HR: 0800h
AN: MR11A-0896    [Abstracts]
TI: Density Measurement of Iron-Bearing Sodium Disilicate by High-Pressure X-ray Absorption Method
AU: * Urakawa, S
EM: urakawa@cc.okayama-u.ac.jp
AF: Department of Earth Sciences, Okayama University, 3-1-1 Tsushima naka, Okayama, 7008530 Japan
AU: Ando, R
EM: andou_rt@ganko.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aramaki, Aoba-ku, Sendai, 9808577 Japan
AU: Suzuki, A
EM: a-suzuki@mail.tains.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aramaki, Aoba-ku, Sendai, 9808577 Japan
AU: Ohtani, E
EM: ohtani@mail.cc.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Aramaki, Aoba-ku, Sendai, 9808577 Japan
AU: Katayama, Y
EM: katayama@spring8.or.jp
AF: Synchrotron radiation Research Center, Japan Atomic Energy Research Institute, 1-1-1 Kouto, Mikaduki, 6795148 Japan
AB: Density is one of the important physical properties of silicate melts to understand the magmatic process in the Earth inteiror. Recently, we have applied x-ray absorption technique to measure density of silicate glasses and melts at high-pressure, using highly brilliant synchrotron x-ray and a multi-anvil apparatus. Very low absorption of silciates for x-ray reduces absorption contrast between silicate samples and surrounding materials to make density measurement difficult. We have overcome this difficulty by use of a single crystal diamond ring as a sample container, which is transparent for x-ray and less reactive with silicate melt. High-pressure and temperature x-ray absorption experiments were conducted using the cubic-type press SMAP-1 at BL22XU of SPring-8, Japan. Starting sample is the Fe-bearing Na disilicate glass with the composition of Na$_{2}$FeSi$_{2}$O$_{6}$. Energy of monochromatic x-ray is tune to be 25 keV and intensities of incident and transmitted x-rays are measured by ion chambers. Density is evaluated from x-ray absorption profile along a radial direction of a cylindrical sample using equation of I = I$_{0}$exp(-\mu\rho t). We reported the results of the density measurements of Na$_{2}$FeSi$_{2}$O$_{6}$ glass up to 5 GPa and 600 K at AGU Fall meeting in 2003. Now we succeed the density measurement of that melt up to 3 GPa and 1400 K. Althogh these pressure and temperature conditions are out of the stability field of diamond, diamond ring survives after several hours heating. Measured density of Na$_{2}$FeSi$_{2}$O$_{6}$ changes discontinuously with phase transitions from glass to crystal and from crystal to melt. Apparent density increase of Na$_{2}$FeSi$_{2}$O$_{6}$ melt with increasing pressure is also observed, indicating that this method has a potential to determine equation of state of silicate melts.
DE: 8439 Physics and chemistry of magma bodies
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
DE: 3994 Instruments and techniques
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting