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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. [ABSTRACT FROM AUTHOR]

A new high‐pressure silicate, (Mg,Fe,Si)2(Si,□)O4 with a tetragonal spinelloid structure, was discovered within shock melt veins in the Tenham and Suizhou meteorites, two highly shocked L6 ordinary chondrites. Relative to ringwoodite, this phase exhibits an inversion of Si coupled with intrinsic vacancies and a consequent reduction of symmetry. Most notably, the spinelloid makes up about 30–40 vol% of the matrix of shock veins with the remainder composed of a vitrified (Mg,Fe)SiO3 phase (in Tenham) or (Mg,Fe)SiO3‐rich clinopyroxene (in Suizhou); these phase assemblages constitute the bulk of the matrix in the shock veins. Previous assessments of the melt matrices concluded that majorite and akimotoite were the major phases. Our contrasting result requires revision of inferred conditions during shock melt cooling of the Tenham and Suizhou meteorites, revealing in particular a much higher quench rate (at least 5 × 103 K s−1) for veins of 100–500 μm diameter, thus overriding formation of the stable phase assemblage majoritic garnet plus periclase. [ABSTRACT FROM AUTHOR]

Maohokite, a post‐spinel polymorph of MgFe2O4, was found in shocked gneiss from the Xiuyan crater in China. Maohokite in shocked gneiss coexists with diamond, reidite, TiO2‐II, as well as diaplectic glasses of quartz and feldspar. Maohokite occurs as nano‐sized crystallites. The empirical formula is (Mg0.62Fe0.35Mn0.03)2+Fe3+2O4. In situ synchrotron X‐ray microdiffraction established maohokite to be orthorhombic with the CaFe2O4‐type structure. The cell parameters are a = 8.907 (1) Å, b = 9.937(8) Å, c = 2.981(1) Å; V = 263.8 (3) Å3; space group Pnma. The calculated density of maohokite is 5.33 g cm−3. Maohokite was formed from subsolidus decomposition of ankerite Ca(Fe2+,Mg)(CO3)2 via a self‐oxidation‐reduction reaction at impact pressure and temperature of 25–45 GPa and 800–900 °C. The formation of maohokite provides a unique example for decomposition of Fe‐Mg carbonate under shock‐induced high pressure and high temperature. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2017‐047). The mineral was named maohokite after Hokwang Mao, a staff scientist at the Geophysical Laboratory, Carnegie Institution of Washington, for his great contribution to high pressure research. [ABSTRACT FROM AUTHOR]

Tuite is a high-pressure γ-form of Ca3( PO4)2. An occurrence of tuite partly transformed from merrillite and chlorapatite was observed in the chondritic area adjacent to the shock veins in the Suizhou meteorite. Tuite grains are found in contact with both merrillite and chlorapatite, indicating two different transformation pathways. Tuite isochemically transformed from merrillite contains much higher contents of Na2O and MgO than those transformed from chlorapatite. Tuite transformed from merrillite does not contain Cl, but tuite transformed from chlorapatite contains 1.90-3.91 wt% of Cl, hence indicating an incomplete phase transformation from chlorapatite to tuite. P-T conditions of above 12 GPa and 1100 °C are probably required for the transformation from merrillite and chlorapatite to tuite. A temperature gradient from the hot vein at 2000 °C to the surrounding chondritic area at 1000 °C corresponds to the partial phase transitions in the Suizhou phosphates. Fast cooling of the thin shock veins plays a key role in the preservation of phosphates that suffered partial high-pressure phase transformation. [ABSTRACT FROM AUTHOR]

Tuite, γ-Ca3(PO4)2, was first discovered as the high-pressure phase of whitlockite in shock veins of the Suizhou L6 meteorite. This study reports the finding of tuite in a shock vein of the same Suizhou chondrite as a product of decomposition of chlorapatite, where it coexists with coarse-grained ringwoodite, majorite, lingunite, fine-grained majorite-pyrope solid solution, and magnesiowüstite. Moreover, we also successfully synthesized tuite with a multianvil apparatus from chlorapatite at 15 GPa and 1573 K over 24 h. Both natural and synthetic tuite crystals were examined by means of optical microscopy, scanning electron microscope, electron microprobe analysis, X-ray diffraction, and Raman spectroscopy. Our results suggest that the Na2O, MgO, and Cl contents in natural tuite may serve as good indicators for distinguishing the precursor phosphate mineral, chlorapatite or whitlockite. [ABSTRACT FROM AUTHOR]