Valence/spin states of iron in peridotite glass to megabar pressure implications for dense ferric-iron-rich silicate melt at the bottom of the mantle

Abstract

We have conducted electrical conductivity and energy-domain synchrotron Mossbauer spectroscopic measurements of peridotite glass as an analogue of silicate melts at the bottom of the mantle. The changes in the Mossbauer parameters and the change in the trend of the electrical conductivity profile have been observed at around 80 GPa, suggesting that the structural change of the glass from akimotoite-like to postperovskite-like structures. We also observed the changes in the Mossbauer parameters above 120 GPa, which might be due to the change in near-neighbor coordination number to iron. On the other hand, we did not observe the trend change in the electrical conductivity. This means that the effect of the coordination number change on the electrical conductivity is small. The pressure conditions of these changes in structure and coordination number are much lower than the lowermost mantle pressure, that is, the melt would become compact at the bottom of the mantle.journal articl