Structural Transitions in Amorphous Mantle Phases Dan Shim Massachusetts Institute of Technology...
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Transcript of Structural Transitions in Amorphous Mantle Phases Dan Shim Massachusetts Institute of Technology...
Structural Transitions in Amorphous Mantle Phases
Dan Shim Massachusetts Institute of Technology
Thanks to: K. Catalli, T. Grove, NSF
CIDER 2004
Melting in EarthCore formation Magma Ocean
Top of the transition zoneBercovici and Karato (2003) Nature 425, 39+Revenaugh and Sipkin (1994) Nature 369, 474+
Core-Mantle BoundaryRevenaugh and Meyer (1997) Science 277, 670+ Williams et al (1998) Science 280, 546+
Stevenson (2008) Nature 451, 261+
Summary
In the present-day mantle, melting will further enhance the degree of differentiation atop the transition zone and the core-mantle boundary.
Si-rich melts undergo the structural transition at systematically lower pressure than Si-poor melts.
Mg-silicate glasses undergo a series of structural transitions at high pressure: increases in the Si—O coordination number and changes in the Si—O polyhedral connectivity.
The compositional sensitivity of the structural transition would result in Si-enrichment of the deeper part of the magma ocean. Therefore, the magma ocean would be compositionally stratified.