Abstract MgFe2O4 was probed to 74(1) GPa and 2,840(130) K as a low‐pressure analog to post‐post spinel Mg2SiO4 predicted in super‐Earths using synchrotron multigrain X‐ray diffraction techniques in the laser‐heated diamond anvil cell. With high‐temperatures above 65 GPa the eight‐fold coordinated δ‐MgFe2O4 (Th3P4‐type) is stable with Mg and Fe disordered into one site, analogous to that predicted in Mg2SiO4. While the phase‐boundary slope between the h‐ and δ‐phases of MgFe2O4 and Fe3O4 differ, the substitution of Fe2+ and Mg2+ has little overall pressure effect on the stability of the post‐post spinel phase. This eight‐fold coordinated δ‐MgFe2O4 is stable at ∼400 GPa lower pressures compared to the predicted δ‐Mg2SiO4, suggesting the need for further explorations into the conditions needed to substitute Fe3+ into δ‐Mg2SiO4 and the effect of ferric iron on the onset of eight‐fold coordination in super‐Earth mantles.
Observations from the Little Bunker
Last updated: February 24, 2026 10:22 PM
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