Screws tighten on the core

Article Abstract:

New experimental data for partitioning of Co and Ni in Earth's upper mantle between metal and Mg-perovsite, the most abundant mineral in the lower mantle, suggest that metal-silicate equilibration would lead to an enrichment of these elements in the lower mantle in relation to the upper mantle. This finding may prompt some changes to the core-formation model that indicates a magma ocean. This research indicates the need for continued investigation of metal-silicate partitioning under lower-mantle conditions.

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A shear pathway to the core

Article Abstract:

Bruhn and colleagues have demonstrated that iron-rich metallic melt can form interconnected channels allowing effective drainage of metal to the core, in a solid silicate mantle, deformed under shear stresses. Shear forces were included in the experiments on mixtures of metal and olivine. The initially trapped metal melt becomes elongated and aligned over a preferred orientation relative to shear direction, and melt pockets interconnect, providing percolation channels.

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An interconnected network of core-forming melts produced by shear deformation

Article Abstract:

The formation mechanisms of terrestrial planetary cores are not well understood. Experiments have been undertaken to demonstrate that shear deformation to large strains can link a significant fraction if isolated pockets of metal and metal sulphide melts in olivine. Percolation therefore remains viable in the segregation and migration of core-forming melts in a solid silicate mantle.

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