Melting of a dry peridotite KLB-1 up to 14 GPa - Implications on the origin of peridotitic upper mantle

A melting phase diagram of a fertile 1herzolite KLB-1 in the pressure range from 1 atm to 14 GPa is established which is relevant to magma generation in the earth's interior. It is found that the melting temperature interval of the peridotite is more than 600 C wide at 1 atm, but narrows to about 150 C at 14 GPa. A diapiric model is shown to be consistent with the forming of komatiite magma by partial melting of mantle peridotite at a depth of 150-200 km. It is noted that the partial melts along the peridotite solidus become increasingly more MgO rich as pressure increases. Observations including the convergence of liquidus and solidus of the peridotite at pressures greater than 14 GPa, and the near solidus partial melt composition being very close to the bulk rock at 14 GPa, suggest that the upper mantle peridotite was originally generated as a magma by partial melting of the primitive earth at 400-500 km depth.