subducting basaltic crust
  22. Mass balance during retrogression of eclogite-facies minerals in the Rongcheng eclogite, eastern Sulu ultrahigh-pressure terrane, China
  23. Synthesis of REE and Y phosphates by Pb-free flux methods and their utilization as standards for electron microprobe analysis and in design of monazite chemical U-Th-Pb dating protocol
  24. The chemistry and crystal structure of okanoganite-(Y) and comparison with vicanite-(Ce)
  25. An automated system for phase identification and quantitative composition determination using the electron microprobe: Theory and applications
  26. Piston-cylinder calibration at 400 to 500 MPa: A comparison of using water solubility in albite melt and NaCl melting
  27. Letter. Comparative planetary mineralogy: V/(Cr + Al) systematics in chromite as an indicator of relative oxygen fugacity
  28. Letter. Porous titanosilicate nanorods in the structure of yuksporite, (Sr,Ba)2K4(Ca,Na)14(⃞,Mn,Fe) {(Ti,Nb)4(O,OH)4[Si6O17]2[Si2O7]3}(H2O,OH)n, resolved using synchrotron radiation
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