Mathematics – Logic
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmgp34a..03w&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #GP34A-03
Mathematics
Logic
1507 Core Processes (1213, 8115), 8115 Core Processes (1213, 1507), 8121 Dynamics: Convection Currents, And Mantle Plumes, 8124 Earth'S Interior: Composition And State (1212, 7207, 7208, 8105), 8147 Planetary Interiors (5430, 5724, 6024)
Scientific paper
Early and rapid core formation is suggested by recent isotopic studies. Accumulation of a short lived liquid metal pond at the base of a magma ocean during early impacts may provide a model for chemical diffusion of silicates and liquid metal to produce the observed abundances of siderophile elements in the Earth's mantle. Here we present results from laboratory fluid experiments of liquid gallium in high viscosity stratified corn syrup solutions to model the physical dynamics of core formation processes in the early Earth. Experiments are designed to consider the instability of a dense liquid metal pond as single droplets, Rayleigh-Taylor instability, and evolution of a liquid metal emulsion layer. We find that in all cases, a wide trailing conduit develops behind rapidly descending metallic plumes which entrains low density fluid to the base of the fluid box. We propose a model where the conduit itself provides a vehicle for thermal and chemical equilibration between metals and silicates at high pressures and temperatures during its path through the lower mantle. Diffusion processes contribute to the formation of this new entrained fluid layer at the base of the fluid box which is buoyant and evolves into a new type of thermo-chemical plume which subsequently rises. Using a range of viscosity and buoyancy ratios, experimental results will constrain the time scales for instability of a liquid metal pond, descent and upwelling times of this unique type of plume, as well as the nature and dynamics of conduit formation. This model provides a high pressure/temperature environment for metal- silicate equilibration consistent with petrologic and isotopic studies, is consistent with rapid core formation, and may also connect core formation to ancient hotspot activity on terrestrial planets.
Olson Peter L.
Weeraratne Dayanthie S.
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