Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmmr41a1791j&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #MR41A-1791
Physics
1015 Composition Of The Core, 1028 Composition Of Meteorites (3662, 6240), 5104 Fracture And Flow, 6205 Asteroids
Scientific paper
The most important event in the early history of the earth was the separation of its iron-rich core. Core formation induced profound chemical fractionations and extracted into the core most of Earth's iron and siderophile elements (Ni, Co, Au, Pt, W, Re), leaving the silicate crust and mantle with strong depletions of these elements relative to primitive planetary material. Recent measurements of radiogenic 182W anomalies in the silicate Earth, Mars and differentiated meteorites imply that planetesimals segregated metallic cores within a few Myr of the origin of the solar system. Various models have been put forward to explain the physical nature of the segregation mechanism (Fe-diapirs, 'raining' through a magma ocean), and more recently melt flow via fractures. In this contribution we present the initial results of a numerical study into Fe segregation in a deforming silicate matrix that captures the temperature-dependent effect of liquid metal viscosity on the transport rate. Flow is driven by pressure gradients associated with impact deformation in a growing planetesimal and the fracture geometry is constrained by experimental data on naturally deformed H6 chondrite. Early results suggest that under dynamic conditions, fracture-driven melt flow can in principle be extremely rapid, leading to a significant draining of the Fe-liquid metal and siderophile trace element component on a timescale of hours to days. Fluid transport in planetesimals where deformation is the driving force provides an attractive and simple way of segregating Fe from host silicate as both precursor and primary agent of core formation
Jones Vaughan
Petford Nick
Rushmer Tracy
Wertheim D.
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