Synthesis of inverse ringwoodite sheds light on the subduction history of Tibetan ophiolites

Luca Bindi*, William L. Griffin, Wendy R. Panero, Ekaterina Sirotkina, Andrey Bobrov, Tetsuo Irifune

*Corresponding author for this work

Research output: Contribution to journalArticle

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Abstract

Tibetan ophiolites are shallow mantle material and crustal slabs that were subducted as deep as the mantle transition zone, a conclusion supported by the discovery of high-pressure phases like inverse ringwoodite in these sequences. Ringwoodite, Mg2SiO4, exhibits the normal spinel structure, with Mg in the octahedral A site and Si in the tetrahedral B site. Through A and B site-disorder, the inverse spinel has four-coordinated A cations and the six-coordinated site hosts a mixture of A and B cations. This process affects the density and impedance contrasts across the boundaries in the transition zone and seismic-wave velocities in this portion of the Earth. We report the first synthesis at high pressure (20 GPa) and high temperature (1600 °C) of a Cr-bearing ringwoodite with a completely inverse-spinel structure. Chemical, structural, and computational analysis confirm the stability of inverse ringwoodite and add further constraints to the subduction history of the Luobusa peridotite of the Tibetan ophiolites.

Original languageEnglish
Article number5457
Number of pages8
JournalScientific Reports
Volume8
DOIs
Publication statusPublished - 3 Apr 2018

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