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Wangdaodeite, the LiNbO 3 ‐structured high‐pressure polymorph of ilmenite, a new mineral from the Suizhou L6 chondrite
Author(s) -
Xie Xiande,
Gu Xiangping,
Yang Hexiong,
Chen Ming,
Li Kai
Publication year - 2020
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.13426
Subject(s) - ilmenite , ringwoodite , raman spectroscopy , chondrite , mineral , mineralogy , materials science , crystallography , geology , geochemistry , chemistry , meteorite , olivine , metallurgy , physics , optics , astronomy
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 FeTiO 3 . The empirical formula is: (Fe 0.85 Mg 0.10 Mn 0.05 ) Σ1.00 Ti 0.99 O 3 , 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 R 3 c ; calculated density = 4.72 g cm −3 . The P–T conditions for formation of wangdaodeite were estimated to be 20–24 GP a 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.