Melting curve of iron to 290 GPa determined in a resistance-heated diamond-anvil cell

Ryosuke Sinmyo, Kei Hirose, Yasuo Ohishi

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The Earth's core is composed mainly of iron. Since the liquid core coexists with solid at the inner core boundary (ICB), the melting point of iron at 330 GPa offers a key constraint on core temperatures. However, previous results using a laser-heated diamond-anvil cell (DAC) have been largely inconsistent with each other, likely because of an intrinsic large temperature gradient and its temporal fluctuation. Here we employed an internal-resistance-heated DAC and determined the melting temperature of pure iron up to 290 GPa, for the first time above 200 GPa by static compression experiments. A small extrapolation of the present experimental results yields a melting point of 5500 ± 220 K at the ICB, higher than 4850 ± 200 K reported by previous laser-heated DAC by Boehler (1993) but is lower than 6230 ± 500 K by Anzellini et al. (2013). Accounting for the melting temperature depression due to core-alloying elements, the upper bounds for the temperature at the ICB and the core–mantle boundary (CMB) are estimated to be 5120 ± 390 K and 3760 ± 290 K, respectively. Such low present-day CMB temperature suggests that the lowermost mantle has avoided global melting, at least since early Proterozoic Eon.

Original languageEnglish
Pages (from-to)45-52
Number of pages8
JournalEarth and Planetary Science Letters
Publication statusPublished - 15 Mar 2019


  • core
  • core–mantle boundary
  • high pressure
  • inner core boundary
  • iron
  • melting

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