TY - JOUR
T1 - Influence of H2 fluid on the stability and dissolution of Mg2SiO4 forsterite under high pressure and high temperature
AU - Shinozaki, Ayako
AU - Hirai, Hisako
AU - Ohfuji, Hiroaki
AU - Okada, Taku
AU - Machida, Shin Ichi
AU - Yagi, Takehiko
N1 - Funding Information:
The synchrotron radiation experiments were performed at the BL10XU of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal No. 2011A1597) and BL18-C of KEK with the approval of the Photon Factory Program Advisory Committee. This study was supported by the G-COE program Deep Earth Mineralogy. A. Shinozaki was supported by a JSPS Research Fellowship for Young Scientists.
PY - 2013
Y1 - 2013
N2 - High-pressure and high-temperature experiments were carried out in a Mg2SiO4-H2 system using laser-heated diamond-anvil cells to understand the influence of H2 fluid on the stability of forsterite. In situ X ray diffraction experiments and Raman spectroscopic measurements showed the decomposition of forsterite, and formation of periclase (MgO) and stishovite/quartz (SiO2) in the presence of H2 after being heated in the range between 2.5 GPa, 1400 K and 15.0 GPa, 1500 K. Transmission electron microscopic observation of the samples recovered from 15.0 GPa and 1500 K showed that the granular to columnar periclase grains maintained the original grain shape of forsterite, indicating that the periclase crystals crystallized under high temperature. On the other hand, euhedral columnar stishovite crystals were found at the boundaries between residual forsterite grains and reacted periclase. This implies that the SiO2 component was dissolved in H2 fluid, and that stishovite was considered to have crystallized when the solubility of the SiO2 component became reduced with decreasing temperature. Additional experiment on a SiO2-H2 system clearly showed the dissolution of quartz in H2 fluid, while those on a MgO-H2 system, periclase was hardly dissolved. These lines of evidence indicate that forsterite was incongruently dissolved in H2 fluid to form periclase crystals in the Mg2SiO4-H2 system, which is different from what was observed in the Mg2SiO4-H 2O system. The results indicate that the stability of forsterite is strongly affected by the composition of coexisting C-O-H fluid.
AB - High-pressure and high-temperature experiments were carried out in a Mg2SiO4-H2 system using laser-heated diamond-anvil cells to understand the influence of H2 fluid on the stability of forsterite. In situ X ray diffraction experiments and Raman spectroscopic measurements showed the decomposition of forsterite, and formation of periclase (MgO) and stishovite/quartz (SiO2) in the presence of H2 after being heated in the range between 2.5 GPa, 1400 K and 15.0 GPa, 1500 K. Transmission electron microscopic observation of the samples recovered from 15.0 GPa and 1500 K showed that the granular to columnar periclase grains maintained the original grain shape of forsterite, indicating that the periclase crystals crystallized under high temperature. On the other hand, euhedral columnar stishovite crystals were found at the boundaries between residual forsterite grains and reacted periclase. This implies that the SiO2 component was dissolved in H2 fluid, and that stishovite was considered to have crystallized when the solubility of the SiO2 component became reduced with decreasing temperature. Additional experiment on a SiO2-H2 system clearly showed the dissolution of quartz in H2 fluid, while those on a MgO-H2 system, periclase was hardly dissolved. These lines of evidence indicate that forsterite was incongruently dissolved in H2 fluid to form periclase crystals in the Mg2SiO4-H2 system, which is different from what was observed in the Mg2SiO4-H 2O system. The results indicate that the stability of forsterite is strongly affected by the composition of coexisting C-O-H fluid.
KW - Forsterite
KW - Laser-heated diamond-anvil cells
KW - Transmission electron microscope
KW - X ray diffraction
UR - http://www.scopus.com/inward/record.url?scp=84882804300&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84882804300&partnerID=8YFLogxK
U2 - 10.2138/am.2013.4434
DO - 10.2138/am.2013.4434
M3 - Article
AN - SCOPUS:84882804300
VL - 98
SP - 1604
EP - 1609
JO - American Mineralogist
JF - American Mineralogist
SN - 0003-004X
IS - 8-9
ER -