  We have performed an experimental and modeling study of the partial melting
behavior of the HED parent body and of the fractional crystallization of
liquids derived from its mantle. We estimated the mantle composition by
assuming chondritic ratios of refractory lithophile elements, adjusting the Mg#
and core size to match the density and moment of inertia of Vesta, and the
compositions of Mg-rich olivines found in diogenites. The liquidus of a mantle
with Mg# (=100*(Mg/(Mg+Fe))) 80 is ~1625oC and, under equilibrium conditions
the melt crystallises olivine alone until it is joined by orthopyroxene at
1350oC. We synthesized melt from our 1350oC experiment and simulated its
fractional crystallization path. Orthopyroxene crystallizes until it is
replaced by pigeonite at 1200oC. Liquids become eucritic and crystal
assemblages resemble diogenites below 1250oC. MELTS correctly predicts the
olivine liquidus but overestimates the orthopyroxene liquidus by ~70oC.
Predicted melt compositions are in reasonable agreement with those generated
experimentally. We used MELTS to determine that the range of mantle
compositions that can produce eucritic liquids and diogenitic solids in a magma
ocean model is Mg# 75-80 (with chondritic ratios of refractory elements). A
mantle with Mg# ~ 70 can produce eucrites and diogenites through sequential
partial melting.
