Physics – Geophysics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmmr42a..02a&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #MR42A-02
Physics
Geophysics
1025 Composition Of The Mantle, 3621 Mantle Processes (1038), 3909 Elasticity And Anelasticity, 3919 Equations Of State, 3924 High-Pressure Behavior
Scientific paper
Phase transition from perovskite (Pv) to Post-Pv (PPv) phase in MgSiO3 has been studied by many groups since its discovery in 2004 (1,2) and the different studies find similar transition pressures. The effect of Al and Fe on the phase transition remains more controversial. The most recent studies suggest an increase of the transition pressure with increasing Fe-content (3,4), but other experimental work (5) as well as ab-initio calculations (6) show the opposite effect. The effect of Al was reported to increase slightly the pressure transition to the CaIrO3 form (4,7), but its influence on the Fe3+ content in the PPv phase has not been documented yet. By means of in situ study of the Fe K-edge fine structures (XANES), we investigated the phase relations between Pv and PPv phases for three different Al-(Mg,Fe)SiO3 compositions. For this, we synthesized various Pv and PPv mixtures using laser-heated diamond anvil cell (DAC) for pressures between 60 and 170 GPa. The sample's mineralogy, i.e. the Pv and PPv phase fractions, was determined using in-situ X-ray diffraction at the ID27 beamline of the ESRF (8,9). Then, we probed the Fe speciation, i.e. the Fe concentration in each phases, in-situ in the DAC using the µ-XANES mapping technique available at the ID24 beamline (10,11). Both pieces of information were combined to retrieve the Fe partitioning coefficient between the two high-pressure phases. Our results show that Fe partitions strongly into the PPv phase, which implies a very large binary loop of coexistence of the two phases. Thus, at the core-mantle boundary pressure (135 GPa), the Pv and PPv phase always coexist for all geophysically relevant Al-(Mg,Fe)SiO3 compositions, and the Fe-content in the PPv-phase is only a few percent. References: 1. M. Murakami, K. Hirose, K. Kawamura, N. Sata, Y. Ohishi, Science 304, 855 (2004). 2. A. R. Oganov, S. Ono, Nature 430, 445 (2004). 3. S. Tateno, K. Hirose, N. Sata, Y. Ohishi, Phys. Earth Planet. Inter. 160, 319 (2007). 4. D. Nishio-Hamane, T. Nagai, K. Fujino, Y. Seto, N. Takafuji, Geophys. Res. Lett. 32, L16306 (2005). 5. W. L. Mao et al., PNAS 101, 15867 (2004). 6. J. P. Brodholt, A. R. Oganov, personal communication. 7. S. Ono, A. R. Oganov, T. Koyama, H. Shimizu, Earth Planet. Sci. 246, 326 (2006). 8. N. Guignot, D. Andrault, G. Morard, M. Mezouar, Earth Planet. Sci. 256, 162 (2007). 9. E. Schultz et al., High Press. Res. 25, 71 (2005). 10. S. Pascarelli, O. Mathon, M. Muñoz, T. Mairs, J. Susini, J. Synch. Rad. 13, 351 (2006). 11. M. Muñoz et al., Geochemistry Geophysics Geosystems 7, Q11020 (2006).
Andrault Denis
Aquilanti Giuliana
Bolfan-Casanova Nathalie
Guignot Nicolas
Muñoz Manuel.
No associations
LandOfFree
The Perovskite to Post-Perovskite phase transition in Al-bearing (Mg,Fe)SiO3: A XANES in-situ analysis at the Fe K-edge 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 The Perovskite to Post-Perovskite phase transition in Al-bearing (Mg,Fe)SiO3: A XANES in-situ analysis at the Fe K-edge, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Perovskite to Post-Perovskite phase transition in Al-bearing (Mg,Fe)SiO3: A XANES in-situ analysis at the Fe K-edge will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1242844