Fig. 4

Variation of observable seismic properties of bridgmanite as a function of iron content at 80 GPa and 300 K. EoS results from this study and previous work summarized in ref. ¹⁹ demonstrate that a density b bulk modulus, and c bulk sound velocity exhibit different dependence on Fe²⁺ and Fe³⁺ content. The red solid lines are linear interpolations between MgSiO₃-Bdg and end members for high-spin (HS) Fe³⁺-Bdg and the red dashed lines are those for B-site low-spin (LS) Fe³⁺ Bdg. The black lines are linear fits for Fe²⁺-Bdg summarized in ref.¹⁹. The Fe³⁺-Bdg end member is from this study, and the open and solid circles are for HS and B-site LS Fe³⁺ Bdg, respectively. Differences between²¹ (red triangles) and solid red line trend for bulk modulus and sound velocity may be caused by compositional changes during Bdg synthesis from glass in the laser heated diamond anvil cell. The purple symbols are for Fe³⁺, Al-bearing Bdg samples^22,70, and the green symbols are for Fe³⁺, Fe²⁺-bearing Bdg samples with Fe³⁺/ΣFe <50%⁴¹