  Reproduction experiments of radial pyroxene (RP) chondrules were carried out
using an Ar-$\mathrm{H_2}$ or Ar gas-jet levitation system in a reducing
atmosphere in order to simulate chondrule formation in the protoplanetary disk.
The experiments reproduced RP-chondrule textures, consisting of sets of thin
pyroxene crystals and mesostasis glass between crystals. However, iron
partition coefficients between pyroxene and glassy mesostasis ($\rm{D_{Fe}}$ =
Fe mol$\rm{\%_{pyroxene}}$ / Fe mol$\rm{\%_{mesostasis}}$) in natural RP
chondrules were much higher than that in experimentally reproduced RP
chondrules. The high $\rm{D_{Fe}}$ in natural RP chondrules suggest that iron
was removed from the mesostasis melt at high temperatures after the growth of
pyroxene crystals. We found that many small iron-metal inclusions had formed in
the mesostasis glass, indicating that FeO in the high-temperature melt of
mesostasis was reduced to metallic iron, and iron in the mesostasis diffused
into the newly formed metal inclusions. The formation of the iron-metal
inclusions in the mesostasis was reproduced by our experiments in a reducing
atmosphere, confirming that $\rm{D_{Fe}}$ in natural RP chondrules increased
after the growth of RP crystals. Therefore, the $\rm{D_{Fe}}$ of RP chondrules
can be an indicator to constrain cooling rates and redox states during
chondrule formation.
