Melting of iron‐magnesium‐silicate perovskite

Iron‐magnesium‐silicate perovskite was melted in a laser‐heated diamond anvil cell and monitored by thermal analysis. Two signals were identified at each pressure: a lower temperature signal and a higher temperature signal. The lower signal may correspond to the temperature where iron diffuses rapidly. The higher signal would then correspond to melting of magnesium‐enriched silicate perovskite. Alternatively, the lower signal may be the solidus where (Fe .14 Mg .86 )SiO 3 undergoes incongruent melting to an iron‐magnesium‐enriched solid plus a silica‐enriched liquid. Then, the higher signal would be the liquidus. The slope for the melting curve (the higher signal) between 30GPa and 94GPa is slightly negative. Fitting to a straight line gives a value for the slope of −2.5 ± 0.6K/GPa. At 30GPa, the lower signal is ≈300K below the melting curve. They converge slightly at higher pressures and differ by ≈140K at 94GPa. Our melting curve is several hundred degrees (K) below previous estimates.