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 MgSiO 3-H2O system, forsterite crystallizes below 3 GPa but not above that pressure. At 1000 °C in the Mg 2SiO3-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 H 2O-saturated peridotite. Somewhere within the upper mantle, these two fluids unite to form a single regime and cannot be distinguished from each other.
| Original language | English |
|---|---|
| Pages (from-to) | 1433-1437 |
| Number of pages | 5 |
| Journal | American Mineralogist |
| Volume | 89 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - Jan 1 2004 |
| Externally published | Yes |
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All Science Journal Classification (ASJC) codes
- Geophysics
- Geochemistry and Petrology
Cite this
Mg/Si ratios of aqueous fluids coexisting with forsterite and enstatite based on the phase relations in the Mg2SiO4-SiO 2-H2O system. / Kawamoto, Tatsuhiko; Matsukage, Kyoko N.; Mibe, Kenji; Nishibori, Maiko; Nishimura, Koshi; Ishimatsu, Naoki; Ono, Shigeaki.
In: American Mineralogist, Vol. 89, No. 10, 01.01.2004, p. 1433-1437.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Mg/Si ratios of aqueous fluids coexisting with forsterite and enstatite based on the phase relations in the Mg2SiO4-SiO 2-H2O system
AU - Kawamoto, Tatsuhiko
AU - Matsukage, Kyoko N.
AU - Mibe, Kenji
AU - Nishibori, Maiko
AU - Nishimura, Koshi
AU - Ishimatsu, Naoki
AU - Ono, Shigeaki
PY - 2004/1/1
Y1 - 2004/1/1
N2 - 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 MgSiO 3-H2O system, forsterite crystallizes below 3 GPa but not above that pressure. At 1000 °C in the Mg 2SiO3-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 H 2O-saturated peridotite. Somewhere within the upper mantle, these two fluids unite to form a single regime and cannot be distinguished from each other.
AB - 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 MgSiO 3-H2O system, forsterite crystallizes below 3 GPa but not above that pressure. At 1000 °C in the Mg 2SiO3-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 H 2O-saturated peridotite. Somewhere within the upper mantle, these two fluids unite to form a single regime and cannot be distinguished from each other.
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U2 - 10.2138/am-2004-1010
DO - 10.2138/am-2004-1010
M3 - Article
AN - SCOPUS:7444227982
VL - 89
SP - 1433
EP - 1437
JO - American Mineralogist
JF - American Mineralogist
SN - 0003-004X
IS - 10
ER -