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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Zhao, Jiyong Li, Zeyu Hu, Michael Y. Chow, Paul Bi, Wenli Li, Jie Xiao, Yuming Liu, Jiachao Alp, E. Ercan Chen, Bin Zhang, Dongzhou |
| Description | Author Affiliation: Chen B ( Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109); Li Z ( Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109); Zhang D ( Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125); Liu J ( Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109); Hu MY ( Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439); Zhao J ( Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439); Bi W ( Department of Geology, University of Illinois at Urbana-Champaign, Urbana, IL 61801); Alp EE ( Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439); Xiao Y ( High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439.); Chow P ( High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439.); Li J ( Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109); |
| Abstract | Earth’s inner core is known to consist of crystalline iron alloyed with a small amount of nickel and lighter elements, but the shear wave (S wave) travels through the inner core at about half the speed expected for most iron-rich alloys under relevant pressures. The anomalously low S-wave velocity $(v_{S})$ has been attributed to the presence of liquid, hence questioning the solidity of the inner core. Here we report new experimental data up to core pressures on iron carbide $Fe_{7}C_{3},$ a candidate component of the inner core, showing that its sound velocities dropped significantly near the end of a pressure-induced spin-pairing transition, which took place gradually between 10 GPa and 53 GPa. Following the transition, the sound velocities increased with density at an exceptionally low rate. Extrapolating the data to the inner core pressure and accounting for the temperature effect, we found that low-spin $Fe_{7}C_{3}$ can reproduce the observed $v_{S}$ of the inner core, thus eliminating the need to invoke partial melting or a postulated large temperature effect. The model of a carbon-rich inner core may be consistent with existing constraints on the Earth's carbon budget and would imply that as much as two thirds of the planet's carbon is hidden in its center sphere. |
| ISSN | 00278424 |
| e-ISSN | 10916490 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Issue Number | 50 |
| Volume Number | 111 |
| Language | English |
| Publisher | National Academy of Sciences |
| Publisher Date | 2014-12-01 |
| Publisher Place | United States |
| Access Restriction | Open |
| Subject Keyword | Multidisciplinary |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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