HR: 11:35h
AN: MR52A-06    [Abstracts]
TI: Water at the Bottom of Upper Mantle: A Key to Reconcile Mineral Physics Composition Model with Seismic Wave Velocity Jump at 410-km Discontinuity
AU: * Chen, J
EM: Jiuhua.Chen@fiu.edu
AF: Mineral Physics Institute, ESS Bldg, Stony Brook University, Stony Brook, NY 11794-1200, United States
AU: * Chen, J
EM: Jiuhua.Chen@fiu.edu
AF: Center for the Study of Matter at Extreme Conditions, Florida International University, VH- 140, University Park, Miami, FL 33199, United States
AU: Liu, H
EM: hliu@hpcat.aps.anl.gov
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd., N.W., Washington, DC 20015-130, United States
AU: Yu, T
EM: Tony.Yu@sunysb.edu
AF: Mineral Physics Institute, ESS Bldg, Stony Brook University, Stony Brook, NY 11794-1200, United States
AU: Hu, J
EM: jzhu@bnl.gov
AF: Mineral Physics Institute, ESS Bldg, Stony Brook University, Stony Brook, NY 11794-1200, United States
AB: Laboratory experiments demonstrate that water can be transported from Earth's surface to its deep interior (e.g. Ohtani 2005). Presence of water significantly influences crytal structure (e.g. Smyth 2006), elasticity (e.g. Jacobsen 2006) and phase stabilities (e.g. Chen et al. 2002, Smyth and Frost 2002) of minerals in Earth's mantle. We report the experimental result of water effect on equation of state of San Carlos olivine measured using synchrotron x-rays in a diamond anvil cell at pressures up to 11 GPa. The bulk modulus of San Carlos olivine is reduced by 5% when the sample contains saturated water (4 wt%) with respect to anhydrous sample. The experiments are conducted at the National Synchrotron Light Source (NSLS); a mixture of methanol and ethanol (4:1 by volume) is used as pressure medium. Based the experimental result and previously published data, we re-estimate the seismic velocity at 410-km discontinuity (1400°C adiabat) based on pyrolite composition model. An Earth model program developed by Weidner and Wang (2000) that calculates phase fractions from experimental data on partitioning coefficients of Ca, Fe, and Al between the olivine- and pyroxene- normative components at any given pressure and temperature condition is used. The results indicate that the long-standing discrepancy in magnitude of seismic velocitie jump at 410km depth between mineral physics model and seismic observations can be reasonably negligible with presence of water. This result supports that water is likely present at the bottom of the Earth's upper mantle.
DE: 1042 Mineral and crystal chemistry (3620)
DE: 3612 Reactions and phase equilibria (1012, 8412)
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting