Structural evolution of iron oxides melts at Earth's outer-core pressures
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| Format: | Preprint |
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2025
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| author | Crépisson, Céline Fitzgerald, Mila Peake, Domenic Heighway, Patrick Stevens, Thomas Descamps, Adrien McGonegle, David Amouretti, Alexis El-Din, Karim K. Alaa Andrzejewski, Michal Azadi, Sam Brambrink, Erik Camarda, Carolina Chin, David A. Cafiso, Samuele Di Dio Dutra, Ana Coutinho Höppner, Hauke Yamamoto, Kohdai Konôpkovà, Zuzana Nakatsutsumi, Motoaki Ozaki, Norimasa Polsin, Danae N. Schwinkendorf, Jan-Patrick Shoulga, Georgiy Strohm, Cornelius Tang, Minxue Taylor, Harry Toncian, Monika Wang, Yizhen Yao, Jin Gregori, Gianluca Wark, Justin S. Appel, Karen Harmand, Marion Vinko, Sam M. |
| author_facet | Crépisson, Céline Fitzgerald, Mila Peake, Domenic Heighway, Patrick Stevens, Thomas Descamps, Adrien McGonegle, David Amouretti, Alexis El-Din, Karim K. Alaa Andrzejewski, Michal Azadi, Sam Brambrink, Erik Camarda, Carolina Chin, David A. Cafiso, Samuele Di Dio Dutra, Ana Coutinho Höppner, Hauke Yamamoto, Kohdai Konôpkovà, Zuzana Nakatsutsumi, Motoaki Ozaki, Norimasa Polsin, Danae N. Schwinkendorf, Jan-Patrick Shoulga, Georgiy Strohm, Cornelius Tang, Minxue Taylor, Harry Toncian, Monika Wang, Yizhen Yao, Jin Gregori, Gianluca Wark, Justin S. Appel, Karen Harmand, Marion Vinko, Sam M. |
| contents | Oxygen and other light elements comprise up to 5 wt% of the Earth's outer-core, and may significantly influence its physical properties and the operation of the geodynamo. Here we report in situ x-ray diffraction measurements of Fe, Fe + 4.5 FeO (atomic proportion), and Fe2O3 melts at 177-438 GPa, achieved using laser-driven shock compression at an x-ray free-electron laser. The melts exhibit Fe-O coordination numbers between 4.0(0.4) and 4.5(0.4), indicating predominantly four-fold coordination environments. These coordination states are significantly smaller than those of Fe-bearing lower-mantle phases such as bridgmanite and ferropericlase. Shorter Fe-Fe interatomic distances in compressed iron oxide melts drive the denser packing relative to ambient melts, while the structural differences between Fe + 4.5 FeO and Fe2O3 melts under shock indicate that the oxidation state modulates oxygen solubility in liquid Fe. At around 177 GPa (380 km below the core-mantle boundary), Fe2O3 melts exhibit higher Fe-O coordination, suggesting that local variations in oxygen content could contribute to the stratification in the uppermost outer-core inferred from seismological and geomagnetic observations. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_20144 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Structural evolution of iron oxides melts at Earth's outer-core pressures Crépisson, Céline Fitzgerald, Mila Peake, Domenic Heighway, Patrick Stevens, Thomas Descamps, Adrien McGonegle, David Amouretti, Alexis El-Din, Karim K. Alaa Andrzejewski, Michal Azadi, Sam Brambrink, Erik Camarda, Carolina Chin, David A. Cafiso, Samuele Di Dio Dutra, Ana Coutinho Höppner, Hauke Yamamoto, Kohdai Konôpkovà, Zuzana Nakatsutsumi, Motoaki Ozaki, Norimasa Polsin, Danae N. Schwinkendorf, Jan-Patrick Shoulga, Georgiy Strohm, Cornelius Tang, Minxue Taylor, Harry Toncian, Monika Wang, Yizhen Yao, Jin Gregori, Gianluca Wark, Justin S. Appel, Karen Harmand, Marion Vinko, Sam M. Materials Science High Energy Physics - Experiment Oxygen and other light elements comprise up to 5 wt% of the Earth's outer-core, and may significantly influence its physical properties and the operation of the geodynamo. Here we report in situ x-ray diffraction measurements of Fe, Fe + 4.5 FeO (atomic proportion), and Fe2O3 melts at 177-438 GPa, achieved using laser-driven shock compression at an x-ray free-electron laser. The melts exhibit Fe-O coordination numbers between 4.0(0.4) and 4.5(0.4), indicating predominantly four-fold coordination environments. These coordination states are significantly smaller than those of Fe-bearing lower-mantle phases such as bridgmanite and ferropericlase. Shorter Fe-Fe interatomic distances in compressed iron oxide melts drive the denser packing relative to ambient melts, while the structural differences between Fe + 4.5 FeO and Fe2O3 melts under shock indicate that the oxidation state modulates oxygen solubility in liquid Fe. At around 177 GPa (380 km below the core-mantle boundary), Fe2O3 melts exhibit higher Fe-O coordination, suggesting that local variations in oxygen content could contribute to the stratification in the uppermost outer-core inferred from seismological and geomagnetic observations. |
| title | Structural evolution of iron oxides melts at Earth's outer-core pressures |
| topic | Materials Science High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2511.20144 |