X-ray Raman scattering study of MgSiO3 glass at high pressure: Implication for triclustered MgSiO3 melt in Earth's mantle

Keun Lee Sung, Jung Fu Lin, Yong Q. Cai, Nozomu Hiraoka, Peter J. Eng, Takuo Okuchi, Ho Kwang Mao, Yue Meng, Michael Y. Hu, Paul Chow, Jinfu Shu, Baosheng Li, Hiroshi Fukui, Han Lee Bum, Na Kim Hyun, Choong Shik Yoo

Research output: Contribution to journalArticlepeer-review

98 Citations (Scopus)

Abstract

Silicate melts at the top of the transition zone and the core-mantle boundary have significant influences on the dynamics and properties of Earth's interior. MgSiO3-rich silicate melts were among the primary components of the magma ocean and thus played essential roles in the chemical differentiation of the early Earth. Diverse macroscopic properties of silicate melts in Earth's interior, such as density, viscosity, and crystal-melt partitioning, depend on their electronic and short-range local structures at high pressures and temperatures. Despite essential roles of silicate melts in many geophysical and geodynamic problems, little is known about their nature under the conditions of Earth's interior, including the densification mechanisms and the atomistic origins of the macroscopic properties at high pressures. Here, we have probed local electronic structures of MgSiO3 glass (as a precursor to Mg-silicate melts), using high-pressure x-ray Raman spectroscopy up to 39 GPa, in which high-pressure oxygen K-edge features suggest the formation of tricluster oxygens (oxygen coordinated with three Si frameworks; [3]O) between 12 and 20 GPa. Our results indicate that the densification in MgSiO3 melt is thus likely to be accompanied with the formation of triculster, in addition to a reduction in nonbridging oxygens. The pressure-induced increase in the fraction of oxygen triclusters >20 GPa would result in enhanced density, viscosity, and crystal-melt partitioning, and reduced element diffusivity in the MgSiO3 melt toward deeper part of the Earth's lower mantle.

Original languageEnglish
Pages (from-to)7925-7929
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number23
DOIs
Publication statusPublished - Jun 10 2008

Keywords

  • Silicate melts at high pressure
  • Tricluster oxygen

ASJC Scopus subject areas

  • General

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