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Bridgmanite-like crystal structure in the novel Ti-rich phase synthesized at transition zone condition

Luca Bindi, Ekaterina Sirotkina, Andrey V. Bobrov, Michael J. Walter, Dmitry Pushcharovsky and Tetsuo Irifune
Bridgmanite-like crystal structure in the novel Ti-rich phase synthesized at transition zone condition
American Mineralogist (2017) 102 (1): 227-230

Abstract

A new Ti-bearing bridgmanite-like phase with a threefold commensurate superstructure of the ideal MgSiO (sub 3) -perovskite structure was observed in a [Mg (sub 5/6) Al (sub 1/6) ][Si (sub 1/2) Ti (sub 1/3) Al (sub 1/6) ]O (sub 3) crystal synthesized in the model system Mg (sub 3) Al (sub 2) Si (sub 3) O (sub 12) -MgTiO (sub 3) at 20 GPa and 1600 degrees C. The compound was found to be orthorhombic, space group Pnma, with lattice parameters a=14.767(3), b=6.958(1), c=4.812(1) Aa, V=494.4(2) Aa (super 3) , which represents a 3aXbXc superstructure of the typical Pnma perovskite structure. The structure was refined to R = 0.024 using 846 independent reflections. The superstructure mainly arises from the ordering of titanium in one of the octahedral positions. Crystal-chemical details of the different polyhedra in the superstructure are discussed in comparison to pure MgSiO (sub 3) This is the first documented superstructure of a bridgmanite phase, and Ti-rich bridgmanite in the lower mantle arising from local Ti-enrichments may exhibit different physical properties and elemental partitioning behavior from Ti-poor, peridotitic bridgmanite. The study also shows that large amounts of Ti can stabilize bridgmanite-like compounds at considerably lower pressure than lower mantle conditions.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 102
Serial Issue: 1
Title: Bridgmanite-like crystal structure in the novel Ti-rich phase synthesized at transition zone condition
Affiliation: Universita di Firenze, Dipartimento di Scienze della Terra, Florence, Italy
Pages: 227-230
Published: 2017
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 37
Accession Number: 2017-006134
Categories: Geophysics of minerals and rocks
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. table
Secondary Affiliation: Istituto di Geoscienze e Georisorse, ITA, ItalyMoscow State University, RUS, Russian FederationVernadskiy Institute of Geochemistry and Analytical Chemistry, RUS, Russian FederationUniversity of Bristol, GBR, United KingdomEhime University, JPN, JapanTokyo Institute of Technology, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201705
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