HR: 1330h
AN: P12B-1067    [PDF]
TI: Stability and P-V-T Equations of State of High-Pressure Iron-Sulfur Compounds
AU: * Frank, M R
EM: mfrank@gl.ciw.edu
AF: Department of Geology and Environmental Geosciences, Northern Illinois University Davis Hall 312, Normal Rd., DeKalb, IL 60115 United States
AU: Fei, Y
EM: fei@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington 5251 Broad Branch Rd. NW, Washington, DC 20015 United States
AU: Mibe, K
EM: mibe@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington 5251 Broad Branch Rd. NW, Washington, DC 20015 United States
AU: Watson, H
EM: h.watson@gl.ciw.edu
AF: Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180 United States
AB: It has long been hypothesized that iron and perhaps sulfur are important contributors to the cores of terrestrial planets. In order to assess the incorporation of sulfur in a metallic iron core, we must understand phase relations in the Fe-S system at high pressure and temperature. The absence of structure and pressure-density data for the Fe$_{3}$S$_{2}$ and Fe$_{2}$S high-pressure phases limits the ability to fully characterize the Fe-S system at high pressure and temperature. In this study, we report new experimental results on the stability, in-situ structure, and P-V-T equations of state of the high-pressure iron-sulfur compounds. Experiments were performed in a multi-anvil apparatus using an 8/3 assembly at beamline BL04B1 in the SPring-8 synchrotron facility. FeS and Fe were mixed in appropriate proportions (Fe$_{3}$S$_{2}$ and Fe$_{2}$S) and loaded into a MgO capsule. The MgO capsule material was also utilized as an internal pressure calibrant. The Fe-FeS mixtures were first pressurized to about 20 GPa at room temperature. The sample was then heated with a rhenium foil heater to 1073 K and held at that temperature for two to four hours to promote formation of the high-pressure Fe-S phase. Temperatures were measured using a W$_{0.05}$Re-W$_{0.26}$Re thermocouple. X-ray diffraction data of the samples were collected at appropriate time intervals to address reaction kinetics. The relative intensities of the diffraction lines associated with metallic Fe and the high-pressure Fe-S compounds (Fe$_{3}$S$_{2}$ or Fe$_{2}$S) decreased and increased, respectively, with time. The observed diffraction peaks at simultaneous high pressure and temperature will be used to determine the in-situ structures of Fe$_{3}$S$_{2}$ and Fe$_{2}$S. We also obtained P-V-T data for Fe$_{3}$S whose structure type has been previously determined, over a wide pressure-temperature range. These data will be used to constructed density profiles of S-bearing iron cores and to evaluate core composition models
DE: 3630 Experimental mineralogy and petrology
DE: 3672 Planetary mineralogy and petrology (5410)
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting