Melting relationships in the Fe–Fe3S system up to the outer core conditions

• Published in: Earth and planetary science letters 2012-12, Vol.359-360, p.26-33
• Main Authors: Kamada, Seiji, Ohtani, Eiji, Terasaki, Hidenori, Sakai, Takeshi, Miyahara, Masaaki, Ohishi, Yasuo, Hirao, Naohisa
• Format: Article
• Language: English
• Subjects: Core-mantle boundary; Diffraction; Earth's outer core; Fe–Fe3S system; in situ X-ray diffraction; inner core boundary; Iron; laser-heated diamond anvil cell; Melting; Seismic phenomena; Surface layer; Texture; X-rays
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2012.09.038

In situ X-ray diffraction experiments in the Fe–Fe3S system were performed up to 175GPa and 3500K using a laser-heated diamond anvil cell to investigate melting relationships in the system. Partial melting in the Fe–Fe3S system was observed based on the disappearance of X-ray diffraction peaks of solid Fe3S and texture observation of the recovered samples. The melting relationship of the Fe–Fe3S system as a function of pressure is evaluated based on Kraut–Kennedy law. Our results of melting relationships suggest that the temperature at the inner core boundary is between 4700(160) and 4930(330) K if sulfur is the only light element in the Earth's core. Assuming the adiabatic temperature gradient in the outer core, the temperature at the core–mantle boundary is estimated to be in the range of 3600–3770K. The present temperature profile of the core is consistent with the core–mantle boundary temperature that can explain the core heat flux to maintain the core dynamo and the seismic structure at the base of the lower mantle. ► Melting relation in Fe–Fe3S system was investigated to 182GPa based on in situ XRD. ► TICB was estimated based on the melting curve. ► TCMB was estimated by assuming the adiabatic temperature gradient in the outer core. ► A recovered sample from 123GPa was observed by FE-SEM. ► A dendritic texure was observed.