Wangdaodeite, the LiNbO3‐structured high‐pressure polymorph of ilmenite, a new mineral from the Suizhou L6 chondrite
Xiande Xie, Xiangping Gu, Hexiong Yang, Ming Chen, Kai Li
Meteoritics & Planetary Science
First Published: 19 December 2019
“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.”
