Loss of solar He and Ne from IDPS in subducting sediment: Diffusion and the effect of phase changes

The results of the diffusion experiment for solar He and Ne in IDP's in a magnetic separate from Pacific Ocean sediment suggest that solar He and Ne would be easily released from IDP grains and hence lost from subducting slabs at shallow depths. However, since the diffusion experiments was conducted under high vacuum, there may be a possibility that magnetite grains, which are supposedly the main constituent of the magnetic fraction, might be partly reduced to form a metal phase due to low oxygen fugacity in the experimental condition. If this is the case, such a phase change might affect the gas release and hence the results of the diffusion coefficients. In order to examine whether or not such a phase change really occurred in the condition of the diffusion experiment, I conducted a heating experiment for a magnetic separate from Pacific Ocean sediment. In the same condition as in the diffusion experiment, and the run products were examined with an x ray diffraction method. Three samples were prepared: they were wrapped with platinum foil, put in a vacuum line, and heated in a molybdenum crucible for two hours at 500 C, 800 C,and 950 C, respectively. After cooling the furnace, the samples were taken out from the crucible and analyzed with an x ray diffraction method.