Journal of Physics of the Earth
Online ISSN : 1884-2305
Print ISSN : 0022-3743
ISSN-L : 0022-3743
MELTING RELATION OF Fe2SiO4 UP TO ABOUT 20Okbar
Eiji OHTANI
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1979 Volume 27 Issue 3 Pages 189-208

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Abstract

The melting relations in fayalite Fe2SiO4 and its high pressure modification γ-Fe2SiO4 have been experimentally studied at pressures up to about 200kbar. Fayalite melts congruently up to the triple point, 70±5kbar and 1, 520±25°C, of fayalite, γ-Fe2SiO4, and liquid. The initial slope of γ-Fe2siO4 is about 12°/kbar. γ-Fe2siO4 melts congruently up to about 130 kbar, above which it melts incongruently into stishovite SiO2 and liquid. The incongruent melting in γ-Fe2SiO4 terminates at about 170kbar and 2, 200°C. Above this pressure, the melting mode switches to the eutectic melting between wustite Fe1-xO and stishovite SiO2, which are the post γ-Fe2SiO4 assembly. The present data suggest a possibility of incongruent melting of γ-(Mg, Fe)2SiO4 at high pressure. Possible roles of the change in melting mode on the chemical fractionation of the earth's mantle are discussed.

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