HR: 0800h
AN: V31B-0608    [Abstracts]
TI: New Measurements of the Densities of Copper, Nickel, and Iron Sulfide Liquids
AU: * Mioduszewski, L
EM: lukem@u.washington.edu
AF: Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310 United States
AU: Kress, V C
EM: kress@u.washington.edu
AF: Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310 United States
AB: Density measurements of sulfide liquids in the Fe-Ni-Cu-S-O system were performed from 1150°C-1250°C under controlled oxygen and sulfur fugacities. Measurements were made using the modified single bob (MSB) Archimedean method using zirconia ceramic bobs and crucibles. A 0.005mm resolution micrometer was attached to an elevator, which raised the crucible and melt relative to the free-hanging, stationary bob. A 0.001 g resolution analytical balance connected to a laptop computer continuously recorded the buoyancy as a function of crucible elevation. Densities were calculated by converting elevation to immersed volume and regressing the slope of buoyancy versus volume immersed. log(fO₂) in the experiments ranged from -7.8 to -12.6 and log(fS₂) ranged from -0.9 to -3.3. 38 successful sulfide liquid density measurements were performed, with values ranging from 3.8 g/cc to 6.6 g/cc. Regression of the resulting data suggests that a simple linear volume mixing model is adequate to represent the compositional dependence of density in copper- and nickel-sulfide liquids. A moderate positive excess mixing volume appears to be justified in iron-sulfide liquids. This result, along with high derived partial molar volumes for oxygen and sulfur components, are qualitatively consistent with the suggestion that increasing pressure will partition oxygen and sulfur out of the sulfide liquid during planetary accretion. The MSB density measurement also provides information on the relative magnitude of gas-zirconia and sulfide-zirconia surface energies. Assuming most of the observed variation results from sulfide chemistry it appears that oxidizing conditions significantly decrease sulfide-zirconia surface energies (increase wetting). If we can extrapolate this result to silicate minerals, this would suggest that oxidizing conditions will decrease wetting angle and thus increase the potential for sulfide segregation during planetary formation. We hope to test this hypothesis soon. Our experience suggests that trivial modifications to the apparatus used in this study may provide an effective and reliable method for measuring liquid-solid surface energies in both sulfide and silicate systems. Such data would prove useful in both melt percolation and bubble nucleation and growth calculations.
DE: 3610 Geochemical modeling (1009, 8410)
DE: 3611 Thermodynamics (0766, 1011, 8411)
DE: 3630 Experimental mineralogy and petrology
DE: 3640 Igneous petrology
DE: 8411 Thermodynamics (0766, 1011, 3611)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005