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A Study of the Oxyhydroxide Presence at the Earth Core  

Kim, Young-Ho (Department of Earth and Environment Sciences and Research Institute of Natural Science, Gyeongsang National University)
Do, Jae-Ki (Department of Earth and Environment Sciences and Research Institute of Natural Science, Gyeongsang National University)
Hwang, Gil-Chan (Department of Earth and Environment Sciences and Research Institute of Natural Science, Gyeongsang National University)
Publication Information
Journal of the Mineralogical Society of Korea / v.21, no.4, 2008 , pp. 415-423 More about this Journal
Abstract
Earth outer core is composed of iron mainly with some diluent elements, which account for the observed ca. 10% density deficit compared to the pure iron. Among candidates as the light diluents, hydrogen and oxygen were selected, and the thermodynamic stability of the following reaction was calculated; hematite + hydrogen $\to$ goethite + iron. At ambient conditions, Gibb's free energy of this reaction is 12.62 kJ/mol. On increasing pressure at room temperature, it decreases to zero at 0.068 GPa. This energy decreases at constant rate down to 200 GPa, which shows -208.26 kJ/mol at that pressure. From these results, this chemical reaction prefers the reduction environment forming the iron element and iron oxyhydroxide, so possible presence of iron oxyhydroxide with iron at proto-core can not be ruled out.
Keywords
outer core; hematite; goethite; Gibb's free energy; oxyhydroxide;
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1 Faure, G. (1991) Principles and applications of inorganic geochemistry, Macmillan Pub. Co., 626
2 Mao, H.K., Jephcoat, A.P., Hemley, R.J., Finger, L.W., Zha C.S., Hazen, R.M., and Cox, D.E. (1988) Synchrotron x-ray diffraction measurements of single-crystal hydrogen to 26.5 GPa, Science, 239, 1131-1134   DOI   ScienceOn
3 Ohtani, E., Ringwood, A.E., and Hibberson, W. (1984) Composition of the core, II. Effect of high pressure on solubility of FeO in molten iron, Earth and Planetary Science Letters, 71, 94-103   DOI   ScienceOn
4 Ruoff, A.L. and Vanderborgh, C.A. (1991) Hydrogen reduction of ruby at high pressure: Implication for claims of metallic hydrogen, Phys. Rev. Lett., 66, 754-757   DOI   ScienceOn
5 Stevenson, D.J. (1981) Models of the Earth's core, Science, 214, 611-619   DOI   ScienceOn
6 Giles, P.M., Longenbach, M.H., and Marder, A.R. (1971) High pressure ${\alpha}{\rightarrow}{\epsilon}$ martensitic transformation in iron, J. Appl. Phys., 42, 4290-4295   DOI
7 Ohtani, E. and Ringwood, A.E. (1984) Composition of the core, I. Solubility of oxygen in molten iron at high temperatures, Earth and Planetary Science Letters, 71, 85-93   DOI   ScienceOn
8 Kim, Y.H., Hwang, G.C., and Do, J.K. (2007) Compression study of goethite at room temperature, J. Miner. Soc., Korea, 20(4), 261-266   과학기술학회마을
9 Saxena, S.K., Liermann, H.-P., and Shen, G. (2004) Formation of iron hydride and high-magnetite at high pressure and temperature, Phys. Earth & Planet. Int., 146, 313-317   DOI   ScienceOn
10 Jephcoat, A.P., Mao, H.K., and Bell, P.M. (1986) Static compression of iron to 78 GPa with rare gas solids pressure-transmitting media, J. Geophys. Res., 91, 4677-4684   DOI
11 Wilburn, D.R. and Bassett, W.A. (1978) Hydrostatic compression of iron and related compounds: an overview, Am. Mineral., 63, 591-596
12 Michels, A., De Graaff, W., Wassenaar, T., Levett, J.M.H., and Lowerse, P. (1959) Compressibility isotherms of hydrogen and deuterium at temperatures between -175${\degrees}C$ and +150${\degrees}C$ (at densities up to 960 Amagat), Physica (Utrecht), 25, 25-42   DOI   ScienceOn
13 Takahashi, T., Bassett, W.A., and Mao, H.K. (1968) Isothermal compress-ion of the alloys of iron up to 300 kbar at room temperature: iron-nickel alloys, J. Geophys. Res., 73, 4717-4725   DOI
14 Badding, J.V., Hemley, R.J., and Mao, H.K. (1991) High-pressure chemistry of hydrogen in metals: In-situ study of iron hydride. Science, 253, 421-424   DOI   ScienceOn
15 Masters, T.G. and Shearer, P.M. (1990) Summary of seismological constraints on the structure of the Earth's core, J. Geophys. Res., 95, 21691-21695   DOI
16 Jeanloz, R. (1990) The nature of the Earth's core, Annu. Rev. Earth Planet. Sci., 18, 357-386   DOI   ScienceOn
17 Fukai, Y. and Suzuki, T. (1986) Iron-water reaction under high pressure and its implication in the evolution of the Earth, J. Geophys. Res., 91, 9222-9230   DOI
18 Mills, R.L., Liebenberg, D.H., Bronson, J.C., and Schmidt, L.C. (1977) Equation of state of fluid n-H2 from P-V-T and sound velocity measurements to 20 kbar, J. Chem. Phys., 66, 3076-3084   DOI
19 Murakami, M., Hirose, K., Yurimoto, H., Nakashima, S., and Takafuji, N. (2002) Water in earth's lower mantle, Science, 295, 1885-1887   DOI   ScienceOn
20 Ashcroft, N.W. (1990) Pairing instabilities in dense hydrogen. Phys. Rev., B41, 10963-10971
21 Ohtani, E., Hirao, N., Kondo, T., Ito, M., and Kikegawa, T. (2005) Iron-water reaction at high pressure and temperature, and hydrogen transport into the core, Phys. Chem. Minerals, 32, 77-82   DOI
22 Knittle, E. and Jeanloz, R. (1991) The high-pressure phase diagram of Fe0.94O: a possible constituent of the earth's core, J. Geophys. Res., 96, 16169-16180   DOI