HR: 0830h
AN: U51B-0017    [PDF]
TI: Argon Partitioning Between Metal and Silicate Liquids in the Laser-Heated DAC to 25 GPa
AU: Bouhifd, M A
EM: Ali.Bouhifd@earth.ox.ac.uk
AF: University of Oxford, Department of Earth Sciences Parks Road, Oxford, OX1 3PR United Kingdom
AU: * Jephcoat, A P
EM: andrew@earth.ox.ac.uk
AF: Diamond Light Source Ltd. and University of Oxford, Department of Earth Sciences Parks Road, Oxford, OX1 3PR United Kingdom
AB: The accretion of the Earth from primordial material and its subsequent segregation into core and mantle are fundamental problems in terrestrial and solar system science. Many of the questions about the process, although well developed as model scenarios over the last few decades, are still open and much debated, and include, for example, whether the core is, or was, a reservoir for the noble (rare) gases. In the present study we use for the first time the laser-heated diamond-anvil cell (LHDAC) to study the Ar partitioning at high-pressure and temperature between metal and silicate liquids. Little work has been reported on noble gas partitioning at pressure since a single multi-anvil experiment to 10 GPa (Matsuda et al., 1993). We used either compacted glass powders simulating that of a model C1 chondrite and iron metal, or pure metal alloys (pure Fe, FeNiCo alloy, FeSi). Thermal insulation from the diamonds was achieved with solid argon as pressure medium. The samples were heated by a multimode YAG laser for an average of 15 minutes and temperatures were determined spectro-radiometrically with a fit to a grey-body Planck function. Samples recovered after the runs were analysed by electron microprobe with spatial resolution near 1 $\mu$m. The argon melts by conductive heating from the molten sample dissolving into the metal/silicate melt. Preliminary results on Ar solubility at lower pressures show good agreement with data reported by White et al. (1986) for Ar solubility in sanidine (KAlSi$_3$O$_8$). With sanidine melt, Ar solubility increases up to around 5-6 GPa where it reaches about 2.5 wt%, and remains roughly constant to higher pressures, suggesting that a threshold concentration is reached. Similar behavior is observed for a mix of C1-chondrite composition and iron and the results imply that the solubility of Ar is intimately related to liquid structure at high pressure. We also present results on Ar solubility into pure silicate liquids of varying composition in the absence of metal phases together with the partitioning of Ar between C1-chondrite and iron-rich metal liquids to 25 GPa.
DE: 3924 High-pressure behavior
DE: 8124 Earth's interior--composition and state (old 8105)
SC: U
MN: 2003 Fall Meeting