ALBERT

Description: 〈span〉〈div〉Abstract〈/div〉The 13 single-crystal adiabatic elastic moduli (〈span〉C〈/span〉〈sub〉ij〈/sub〉) of a 〈span〉C〈/span〉2〈span〉/c〈/span〉 jadeite sample close to the ideal composition (NaAlSi〈sub〉2〈/sub〉O〈sub〉6〈/sub〉) and a natural 〈span〉P〈/span〉2〈span〉/n〈/span〉 diopside-rich omphacite sample have been measured at ambient condition by Brillouin spectroscopy. The obtained 〈span〉C〈/span〉〈sub〉ij〈/sub〉 values for the jadeite sample are: 〈span〉C〈/span〉〈sub〉11〈/sub〉 = 265.4(9) GPa, 〈span〉C〈/span〉〈sub〉22〈/sub〉 = 247(1) GPa, 〈span〉C〈/span〉〈sub〉33〈/sub〉 = 274(1) GPa, 〈span〉C〈/span〉〈sub〉44〈/sub〉 = 85.8(7) GPa, 〈span〉C〈/span〉〈sub〉55〈/sub〉 = 69.3(5) GPa, 〈span〉C〈/span〉〈sub〉66〈/sub〉 = 93.0(7) GPa, 〈span〉C〈/span〉〈sub〉12〈/sub〉 = 84(1) GPa, 〈span〉C〈/span〉〈sub〉13〈/sub〉 = 66(1) GPa, 〈span〉C〈/span〉〈sub〉23〈/sub〉 = 87(2) GPa, 〈span〉C〈/span〉〈sub〉15〈/sub〉 = 5.4(7) GPa, 〈span〉C〈/span〉〈sub〉25〈/sub〉 = 17(1) GPa, 〈span〉C〈/span〉〈sub〉35〈/sub〉 = 28.7(6) GPa, 〈span〉C〈/span〉〈sub〉46〈/sub〉 = 14.6(6) GPa. Voigt-Reuss-Hill averaging of the 〈span〉C〈/span〉〈sub〉ij〈/sub〉 values yields aggregate bulk modulus 〈span〉KS〈/span〉 = 138(3) GPa and shear modulus 〈span〉G〈/span〉 = 84(2) GPa for jadeite. Systematic analysis combing previous single-crystal elasticity measurements within the diopside-jadeite solid solution indicates that the linear trends are valid for most 〈span〉C〈/span〉〈sub〉ij〈/sub〉 values. The 〈span〉ν〈/span〉〈sub〉p〈/sub〉 and 〈span〉ν〈/span〉〈sub〉s〈/sub〉 of omphacite decrease with diopside content, though the velocity changes are small as diopside component exceeds 70%. We also found that both the isotropic 〈span〉ν〈/span〉〈sub〉p〈/sub〉 and 〈span〉ν〈/span〉〈sub〉s〈/sub〉, as well as the seismic anisotropy of eclogite, changed strongly with the bulk-chemical composition. The relationship between the anisotropic velocities of eclogite and the chemical composition can be a useful tool to trace the origin of the eclogitic materials in the Earth's mantle.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉The Dahutang tungsten deposit, located in the Yangtze Block, South China, is one of the largest tungsten deposits in the world. Tungsten mineralization is closely related to Mesozoic granitic plutons. A drill core through a pluton in the Dalingshang ore block in the Central segment of the Dahutang tungsten deposit shows that the pluton is characterized by multi-stage intrusive phases including biotite granite, muscovite granite, and Li-mica granite. The granites are strongly peraluminous and rich in P and F. Decreasing bulk-rock (La/Yb)〈sub〉N〈/sub〉 ratios and total rare earth element (ΣREE) concentrations from the biotite granite to muscovite granite and Li-mica granite suggest an evolution involving the fractional crystallization of plagioclase. Bulk-rock Li, Rb, Cs, P, Sn, Nb, and Ta contents increase with decreasing Zr/Hf and Nb/Ta ratios, denoting that the muscovite granite and Li-mica granite have experienced a higher degree of magmatic fractionation than the biotite granite. In addition, the muscovite and Li-mica granites show M-type lanthanide tetrad effect, which indicates hydrothermal alteration during the post-magmatic stage. The micas are classified as lithian biotite and muscovite in the biotite granite, muscovite in the muscovite granite, and Li-muscovite and lepidolite in the Li-mica granite. The Li, F, Rb, and Cs contents of micas increase, while FeO〈sup〉T〈/sup〉, MgO, and TiO〈sub〉2〈/sub〉 contents decrease with increasing degree of magmatic fractionation. Micas in the muscovite granite and Li-mica granite exhibit compositional zonation in which Si, Rb, F, Fe, and Li increase, and Al decreases gradually from core to mantle, consistent with magmatic differentiation. However, the outermost rim contains much lower contents of Si, Rb, F, Fe, and Li, and higher Al than the mantle domains due to metasomatism in the presence of fluids. The variability in W contents of the micas matches the variability in Li, F, Rb, and Cs contents, indicating that both the magmatic and hydrothermal evolutions were closely associated with W mineralization in the Dahutang deposit. The chemical zoning of muscovite and Li-micas not only traces the processes of W enrichment by magmatic differentiation and volatiles but also traces the leaching of W by the fluids. Therefore, micas are indicators not only for the magmatic–hydrothermal evolution of granite, but also for tungsten mineralization.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Synchrotron powder X-ray diffraction (XRD) experiments and transmission electron microscopy (TEM) observations of heat-treated sillimanite at various pressures were conducted to clarify the detailed phase relation between sillimanite and mullite. Under TEM, heat-treated sillimanite frequently showed anti-phase boundary (APB)-like textures with a displacement vector of ½[001]〈sub〉sil〈/sub〉. Additional scanning TEM energy-dispersive X-ray spectroscopy analysis of regions with APB-like texture showed that they were clearly enriched in Al and accompanied by very fine, Si-rich glass inclusions, which indicates that the APB-like textures are composed of fine mullite. Moreover, synchrotron XRD patterns of these samples clearly showed double peaks of newly formed mullite and remnant sillimanite, indicating that the compositional transformation from sillimanite to mullite and glass is discontinuous. We separately determined the cell parameters of the sillimanite and mullite from the XRD pattern and found that the 〈span〉b〈/span〉 axial length of the sillimanite increased with the treatment temperature, reflecting disordering of tetrahedral Al and Si in the sillimanite. In contrast, the positions of the deconvoluted mullite peaks indicated that the 〈span〉a〈/span〉 axial length of mullite decreased as experimental pressure increased, owing to enrichment of the Si component. By projecting the cell parameters onto the 〈span〉a–b〈/span〉 axial plane, the detailed changes in the crystallographic state of the sillimanite and mullite could be easily and comprehensively identified. On the basis of our results, we propose a new 〈span〉P-T〈/span〉 diagram for the Al〈sub〉2〈/sub〉SiO〈sub〉5〈/sub〉 system that shows the transformation boundary between sillimanite and mullite + SiO〈sub〉2〈/sub〉-rich melt and the contour of the Al/Si order parameter of sillimanite.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉A series of synthetic Mid-Ocean Ridge Basalt (MORB) glasses with Fe〈sup〉3+〈/sup〉/Fe〈sup〉TOT〈/sup〉 from 0 to 1, determined previously by Mössbauer spectroscopy, were used to test methods for quantifying Fe〈sup〉3+〈/sup〉/Fe〈sup〉TOT〈/sup〉 by Raman spectroscopy. Six numerical data reduction methods were investigated, based on conventional approaches as well as supervised and unsupervised machine learning algorithms. For the set of MORB glass standards, with fixed composition, the precision of all methods was ≤±0.04 (1 St.dev.). However, Raman spectra recorded for 42 natural MORB glasses from a wide range of locations revealed a strong correlation between the spectra and composition, despite the latter varying only over a relatively limited range, such that the methods calibrated using the glass standards are not directly applicable to the natural samples. This compositional effect can be corrected by using a compositional term that links spectral variations to the Fe〈sup〉3+〈/sup〉/Fe〈sup〉TOT〈/sup〉 value of the glass. The resulting average Fe〈sup〉3+〈/sup〉/Fe〈sup〉TOT〈/sup〉 determined by Raman spectroscopy was 0.090 ± 0.067 (n = 42). This value agrees with the latest Fe 〈span〉K〈/span〉-edge XANES and wet-chemistry estimates of 0.10 ± 0.02. The larger uncertainty of the Raman determination reflects the sensitivity of Raman spectroscopy to small changes in the glass structure. While this sensitivity is detrimental for high precision Fe〈sup〉3+〈/sup〉/Fe〈sup〉TOT〈/sup〉 determinations, it allows the major element composition of natural MORB glasses to be determined within 1 mol% through the use of an artificial neural network. This suggests that Raman spectrometers may be used to determine the composition of samples in situ at difficult to access locations that are incompatible with X-ray spectrometry (e.g., mid-ocean ridges).〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Phoxite, (NH〈sub〉4〈/sub〉)〈sub〉2〈/sub〉Mg〈sub〉2〈/sub〉(C〈sub〉2〈/sub〉O〈sub〉4〈/sub〉)(PO〈sub〉3〈/sub〉OH)〈sub〉2〈/sub〉(H〈sub〉2〈/sub〉O)〈sub〉4〈/sub〉, is a new mineral species from the Rowley mine, Maricopa County, Arizona, U.S.A., and it has potential uses in agricultural applications for soil conditioning, fertilizing, and as a natural pesticide. It was found in an unusual bat-guano-related, post-mining assemblage of phases that include a variety of vanadates, phosphates, oxalates, and chlorides, some containing NH4+. Other secondary minerals found in association with phoxite are antipinite, aphithitalite, bassanite, struvite, thenardite, and weddellite. Crystals of phoxite are colorless composite blades up to about 0.4 mm. The streak is white, and the luster is vitreous to oily. The Mohs hardness is 2½, the tenacity is brittle, fracture is irregular, there is fair {100} cleavage, and the measured density is 1.98(2) g/cm〈sup〉3〈/sup〉. Phoxite is optically biaxial (–) with α = 1.499(1), β = 1.541(1), γ = 1.542(1) (white light); 2〈span〉V〈/span〉 = 16(1)°; dispersion 〈span〉r〈/span〉 〈 〈span〉ν〈/span〉, slight; orientation 〈span〉Y〈/span〉 = 〈strong〉b〈/strong〉, 〈span〉X〈/span〉 ^ 〈strong〉a〈/strong〉 ≈ 9° in obtuse β. Electron microprobe analyses yielded the empirical formula [(NH〈sub〉4〈/sub〉)〈sub〉1.77〈/sub〉K〈sub〉0.23〈/sub〉]〈sub〉Σ2〈/sub〉Mg〈sub〉2.00〈/sub〉(C〈sub〉2〈/sub〉O〈sub〉4〈/sub〉)(PO〈sub〉3〈/sub〉OH)〈sub〉2〈/sub〉(H〈sub〉2〈/sub〉O)〈sub〉4〈/sub〉, with the C and H content inferred from the crystal structure. Raman spectroscopy confirmed the presence of NH〈sub〉4〈/sub〉 and C〈sub〉2〈/sub〉O〈sub〉4〈/sub〉. Phoxite is monoclinic, 〈span〉P〈/span〉2〈sub〉1〈/sub〉/〈span〉c〈/span〉, with 〈span〉a〈/span〉 = 7.2962(3), 〈span〉b〈/span〉 = 13.5993(4), 〈span〉c〈/span〉 = 7.8334(6) Å, β = 108.271(8)°, 〈span〉V〈/span〉 = 738.07(7) Å〈sup〉3〈/sup〉, and 〈span〉Z〈/span〉 = 2. In the crystal structure of phoxite (〈span〉R〈/span〉〈sub〉1〈/sub〉 = 0.0275 for 1147 〈span〉I〈/span〉〈sub〉o〈/sub〉 〉 2σ〈span〉I〈/span〉 reflections), bidentate linkages between C〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 groups and Mg-centered octahedra yield chains, which link to one another via PO〈sub〉3〈/sub〉OH tetrahedra to create undulating[Mg〈sub〉2〈/sub〉(C〈sub〉2〈/sub〉O〈sub〉4〈/sub〉)(PO〈sub〉3〈/sub〉OH)〈sub〉2〈/sub〉(H〈sub〉2〈/sub〉O)〈sub〉4〈/sub〉]〈sup〉2–〈/sup〉 sheets. Strong hydrogen bonds link the sheets into a “soft framework,” with channels containing NH4+. The NH4+ forms both ordered hydrogen bonds and electrostatic bonds with O atoms in the framework. Phoxite is the first mineral known to contain both phosphate and oxalate groups as essential components.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉The elasticity of single-crystal hydrous pyrope with ~900 ppmw H〈sub〉2〈/sub〉O has been derived from sound velocity and density measurements using in situ Brillouin light spectroscopy (BLS) and synchrotron X-ray diffraction (XRD) in the diamond-anvil cell (DAC) up to 18.6 GPa at room temperature and up to 700 K at ambient pressure. These experimental results are used to evaluate the effect of hydration on the single-crystal elasticity of pyrope at high pressure and high temperature (〈span〉P-T〈/span〉) conditions to better understand its velocity profiles and anisotropies in the upper mantle. Analysis of the results shows that all of the elastic moduli increase almost linearly with increasing pressure at room temperature, and decrease linearly with increasing temperature at ambient pressure. At ambient conditions, the aggregate adiabatic bulk and shear moduli (〈span〉K〈/span〉〈sub〉S0〈/sub〉, 〈span〉G〈/span〉〈sub〉0〈/sub〉) are 168.6(4) and 92.0(3) GPa, respectively. Compared to anhydrous pyrope, the presence of ~900 ppmw H〈sub〉2〈/sub〉O in pyrope does not significantly affect its 〈span〉K〈/span〉〈sub〉S0〈/sub〉 and 〈span〉G〈/span〉〈sub〉0〈/sub〉 within their uncertainties. Using the third-order Eulerian finite-strain equation to model the elasticity data, the pressure derivatives of the bulk [(∂〈span〉K〈/span〉〈sub〉S〈/sub〉/∂〈span〉P〈/span〉)〈sub〉T〈/sub〉] and shear moduli [(∂〈span〉G/〈/span〉∂〈span〉P〈/span〉)〈sub〉T〈/sub〉] at 300 K are derived as 4.6(1) and 1.3(1), respectively. Compared to previous BLS results of anhydrous pyrope, an addition of ~900 ppmw H〈sub〉2〈/sub〉O in pyrope slightly increases the (∂〈span〉K〈/span〉〈sub〉S〈/sub〉/∂〈span〉P〈/span〉)〈sub〉T〈/sub〉, but has a negligible effect on the (∂〈span〉G/〈/span〉∂〈span〉P〈/span〉)〈sub〉T〈/sub〉 within their uncertainties. The temperature derivatives of the bulk and shear moduli at ambient pressure are (∂〈span〉K〈/span〉〈sub〉S〈/sub〉/∂〈span〉T〈/span〉)〈sub〉P〈/sub〉 = –0.015(1) GPa/K and (∂〈span〉G/〈/span〉∂〈span〉T〈/span〉)〈sub〉P〈/sub〉 = –0.008(1) GPa/K, which are similar to those of anhydrous pyrope in previous BLS studies within their uncertainties. Meanwhile, our results also indicate that hydrous pyrope remains almost elastically isotropic at relevant high 〈span〉P-T〈/span〉 conditions, and may have no significant contribution to seismic anisotropy in the upper mantle. In addition, we evaluated the seismic velocities (〈span〉ν〈/span〉〈sub〉P〈/sub〉 and 〈span〉ν〈/span〉〈sub〉S〈/sub〉) and the 〈span〉ν〈/span〉〈sub〉P〈/sub〉/〈span〉ν〈/span〉〈sub〉S〈/sub〉 ratio of hydrous pyrope along the upper mantle geotherm and a cold subducted slabs geotherm. It displays that hydrogen also has no significant effect on the seismic velocities and the 〈span〉ν〈/span〉〈sub〉P〈/sub〉/〈span〉ν〈/span〉〈sub〉S〈/sub〉 ratio of pyrope at the upper mantle conditions.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉The effect of aluminum (Al) on the elasticity of majorite-pyrope garnets was investigated by means of ultrasonic interferometry measurements on well-fabricated polycrystalline specimens. Both velocities and elastic moduli increase almost linearly with increasing Al content within analytical uncertainty. No significant variation of the velocities and elastic moduli is observed across the tetragonal-to-cubic phase transition at majorite with the pyrope content up to 26 mol% along the majorite-pyrope system. The elasticity variation of majorite-pyrope garnets is largely dominated by the Al content, while the phase transition as a result of cation ordering/disordering of Mg and Si via substitution of Al on octahedral sites cannot significantly affect elastic properties. Seismic velocity variations of a garnet-bearing mantle transition zone are therefore dominated by garnet composition (e.g., Al, Fe, Ca, and Na) rather than the tetragonal-to-cubic phase transition because of cation ordering/disordering.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Here we present a study on the quenchability of hydrous mafic melts. We show via hydrothermal experiments that the ability to quench a mafic hydrous melt to a homogeneous glass at cooling rates relevant to natural samples has a limit of no more than 9 ± 1 wt% of dissolved H〈sub〉2〈/sub〉O in the melt. We performed supra-liquidus experiments on a mafic starting composition at 1–1.5 GPa spanning H〈sub〉2〈/sub〉O-undersaturated to H〈sub〉2〈/sub〉O-saturated conditions (from ~1 to ~21 wt%). After dissolving H〈sub〉2〈/sub〉O and equilibrating, the hydrous mafic melt experiments were quenched. Quenching rates of 20 to 90 K/s at the glass transition temperature were achieved, and some experiments were allowed to decompress from thermal contraction while others were held at an isobaric condition during quench. We found that quenching of a hydrous melt to a homogeneous glass at quench rates comparable to natural conditions is possible at water contents up to 6 wt%. Melts containing 6–9 wt% of H〈sub〉2〈/sub〉O are partially quenched to a glass, and always contain significant fractions of quench crystals and glass alteration/devitrification products. Experiments with water contents greater than 9 wt% have no optically clear glass after quench and result in fine-grained mixtures of alteration/devitrification products (minerals and amorphous materials). Our limit of 9 ± 1 wt% agrees well with the maximum of dissolved H〈sub〉2〈/sub〉O contents found in natural glassy melt inclusions (8.5 wt% H〈sub〉2〈/sub〉O). Other techniques for estimating pre-eruptive dissolved H〈sub〉2〈/sub〉O content using petrologic and geochemical modeling have been used to argue that some arc magmas are as hydrous as 16 wt% H〈sub〉2〈/sub〉O. Thus, our results raise the question of whether the observed record of glassy melt inclusions has an upper limit that is partially controlled by the quenching process. This potentially leads to underestimating the maximum amount of H〈sub〉2〈/sub〉O recycled at arcs when results from glassy melt inclusions are predominantly used to estimate water fluxes from the mantle.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉High-pressure single-crystal X-ray diffraction patterns on five synthetic Mg-Al tourmalines with near end-member compositions [dravite NaMg〈sub〉3〈/sub〉Al〈sub〉6〈/sub〉Si〈sub〉6〈/sub〉O〈sub〉18〈/sub〉(BO〈sub〉3〈/sub〉)〈sub〉3〈/sub〉(OH)〈sub〉3〈/sub〉OH, K-dravite KMg〈sub〉3〈/sub〉Al〈sub〉6〈/sub〉Si〈sub〉6〈/sub〉O〈sub〉18〈/sub〉(BO〈sub〉3〈/sub〉)〈sub〉3〈/sub〉(OH)〈sub〉3〈/sub〉OH, magnesio-foitite □(Mg〈sub〉2〈/sub〉Al)Al〈sub〉6〈/sub〉Si〈sub〉6〈/sub〉O〈sub〉18〈/sub〉(BO〈sub〉3〈/sub〉)〈sub〉3〈/sub〉(OH)〈sub〉3〈/sub〉OH, oxy-uvite CaMg〈sub〉3〈/sub〉Al〈sub〉6〈/sub〉Si〈sub〉6〈/sub〉O〈sub〉18〈/sub〉(BO〈sub〉3〈/sub〉)〈sub〉3〈/sub〉(OH)〈sub〉3〈/sub〉O, and olenite NaAl〈sub〉3〈/sub〉Al〈sub〉6〈/sub〉Si〈sub〉6〈/sub〉O〈sub〉18〈/sub〉(BO〈sub〉3〈/sub〉)〈sub〉3〈/sub〉O〈sub〉3〈/sub〉OH, where □ represents an 〈span〉X〈/span〉-site vacancy] were collected to 60 GPa at 300 K using a diamond-anvil cell and synchrotron radiation. No phase transitions were observed for any of the investigated compositions. The refined unit-cell parameters were used to constrain third-order Birch-Murnaghan pressure-volume equation of states with the following isothermal bulk moduli (〈span〉K〈/span〉〈sub〉0〈/sub〉 in GPa) and corresponding pressure derivatives (K0′ = ∂〈span〉K〈/span〉〈sub〉0〈/sub〉/∂〈span〉P〈/span〉)〈sub〉T〈/sub〉: dravite 〈span〉K〈/span〉〈sub〉0〈/sub〉 = 97(6), K0′ = 5.0(5); K-dravite 〈span〉K〈/span〉〈sub〉0〈/sub〉 = 109(4), K0′ = 4.3(2); oxy-uvite 〈span〉K〈/span〉〈sub〉0〈/sub〉 = 110(2), K0′ = 4.1(1); magnesio-foitite 〈span〉K〈/span〉〈sub〉0〈/sub〉 = 116(2), K0′ = 3.5(1); olenite 〈span〉K〈/span〉〈sub〉0〈/sub〉 = 116(6), K0′ = 4.7(4). Each tour-maline exhibits highly anisotropic behavior under compression, with the 〈strong〉c〈/strong〉 axis 2.8–3.6 times more compressible than the 〈strong〉a〈/strong〉 axis at ambient conditions. This anisotropy decreases strongly with increasing pressure and the 〈strong〉c〈/strong〉 axis is onlŷ14% more compressible than the 〈strong〉a〈/strong〉 axis near 60 GPa. The octahedral 〈span〉Y〈/span〉- and 〈span〉Z〈/span〉-sites' composition exerts a primary control on tourmaline's compressibility, whereby Al content is correlated with a decrease in the 〈strong〉c〈/strong〉-axis compressibility and a corresponding increase in 〈span〉K〈/span〉〈sub〉0〈/sub〉 and K0′. Contrary to expectations, the identity of the 〈span〉X〈/span〉-site-occupying ion (Na, K, or Ca) does not have a demonstrable effect on tourmaline's compression curve. The presence of a fully vacant 〈span〉X〈/span〉 site in magnesio-foitite results in a decrease of K0′ relative to the alkali and Ca tourmalines. The decrease in K0′ for magnesio-foitite is accounted for by an increase in compressibility along the 〈strong〉a〈/strong〉 axis at high pressure, reflecting increased compression of tourmaline's ring structure in the presence of a vacant 〈span〉X〈/span〉 site. This study highlights the utility of synthetic crystals in untangling the effect of composition on tourmaline's compression behavior.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉A new (Mg〈sub〉0.5〈/sub〉Fe0.53+)(Si〈sub〉0.5〈/sub〉Al0.53+)O〈sub〉3〈/sub〉 LiNbO〈sub〉3〈/sub〉-type phase was synthesized at 27 GPa and 2000 K under highly oxidized conditions using an advanced multi-anvil apparatus. Single crystals for this phase are 0.2–0.3 mm in dimension and maroon in color. They crystallize in a noncentrosymmetric structure with space group 〈span〉R〈/span〉3〈span〉c〈/span〉 and lattice parameters of 〈span〉a〈/span〉 = 〈span〉b〈/span〉 = 4.8720(6) Å, 〈span〉c〈/span〉 = 12.898(2) Å, and 〈span〉V〈/span〉 = 265.14(8) Å〈sup〉3〈/sup〉. Fe〈sup〉3+〈/sup〉 and Al〈sup〉3+〈/sup〉 cations substitute into 〈span〉A〈/span〉 (Mg〈sup〉2+〈/sup〉) and 〈span〉B〈/span〉 (Si〈sup〉4+〈/sup〉) sites through charge-coupled substitution mechanism, respectively. The distortion of 〈span〉B〈/span〉O〈sub〉6〈/sub〉 (〈span〉B〈/span〉 = Si〈sub〉0.5〈/sub〉Al0.53+) octahedra is 1.6 times higher than that of AO〈sub〉6〈/sub〉 (A = Mg〈sub〉0.5〈/sub〉Fe0.53+) octahedra. This phase is probably recovered from bridgmanite at lower-mantle conditions by a diffusionless transition because of the displacement of 〈span〉A〈/span〉 cations and distortion of 〈span〉B〈/span〉O〈sub〉6〈/sub〉 octahedra on releasing pressure. Bridgmanite can thus contain the FeAlO〈sub〉3〈/sub〉 component (50 mol%) beyond previously reported solubility limit (37 mol%). The present study shows that the Earth's most abundant elements form a new Fe〈sup〉3+〈/sup〉- and Al〈sup〉3+〈/sup〉-rich LiNbO〈sub〉3〈/sub〉-type compound from bridgmanite at lower mantle conditions. This new compound provides a new insight into the complicated crystal chemistry of LiNbO〈sub〉3〈/sub〉-type phase/bridgmanite and constrains the pressure and temperature conditions for shocked meteorites.〈/span〉