Frontiers in Earth Science (Aug 2020)

Pore Network Modeling of Core Forming Melts in Planetesimals

  • Giulio F. D. Solferino,
  • Paul-Ross Thomson,
  • Saswata Hier-Majumder

DOI
https://doi.org/10.3389/feart.2020.00339
Journal volume & issue
Vol. 8

Abstract

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Early in the history of the solar system, planetesimals were differentiated into metallic cores. In some planetesimals, this differentiation took place by percolation of the denser core forming liquid through a lighter solid silicate matrix. A key factor in core formation by percolation is the establishment of a connection threshold of the melt. In this work, we report new results from pore network modeling of 3D microtomographic images of 11 synthetic olivine aggregates containing Fe-FeS melt. Our results demonstrate that a melt volume fraction of 0.14 is required to achieve connectivity of the melt. We also show that surface-tension driven melt segregation during annealing experiments plays an important role in controlling this threshold melt fraction. We also report that, contrary to the generally accepted notion, melt pinch-off is caused by reduction in pore size, rather than melt drainage out of throats. Using the results of our study, we estimate that the peak melt segregation velocity in a planetesimal of 100 km radius can be as high as 41 m/yr and core segregation can be completed in less than 0.5 million years.

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