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Effect of water on the spinel‐postspinel transformation in Mg 2 SiO 4
Author(s) -
Higo Yuji,
Inoue Toru,
Irifune Tetsuo,
Yurimoto Hisayoshi
Publication year - 2001
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2001gl013194
Subject(s) - ringwoodite , periclase , anhydrous , spinel , mineralogy , geology , discontinuity (linguistics) , phase (matter) , analytical chemistry (journal) , materials science , olivine , chemistry , metallurgy , environmental chemistry , mathematical analysis , mathematics , organic chemistry
The phase boundary between ringwoodite and perovskite plus periclase in Mg 2 SiO 4 was determined at 1600 °C under hydrous conditions with 1∼3 wt% H 2 O. We found that the boundary moved to high‐pressure side by ∼0.2 GPa in these hydrous conditions compared with that in anhydrous condition. The SIMS measurements confirmed that the ringwoodite in hydrous condition contained a significant amount (∼1 wt%) of water, whereas the perovskite accepted only very little (∼0.05 wt%) water in its crystal structure. The discrepancy between the pressure of 660 km seismic discontinuity and that of the postspinel transformation reported in a recent in situ x‐ray study is not explained by the effect of water on the transformation.