High-pressure, high-temperature phases of Canyon Diablo iron meteorite: A natural analog for terrestrial planetary cores

Synchrotron-based x-ray diffraction of Canyon Diablo iron meteorite at simultaneously high pressures and temperatures reveals evidence for the face-centered cubic γ high-temperature phase being present above ~1500 K (and up to ~2500 K) at 60 GPa, and the hexagonal close-packed ɛ high-pressure phase from room temperature up to ~1700 K at 60 GPa, and up to ~1500 K at 32 GPa. These results are approximately consistent with previous experimental reports on the high P-T crystalline phase transitions in pure iron, providing reassurance that impurities and minor elements in natural samples may not significantly affect the crystal-structural phase-transition conditions. Understanding these effects is critical in determining thermal properties of the core, which has been challenging due to the core's unconstrained composition. Additionally, iron meteorites are considered to be remnants of the Solar System's terrestrial core-forming material and as such can provide insight into potential changes in Earth's core over time.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.