Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmmr52a1007t&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #MR52A-1007
Physics
3630 Experimental Mineralogy And Petrology, 3924 High-Pressure Behavior, 5114 Permeability And Porosity, 5139 Transport Properties, 8147 Planetary Interiors (5430, 5724)
Scientific paper
The determination of whether a liquid iron-alloy can segregate from a solid silicate matrix is a crucial factor in the investigation of terrestrial planet core formation. It is well known that the dihedral angle between liquid iron-alloy and solid silicate controls the connectivity of the liquid iron-alloy. The effects of physical and chemical properties, such as pressure and composition of the liquid, on the dihedral angle have been widely reported in recent years in a range of experimental studies. In such experiments textural equilibrium between the liquid iron-alloy and the solid silicate has to be take place within the duration of the experiment for the equilibrium dihedral angle to be measured. The timescale for textural equilibrium to occur is not well established, however, especially under high-pressure conditions. In this study, we have determined the dihedral angle between liquid iron-sulfide and olivine crystals as a function of time and estimated the time scale of textural equilibrium at certain P, T conditions. High pressure experiments were performed using Kawai-type and Walker-type multi-anvil apparatuses with LaCrO3 stepped heaters and graphite capsules. Mixtures of powdered iron-sulfide and synthetic olivine (Mg # =77) were used as starting materials. We have used two iron-sulfide compositions (Fe78S22 and FeS). Experimental conditions were at 4.6 GPa and 1830 K for FeS and 1960 K for Fe78S22. Experimental durations were 0.5, 4, 8, 15, 24, 48 hours. Apparent dihedral angles were measured from backscattered electron images of the recovered samples with magnifications of x1200 and x2000. The true dihedral angle was taken to be the median value of the apparent dihedral angle distribution. The distribution of measured angles was close to the theoretical distribution reported by Harker and Parker (1945). The median dihedral angle for the olivine-FeS liquid experiments was observed to decrease with time from 81 (5) degrees after 0.5 hours to a minimum of approximately 65 (5) degrees after 8 hours. This behavior may reflect the time scale for textural equilibrium to be achieved but could also result in part from an increase in the carbon or oxygen content of the sulfide liquid with time.
Frost Dan J.
Rubie David C.
Terasaki Hidenori
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