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Solving controversies on the iron phase diagram under high pressure

DOI: 10.1029/2018GL079950 DOI Help

Authors: Guillaume Morard (Sorbonne UniversitéCosmochimie, IMPMC, Museum National d’Histoire Naturelle) , Silvia Boccato (European Synchrotron Radiation Facility) , Angelika D. Rosa (European Synchrotron Radiation Facility) , Simone Anzellini (Diamond Light Source) , Francesca Miozzi (Sorbonne UniversitéCosmochimie, IMPMC, Museum National d’Histoire Naturelle) , Laura Henry (European Synchrotron Radiation Facility) , Gaston Garbarino (European Synchrotron Radiation Facility) , Mohamed Mezouar (European Synchrotron Radiation Facility) , Marion Harmand (Sorbonne UniversitéCosmochimie, IMPMC, Museum National d’Histoire Naturelle) , François Guyot (Sorbonne UniversitéCosmochimie, IMPMC, Museum National d’Histoire Naturelle) , Eglantine Boulard (Sorbonne UniversitéCosmochimie, IMPMC, Museum National d’Histoire Naturelle) , Innokenty Kantor (European Synchrotron Radiation Facility; Danmarks Tekniske Universitet) , Tetsuo Irifune (Ehime University) , Raffaella Torchio (European Synchrotron Radiation Facility)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Geophysical Research Letters , VOL 96

State: Published (Approved)
Published: October 2018

Abstract: As the main constituent of planetary cores, pure iron phase diagram under high pressure and temperature is of fundamental importance in geophysics and planetary science. However, previously reported iron‐melting curves show large discrepancies (up to 1000 K at the Earth's core–mantle boundary, 136 GPa), resulting in persisting high uncertainties on the solid‐liquid phase boundary. Here we unambiguously show that the observed differences commonly attributed to the nature of the used melting diagnostic are due to a carbon contamination of the sample as well as pressure overestimation at high temperature. The high melting temperature of pure iron under core‐mantle boundary (4250 ± 250 K), here determined by X‐ray absorption experiments at the Fe K‐edge, indicates that volatile light elements such as sulfur, carbon, or hydrogen are required to lower the crystallization temperature of the Earth's liquid outer core in order to prevent extended melting of the surrounding silicate mantle.

Subject Areas: Earth Science

Facility: European Synchrotron Radiation Facility

Added On: 15/11/2018 14:37

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Earth Sciences & Environment Geology Geophysics

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