Wangdaodeite, the LiNbO3‐structured high‐pressure polymorph of ilmenite, a new mineral from the Suizhou L6 chondrite

1,2Xiande Xie,3Xiangping Gu,4Hexiong Yang,2Ming Chen,4Kai Li
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13426]
1Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640 China
2Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou, 510640 China
3School of Geosciences and Info‐Physics, Central South University, Changsha, Hunan, 410083 China
4Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona, 85721‐0077 USA
5Institute for Materials Microstructure, Central South University, 410083 Changsha, Hunan, PR China
Published by arrangement with John Wiley & Sons

Wangdaodeite, the shock‐induced lithium niobate–structured polymorph of ilmenite, was found in the Suizhou L6 chondrite. It occurs as small irregular particles (2–20 μm in size) inside or adjacent to the shock melt veins. Wangdaodeite coexists in veins with ringwoodite, majorite, and xieite. The chemical formula of wangdaodeite is FeTiO3. The empirical formula is: (Fe0.85Mg0.10Mn0.05)Σ1.00Ti0.99O3, which is similar to that of its host ilmenite. The Raman spectra of wangdaodeite display the bands at 174–179, 273–277, 560–567, 738–743 cm−1, which are different to those for ilmenite. TEM images show that ilmenite is composed of polysynthetic‐twinned crystals while wangdaodeite is composed of random‐oriented nanometric domains sized 20–50 nm. Electron diffraction established wangdaodeite to be trigonal with the lithium niobate structure. Cell parameters are: a = 5.13(1) Å, c = 13.78(1) Å; c/a = 2.69; space group R3c; calculated density = 4.72 g cm−3. The P–T conditions for formation of wangdaodeite were estimated to be 20–24 GPa and >1200 °C. The mineral name was approved by the Commission on New Minerals, Nomenclature, and Classification of the International Mineralogical Association (IMA 2016‐007). The name is for Daode Wang, Professor at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences.

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