For more than 20 years, most of the technological achievements for the realization of positive electrodes for practical rechargeable Li battery systems have been devoted to transition metal oxides such as LixMO2 (M = Co, Ni, Mn), LixMn2O4, LixV2O5, or LixV3O8. The first two classes of materials built on close-packed oxygen stacking adopt bidimensional and tridimensional crystal structures, respectively (Figure 1), from which lithium ions may be easily intercalated or extracted in a reversible manner. These oxides are reasonably good ionic and electronic conductors, and lithium insertion/extraction proceeds while operating on the M4+/M3+ redox couple, located between 4 and 5 V versus Li+/Li...

Polyanionic (phosphates, silicates, sulfates) frameworks as electrode materials for rechargeable Li (or Na) batteries.

Most minerals of Earth's upper mantle contain small amounts of hydrogen, structurally bound as hydroxyl (OH). The OH concentration in each mineral species is variable, in some cases reflecting the geological environment of mineral formation. Of the major mantle minerals, pyroxenes are the most hydrous, typically containing ∼200 to 500 parts per million H_2O by weight, and probably dominate the water budget and hydrogen geochemistry of mantle rocks that do not contain a hydrous phase. Garnets and olivines commonly contain ∼1 to 50 parts per million. Nominally anhydrous minerals constitute a significant reservoir for mantle hydrogen, possibly accommodating all water in the depleted mantle and providing a possible mechanism to recycle water from Earth's surface into the deep mantle.

https://science.sciencemag.org/content/sci/255/5050/1391.full.pdf

Water in Earth's Mantle: The Role of Nominally Anhydrous Minerals

We review recent results concerning the rheology of the lithosphere with special attention to the following topics: 1) the flexure of the oceanic lithosphere, 2) deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins, 3) the rheological stratification of the continents, 4) strain localization and shear zone development, and 5) strain-induced crystallographic preferred orientations and anisotropies in body-wave velocities. We conclude with a section citing the 1983–1986 rock mechanics literature by category.

Rheology of the lithosphere: Selected topics

To investigate the kinetics of diffusion of hydrogen in olivine, single crystals from San Carlos in Arizona have been annealed at temperatures between 800° and 1000°C under hydrothermal conditions at a confining pressure of 300 MPa. The hydrogen diffusivities were determined for the [100], [010], and [001] directions from concentration profiles for hydroxyl in the samples. These profiles were obtained from infrared spectra taken at 100-μm intervals across a thin slice which was cut from the central portion of each annealed crystal. The rate of diffusion is anisotropic, with fastest transport along the [100] axis and slowest along the [010] axis. The fit of the data to an Arrhenius law for diffusion parallel to [100] yields an activation enthalpy of 130±30 kJ/mol with a preexponential term of (6±3)×10−5 m2 s−1. For diffusion parallel to [001], as there are insufficient data to calculate the activation enthalpy for diffusion, we used the same value as that for diffusion parallel to [100] and determined a preexponential term of (5±4)×10−6 m2 s−1. The diffusion rate parallel to [010] is about 1 order of magnitude slower than along [001]. The measured diffusivities are large enough that the hydrogen content of olivine grains which are millimeters in diameter will adjust to changing environmental conditions in time scales of hours at temperatures as low as 800°C. As xenoliths ascending from the mantle remain at high temperatures (i.e., >1000°C) but experience a rapid decrease in pressure, and hence hydrogen fugacity, olivine grains may dehydrate during ascent. By comparison, slow rates of carbon diffusion (Tingle et al., 1988) suggest that carbon will not be lost from olivine during ascent. Thus, low hydrogen contents within olivine and within fluid inclusions in olivine cannot be taken as support for low water contents in the mantle.

Diffusion of hydrogen in olivine: Implications for water in the mantle

To calibrate infrared (IR) spectroscopy for quantitative analysis of trace structural OH in specific minerals, we have determined concentrations of H in pure separates of mantle derived pyrope garnet (56 ± 6 ppm H_2O by weight), augite (268 ± 8, ppm H_2O, and enstatite (217 ± 11 ppm H_2O) by manometry after heating the samples and extracting H_2 gas under vacuum. IR spectroscopy confirmed the presence of intrinsic OH in these samples prior to extraction and indicated between 86 and 100% removal of H during the extraction procedure. The integral specific absorption coefficients of 1.39 ± 0.14(lσ),7.09
± 0.32, and 15.6 ± 0.94 /(ppm H_2O.cm^2) for pyrope, augite, and enstatite, respectively, allow precise spectroscopic determination of the OH content of upper mantle garnets and pyroxenes to concentration levels of a few parts per million. Uncertainties in accuracy depend on mineral composition and characteristics of the OH absorption spectrum and are estimated to range between ± 10 and ± 50%.

http://minsocam.org/msa/ammin/toc/articles_free/1995/bell_p465-474_95.pdf

Quantitative analysis of trace OH in garnet and pyroxenes

Clinoenstatite crystals from a boninite and the Yamato-74191 chondrite have been studied with an analytical electron microscope. (100) twins and cracks perpendicular and parallel to the c axis are characteristic of their submicroscopic textures. The frequency in appearance along the c axis and widths of the cracks have been explained by the dimensional change of the c axis in the direct transformation of protoenstatite to clinoenstatite and by the cooling rate around the transformation temperature. The cracks in the crystals from the boninite are filled with fibrous crystals of talc, while those from the chondrite are open or filled with glass in which fine crystals of plagioclase are common.

Electron microscopy of clinoenstatite from a boninite and a chondrite

Laihunite, an apparent nonstoichiometric olivine-type mineral, shows a 3C type superstructure. This mineral has a basic cell of a=4.805(2)A, b=10.189(9)A, c=5.801(3)A and α=91.0(2)° and the space group P21⁄b(a=unique axis) for the average structure. The basic structure has been studied by the single crystal X-ray method, starting from the model presented by Fu et al. (1979) with 889 reflections collected by four-circle diffractometry. The final weighted R and R factors are 0. 067 and 0. 075, respectively, after the three-dimensional least squares refinements. The mean T–O, M(1)–O, M(2)–O and V–O distances are 1.637(3), 2.185(1), 2.040(2) and 2.205(2)A, respectively. The site occupancies and the bond distances of M(1), M(2) and V sites indicate the following distribution of iron atoms; V (Fe2+ 0.20), M(1) (Fe2+ and Mg2+, ∼1.00) and M(2) (Fe2+∼0.20, Fe3+∼0.80). The chemical formula of laihunite in this study is, therefore, approximately     0.40Fe0.802+Fe0.803+SiO4, indicating nonstoichiometry of laihunite.

The crystal structure of laihunite ( 0.40Fe0.802+Fe0.803+SiO4)—nonstoichiometric olivine-type mineral—

Cooling history of pyroxene chondrules in the Yamato-74191 chondrite (L3)—an electron microscopic study

Superstructure of laihunite-3M (□0.40) Fe(super 2+) (sub 0.80) Fe (super 3+) (sub 0.80) SiO 4 )

A modulation function representing the position and density of (Na, Ca) atoms in the superstructure of the e-plagioclase has been derived from the average structures of different plagioclase and a general modulation theory. Based on this function the superstructure of bytownite (An73) has been studied with the single crystal X-ray method. The cell dimensions by Megaw's axes are a=7.946(3)A, b=67.09(2)A, c=12.236(4)A, α=39.03(1)°, β=45.63(1)° and γ=59.63(1)°. Z=18(Na, Ca) Al(Al, Si)Si2O8. The initial phase factor of the modulation function for bytownite has been obtained from the intensity data of the satellite reflections. This modulation function indicates a coherent small-scale alternation of the Na-rich and Ca-rich bands in the superstructure. This superstructure has been refined by applying the albite and anorthite structures to the Na-rich and Ca-rich bands, respectively.The change of the superstructure of the e-plagioclase due to the compositional change has been described based on the movements of the satellites in reciprocal space. The direction of the coherent small-scale intergrowth of the anorthite-like and albite-like bands is perpendicular to the t vector. The thickness of the intergrowth is 1/|t|. Both direction and thickness change regularly from An75 to An25.

Nobuo Morimoto

Papers

Electron microscopy of clinoenstatite from a boninite and a chondrite

The crystal structure of laihunite ( 0.40Fe0.802+Fe0.803+SiO4)—nonstoichiometric olivine-type mineral—

Cooling history of pyroxene chondrules in the Yamato-74191 chondrite (L3)—an electron microscopic study

Superstructure of laihunite-3M (□0.40) Fe(super 2+) (sub 0.80) Fe (super 3+) (sub 0.80) SiO 4 )

The superstructure of plagioclase feldspars: A modulated coherent structure of the e-plagioclase