HR: 0800h
AN: MR41A-0903    [Abstracts]
TI: High-pressure synchrotron-IR studies of hydrous transition zone and lower-mantle minerals in the laser-heated diamond cell
AU: * Jacobsen, S D
EM: s.jacobsen@gl.ciw.edu
AF: Carnegie Institution of Washington, Geophysical Laboratory, Washington, DC 20015
AU: Liu, Z
MR41A-0903 AF: Carnegie Institution of Washington, Geophysical Laboratory, Washington, DC 20015
AU: Lin, J
MR41A-0903 AF: Carnegie Institution of Washington, Geophysical Laboratory, Washington, DC 20015
AU: Lin, J
MR41A-0903 AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550
AU: Littlefield, E F
MR41A-0903 AF: Colby College, Department of Geology, Waterville, ME 04901
AU: Demouchy, S
MR41A-0903 AF: Lunar & Planetary Institute USRA, 3600 Bay Area Blvd., Houston, TX 77058
AU: Shen, G
MR41A-0903 AF: HPCAT, Advanced Photon Source, Argonne, IL 60439
AU: Prakapenka, V
MR41A-0903 AF: CARS, University of Chicago, Argonne, IL 60439
AU: Langenhorst, F
MR41A-0903 AF: Friedrich-Schiller-University, Institut fur Geowissenschaften, Jena, 07749 Germany
AU: Hemley, R J
MR41A-0903 AF: Carnegie Institution of Washington, Geophysical Laboratory, Washington, DC 20015
AB: Synchrotron-based infrared spectroscopy has been used to study the high-pressure behavior of near-IR absorption bands in single-crystal samples of hydrous wadsleyite and laser-heated hydrous ringwoodite in a diamond-anvil cell. Experiments were carried out at the U2A beamline of the National Synchrotron Light Source (NSLS). The sample of pure-Mg hydrous wadsleyite contained roughly 1 wt% of water and was studied to 20 GPa. In agreement with previous results on Fe-bearing samples [Cynn and Hofmeister 1994, JGR 99, 17,717], the band group at lower wavenumbers (3200-3400 cm^-1) displays a negative shift upon compression whereas the group at higher wavenumbers (3580-3700 cm^-1) displays zero or slightly positive shifts. The results confirm that there are at least two different hydrogen bond geometries in wadsleyite. A single-crystal of Fo90 hydrous ringwoodite also containing about 1 wt% of water was transformed to the silicate-perovskite plus magnesiowustite assemblage at 35 GPa and various temperatures between 1200 and 1800C. Laser heating and phase analysis was carried out with in-situ X-ray diffraction on the 13-IDD beamline of GSECARS. The use of synchrotron-IR techniques facilitated study of the recovered sample at 35 GPa at various points of the sample where heating was carried out at different temperatures. In addition to spectra corresponding to unconverted ringwoodite, magnesiowustite, possibly phase D and quench, we observe two new sharp bands at 3060 and 3160 cm^-1, which may correspond to the elusive O-H stretching of structurally bound hydroxyl in silicate perovskite not normally observed in recovered samples at room pressure.
DE: 1042 Mineral and crystal chemistry (3620)
DE: 3900 MINERAL PHYSICS
DE: 3904 Defects
DE: 3934 Optical, infrared, and Raman spectroscopy
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005