HR: 0800h
AN: MR31B-0371    [Abstracts]
TI: Partitioning of Potassium Between Fe-S and K-rich Silicate at High Temperature
AU: * Kamada, S
EM: kmdseiji@ganko.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology, and Economic Geology, Tohoku university, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
AU: Sakai, T
EM: sakai@ganko.tohoku.ac.jp
AF: International Advanced Research and Education Organaization, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
AU: Ohtani, E
EM: ohtani@mail.tains.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology, and Economic Geology, Tohoku university, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
AU: Kondo, T
EM: tdskondo@ess.sci.osaka-u.ac.jp
AF: Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, 560-0043, Japan
AU: Miyahara, M
AF: Institute of Mineralogy, Petrology, and Economic Geology, Tohoku university, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
AU: Nishijima, M
EM: ni_shi@imr.tohoku.ac.jp
AF: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980- 8577, Japan
AU: Kikegawa, T
EM: kikegawa@post.kek.jp
AF: Photon Factory, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, 305- 0801, Japan
AB: Partitioning of potassium between liquid iron and silicate melt at high pressure and temperature is important to estimate the amount of potassium in the Earth's core. In the previous works, the partitioning experiments were performed below 26 GPa using a large volume press (e.g. Ito et al., 1993; Gessmann et al., 2002; Murthy et al., 2003), except for the work by Hirao et al. (2006) using a laser heated diamond anvil cell (LHDAC). The aim of this work is to clarify the effects of pressure, temperature and sulfur content on the partitioning coefficients of potassium (D_K) in a wide pressure and temperature range using LHDAC. We performed partitioning experiments at 50 GPa and the temperature range of 2500-3000 K using a LHDAC. The starting material was foil of Fe₇₉S₂₁, which was sandwiched by a natural Aduralia (KAlSi₃O₈). Powder X-ray diffraction experiments were carried out at the ambient pressure to identify the reaction phases at BL13A and BL18C Photon Factory, KEK. Chemical analysis was performed using EPMA and ATEM (Institute for Materials Research, Tohoku Univ.). D_K increases from 0.011 to 0.136 with increasing temperature (2500-3000 K) at 50 GPa. This trend is consistent with previous studies (e.g. Gessmann and Wood, 2002; Murthy et al., 2003). Our result indicates that D_K decreases with increasing pressure. D_K at 50 GPa and 3000 K in the sulfur- bearing system is larger than that reported by Ito et al.(1993) at 26 GPa and 2900 K in the sulfur-free system. This results show that sulfur may increase the solubility of potassium into metallic iron melt. D_K of 0.005-0.12 at 135 GPa and 3000-4000 K is estimated by extrapolation of the D_K to the condition of the core-mantle boundary (CMB) using the dependence of temperature and pressure observed in this study. This value suggests that the total potassium content in the core is about 1.2-29 ppm assuming that a primitive mantle concentration of potassium is 240 ppm (McDounough and Sun, 1995). It can produce only the radiogenic heat of 0.005-0.12 TW in the core, which is 1.2-6.0 % of the total current heat flux from the core.
DE: 0772 Distribution
DE: 7207 Core (1212, 1213, 8124)
DE: 7208 Mantle (1212, 1213, 8124)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8130 Heat generation and transport
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting