Fe-57 and Co tracer diffusion in liquid Fe-FeS at 2 and 5 GPa.
PHYS EARTH PLANET IN
137 - 144.
Tracer diffusion in Fe-FeS eutectic melts has been measured at 2.2 and 5 Cpa up to 150 degrees C above the solidus using Fe-57 and Co thin foils. A new horizontal furnace arrangement for the multi-anvil press is presented, which inhibits convection in the sample and allows diffusion measurements in inviscid materials. The measured diffusivities are identical for Fe-57 and Co, and similar to those of pure metals (10(-4)-10(-5) cm(2)/s). The remarkable agreement between the measured diffusivities at 5 Cpa and the value for the inner core boundary derived from ab initio simulations supports the semi-empirical prediction of Poirier [Poirier, J.P., 1988. Transport properties of liquid metals and viscosity of the Earth's core. Geophys. J. 92, 99-105.] and others that transport properties should be constant along a homologous path. The very high activation energies for diffusion (Q(D) (5 GPa) = 252 +/- 23 W/mol) agree well with published values for viscosity (Q(V 5 GPa) = 240 +/- 72 kJ/mol) and imply a stronger causational link between metal diffusion and viscosity than previously suggested. That is, viscosity is not solely controlled by sulfur polymerization in the melt. (C) 2000 Elsevier Science B.V. All rights reserved.
|Title:||Fe-57 and Co tracer diffusion in liquid Fe-FeS at 2 and 5 GPa|
|Keywords:||Fe-57, Co tracer diffusion, Fe-FeS, EARTHS CORE, VISCOSITY, PRESSURE, IRON|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences|
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