HR: 0830h
AN: V31D-0965    [PDF]
TI: Ultrasonic Shear Waves in the Diamond-Anvil Cell and Shear-Mode Softening in (Mg,Fe)O
AU: * Jacobsen, S D
EM: steven.jacobsen@uni-bayreuth.de
AF: Bayerisches Geoinstitut, Univ. Bayreuth, Bayreuth, D-95440 Germany
AU: Spetzler, H
EM: hartmut.spetzler@colorado.edu
AF: CIRES, Univ. Colorado, Boulder, CO 80309-0216 United States
AU: Spetzler, H
EM: hartmut.spetzler@colorado.edu
AF: Dept. Geological Sciences, Univ. Colorado, Boulder, CO 80309-0399 United States
AU: Reichmann, H J
EM: hanni@gfz-potsdam.de
AF: GeoForschungsZentrum, Telegrafenberg, Potsdam, D-14473 Germany
AU: Smyth, J R
EM: joseph.smyth@colorado.edu
AF: Dept. Geological Sciences, Univ. Colorado, Boulder, CO 80309-0399 United States
AU: Kantor, A
EM: anastasia.kantor@uni-bayreuth.de
AF: Bayerisches Geoinstitut, Univ. Bayreuth, Bayreuth, D-95440 Germany
AU: Dubrovinsky, L S
EM: Leonid.Dubrovinsky@uni-bayreuth.de
AF: Bayerisches Geoinstitut, Univ. Bayreuth, Bayreuth, D-95440 Germany
AU: Hemley, R J
EM: r.hemley@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington D.C., 20015 United States
AU: Mao, H
EM: h.mao@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington D.C., 20015 United States
AB: Pure-mode elastic shear waves have been transmitted into the DAC using a new P-to-S conversion buffer rod for GHz-ultrasonic interferometry. The advance has wide application to the Earth and material sciences. Both longitudinal and shear-wave travel times can now be measured in optically dark (or opaque) single-crystal minerals (or metals) at mantle pressures. W\"{u}stite-FeO and magnesiow\"{u}stite-(Mg,Fe)O containing more than 50% iron exhibit pressure-induced {\it C}44 mode softening over the experimental pressure range to 10 GPa, whereas ferropericlase closer to expected lower-mantle compositions (~25%) exhibits increasing shear velocities more similar to MgO. The pressure derivatives ({\it dC}44/{\it dP}) are: -1.06(3), -0.95(1), -0.16(1) and 1.24(5) for Fe0.95O, and (Mg,Fe)O with 78, 56, and 24 mol% FeO respectively. The observed shear-mode softening in iron-rich (Mg,Fe)O may be due to strong magnetoelastic coupling (as in FeO) and indicates an instability in the rocksalt ({\it B}1) structure at high pressure.
DE: 3909 Elasticity and anelasticity
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting