Melting of lherzolite from Ichinomegata at high pressures

Abstract The solidi of two mixtures of separated minerals of the lherzolite from Ichinomegata, Japan, were determined at pressures between 1 atm and 50 kb. They are almost identical, with a slope of about 7 °C/kb. The solidus of the original lherzolite was also determined. This is negatively inclined in the range of 1 atm to 3 kb due to the contained water and nearly parallel to the solidi of the mixtures at higher pressures. In any runs close to the solidus, olivine, orthopyroxene and clinopyroxene are the principal minerals. The determined solidus temperature at lower pressures is higher than any basaltic liquidus temperature so far reported except that of picritic basalt. This is explained by the higher value of MgO/(MgO+FeO) of the starting materials. The lherzolite from Ichinomegata may be a residue of partial melting of mantle material that had produced basaltic magmas. The solidi show smaller slopes ( m dT m / d P) than those previously reported.