Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmmr13a0990m&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #MR13A-0990
Physics
3924 High-Pressure Behavior, 3954 X-Ray, Neutron, And Electron Spectroscopy And Diffraction
Scientific paper
Sulfur is believed to be an alloying light element in iron-rich planetary cores such as those of the Earth and Mars 1, 2. Recent studies have suggested that Mars, like the Earth, could have a liquid metallic outer core together with a solid inner core 3. Hence, it is important to investigate the evolution of the Fe-FeS phase diagram and of the structural properties of the liquid Fe-FeS alloys in respect to pressure, temperature and sulphur content. A new cell assembly has been developed to heat samples to more than 1300 K at 17 GPa using the Paris Edinburgh Press4. This allows us to conduct detailed structural investigations of the Fe-FeS eutectic liquid by in situ X-ray diffraction5 . Analysis of these data highlights an increase of the liquid compacity with increasing pressure. We also show that the eutectic liquid structure is closer to that of FeSi, explaining the closure of the miscibility gap in the Fe-S-Si system 6. The evolution of the Fe-FeS eutectic liquid structure at high pressure could have significant effect on extrapolated wave speed of metallic Fe-FeS alloy at core pressures. We have used a double-sided laser-heated diamond-anvil cell 7 to study the Fe-FeS phase diagram up to 65 GPa and 2500 K8. We used laser heated diamond anvil cell coupled with synchrotron radiation and confirm a S- solubility below 4 at% (2.3 %wt) up to 65 GPa. The eutectic temperatures present a uniform increase, with a rate of ~15K/GPa, up to 65 GPa and 2200 K. Finally, we present new constraints on the phase diagram evolution to very high pressures which provide unambiguous evidence for an upper limit of 4-8 %wt for the inner core S- content. Therefore, sulphur is not favoured to be the major light element in the Earth's core. 1. Allegre, C. J., Poirier, J. P., Humler, E. & Hofmann, A. W. The chemical composition of the Earth. Earth Planet. Sc. Lett. 134, 515-526 (1995). 2. Sohl, F. & Spohn, T. The interior structure of Mars : Implications from SNC meteorites. J. Geophys. Res. 102, 1613-1635 (1997). 3. Yoder, C. F., Konopliv, A. S., Yuan, D. N., Standish, E. M. & Folkner, W. M. Fluid core size of Mars from detection of the solar tide. Science 300, 299-303 (2003). 4. Morard, G. et al. Optimization of Paris Edinburgh cell assemblies for in situ monochromatic X-ray diffraction and X-ray absorption. High Press. Res. 27, 1-11 (2007). 5. Morard, G. et al. Structure of eutectic Fe-FeS melts up to 17 GPa: Implications for planetary cores. Earth Planet. Sc. Lett. in press (2007). 6. Sanloup, C. & Fei, Y. Closure of the Fe-S-Si liquid miscibility gap at high pressure. Phys. Earth Plan. Int. 147, 57 (2004). 7. Mezouar, M. et al. Development of a new state-of-the-art beamline optimized for monochromatic single crystal and powder X-ray diffraction under extreme conditions at the ESRF. J. Synch. Rad. 12, 659-664 (2005). 8. Morard, G. et al. Experimental constraints on the Earth's core sulphur content. Nature (Submitted).
Andrault Denis
Fiquet Guillaume
Guignot Nicolas
Mezouar Mohamed
Morard Guillaume
No associations
LandOfFree
Investigation of Fe-FeS phase diagram and liquid structure at high pressure and high temperature does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Investigation of Fe-FeS phase diagram and liquid structure at high pressure and high temperature, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Investigation of Fe-FeS phase diagram and liquid structure at high pressure and high temperature will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1410222